1.
Welding
–
In addition to melting the base metal, a filler material is typically added to the joint to form a pool of molten material that cools to form a joint that is usually stronger than the base material. Pressure may also be used in conjunction with heat, or by itself, although less common, there are also solid state welding processes such as friction welding or shielded active gas welding in which metal does not melt. Some of the best known welding methods include, Oxy-fuel welding - also known as oxyacetylene welding or oxy welding, uses fuel gases and oxygen to weld and cut metals. Shielded metal arc welding – also known as stick welding or electric welding, the electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from atmospheric contamination, gas tungsten arc welding – also known as TIG, uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from contamination by an inert shielding gas such as argon or helium. Flux-cored arc welding – almost identical to MIG welding except it uses a special tubular wire filled with flux, it can be used with or without shielding gas, submerged arc welding – uses an automatically fed consumable electrode and a blanket of granular fusible flux. The molten weld and the arc zone are protected from contamination by being submerged under the flux blanket. Electroslag welding – a highly productive, single pass welding process for thicker materials between 1 inch and 12 inches in a vertical or close to vertical position. Electric resistance welding - a welding process that produces coalescence of laying surfaces where heat to form the weld is generated by the resistance of the material. In general, an efficient method, but limited to relatively thin material, many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often a process, welding may be performed in many different environments, including in open air, under water. Welding is an undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes. Until the end of the 19th century, the welding process was forge welding. Arc welding and oxyfuel welding were among the first processes to develop late in the century, Welding technology advanced quickly during the early 20th century as the world wars drove the demand for reliable and inexpensive joining methods. Developments continued with the invention of laser welding, electron beam welding, magnetic pulse welding. Today, the continues to advance. Robot welding is commonplace in industrial settings, and researchers continue to develop new welding methods, the history of joining metals goes back several millennia
2.
Acetylene
–
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne and this colorless gas is widely used as a fuel and a chemical building block. It is unstable in its form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities, as an alkyne, acetylene is unsaturated because its two carbon atoms are bonded together in a triple bond. The carbon–carbon triple bond places all four atoms in the straight line. Acetylene was discovered in 1836 by Edmund Davy, who identified it as a new carburet of hydrogen and it was rediscovered in 1860 by French chemist Marcellin Berthelot, who coined the name acétylène. Berthelots empirical formula for acetylene, as well as the alternative name quadricarbure dhydrogène were incorrect because chemists at that used the wrong atomic mass for carbon. Berthelot was able to prepare this gas by passing vapours of organic compounds through a red-hot tube and he also found acetylene was formed by sparking electricity through mixed cyanogen and hydrogen gases. Berthelot later obtained acetylene directly by passing hydrogen between the poles of a carbon arc, commercially available acetylene gas could smell foul due to the common impurities hydrogen sulfide and phosphine. However, as purity increases it will become odourless, since the 1950s, acetylene has mainly been manufactured by the partial combustion of methane or appears as a side product in the ethylene stream from cracking of hydrocarbons. Approximately 400,000 tonnes were produced by method in 1983. Its presence in ethylene is usually undesirable because of its explosive character and it is selectively hydrogenated into ethylene, usually using Pd–Ag catalysts. Until the 1950s, when oil supplanted coal as the source of reduced carbon. In the US, this process was an important part of the late-19th century revolution in chemistry enabled by the hydroelectric power project at Niagara Falls. In terms of valence bond theory, in each carbon atom the 2s orbital hybridizes with one 2p orbital thus forming an sp hybrid, the other two 2p orbitals remain unhybridized. The two ends of the two sp hybrid orbital overlap to form a strong σ valence bond between the carbons, while on each of the two ends hydrogen atoms attach also by σ bonds. The two unchanged 2p orbitals form a pair of weaker π bonds, since acetylene is a linear symmetrical molecule, it possesses the D∞h point group. At atmospheric pressure, acetylene cannot exist as a liquid and does not have a melting point, the triple point on the phase diagram corresponds to the melting point at the minimum pressure at which liquid acetylene can exist
3.
Atmosphere of Earth
–
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
4.
Adiabatic flame temperature
–
The constant pressure adiabatic flame temperature is the temperature that results from a complete combustion process that occurs without any heat transfer or changes in kinetic or potential energy. Its temperature is lower than the constant volume process because some of the energy is utilized to change the volume of the system. In daily life, the vast majority of flames one encounters are those of organic compounds including wood, wax, fat, common plastics, propane, the constant-pressure adiabatic flame temperature of such substances in air is in a relatively narrow range around 1950 °C. Because most combustion processes that happen naturally occur in the open air, as a result, these substances will burn at a constant pressure allowing the gas to expand during the process. Assuming initial atmospheric conditions, the table lists the adiabatic flame temperature for various gases under constant pressure conditions. The temperatures mentioned here are for a stoichiometric fuel-oxidizer mixture, note these are theoretical, not actual, flame temperatures produced by a flame that loses no heat. The closest will be the hottest part of a flame, where the reaction is most efficient. As a result, the energy of the products is equal to the internal energy of the reactants. From the first law, we find that, − p = U P − U R ⇒ U P + p V P = U R + p V R Recalling the definition of enthalpy we recover, H P = H R. We see that the flame temperature of the constant pressure process is lower than that of the constant volume process. This is because some of the released during combustion goes into changing the volume of the control system. One analogy that is made between the two processes is through combustion in an internal combustion engine. For the constant volume process, combustion is thought to occur instantaneously when the piston reaches the top of its apex. For the constant pressure process, while combustion is occurring the piston is moving in order to keep the pressure constant. If we make the assumption that combustion goes to completion, we can calculate the adiabatic flame temperature by hand either at stoichiometric conditions or lean of stoichiometry, different fuels with different levels of energy and molar constituents will have different adiabatic flame temperatures. We can see by the figure why nitromethane is often used as a power boost for cars. Since each mole of nitromethane contains two moles of oxygen, it can burn much hotter because it provides its own oxidant along with fuel and this in turn allows it to build up more pressure during a constant volume process. The higher the pressure, the force upon the piston creating more work
5.
Oxyhydrogen
–
Oxyhydrogen is a mixture of hydrogen and oxygen gases. This gaseous mixture is used for torches to process refractory materials and was the first gaseous mixture used for welding. Theoretically, a ratio of 2,1 hydrogen, oxygen is enough to achieve maximum efficiency, Browns gas and HHO are fringe science terms for a 2,1 mixture of oxyhydrogen obtained under certain special conditions, its proponents claim that it has special properties. Oxyhydrogen will combust when brought to its autoignition temperature, for the stoichiometric mixture,2,1 hydrogen, oxygen, at normal atmospheric pressure, autoignition occurs at about 570 °C. The minimum energy required to ignite such a mixture with a spark is about 20 microjoules, at standard temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume. When ignited, the gas mixture converts to water vapor and releases energy, the amount of heat energy released is independent of the mode of combustion, but the temperature of the flame varies. The maximum temperature of about 2,800 °C is achieved with a stoichiometric mixture. In theory, the energy of a closed system will always equal the output energy. Many forms of oxyhydrogen lamps have been described, such as the limelight, because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting. The oxy-hydrogen blowpipe was developed by English mineralogist Edward Daniel Clarke and it produced a flame hot enough to melt such refractory materials as platinum, porcelain, fire brick, and corundum, and was a valuable tool in several fields of science. It is used in the Verneuil process to produce synthetic corundum, an oxyhydrogen torch is an oxy-gas torch, which burns hydrogen with oxygen. It is used for cutting and welding, metals, glass, oxyhydrogen was once used in working platinum because at the time such a torch was the only device that could attain the temperature required to melt the metal 1,768.3 °C. These techniques have been superseded by the electric arc furnace, Browns Gas is oxyhydrogen with a 2,1 molar ratio of H2 and O2 gases, the same proportion as in water. It is named after Yull Brown, who claimed that it could be used as a fuel for the combustion engine. Many other pseudoscientific claims have made about Browns Gass pretended ability to neutralize radioactive waste, help plants to germinate. Oxyhydrogen is often mentioned in conjunction with vehicles that claim to use water as a fuel, additionally, the volume of gas that can be produced for on-demand consumption through electrolysis is very small in comparison to the volume consumed by an internal combustion engine. An article in Popular Mechanics reported that Browns Gas does not increase the economy in automobiles. Water-fueled cars should not be confused with hydrogen-fueled cars, where the hydrogen is produced elsewhere and used as fuel or where it is used as fuel enhancement
6.
Arc welding
–
Arc welding is a process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals when cool result in a binding of the metals. It is a type of welding that uses a power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes, the welding region is usually protected by some type of shielding gas, vapor, or slag. Arc welding processes may be manual, semi-automatic, or fully automated, first developed in the late part of the 19th century, arc welding became commercially important in shipbuilding during the Second World War. Today it remains an important process for the fabrication of steel structures and vehicles, to supply the electrical energy necessary for arc welding processes, a number of different power supplies can be used. The most common classification is constant current power supplies and constant voltage power supplies, in arc welding, the voltage is directly related to the length of the arc, and the current is related to the amount of heat input. This is important because in manual welding, it can be difficult to hold the electrode perfectly steady, and as a result, the arc length and thus voltage tend to fluctuate. In these processes, arc length is constant, since any fluctuation in the distance between the wire and the base material is quickly rectified by a large change in current. The direction of current used in arc welding also plays an important role in welding, consumable electrode processes such as shielded metal arc welding and gas metal arc welding generally use direct current, but the electrode can be charged either positively or negatively. In welding, the positively charged anode will have a greater concentration and, as a result. If the electrode is charged, it will melt more quickly, increasing weld penetration. Alternatively, a negatively charged electrode results in more shallow welds, non-consumable electrode processes, such as gas tungsten arc welding, can use either type of direct current, as well as alternating current. Alternating current rapidly moves between two, resulting in medium-penetration welds. Duty cycle is an equipment specification which defines the number of minutes, within a 10-minute period. For example, an 80 A welder with a 60% duty cycle must be rested for at least 4 minutes after 6 minutes of continuous welding, failure to observe duty cycle limitations could damage the welder. Commercial- or professional-grade welders typically have a 100% duty cycle, one of the most common types of arc welding is shielded metal arc welding, which is also known as manual metal arc welding or stick welding. An electric current is used to strike an arc between the material and a consumable electrode rod or stick. The electrode core itself acts as filler material, making a separate filler unnecessary, the process is very versatile, requiring little operator training and inexpensive equipment
7.
Combustion
–
Combustion in a fire produces a flame, and the heat produced can make combustion self-sustaining. Combustion is often a sequence of elementary radical reactions. Solid fuels, such as wood, first undergo endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the required to produce more of them. Combustion is often hot enough that light in the form of either glowing or a flame is produced, a simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction commonly used to fuel rocket engines. The bond energies in the play only a minor role, since they are similar to those in the combustion products. The heat of combustion is approximately -418 kJ per mole of O2 used up in the combustion reaction, uncatalyzed combustion in air requires fairly high temperatures. Complete combustion is stoichiometric with respect to the fuel, where there is no remaining fuel, thermodynamically, the chemical equilibrium of combustion in air is overwhelmingly on the side of the products. Thus, the smoke is usually toxic and contains unburned or partially oxidized products. Since combustion is rarely clean, flue gas cleaning or catalytic converters may be required by law, fires occur naturally, ignited by lightning strikes or by volcanic products. Combustion was the first controlled chemical reaction discovered by humans, in the form of campfires and bonfires, usually, the fuel is carbon, hydrocarbons or more complicated mixtures such as wood that contains partially oxidized hydrocarbons. Combustion is also currently the only used to power rockets. Combustion is also used to destroy waste, both nonhazardous and hazardous, oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen, chlorine, fluorine, chlorine trifluoride, nitrous oxide and nitric acid. For instance, hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat, although usually not catalyzed, combustion can be catalyzed by platinum or vanadium, as in the contact process. In complete combustion, the reactant burns in oxygen, producing a number of products. When a hydrocarbon burns in oxygen, the reaction will yield carbon dioxide. When elements are burned, the products are primarily the most common oxides, carbon will yield carbon dioxide, sulfur will yield sulfur dioxide, and iron will yield iron oxide. Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, Combustion is not necessarily favorable to the maximum degree of oxidation, and it can be temperature-dependent. For example, sulfur trioxide is not produced quantitatively by the combustion of sulfur, NOx species appear in significant amounts above about 2,800 °F, and more is produced at higher temperatures
8.
Slag
–
Slag is the glass-like by-product left over after a desired metal has been separated from its raw ore. Slag is usually a mixture of oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals, in nature, iron, copper, lead, nickel and other metals are found in impure states called ores, often oxidized and mixed in with silicates of other metals. During smelting, when the ore is exposed to high temperatures, Slag is the collection of compounds that are removed. In many smelting processes, oxides are introduced to control the slag chemistry, assisting in the removal of impurities, in this case, the slag is termed synthetic. Ferrous and non-ferrous smelting processes produce different slags, the smelting of copper and lead in non-ferrous smelting, for instance, is designed to remove the iron and silica that often occurs with those ores, and separates them as iron-silicate-based slags. Slag from steel mills in ferrous smelting, on the hand, is designed to minimize iron loss and so mainly contains oxides of calcium, silicon, magnesium. Any sandy component or quartz component of the original ore automatically carries through the process as silicon dioxide. As the slag is channeled out of the furnace, water is poured over it and this rapid cooling, often from a temperature of around 2,600 °F, is the start of the granulating process. This process causes several chemical reactions to take place within the slag, the water carries the slag in its slurry format to a large agitation tank, from where it is pumped along a piping system into a number of gravel based filter beds. The filter beds then retain the slag granules, while the drains away and is returned to the system. During the Bronze Age of the Mediterranean there were a vast number of metallurgical processes in use. A slag by-product of such workings was a colorful, glassy and it was primarily blue or green and was formerly chipped away and melted down to make glassware products and jewelry. It was also ground into powder to add to glazes for use in ceramics, some of the earliest such uses for the by-products of slag have been found in ancient Egypt. Historically, the re-smelting of iron ore slag was common practice, during the early 20th century, iron ore slag was also ground to a powder and used to make agate glass, also known as slag glass. Ground granulated slag is used in concrete in combination with Portland cement as part of a blended cement. Ground granulated slag reacts with water to produce cementitious properties, concrete containing ground granulated slag develops strength over a longer period, leading to reduced permeability and better durability. Since the unit volume of Portland cement is reduced, this concrete is less vulnerable to alkali-silica, the slag can also be used to create fibers used as an insulation material called slag wool
9.
Soldering
–
Soldering, is a process in which two or more items are joined together by melting and putting a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal. Soldering differs from welding in that soldering does not involve melting the work pieces, in brazing, the filler metal melts at a higher temperature, but the work piece metal does not melt. In the past, nearly all solders contained lead, but environmental and health concerns have increasingly dictated use of alloys for electronics. There is evidence that soldering was employed as early as 5000 years ago in Mesopotamia, soldering and brazing are thought to have originated very early in the history of metal-working, probably before 4000 BC. Sumerian swords from ~3000 BC were assembled using hard soldering, soldering was historically used to make jewelry items, cooking ware and tools, as well as other uses such as in assembling stained glass. Soldering is used in plumbing, electronics, and metalwork from flashing to jewelry, jewelry components, machine tools and some refrigeration and plumbing components are often assembled and repaired by the higher temperature silver soldering process. Small mechanical parts are often soldered or brazed as well, soldering is also used to join lead came and copper foil in stained glass work. Electronic soldering connects electrical wiring and electronic components to printed circuit boards, soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the alloy of 63% tin and 37% lead has been the alloy of choice. Other alloys are used for plumbing, mechanical assembly, and other applications, a eutectic formulation has advantages when applied to soldering, the liquidus and solidus temperatures are the same, so there is no plastic phase, and it has the lowest possible melting point. Having the lowest possible melting point minimizes heat stress on electronic components during soldering, and, having no plastic phase allows for quicker wetting as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures, any movement during the plastic phase may result in cracks, resulting in an unreliable joint. Common solder formulations based on tin and lead are listed below and they are also suggested anywhere young children may come into contact with, or for outdoor use where rain and other precipitation may wash the lead into the groundwater. Unfortunately, most lead-free solders are not eutectic formulations, melting at around 250 °C, alloying silver with other metals changes the melting point, adhesion and wetting characteristics, and tensile strength. Of all the brazing alloys, silver solders have the greatest strength, specialty alloys are available with properties such as higher strength, the ability to solder aluminum, better electrical conductivity, and higher corrosion resistance. The purpose of flux is to facilitate the soldering process, one of the obstacles to a successful solder joint is an impurity at the site of the joint, for example, dirt, oil or oxidation. The impurities can be removed by mechanical cleaning or by chemical means and this effect is accelerated as the soldering temperatures increase and can completely prevent the solder from joining to the workpiece. One of the earliest forms of flux was charcoal, which acts as a reducing agent, some fluxes go beyond the simple prevention of oxidation and also provide some form of chemical cleaning
10.
Brazing
–
The filler metal flows into the gap between close-fitting parts by capillary action. The filler metal is slightly above its melting temperature while protected by a suitable atmosphere. It then flows over the metal and is then cooled to join the work pieces together. It is similar to soldering, except for the use of higher temperatures, a major advantage of brazing is the ability to join the same or different metals with considerable strength. High-quality brazed joints require that parts be closely fitted, and the base metals exceptionally clean, in most cases, joint clearances of 0.03 to 0.08 mm are recommended for the best capillary action and joint strength. However, in some brazing operations it is not uncommon to have joint clearances around 0.6 mm, cleanliness of the brazing surfaces is also important, as any contamination can cause poor wetting. The two main methods for cleaning parts, prior to brazing, are cleaning and abrasive or mechanical cleaning. In the case of mechanical cleaning, it is important to maintain the surface roughness as wetting on a rough surface occurs much more readily than on a smooth surface of the same geometry. Another consideration is the effect of temperature and time on the quality of brazed joints, as the temperature of the braze alloy is increased, the alloying and wetting action of the filler metal increases as well. In general, the brazing temperature selected must be above the point of the filler metal. However, several factors influence the joint designers temperature selection, the effect of time on the brazed joint primarily affects the extent to which these effects are present. In general, however, most production processes are selected to minimize brazing time and this is not always the case, however, since in some non-production settings, time and cost are secondary to other joint attributes. Unless brazing operations are contained within an inert or reducing atmosphere environment, the flux also serves the purpose of cleaning any contamination left on the brazing surfaces. Flux can be applied in any number of forms including flux paste, liquid, flux can also be applied using brazing rods with a coating of flux, or a flux core. In either case, the flows into the joint when applied to the heated joint and is displaced by the molten filler metal entering the joint. Excess flux should be removed when the cycle is completed because flux left in the joint can lead to corrosion, impede joint inspection, phosphorus-containing brazing alloys can be self-fluxing when joining copper to copper. Fluxes are generally selected based on their performance on particular base metals, to be effective, the flux must be chemically compatible with both the base metal and the filler metal being used. Self-fluxing phosphorus filler alloys produce brittle phosphides if used on iron or nickel, as a general rule, longer brazing cycles should use less active fluxes than short brazing operations
11.
Screw
–
A screw is a type of fastener, sometimes similar to a bolt, typically made of metal, and characterized by a helical ridge, known as a male thread or just thread. A screw is an inclined plane wrapped around a nail, some screw threads are designed to mate with a complementary thread, known as a female thread, often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together, a screw will usually have a head on one end that contains a specially formed shape that allows it to be turned, or driven, with a tool. Common tools for driving screws include screwdrivers and wrenches, the head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw and to provide a bearing surface. The cylindrical portion of the screw from the underside of the head to the tip is known as the shank, the distance between each thread is called the pitch. Another rule is this, curl the fingers of right hand around the screw with your thumb pointing is the direction you want the screw to go. If the screw is right-handed and you turn the screw in the direction of your fingers the screw will move in the direction of your thumb, Screws with left-hand threads are used in exceptional cases. For example, when the screw will be subject to counterclockwise torque, the right side pedal of a bicycle has a left-hand thread. More generally, screw may mean any helical device, such as a clamp, a micrometer, there is no universally accepted distinction between a screw and a bolt. So, as a rule, when buying a packet of screws you would not expect nuts to be included. Part of the confusion over this is due to regional or dialectical differences. An externally threaded fastener which is prevented from being turned during assembly, an externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw. This distinction is consistent with ASME B18.2.1 and some dictionary definitions for screw, some of these issues are discussed below, ASME standards specify a variety of Machine Screws in diameters ranging up to 0.75 in. These fasteners are used with nuts but also often driven into tapped holes. They might be considered a screw or a bolt based on the Machinerys Handbook distinction, ASME standard B18.2. 1-1996 specifies Hex Cap Screws that range in size from 0. 25–3 in in diameter. These fasteners are very similar to hex bolts and they differ mostly in that they are manufactured to tighter tolerances than the corresponding bolts. Machinerys Handbook refers parenthetically to these fasteners as Finished Hex Bolts, in 1991 responding to an influx of counterfeit fasteners Congress passed PL 101-592 Fastener Quality Act This resulted in the rewriting of specifications by the ASME B18 committee
12.
Calcium oxide
–
Calcium oxide, commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature, the broadly used term lime connotes calcium-containing inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, quicklime specifically applies to the chemical compound calcium oxide. Calcium oxide that survives processing without reacting in building such as cement is called free lime. Both it and a chemical derivative are important commodity chemicals, Calcium oxide is usually made by the thermal decomposition of materials, such as limestone or seashells, that contain calcium carbonate in a lime kiln. This is accomplished by heating the material to above 825 °C, annual worldwide production of quicklime is around 283 million tonnes. China is by far the worlds largest producer, with a total of around 170 million tonnes per year, the United States is the next largest, with around 20 million tonnes per year. Approximately 1.8 t of limestone is required per 1.0 t of quicklime, quicklime has a high affinity for water and is a more efficient desiccant than silica gel. The reaction of quicklime with water is associated with an increase in volume by a factor of at least 2.5, the major use of quicklime is in the Basic oxygen steelmaking process. Its usage varies from about 30–50 kg/t of steel, the quicklime neutralizes the acidic oxides, SiO2, Al2O3, and Fe2O3, to produce a basic molten slag. Ground quicklime is used in the production of aerated concrete blocks, quicklime and hydrated lime can considerably increase the load carrying capacity of clay-containing soils. They do this by reacting with finely divided silica and alumina to produce calcium silicates and aluminates, small quantities of quicklime are used in other processes, e. g. the production of glass, calcium aluminate cement, and organic chemicals. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction, one litre of water combines with approximately 3.1 kilograms of quicklime to give calcium hydroxide plus 3.54 MJ of energy. This process can be used to provide a convenient portable source of heat, light, When quicklime is heated to 2,400 °C, it emits an intense glow. This form of illumination is known as a limelight, and was used broadly in theatrical productions prior to the invention of electric lighting, cement, Calcium oxide is a key ingredient for the process of making cement. As a cheap and widely available alkali, about 50% of the total quicklime production is converted to calcium hydroxide before use. Both quick- and hydrated lime are used in the treatment of drinking water, petroleum industry, Water detection pastes contain a mix of calcium oxide and phenolphthalein. Should this paste come into contact with water in a storage tank
13.
Limelight
–
Limelight is a type of stage lighting once used in theatres and music halls. An intense illumination is created when a flame is directed at a cylinder of quicklime. The light is produced by a combination of incandescence and candoluminescence. Although it has long since replaced by electric lighting, the term has nonetheless survived, as someone in the public eye is still said to be “in the limelight. ”The actual lights are called limes. The limelight effect was discovered in the 1820s by Goldsworthy Gurney, based on his work with the oxy-hydrogen blowpipe, in 1825, a Scottish engineer, Thomas Drummond, saw a demonstration of the effect by Michael Faraday and realized that the light would be useful for surveying. Drummond built a version in 1826, and the device is sometimes called the Drummond Light after him. The earliest known use of limelight at a performance was outdoors, over Herne Bay Pier, Kent. This performance was part of the following the laying of the foundation stone of the Clock Tower. The advertising leaflet called it light, and announced that. Limelight was first used for indoor stage illumination in the Covent Garden Theatre in London in 1837, limelights were employed to highlight solo performers in the same manner as modern followspots. Limelight was replaced by electric arc lighting in the late 19th century, klieg light List of light sources Nineteenth-century theatrical scenery Timeline of hydrogen technologies Zirconia light
14.
Platinum
–
Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious and its name is derived from the Spanish term platina, translated into little silver. Platinum is a member of the group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes and it is one of the rarer elements in Earths crust with an average abundance of approximately 5 μg/kg. It occurs in some nickel and copper ores along with some deposits, mostly in South Africa. Because of its scarcity in Earths crust, only a few hundred tonnes are produced annually, Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the sands of various rivers. Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Being a heavy metal, it leads to health issues upon exposure to its salts, compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy against certain types of cancer. Pure platinum is a lustrous, ductile, and malleable, silver-white metal, Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold. The metal has excellent resistance to corrosion, is stable at temperatures and has stable electrical properties. Platinum reacts with oxygen slowly at high temperatures. It reacts vigorously with fluorine at 500 °C to form platinum tetrafluoride and it is also attacked by chlorine, bromine, iodine, and sulfur. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot aqua regia to form chloroplatinic acid and its physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and tarnish is well suited to use in fine jewelry, the most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are common, and are often stabilized by metal bonding in bimetallic species. As is expected, tetracoordinate platinum compounds tend to adopt 16-electron square planar geometries, Platinum has six naturally occurring isotopes, 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt
15.
Gas cylinder
–
A gas cylinder or tank is a pressure vessel used to store gases at above atmospheric pressure. High-pressure gas cylinders are also called bottles, in the United States, bottled gas typically refers to liquefied petroleum gas. Bottled gas is used in medical supply, especially for portable oxygen tanks. Packaged industrial gases are frequently called cylinder gas, though bottled gas is sometimes used, the United Kingdom and other parts of Europe more commonly refer to bottled gas when discussing any usage whether industrial, medical or liquefied petroleum. For a detailed discussion about the materials for gas cylinders see pressure vessel, design codes and application standards along with the cost of materials dictated the choice of steel with no welds for most gas cylinders, treated to be anti corrosive. There have been some newly developed lightweight gas cylinders from composite materials, due to the very high tensile strength of carbon fiber, these vessels can be very light, but are much more difficult to manufacture. The transportation of high-pressure cylinders is regulated by many throughout the world. Various levels of testing are required by the governing authority for the country in which it is to be transported. In the United States, this authority is the United States Department of Transportation, similarly in the UK, the European transport regulations are implemented by the Department for Transport. For Canada, this authority is Transport Canada, cylinders may have additional requirements placed on design and or performance from independent testing agencies such as Underwriters Laboratory. Each manufacturer of high-pressure cylinders is required to have an independent quality agent that will inspect the product for quality and safety, there are a variety of tests that may be performed on various cylinders. Some of the most common types of tests are hydrostatic test, burst test, tensile strength, Charpy impact test, during the manufacturing process, vital information is usually stamped or permanently marked on the cylinder. This information usually includes the type of cylinder, the working or service pressure, the number, date of manufacture. Other information may also be stamped depending on the regulation requirements, high-pressure cylinders that are used multiple times — as most are — can be hydrostatically or ultrasonically tested and visually examined every few years. In the United States, hydrostatic/ultrasonic testing is required every five years or every ten years, depending on cylinder. Helium gas cylinders have the highest pressures possible when full, around 1000 atmospheres, when gases are supplied in gas cylinders, the cylinders have a stop angle valve at the end on top. Often, gas cylinders are somewhat long and narrow and may stand upright on a bottom at one end with the valve at the top. Instead of a cap, cylinders commonly have a collar or neck ring around the service valve assembly
16.
Pressure
–
Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
17.
Solder
–
Solder is a fusible metal alloy used to create a permanent bond between metal workpieces. The word solder comes from the Middle English word soudur, via Old French solduree and soulder, from the Latin solidare, meaning to make solid. In fact, solder must be melted in order to adhere to and connect the pieces together, whenever possible, the solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder that is intended for use in making connections between electronic components also usually has favorable electrical characteristics. Soft solder typically has a melting point range of 90 to 450 °C, and is used in electronics, plumbing. Manual soldering uses an iron or soldering gun. Alloys that melt between 180 and 190 °C are the most commonly used, soldering performed using alloys with a melting point above 450 °C is called hard soldering, silver soldering, or brazing. In specific proportions, some alloys can become eutectic — that is, non-eutectic alloys have markedly different solidus and liquidus temperatures, and within that range they exist as a paste of solid particles in a melt of the lower-melting phase. In electrical work, if the joint is disturbed in the pasty state before it has solidified totally, for electrical and electronics work, solder wire is available in a range of thicknesses for hand-soldering, and with cores containing flux. It is also available as a paste or as a preformed foil shaped to match the workpiece, alloys of lead and tin were commonly used in the past, and are still available, they are particularly convenient for hand-soldering. Lead-free solders have been increasing in use due to regulatory requirements plus the health and they are almost exclusively used today in consumer electronics. Plumbers often use bars of solder, much thicker than the used for electrical applications. Jewelers often use solder in thin sheets, which cut into snippets. In the US, manufacturers may receive tax benefits by reducing the use of lead-based solder, lead-free solders in commercial use may contain tin, copper, silver, bismuth, indium, zinc, antimony, and traces of other metals. Most lead-free replacements for conventional 60/40 and 63/37 Sn-Pb solder have melting points from 5 to 20 °C higher and it may be desirable to use minor modification of the solder pots used in wave-soldering, to reduce maintenance cost due to increased tin-scavenging of high-tin solder. Lead-free solder may be desirable for critical applications, such as aerospace and medical projects. Tin-Silver-Copper solders are used by two-thirds of Japanese manufacturers for reflow and wave soldering, tin-based solders readily dissolve gold, forming brittle intermetallics, for Sn-Pb alloys the critical concentration of gold to embrittle the joint is about 4%. Indium-rich solders are more suitable for soldering thicker gold layer as the rate of gold in indium is much slower
18.
Cart
–
A cart is a vehicle designed for transport, using two wheels and normally pulled by one or a pair of draught animals. A handcart is pulled or pushed by one or more people and it is different from a dray or wagon, which is a heavy transport vehicle with four wheels and typically two or more horses, or a carriage, which is used exclusively for transporting humans. Over time, the cart has come to mean nearly any small conveyance, from shopping carts to golf carts, without regard to number of wheels, load carried. The draught animals used for carts may be horses or ponies, mules, oxen, water buffalo or donkeys, carts have been mentioned in literature as far back as the second millennium B. C. The Indian sacred book Rigveda states that men and women are as equal as two wheels of a cart, hand-carts pushed by humans have been used around the world. In the 19th century, for instance, some Mormons travelling across the plains of the United States between 1856 and 1860 used handcarts, the history of the cart is closely tied to the history of the wheel. Larger carts may be drawn by animals, such as horses, mules and they have been in continuous use since the invention of the wheel, in the 4th millennium BC. Carts may be named for the animal that pulls them, such as horsecart or oxcart, in modern times, horsecarts are used in competition while draft horse showing. A dogcart, however, is usually a cart designed to carry hunting dogs, the term cart is also used for various kinds of lightweight, two-wheeled carriages, some of them sprung carts, especially those used as open pleasure or sporting vehicles. They could be drawn by a horse, pony or dog, the name survives today as a milkfloat. The seat is adjustable fore-and-aft to keep the vehicle balanced for two or four people, carts have many different shapes, but the basic idea of transporting material remains. Carts may have a pair of shafts, one each side of the draught animal that supports the forward-balanced load in the cart. The shafts are supported by a saddle on the horse, alternatively, the cart may have a single pole between a pair of animals. The draught traces attach to the axle of the vehicle or to the shafts, the traces are attached to a collar, to a yoke or to a harness on dogs or other light animals. Traces are made from a range of materials depending on the load, heavy draught traces are made from iron or steel chain. Lighter traces are often leather and sometimes rope, but plaited horse-hair. The dray is often associated with the transport of barrels, particularly of beer, of the cart types not animal-drawn, perhaps the most common example today is the shopping cart, which has also come to have a metaphorical meaning in relation to online purchases. Shopping carts first made their appearance in Oklahoma City in 1937, in golf, both manual push or pull and electric golf trolleys are designed to carry a golfers bag, clubs and other equipment
19.
Diving tank
–
A diving cylinder, scuba tank or diving tank is a gas cylinder used to store and transport the high pressure breathing gas required by a scuba set. It may also be used for surface-supplied diving or as decompression gas or a gas supply for surface supplied diving or scuba. Cylinders provide gas to the diver through the valve of a diving regulator or the breathing loop of a diving rebreather. Diving cylinders are manufactured from aluminium or steel alloys, and are normally fitted with one of two common types of cylinder valve for filling and connection to the regulator. Other accessories such as manifolds, cylinder bands, protective nets and boots, various configurations of harness may be used to carry the cylinder or cylinders while diving, depending on the application. Cylinders used for scuba typically have a volume of between 3 and 18 litres and a maximum working pressure rating from 184 to 300 bars. Scuba divers may dive with a cylinder, a pair of similar cylinders, or a main cylinder. Paired cylinders may be manifolded together or independent, in some cases, more that two cylinders are needed. When pressurised, an carries a equivalent volume of free gas greater than its water capacity. The selection of a set of diving cylinders for a diving operation is based on the amount of gas required to safely complete the dive. Many jurisdictions have regulations that govern the filling, recording of contents, periodic inspection and testing of cylinders is often obligatory to ensure the safety of operators of filling stations. Pressurised diving cylinders are considered dangerous goods for transportation. The term diving cylinder tends to be used by gas equipment engineers, manufacturers, support professionals, scuba tank or diving tank is more often used colloquially by non-professionals and native speakers of American English. The term oxygen tank is used by non-divers, however. They rarely contain pure oxygen, except when used for rebreather diving, breathing pure oxygen at depths greater than 6 metres can result in oxygen toxicity. Diving cylinders have also referred to as bottles or flasks, usually preceded with the word scuba, diving, air. Diving cylinders may also be specified by their application, as in bailout cylinders, stage cylinders, deco cylinders, sidemount cylinders, pony cylinders, suit inflation cylinders, the functional diving cylinder consists of a pressure vessel and a cylinder valve. There are usually one or more optional accessories depending on the specific application, the pressure vessel is a seamless cylinder normally made of cold-extruded aluminium or forged steel
20.
Backpack
–
Lightweight types of backpacks are sometimes worn on only one shoulder strap. This improves the potential to carry loads, as the hips are stronger than the shoulders. In ancient times, the backpack was used as a means to carry the larger game and other types of prey. They were also easy to carry and made of cloths, the bag itself would be made up of animal hide and skin and sewn together by animal intestines, which would be woven together tightly to make a sturdy thread-like material. The word backpack was coined in the United States in the 1910s, moneybag and packsack were used prior, and now occur mainly as regionalisms. The word rucksack is a German loanword mainly used in the UK, in German, Rücken means back and Sack means bag. The name rucksack is cognate with the Danish rygsæk, Norwegian ryggsekk, Dutch rugzak, Afrikaans rugsak, the word knapsack was the usual name for a rucksack or backpack up until the middle of the 20th century. Alternative names include haversack, Kraxe, and bergen, in fact, Britons used to call Alpine-style backpacks Bergen rucksacks, maybe from the name of their creator, Norwegian Ole F. Bergan, combined with the name of the Norwegian city of Bergen. Backpacks in general fall into one of four categories, frameless, external frame, internal frame, and bodypack. A pack frame, when present, serves to support the pack and distribute the weight of its contents across the more appropriately, by transferring much of the weight to the hips. Most of the weight is taken off the shoulders, reducing the chance of injury from shoulder strap pressure. Most backpacks are capable of being closed with either a buckle mechanism, a zipper, or a dry-bag type closure though a few models use a drawstring fitted with a cord lock for the main compartment. A bodypack is a backpack fitted with one or more pockets that are suspended on the wearers chest and loaded in such a way that the load in the front, the majority of the load in a bodypack is carried by the hips. The ideal load carrying system should not disturb the wearers natural posture, balance, the load must be dispersed onto the skeletal structure in an even manner, and should not produce unbalanced forces on the body. The simplest backpack design is a bag attached to a set of shoulder straps, such packs are used for general transportation of goods, and have variable capacity. The simplest designs consist of one main pocket and these packs are generally produced inexpensively. Some outdoor packs, particularly those sold for day hikes, ultralight backpacking and mountaineering are sometimes frameless as well. Sports and hydration backpacks are smaller with a closer to the body, wider straps and can come with water bladders
21.
Pressure regulator
–
A pressure regulator is a control valve that reduces the input pressure of a fluid to a desired value at its output. A pressure regulators primary function is to match the flow of gas through the regulator to the demand for gas placed upon it, if the load flow decreases, then the regulator flow must decrease also. If the load increases, then the regulator flow must increase in order to keep the controlled pressure from decreasing due to a shortage of gas in the pressure system. The loading element is a part that can apply the force to the restricting element. This loading can be provided by a weight, a spring, the measuring element functions to determine when the inlet flow is equal to the outlet flow. The diaphragm itself is used as a measuring element, it can serve as a combined element. In the pictured single-stage regulator, a balance is used on the diaphragm to control a poppet valve in order to regulate pressure. With no inlet pressure, the spring above the diaphragm pushes it down on the poppet valve, by adjusting the top screw, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain equilibrium. In this way, the pressure of the regulator is controlled. High pressure gas from the supply enters into the regulator through the inlet valve, the gas then enters the body of the regulator, which is controlled by the needle valve. The pressure rises, which pushes the diaphragm, closing the valve to which it is attached. The outlet side is fitted with a pressure gauge, as gas is drawn from the outlet side, the pressure inside the regulator body falls. The diaphragm is pushed back by the spring and the valve opens, the outlet pressure therefore depends on the spring force, which can be adjusted by means of an adjustment handle or knob. The outlet pressure and the inlet pressure hold the assembly in the closed position against the force of the large spring. If the supply falls, it is as if the large spring compression is increased allowing more gas. Thus, if the pressure falls, the outlet pressure will increase. This is the cause of end-of-tank dump where the supply is provided by a gas tank. With a single regulator, when the supply tank gets low
22.
Needle valve
–
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is only capable of relatively low flow rates. An instrument needle valve uses a pin to gradually open a space for fine control of flow. The flow can be controlled and regulated with the use of a spindle, a needle valve has a relatively small orifice with a long, tapered seat, and a needle-shaped plunger on the end of a screw, which exactly fits the seat. As the screw is turned and the retracted, flow between the seat and the plunger is possible, however, until the plunger is completely retracted. Since it takes many turns of the screw to retract the plunger. The virtue of the valve is from the vernier effect of the ratio between the needles length and its diameter, or the difference in diameter between needle and seat. A long travel axially makes for a small and precise change radially. Needle valves may also be used in systems, when a precise control of gas flow is required, at low pressure, such as when filling gas-filled vacuum tubes, gas lasers. Needle valves are used in flow-metering applications, especially when a constant, calibrated, low flow rate must be maintained for some time. Note that the valve of a carburetor is not a needle valve. It uses a bluntly conical needle, but it seats against a square-edged seat rather than a matching cone, the intention here is to obtain a well-defined seat between two narrow mating surfaces, giving firm shutoff of the flow from only a light float pressure. Needle valves are commonly used to provide shut off for the pressure gauge or on applicators to shut off the supply of NH3 to the knives in Anhydrous Ammonia applications. Since flow rates are low and many turns of the stem are required to completely open or close. Since the orifice is small and the advantage of the fine-threaded stem is high, needle valves are usually easy to shut off completely. The spindle and/or seat of a valve, especially one made from brass, are easily damaged by excessive turning force when shutting off the flow. Small, simple needle valves are used as bleed valves in water-heating applications. Unlike a ball valve or valves with a stem, it is not easy to tell from examining the handle position whether the valve is open or closed
23.
Diving regulator
–
A diving regulator is a pressure regulator that reduces pressurized breathing gas to ambient pressure and delivers it to the diver. The gas may be air or one of a variety of specially blended breathing gases, the gas may be supplied from a scuba cylinder carried by the diver or via a hose from a compressor or high pressure storage cylinders at the surface in surface-supplied diving. The terms regulator and demand valve are used interchangeably, but a demand valve is a regulator that delivers gas only while the diver is inhaling. In single hose regulators, the valve is the second stage. In twin hose regulators the demand valve is included in the body of the regulator which is attached directly to the cylinder valve or manifold outlet. Rebreather systems may also use regulators to control the flow of fresh gas, for some applications the capacity to deliver high flow rates at low ambient temperatures without freezing is important. The diving regulator is a mechanism which reduces the pressure of the supply of breathing gas, the gas may be provided directly to the diver, or to a rebreather circuit, to make up for used gas and volume changes due to depth variations. Gas supply may be from a scuba cylinder carried by the diver. A demand valve detects when the diver starts inhaling and supplies the diver with a breath of gas at ambient pressure and this is done by a mechanical system linking a pressure differential sensor to a valve which is opened to an extent proportional to the displacement of the diaphragm difference. The pressure difference between the inside of the mouthpiece and the ambient pressure outside the required to open the valve is known as the cracking pressure. This cracking pressure difference is negative but may be slightly positive on a positive pressure regulator. Once the valve has opened, gas flow should continue at the smallest stable pressure difference reasonably practicable while the diver inhales, several mechanisms have been devised to provide this function. Some of them simple and robust, and others somewhat more complex. The demand valve has a chamber, which in normal use contains breathing gas at ambient pressure, a valve which supplies medium pressure gas can vent into the chamber. Either a mouthpiece or a mask is connected to the chamber for the diver to breathe from. The mouthpiece can be coupled or connected by a flexible low-pressure hose. On one side of the chamber is a flexible diaphragm to control the operation of the valve, the diaphragm is protected by a cover with holes or slits through which outside water can enter freely. When the diver starts to inhale, the removal of gas from the casing lowers the pressure inside the chamber, and this lifts the valve off its seat, releasing gas into the chamber
24.
United States
–
Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
25.
United Kingdom
–
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain, is a sovereign country in western Europe. Lying off the north-western coast of the European mainland, the United Kingdom includes the island of Great Britain, Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. The Irish Sea lies between Great Britain and Ireland, with an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 65.1 million inhabitants, together, this makes it the fourth-most densely populated country in the European Union. The United Kingdom is a monarchy with a parliamentary system of governance. The monarch is Queen Elizabeth II, who has reigned since 6 February 1952, other major urban areas in the United Kingdom include the regions of Birmingham, Leeds, Glasgow, Liverpool and Manchester. The United Kingdom consists of four countries—England, Scotland, Wales, the last three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff and Belfast, respectively. The relationships among the countries of the UK have changed over time, Wales was annexed by the Kingdom of England under the Laws in Wales Acts 1535 and 1542. A treaty between England and Scotland resulted in 1707 in a unified Kingdom of Great Britain, which merged in 1801 with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland. Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain, there are fourteen British Overseas Territories. These are the remnants of the British Empire which, at its height in the 1920s, British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a country and has the worlds fifth-largest economy by nominal GDP. The UK is considered to have an economy and is categorised as very high in the Human Development Index. It was the worlds first industrialised country and the worlds foremost power during the 19th, the UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a nuclear weapons state and its military expenditure ranks fourth or fifth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946 and it has been a leading member state of the EU and its predecessor, the European Economic Community, since 1973. However, on 23 June 2016, a referendum on the UKs membership of the EU resulted in a decision to leave. The Acts of Union 1800 united the Kingdom of Great Britain, Scotland, Wales and Northern Ireland have devolved self-government
26.
Liquefied petroleum gas
–
It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer. When specifically used as a fuel it is often referred to as autogas. Varieties of LPG bought and sold include mixes that are mostly propane, mostly butane and, most commonly, in the northern hemisphere winter, the mixes contain more propane, while in summer, they contain more butane. In the United States, mainly two grades of LPG are sold, commercial propane and HD-5 and these specifications are published by the Gas Processors Association and the American Society of Testing and Materials. Propane/butane blends are also listed in these specifications, propylene, butylenes and various other hydrocarbons are usually also present in small concentrations. HD-5 limits the amount of propylene that can be placed in LPG to 5%, a powerful odorant, ethanethiol, is added so that leaks can be detected easily. The internationally recognized European Standard is EN589, in the United States, tetrahydrothiophene or amyl mercaptan are also approved odorants, although neither is currently being utilized. It was first produced in 1910 by Dr. Walter Snelling, and it currently provides about 3% of all energy consumed, and burns relatively cleanly with no soot and very few sulfur emissions. As it is a gas, it does not pose ground or water pollution hazards, LPG has a typical specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium grade petrol. However, its energy density per unit of 26 MJ/L is lower than either that of petrol or fuel oil. As its boiling point is below room temperature, LPG will evaporate quickly at temperatures and pressures and is usually supplied in pressurised steel vessels. They are typically filled to 80–85% of their capacity to allow for expansion of the contained liquid. The ratio between the volumes of the gas and the liquefied gas varies depending on composition, pressure, and temperature. LPG is heavier than air, unlike natural gas, and thus will flow along floors and tend to settle in low spots, there are two main dangers from this. The first is an explosion if the mixture of LPG and air is within the explosive limits. The second is due to LPG displacing air, causing a decrease in oxygen concentration. It can serve as fuel for cooking, central heating and to water heating and is a particularly cost-effective, LPG is used for cooking in many countries for economic reasons, for convenience or because it is the preferred fuel source. According to the 2011 census of India,33.6 million Indian households used LPG as cooking fuel in 2011, LPG is subsidised by the government in India
27.
Propane
–
Propane is a three-carbon alkane with the molecular formula C3H8, a gas, at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is used as a fuel for engines, oxy-gas torches, portable stoves. Propane is one of a group of liquefied petroleum gases, the others include butane, propylene, butadiene, butylene, isobutylene, and mixtures thereof. Propane was first identified as a component in gasoline by Walter O. Snelling of the U. S. Bureau of Mines in 1910. The volatility of these lighter hydrocarbons caused them to be known as wild because of the vapor pressures of unrefined gasoline. On March 31, the New York Times reported on Snellings work with liquefied gas and that a steel bottle will carry enough gas to light an ordinary home for three weeks. It was during this time that Snelling, in cooperation with Frank P. Peterson, Chester Kerr, together, they established American Gasol Co. the first commercial marketer of propane. Snelling had produced relatively pure propane by 1911, and on March 25,1913, a separate method of producing LP gas through compression was created by Frank Peterson and its patent granted on July 2,1912. The 1920s saw increased production of LP gas, with the first year of recorded production totaling 223,000 US gallons in 1922. In 1927, annual marketed LP gas production reached 1 million US gallons, and by 1935, major industry developments in the 1930s included the introduction of railroad tank car transport, gas odorization, and the construction of local bottle-filling plants. The year 1945 marked the first year that annual LP gas sales reached a billion gallons, by 1947, 62% of all U. S. homes had been equipped with either natural gas or propane for cooking. In 1950,1,000 propane-fueled buses were ordered by the Chicago Transit Authority, in 2004 it was reported to be a growing $8-billion to $10-billion industry with over 15 billion US gallons of propane being used annually in the U. S. The prop- root found in propane and names of compounds with three-carbon chains was derived from propionic acid. Propane is produced as a by-product of two processes, natural gas processing and petroleum refining. The processing of natural gas involves removal of butane, propane, additionally, oil refineries produce some propane as a by-product of cracking petroleum into gasoline or heating oil. The supply of propane cannot easily be adjusted to meet increased demand, about 90% of U. S. propane is domestically produced. The United States imports about 10% of the propane consumed each year, with about 70% of that coming from Canada via pipeline, the remaining 30% of imported propane comes to the United States from other sources via ocean transport. After it is produced, North American propane is stored in salt caverns
28.
Hose clamp
–
A hose clamp or hose clip is a device used to attach and seal a hose onto a fitting such as a barb or nipple. Many types are available, including, Screw clamps consist of a galvanized or stainless steel band into which a screw thread pattern has been cut or pressed, one end of the band contains a captive screw. The clamp is put around the hose or tube to be connected, when the screw is turned, it acts as a worm drive pulling the threads of the band, causing the band to tighten around the hose. Screw clamps are used for hoses 1/2 in diameter and up. Pairs of screw clamps on a rubber tube form a no-hub band, often used for attaching sections of domestic wastewater piping. They can also be used in a way, as a simple means for the transmission of small amounts of power. A short length of hose is clipped between two shafts where vibration or variations in alignment may be taken up by the flexibility of the hose and this technique is well adapted to use for mock-ups in a development laboratory. This type of clamp was invented in 1921 by ex Royal Navy Commander, Lumley Robinson, the company owns the trademark for Jubilee Clip. A similar type of clamp to the band, also with a solid screw, is the Marman clamp. Spring clamps are made from a strip of spring steel, cut so that one side has a narrow protrusion centered on the end. The ends of these protrusions are then bent outwards, and the strip rolled to form a ring, with the protruding tabs intermeshing. To use the clamp, the tabs are pressed towards each other, increasing the diameter of the ring. The hose is then fit onto the barb, the clamp expanded again, slid onto the portion of the hose over the barb, then released and they are commonly used on automotive cooling system hoses several inches in diameter, for example on most water-cooled Volkswagen automobiles. Spring clamps are particularly suited for confined or otherwise awkward places where other types would require tightening tools applied from narrow. This has made them popular for applications such as automotive engine bays. Another type of spring clamp, typically used on vacuum hoses, is just a piece of spring steel wire bent into a loop. These are used similar to spring clamps, but are just pinched by hand. Rather than attempting to seal a hose into a barb, they just place a slight pressure on the hose, helping to keep it from sliding off the barb
29.
Ferrule
–
A ferrule is any of a number of types of objects, generally used for fastening, joining, sealing or reinforcement. They are often narrow circular rings made from metal, or less commonly, ferrules are also often referred to as eyelets or grommets within the manufacturing industry. A metal or plastic ring used in plumbing as part of a compression fitting along with a nut for making a liquid-tight connection when joining pipe or tubing. Some of the people use ferrules include, To shield parts or cables from electromagnetic pulses, environmental damage, the elements, thermal factors. To cover parts, adding wear resistance, damage protection, or packaging, as a connector, to connect wires, structural devices, and systems To bind parts together, including bundles of wires, or cloth threads to the end of the mop, as an example. To act as conveyance for fluids like oil and water, or for gasses like air
30.
Jubilee Clip
–
A Jubilee Clip is a circular metal band or strip combined with a worm gear fixed to one end. It is designed to hold a soft, pliable hose onto a circular pipe, or sometimes a solid spigot. Jubilee Clips are generally made of steel or galvanised or electro-plated steel. Rotating the screw has the effect of changing the diameter of the circle formed by the band, Jubilee Clips are available in a range of sizes. Larger-diameter Jubilee Clips tend to have wider bands, in many countries, Jubilee Clips tend to be known almost exclusively by their brand name, but elsewhere, they are known by generic names such as worm drive hose clip or hose clamp or hose clip. It remains the term used in speech in the UK. It is now subject to a trademark in many countries around the world. The design has been copied with many variations, and there are many other hose clips of a similar design, Lumley Robinson was born in Leeds, Yorkshire in 1877 to a family of strict Methodists. In his first job he worked for John Fowlers, a highly respected engineering firm in Leeds before later joining the Royal Navy. During his time in the Navy, Lumley was on HMS Aboukir when it was sunk in the North Sea, during his time in the navy it had often seemed obvious to Lumley that a new way needed to be found to attach a hose to a pipe. On leaving the Navy he spent much time with a friend who had a lathe in his garage, making things, once he had the first clips made he went to London every day attempting to sell them. His wife Emily had such faith in her husband that she suggested re-mortgaging their house to pay for the first lot of steel, Commander Lumley Robinson died of a heart attack on holiday in Jersey on 20 August 1939 aged 62. The UK declared war on Germany on 3 September 1939, just 14 days after Commander Robinsons death, before the end of the month, the War Ministry had realised the importance of Jubilee clips for the war effort and men arrived from the Ministry to take over the company. His widow, Emily, wasnt having any of it however and she changed her name by deed poll to Lumley-Robinson and ran the business herself throughout the war. After the end of the war, she continued to run the business until her youngest son, during and after the war other hose clip manufacturers started to emerge all over Europe, but Jubilee continued to be successful. The business was incorporated on 1 April 1948 as L. Robinson & Co Ltd. This company continues to be a success selling Jubilee products in Germany, marman clamp Hose clamp Cable tie Jubilee Clips Vintage advertisements for Jubilee Clips
31.
Explosive material
–
An explosive charge is a measured quantity of explosive material, which may be composed of a single ingredient or a combination of two or more. Materials that detonate are said to be high explosives and materials that deflagrate are said to be low explosives, Explosives may also be categorized by their sensitivity. Sensitive materials that can be initiated by a small amount of heat or pressure are primary explosives. A wide variety of chemicals can explode, a number are manufactured specifically for the purpose of being used as explosives. The remainder are too dangerous, sensitive, toxic, expensive, unstable, in contrast, some materials are merely combustible or flammable if they burn without exploding. The distinction, however, is not razor-sharp, though early thermal weapons, such as Greek fire, have existed since ancient times, the first widely used explosive in warfare and mining was black powder, invented in 9th century China. This material was sensitive to water, and it produced copious amounts of dark smoke, the first useful explosive stronger than black powder was nitroglycerin, developed in 1847. Since nitroglycerin is a liquid and highly unstable, it was replaced by nitrocellulose, TNT in 1863, smokeless powder, dynamite in 1867, World War I saw the adoption of TNT trinitrotoluene in artillery shells. World War II saw a use of new explosives. In turn, these have largely replaced by more powerful explosives such as C-4. However, C-4 and PETN react with metal and catch fire easily, yet unlike TNT, C-4 and PETN are waterproof, the largest commercial application of explosives is mining. In Materials Science and Engineering, explosives are used in cladding, a thin plate of some material is placed atop a thick layer of a different material, both layers typically of metal. Atop the thin layer is placed an explosive, at one end of the layer of explosive, the explosion is initiated. The two metallic layers are forced together at high speed and with great force, the explosion spreads from the initiation site throughout the explosive. Ideally, this produces a metallurgical bond between the two layers and it is possible that some fraction of the surface material from either layer eventually gets ejected when the end of material is reached. Hence, the mass of the now welded bilayer, may be less than the sum of the masses of the two initial layers, there are applications where a shock wave, and electrostatics, can result in high velocity projectiles. Thus, explosives are substances that contain an amount of energy stored in chemical bonds. Consequently, most commercial explosives are compounds containing -NO2, -ONO2 and -NHNO2 groups that
32.
Flashback arrestor
–
These devices are mainly used in different industrial processes where oxy-fuel gas mixures are handled and used. Flashback arrestors as safety products are essential to secure the workplaces, in former times there were also wet flashback arrestors used. Today the industry standard is to use dry flashback arrestors with at least two safety elements, dry flashback arrestors typically use a combination of different safety elements to stop a flashback or reverse flow of gas. Depending on the application they are often used at the torch side as an additional safety device. Flashback arrestors help prevent, Further gas flow in the case of pressure shocks, the entry of air or oxygen into the distribution line or single cylinders. Flashbacks which are the propagation of a flame down the hose. Further gas flow in the event of a burnback, according to the norm EN 730-1 / ISO5175 they include a minimum of two safety elements, A gas non-return valve, which, prevents dangerous gas mixtures. Ensures the gas flows in the intended direction. And a flame arrestor, which, cools the flame to below the temperature of the gas or gas mixture. In addition to two basic safety functions a flashback arrestor can also have a, Thermal cut-off valve, which. Closes automatically at a temperature and cuts off the gas flow long before the ignition temperature of the gas mixture is reached. Flashback arrestors have to be tested for gas non-return, for tightness and they stop the flame by preventing it from reaching the submerged intake. These devices are very effective at stopping flashbacks from reaching the protected side of the system. They have the disadvantages of working in one orientation and tend to be much larger than dry type arrestors. This makes them mainly only suitable for large or fixed installations, video and explanation of flashback arrestor with four safety elements Flash Back And Flame Arrestor Saffire 36ec Flashback Arrestor internals. Archived from the original on 2010-10-09
33.
Shock wave
–
In physics, a shock wave, or shock, is a type of propagating disturbance. When a wave moves faster than the speed of sound in a fluid it is a shock wave. In supersonic flows, expansion is achieved through an expansion fan also known as a Prandtl-Meyer expansion fan, unlike solitons, the energy of a shock wave dissipates relatively quickly with distance. Also, the accompanying expansion wave approaches and eventually merges with the shock wave, when a shock wave passes through matter, energy is preserved but entropy increases. Shock waves can be, Normal, at 90° to the shock mediums flow direction, oblique, at an angle to the direction of flow. Bow, Occurs upstream of the front of a blunt object when the flow velocity exceeds Mach 1. Some other terms Shock Front, The boundary over which the physical conditions undergo a change because of a shock wave. Contact Front, in a wave caused by a driver gas. The Contact Front trails the Shock Front, when an object moves faster than the information about it can propagate into the surrounding fluid, fluid near the disturbance cannot react or get out of the way before the disturbance arrives. In a shock wave the properties of the fluid change almost instantaneously, measurements of the thickness of shock waves in air have resulted in values around 200 nm, which is on the same order of magnitude as the mean free gas molecule path. In reference to the continuum, this implies the shock wave can be treated as either a line or a plane if the field is two-dimensional or three-dimensional. Shock waves are formed when a pressure front moves at supersonic speeds, Shock waves are not conventional sound waves, a shock wave takes the form of a very sharp change in the gas properties. Shock waves in air are heard as a crack or snap noise. Over longer distances, a wave can change from a nonlinear wave into a linear wave, degenerating into a conventional sound wave as it heats the air. The sound wave is heard as the familiar thud or thump of a sonic boom, the shock wave is one of several different ways in which a gas in a supersonic flow can be compressed. Some other methods are isentropic compressions, including Prandtl-Meyer compressions, the method of compression of a gas results in different temperatures and densities for a given pressure ratio which can be analytically calculated for a non-reacting gas. A shock wave compression results in a loss of pressure, meaning that it is a less efficient method of compressing gases for some purposes. The appearance of pressure-drag on supersonic aircraft is due to the effect of shock compression on the flow
34.
Rose
–
A rose is a woody perennial flowering plant of the genus Rosa, in the family Rosaceae, or the flower it bears. There are over a species and thousands of cultivars. They form a group of plants that can be erect shrubs, flowers vary in size and shape and are usually large and showy, in colours ranging from white through yellows and reds. Most species are native to Asia, with smaller numbers native to Europe, North America, species, cultivars and hybrids are all widely grown for their beauty and often are fragrant. Roses have acquired cultural significance in many societies, Rose plants range in size from compact, miniature roses, to climbers that can reach seven meters in height. Different species hybridize easily, and this has used in the development of the wide range of garden roses. The leaves are borne alternately on the stem, most roses are deciduous but a few are evergreen or nearly so. The flowers of most species have five petals, with the exception of Rosa sericea, each petal is divided into two distinct lobes and is usually white or pink, though in a few species yellow or red. Beneath the petals are five sepals and these may be long enough to be visible when viewed from above and appear as green points alternating with the rounded petals. There are multiple superior ovaries that develop into achenes, the aggregate fruit of the rose is a berry-like structure called a rose hip. Many of the domestic cultivars do not produce hips, as the flowers are so tightly petalled that they do not provide access for pollination, the hips of most species are red, but a few have dark purple to black hips. Each hip comprises an outer layer, the hypanthium, which contains 5–160 seeds embedded in a matrix of fine. Rose hips of some species, especially the dog rose and rugosa rose, are rich in vitamin C. The hips are eaten by fruit-eating birds such as thrushes and waxwings, some birds, particularly finches, also eat the seeds. While the sharp objects along a stem are commonly called thorns. Rose prickles are typically sickle-shaped hooks, which aid the rose in hanging onto other vegetation growing over it. Despite the presence of prickles, roses are frequently browsed by deer, a few species of roses have only vestigial prickles that have no points. Hesperrhodos contains Rosa minutifolia and Rosa stellata, from North America, platyrhodon with one species from east Asia, Rosa roxburghii
35.
Venturi effect
–
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of a pipe. The Venturi effect is named after Giovanni Battista Venturi, an Italian physicist, thus any gain in kinetic energy a fluid may accrue due to its increased velocity through a constriction is balanced by a drop in pressure. By measuring the change in pressure, the rate can be determined, as in various flow measurement devices such as venturi meters, venturi nozzles. The limiting case of the Venturi effect is when a fluid reaches the state of choked flow, when a fluid system is in a state of choked flow, a further decrease in the downstream pressure environment will not lead to an increase in the mass flow rate. However, mass flow rate for a fluid can increase with increased upstream pressure. This is the principle of operation of a de Laval nozzle, the simplest apparatus, as shown in the photograph and diagram, is a tubular setup known as a Venturi tube or simply a venturi. Fluid flows through a length of pipe of varying diameter, to avoid undue aerodynamic drag, a Venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees. Venturi tubes are used in processes where permanent pressure loss is not tolerable, Venturi tubes are more expensive to construct than a simple orifice plate which uses the same principle as a tubular scheme, but the orifice plate causes significantly more permanent energy loss. Venturis are used in applications and in scientific laboratories for measuring the flow rate of liquids. A venturi can be used to measure the flow rate. At the end of the system, a mixture of liquid, see aspirator and pressure head for discussion of this type of siphon. As fluid flows through a venturi, the expansion and compression of the cause the pressure inside the venturi to change. This principle can be used in metrology for gauges calibrated for differential pressures and this type of pressure measurement may be more convenient, for example, to measure fuel or combustion pressures in jet or rocket engines. In fact, some gusts were so high that travel had to be aided by ropes. Venturi tubes are used to measure the speed of a fluid. Placing a liquid in a U-shaped tube and connecting the ends of the tubes to both ends of a Venturi is all that is needed. When the fluid flows though the Venturi the pressure in the two ends of the tube will differ, forcing the liquid to the low pressure side, the amount of that move can be calibrated to the speed of the fluid flow
36.
Propene
–
Propene, also known as propylene or methyl ethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the class of hydrocarbons. At room temperature and atmospheric pressure, propene is a gas, propene has a higher density and boiling point than ethylene due to its greater mass. It has a lower boiling point than propane and is thus more volatile. It lacks strongly polar bonds, yet the molecule has a dipole moment due to its reduced symmetry. Propene has the empirical formula as cyclopropane but their atoms are connected in different ways. Propene is found in nature as a byproduct of vegetation and fermentation processes, propene is produced from fossil fuels—petroleum, natural gas, and, to a much lesser extent, coal. Propene is a byproduct of oil refining and natural gas processing, during oil refining, ethylene, propene, and other compounds are produced as a result of cracking larger hydrocarbon molecules to produce hydrocarbons more in demand. A major source of propene is naphtha cracking intended to produce ethylene, propene can be separated by fractional distillation from hydrocarbon mixtures obtained from cracking and other refining processes, refinery-grade propene is about 50 to 70%. A shift to lighter steam cracker feedstocks with relatively lower propene yields, on-purpose production methods are becoming increasingly significant. Propene yields of about 90 wt% are achieved and this option may also be used when there is no butene feedstock. In this case, part of the ethylene feeds an ethylene-dimerization unit that converts ethylene into butene, propane dehydrogenation converts propane into propene and by-product hydrogen. The propene from propane yield is about 85 m%, reaction by-products are usually used as fuel for the propane dehydrogenation reaction. As a result, propene tends to be the only product and this route is popular in regions, such as the Middle East, where there is an abundance of propane from oil/gas operations. In this region, the output is expected to be capable of supplying not only domestic needs, but also the demand from China. However, as natural gas offerings in the United States are significantly increasing due to the exploitation of shale gas. Chemical companies are planning to establish PDH plants in the USA to take advantage of the low price raw material. Numerous plants dedicated to propane dehydrogenation are currently under construction around the world, there are already five licensed technologies
37.
Natural gas
–
It is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure under the surface of the Earth over millions of years. The energy that the plants originally obtained from the sun is stored in the form of bonds in the gas. Natural gas is a fuel used as a source of energy for heating, cooking. It is also used as fuel for vehicles and as a feedstock in the manufacture of plastics. Natural gas is found in underground rock formations or associated with other hydrocarbon reservoirs in coal beds. Petroleum is another resource and fossil fuel found in proximity to. Most natural gas was created over time by two mechanisms, biogenic and thermogenic, biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at temperature and pressure, thermogenic gas is created from buried organic material. In petroleum production gas is burnt as flare gas. The World Bank estimates that over 150 cubic kilometers of gas are flared or vented annually. Before natural gas can be used as a fuel, most, Natural gas is often informally referred to simply as gas, especially when compared to other energy sources such as oil or coal. However, it is not to be confused with gasoline, especially in North America, Natural gas was used by the Chinese in about 500 BCE. They discovered a way to transport gas seeping from the ground in crude pipelines of bamboo to where it was used to salt water to extract the salt. The worlds first industrial extraction of gas started at Fredonia, New York. By 2009,66000 km³ had been used out of the total 850000 km³ of estimated remaining reserves of natural gas. An annual increase in usage of 2–3% could result in currently recoverable reserves lasting significantly less, unwanted natural gas was a disposal problem in the active oil fields. If there was not a market for natural gas near the wellhead it was expensive to pipe to the end user. In the 19th century and early 20th century, unwanted gas was burned off at oil fields
38.
Hydrogen
–
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity
39.
MAPP gas
–
MAPP gas is a trademarked name, belonging to The Linde Group, and previously belonging to the Dow Chemical Company, for a fuel gas based on a stabilized mixture of methylacetylene and propadiene. The name comes from the chemical composition, methylacetylene-propadiene propane. MAPP gas is widely used as a generic name for UN1060 stabilised methylacetylene-propadiene. MAPP gas is regarded as a safer and easier-to-use substitute for acetylene. In the spring of 2008, true MAPP gas production ended in North America when production was discontinued at the remaining plant in North America that still manufactured it. Current products labeled MAPP are, in fact, MAPP substitutes and these versions are stabilized liquefied petroleum gas with high levels of propylene. MAPP gas can be used in combination with oxygen for heating, soldering, brazing, the hydrogen infuses into the molten steel and renders the welds brittle. For small-scale welding with MAPP this is not a problem, as the hydrogen escapes readily. MAPP/oxygen was advantageously used in cutting, which requires high gas pressures. However, underwater oxy/fuel gas cutting of any kind has been replaced by exothermic cutting due to the much faster cut rate and greater safety. MAPP gas is used in combustion with air for brazing and soldering. The biggest disadvantage of MAPP gas is cost, it is typically one-and-a-half times as expensive as propane at the refinery, jewellers, glassbead makers, and many others find it very useful. MAPP is colorless in both liquid and gas form, the gas has a pronounced acetylene-like or fishy odor at concentrations above 100 ppm, due to the addition of substituted amines as a polymerization inhibitor. Low molecular weight alkynes have strong odors, MAPP gas is toxic if inhaled at high concentrations. For a later Dow/Petromont gas propyne 30%, propadiene 14%, propylene 43%, propane 7%, MAPP has an energy content of 2100 BTU/lb while acetylenes energy content is 2500 BTU/lb. People can be exposed to MAPP gas or its substitutes in the workplace by inhaling the gas or skin/eye contact with the liquid, the Occupational Safety and Health Administration has set the legal limit for MAPP gas exposure in the workplace as 1000 ppm over an 8-hour workday. The National Institute for Occupational Safety and Health has set a recommended limit of 1000 ppm over an 8-hour workday and 1250 ppm for short-term exposure. At levels of 3400 ppm, 10% of the explosive limit, MAPP gas is immediately dangerous to life
40.
Calcium carbide
–
Calcium carbide is a chemical compound with the chemical formula of CaC2. Its main use industrially is in the production of acetylene and calcium cyanamide, the pure material is colorless, however pieces of technical-grade calcium carbide are grey or brown and consist of about 80–85% of CaC2. In the presence of moisture, technical-grade calcium carbide emits an unpleasant odor reminiscent of garlic. Applications of calcium carbide include manufacture of gas, and for generation of acetylene in carbide lamps, manufacture of chemicals for fertilizer. Calcium carbide is produced industrially in an arc furnace from a mixture of lime. The carbide product produced generally contains around 80% calcium carbide by weight, the carbide is crushed to produce small lumps that can range from a few mm up to 50 mm. The impurities are concentrated in the finer fractions, the CaC2 content of the product is assayed by measuring the amount of acetylene produced on hydrolysis. As an example, the British and German standards for the content of the fractions are 295 L/kg and 300 L/kg respectively. Impurities present in the carbide include phosphide, which produces phosphine when hydrolysed, the method for the production in an electric arc furnace was discovered in 1892 by T. L Willson and independently by H. Moissan in the same year. Pure calcium carbide is a colourless solid, the common crystalline form at room temperature is a distorted rock-salt structure with the C22− units lying parallel. The reaction of carbide with water, producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862. CaC2 +2 H2O → C2H2 + Ca2 This reaction was the basis of the manufacture of acetylene. At high temperatures, CaC2 reacts with water vapor to give calcium carbonate, carbon dioxide, today acetylene is mainly manufactured by the partial combustion of methane or appears as a side product in the ethylene stream from cracking of hydrocarbons. Approximately 400,000 tonnes are produced this way annually, in China, acetylene derived from calcium carbide remains a raw material for the chemical industry, in particular for the production of polyvinyl chloride. Locally produced acetylene is more economical than using imported oil, production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons, with the capacity to produce 17 million tons, in the USA, Europe, and Japan, consumption of calcium carbide is generally declining. Production levels in the USA in 1990s were 236,000 tons per year, Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide, CaC2 + N2 → CaCN2 + C Commonly known as nitrolim, calcium cyanamide is used as fertilizer. It is hydrolysed to cyanamide, H2NCN, Calcium carbide is used, in the desulfurisation of iron as a fuel in steelmaking to extend the scrap ratio to liquid iron, depending on economics
41.
Ceiba pentandra
–
Ceiba pentandra is a tropical tree of the order Malvales and the family Malvaceae, native to Mexico, Central America and the Caribbean, northern South America, and to tropical west Africa. A somewhat smaller variety is found throughout southern Asia and the East Indies, Kapok is the most used common name for the tree and may also refer to the cotton-like fluff obtained from its seed pods. The tree is cultivated for the fibre, particularly in south-east Asia. The very largest individuals however can be 19 feet thick or more above the buttresses, the trunk and many of the larger branches are often crowded with large simple thorns. These major branches, usually 4 to 6 in number and up to six feet thick form a crown of foliage as much as 201 feet in width, the palmate leaves are composed of 5 to 9 leaflets, each up to 20 cm long. The trees produce several hundred 15 cm pods containing seeds surrounded by a fluffy, yellowish fibre that is a mix of lignin, pentandra is among the largest trees in the world. One of the oldest known Kapok trees, at 200 years, lives in Miami, Kapok fibre is light, very buoyant, resilient, resistant to water, but it is very flammable. The process of harvesting and separating the fibre is labour-intensive and manual and it is difficult to spin, but is used as an alternative to down as filling in mattresses, pillows, upholstery, zafus, and stuffed toys such as teddy bears, and for insulation. It was previously used in life jackets and similar devices until synthetic materials largely replaced the fibre. The seeds produce an oil that is used locally in soap, native tribes along the Amazon River harvest kapok fibre to wrap around their blowgun darts. The fibres create a seal that allows the pressure to force the dart through the tube, when Pearl Harbor was bombed by the Japanese, a council was summoned that night in Washington, to consider what strategic commodities were threatened. The commercial tree is most heavily cultivated in the rainforests of Asia, notably in Java, Philippines, Malaysia, the flowers are an important source of nectar and pollen for honey bees. Ceiba pentandra bark decoction has been used as a diuretic, aphrodisiac and it is used as an additive in some versions of the hallucinogenic drink Ayahuasca. A vegetable oil can be pressed from kapok seeds, the oil has a yellow colour and a pleasant, mild odour and taste, resembling cottonseed oil. It becomes rancid quickly when exposed to air, Kapok oil is produced in India, Indonesia and Malaysia. It has a value of 85–100, this makes it a nondrying oil. Kapok oil has potential as a biofuel and in paint preparation. The kapok is a symbol in Maya mythology
42.
Diatomaceous earth
–
Diatomaceous earth, also known as D. E. diatomite, or kieselgur/kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It has a size ranging from less than 3 micrometres to more than 1 millimetre. Depending on the granularity, this powder can have a feel, similar to pumice powder. The typical chemical composition of oven-dried diatomaceous earth is 80 to 90% silica, Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. Each deposit of diatomaceous earth is different, with varying blends of pure diatomaceous earth combined with other natural clays, the diatoms in each deposit contain different amounts of silica, depending on the age of the deposit. The species of diatom may also differ among deposits, the species of diatom is dependent upon the age and paleo-environment of the deposit. In turn, the shape of a diatom is determined by its species, many deposits throughout British Columbia, Canada, such as Red Lake Earth, are from the Miocene age and contain a species of diatom known as Melosira granulata. These diatoms are approximately 12 to 13 million years old and have a globular shape. A deposit containing diatoms from this age can provide more benefits than that of an older deposit. For example, diatoms from the Eocene age are not as effective in their ability to absorb fluids because older diatoms recrystallize, Diatomite forms by the accumulation of the amorphous silica remains of dead diatoms in lacustrine or marine sediments. The fossil remains consist of a pair of shells or frustules. In 1836 or 1837, the peasant and goods waggoner Peter Kasten discovered diatomaceous earth when sinking a well on the slopes of the Haußelberg hill. Initially, it was thought that limestone had been found, which could be used as fertilizer, until the First World War almost the entire worldwide production of diatomaceous earth was from this region. In Germany, diatomaceous earth was also extracted at Altenschlirf on the Vogelsberg, there is a layer of diatomaceous earth up to 4 metres thick in the nature reserve of Soos in the Czech Republic. Deposits on the isle of Skye, off the west coast of Scotland, were mined until 1960, in Colorado and in Clark County, Nevada, United States, there are deposits that are up to several hundred metres thick in places. Marine deposits have been worked in the Sisquoc Formation in Santa Barbara County, California near Lompoc, additional marine deposits have been worked in Maryland, Virginia, Algeria and the MoClay of Denmark. Freshwater lake deposits occur in Nevada, Oregon, Washington and California, Lake deposits also occur in interglacial lakes in the eastern United States, in Canada and in Europe in Germany, France, Denmark and the Czech Republic. The worldwide association of diatomite deposits and volcanic deposits suggests that the availability of silica from volcanic ash may be necessary for thick diatomite deposits, sometimes diatomaceous earth is found on the surfaces of deserts
43.
Asbestos
–
They are commonly known by their colors, as blue asbestos, brown asbestos, white asbestos, and green asbestos. It was used in applications as electrical insulation for hotplate wiring. When asbestos is used for its resistance to fire or heat and these desirable properties made asbestos very widely used. Prolonged inhalation of asbestos fibers can cause serious and fatal illnesses including cancer, mesothelioma. Concern of asbestos-related illness in modern times began in the 20th century, by the 1980s and 1990s, asbestos trade and use were heavily restricted, phased out, or banned outright in an increasing number of countries. S. History and a much lesser legal issue in most other countries involved, asbestos-related liability also remains an ongoing concern for many manufacturers, insurers and reinsurers. Asbestos derives from the ancient Greek ἄσβεστος, meaning unquenchable or inextinguishable, the word is pronounced /æsˈbɛstəs/, /æzˈbɛstəs/ or /æzˈbɛstɒs/. Six mineral types are defined by the United States Environmental Protection Agency as asbestos including those belonging to the serpentine class, all six asbestos mineral types are known to be human carcinogens. The visible fibers are themselves composed of millions of microscopic fibrils that can be released by abrasion. Chrysotile is the member of the serpentine class. 12001-29-5, is obtained from rocks which are common throughout the world. Its idealized chemical formula is Mg34, chrysotile appears under the microscope as a white fiber. Chrysotile has been used more than any type and accounts for about 95% of the asbestos found in buildings in America. Chrysotile is more flexible than amphibole types of asbestos, and can be spun, the most common use was corrugated asbestos cement roofing primarily for outbuildings, warehouses and garages. It may also be found in sheets or panels used for ceilings and sometimes for walls, chrysotile has been a component in joint compound and some plasters. Amosite, crocidolite, tremolite, anthophyllite and actinolite are members of the amphibole class, one formula given for amosite is Fe7Si8O222. Amosite is seen under a microscope as a grey-white vitreous fiber and it is found most frequently as a fire retardant in thermal insulation products, asbestos insulating board and ceiling tiles. 12001-28-4, is the form of the amphibole riebeckite, found primarily in southern Africa
44.
Pascal (unit)
–
The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
