1.
Valve
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A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure, the word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll. The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct fluid flow in one direction and this is called a check valve, as it prevents or checks the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems, even aerosols have a tiny valve built in. Valves are also used in the military and transport sectors, valves may be operated manually, either by a handle, lever, pedal or wheel. Valves may also be automatic, driven by changes in pressure, temperature and these changes may act upon a diaphragm or a piston which in turn activates the valve, examples of this type of valve found commonly are safety valves fitted to hot water systems or boilers. More complex control systems using valves requiring automatic control based on an external input require an actuator, an actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned accurately, and allowing control over a variety of requirements. Valves vary widely in form and application, sizes typically range from 0.1 mm to 60 cm. Special valves can have a diameter exceeding 5 meters, valve costs range from simple inexpensive disposable valves to specialized valves which cost thousands of US dollars per inch of the diameter of the valve. Disposable valves may be found in household items including mini-pump dispensers. Valves are quite diverse and may be classified into a number of basic types, valves may also be classified by how they are actuated, Hydraulic Pneumatic Manual Solenoid valve Motor The main parts of the most usual type of valve are the body and the bonnet. These two parts form the casing that holds the fluid going through the valve, the valves body is the outer casing of most or all of the valve that contains the internal parts or trim. The bonnet is the part of the encasing through which the stem passes, the bonnet typically screws into or is bolted to the valve body. Valve bodies are usually metallic or plastic, brass, bronze, gunmetal, cast iron, steel, alloy steels and stainless steels are very common. Seawater applications, like plants, often use duplex valves, as well as super duplex valves, due to their corrosion resistant properties. Alloy 20 valves are used in sulphuric acid plants, whilst monel valves are used in hydrofluoric acid plants. Hastelloy valves are used in high temperature applications, such as nuclear plants
2.
Gate valve
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A gate valve, also known as a sluice valve, is a valve which opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The gate faces can be parallel, but are most commonly wedge-shaped, gate valves are primarily used to permit or prevent the flow of liquids, but typical gate valves shouldnt be used for regulating flow, unless they are specifically designed for that purpose. Because of their ability to cut through liquids, gate valves are used in the petroleum industry. For extremely thick fluids, a specialty valve often known as a gate valve is used to cut through the liquid. On opening the valve, the flow path is enlarged in a highly nonlinear manner with respect to percent of opening. This means that flow rate does not change evenly with stem travel, also, a partially open gate tends to vibrate from the fluid flow. Most of the change occurs near shutoff with a relatively high fluid velocity causing gate and seat wear. Typical gate valves are designed to be opened or closed. When fully open, the gate valve has no obstruction in the flow path. Gate valves are actuated by a stem which connects the actuator to the gate. They are characterised as having either a rising or a nonrising stem, rising stems are fixed to the gate and rise and lower together as the valve is operated, providing a visual indication of valve position. The actuator takes the form of a nut which is rotated around the stem to move it. Nonrising stem valves are fixed to, and rotate with, the actuator and they may have a pointer threaded onto the upper end of the stem to indicate valve position, since the gates motion is concealed inside the valve. Nonrising stems are used underground or where space is limited. Bonnets provide leakproof closure for the valve body, gate valves may have a screw-in, union, or bolted bonnet. Screw-in bonnet is the simplest, offering a durable, pressure-tight seal, union bonnet is suitable for applications requiring frequent inspection and cleaning. It also gives the added strength. Bolted bonnet is used for larger valves and higher pressure applications, another type of bonnet construction in a gate valve is pressure seal bonnet
3.
Metal
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A metal is a material that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed. In bcc, each atom is positioned at the center of a cube of eight others, in fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium, platinum and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades. The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
4.
Plastic
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Plastic is a material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and can be molded into solid objects. Plastics are typically organic polymers of high mass, but they often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, due to their relatively low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such as wood, stone, horn and bone, leather, paper, metal, glass, and ceramic, in most of their former uses. In developed countries, about a third of plastic is used in packaging, other uses include automobiles, furniture, and toys. In the developing world, the ratios may be different - for example, the worlds first fully synthetic plastic was bakelite, invented in New York in 1907 by Leo Baekeland who coined the term plastics. Toward the end of the century, one approach to this problem was met with wide efforts toward recycling, the word plastic is derived from the Greek πλαστικός meaning capable of being shaped or molded, from πλαστός meaning molded. The common word plastic should not be confused with the technical adjective plastic, used for insulating parts in electrical fixtures, paper laminated products, thermally insulation foams. Problems include the probability of moldings naturally being dark colors, One of the most expensive commercial polymers. It forms the basis of artistic and commercial acrylic paints when suspended in water with the use of other agents, polytetrafluoroethylene – Heat-resistant, low-friction coatings, used in things like non-stick surfaces for frying pans, plumbers tape and water slides. It is more known as Teflon. Urea-formaldehyde – One of the aminoplasts and used as an alternative to phenolics. Used as an adhesive and electrical switch housings. Early plastics were bio-derived materials such as egg and blood proteins, in 1600 BC, Mesoamericans used natural rubber for balls, bands, and figurines. Treated cattle horns were used as windows for lanterns in the Middle Ages, materials that mimicked the properties of horns were developed by treating milk-proteins with lye. In the 1800s, as industrial chemistry developed during the Industrial Revolution, the development of plastics also accelerated with Charles Goodyears discovery of vulcanization to thermoset materials derived from natural rubber. Parkesine is considered the first man-made plastic, the plastic material was patented by Alexander Parkes, In Birmingham, UK in 1856. It was unveiled at the 1862 Great International Exhibition in London, parkesine won a bronze medal at the 1862 Worlds fair in London
5.
Ceramic
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A ceramic is an inorganic, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. This article gives an overview of ceramic materials from the point of view of materials science, the crystallinity of ceramic materials ranges from highly oriented to semi-crystalline, vitrified, and often completely amorphous. Most often, fired ceramics are either vitrified or semi-vitrified as is the case with earthenware, stoneware, varying crystallinity and electron consumption in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators. With such a range of possible options for the composition/structure of a ceramic, the breadth of the subject is vast. Many composites, such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family. The earliest ceramics made by humans were pottery objects or figurines made from clay, either by itself or mixed with materials like silica, hardened, sintered. Later ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, ceramics now include domestic, industrial and building products, as well as a wide range of ceramic art. In the 20th century, new materials were developed for use in advanced ceramic engineering. The word ceramic comes from the Greek word κεραμικός, of pottery or for pottery, from κέραμος, potters clay, tile, the earliest known mention of the root ceram- is the Mycenaean Greek ke-ra-me-we, workers of ceramics, written in Linear B syllabic script. The word ceramic may be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or, more commonly, as the plural noun ceramics. A ceramic material is an inorganic, non-metallic, often crystalline oxide, nitride or carbide material, some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, weak in shearing and they withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand high temperatures, such as temperatures that range from 1,000 °C to 1,600 °C. Glass is often not considered a ceramic because of its amorphous character. However, glassmaking involves several steps of the process and its mechanical properties are similar to ceramic materials. Traditional ceramic raw materials include minerals such as kaolinite, whereas more recent materials include aluminium oxide. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide, both are valued for their abrasion resistance, and hence find use in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are used in the medicine, electrical, electronics industries. Crystalline ceramic materials are not amenable to a range of processing
6.
Check valve
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A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave, there are various types of check valves used in a wide variety of applications. Check valves are often part of household items. Although they are available in a range of sizes and costs, check valves generally are very small, simple. Check valves work automatically and most are not controlled by a person or any control, accordingly. The bodies of most check valves are made of plastic or metal, an important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically the check valve is designed for and can therefore be specified for a specific cracking pressure, heart valves are essentially inlet and outlet check valves for the heart ventricles, since the ventricles act as pumps. Cracking pressure — the inlet pressure at which the first indication of flow occurs, reseal pressure — the pressure at which there is no indication of flow. In some ball check valves, the ball is spring-loaded to help keep it shut, for those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the seats of ball check valves are more or less conically-tapered to guide the ball into the seat. Ball check valves are often small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc. manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, high pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, there are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with ball valves, which is a different type of valve in which a ball acts as a rotor to stop or direct flow. A diaphragm check valve uses a rubber diaphragm positioned to create a normally-closed valve. Pressure on the side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential. Once positive pressure stops, the diaphragm automatically flexes back to its closed position
7.
Butterfly valve
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A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk, operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other designs as well as being lighter in weight. The disc is positioned in the center of the pipe, passing through the disc is a rod connected to an actuator on the outside of the valve, rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is present within the flow, so a pressure drop is always induced in the flow. A butterfly valve is from a family of valves called quarter-turn valves, in operation, the valve is fully open or closed when the disc is rotated a quarter turn. The butterfly is a disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway, when the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid. The valve may also be opened incrementally to throttle flow, there are different kinds of butterfly valves, each adapted for different pressures and different usage. The zero-offset butterfly valve, which uses the flexibility of rubber, has the lowest pressure rating. The high-performance double offset butterfly valve, used in slightly higher-pressure systems, is offset from the line of the disc seat and body seal. This creates a cam action during operation to lift the seat out of the resulting in less friction than is created in the zero offset design. The valve best suited for high-pressure systems is the triple offset butterfly valve, in this valve the disc seat contact axis is offset, which acts to virtually eliminate sliding contact between disc and seat. In the case of triple offset valves the seat is made of metal so that it can be machined such as to achieve a bubble tight shut-off when in contact with the disc, concentric butterfly valves – this type of valve has a resilient rubber seat with a metal disc. Doubly-eccentric butterfly valves – different type of materials is used for seat, triply-eccentric butterfly valves – the seats are either laminated or solid metal seat design. The wafer style butterfly valve is designed to maintain a seal against bi-directional pressure differential to prevent any backflow in systems designed for unidirectional flow. It accomplishes this with a tightly fitting seal, i. e. gasket, o-ring, precision machined, lug-style valves have threaded inserts at both sides of the valve body. This allows them to be installed into a system using two sets of bolts and no nuts, the valve is installed between two flanges using a separate set of bolts for each flange
8.
Pipeline transport
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Pipeline transport is the transportation of goods or material through a pipe. The latest data, in 2014, gives a total of less than 2,175,000 miles of pipeline in 120 countries of the world. The United States had 65%, Russia had 8%, and Canada had 3%, Pipeline and Gas Journal’s worldwide survey figures indicate that 118,623 miles of pipelines are planned and under construction. Of these,88,976 miles represent projects in the planning, Liquids and gases are transported in pipelines and any chemically stable substance can be sent through a pipeline. Pipelines exist for the transport of crude and refined petroleum, fuels - such as oil, natural gas and biofuels - and other fluids including sewage, slurry, water, pneumatic tubes using compressed air can be used to transport solid capsules. Oil pipelines are made from steel or plastic tubes which are usually buried, the oil is moved through the pipelines by pump stations along the pipeline. Natural gas are lightly pressurised into liquids known as Natural Gas Liquids, Natural gas pipelines are constructed of carbon steel. Highly toxic ammonia is theoretically the most dangerous substance to be transported through long-distance pipelines, hydrogen pipeline transport is the transportation of hydrogen through a pipe. District heating or teleheating systems use a network of insulated pipes which transport heated water, pipelines conveying flammable or explosive material, such as natural gas or oil, pose special safety concerns and there have been various accidents. Pipelines can be the target of vandalism, sabotage, or even terrorist attacks, in war, pipelines are often the target of military attacks. It is uncertain when the first crude oil pipeline was built, pipelines are generally the most economical way to transport large quantities of oil, refined oil products or natural gas over land. Natural gas are lightly pressurized into liquids knows as Natural Gas Liquids, small NGL processing facilities can be located in oil fields so the butane and propane liquid under light pressure of 125 pounds per square inch, can be shipped by rail, truck or pipeline. Propane can be used as a fuel in oil fields to heat various facilities used by the oil drillers or equipment and trucks used in the oil patch. EG, Propane will convert from a gas to a liquid under pressure,100 psi, give or take depending on temperature. Pipelines and rail cars use about double that pressure to pump at 250 psi, the distance to ship propane to markets is much shorter, as thousands of natural-gas processing plants are located in or near oil fields. Compared to shipping by railroad, pipelines have lower cost per unit, pipelines are preferable to transportation by truck for a number of reasons. Employment on completed pipelines represents only 1% of that of the trucking industry and this allows the Bakken Basin and Three Forks oil producers to get higher negotiated prices for their oil because they will not be restricted to just one wholesale market in the US. The distance from the biggest oil patch in North Dakota, is Williston, North Dakota, only about 85 miles or 137 kilometers to the Canada–US border, mutual funds and joint ventures are big investors in new oil and gas pipelines
9.
Pigging
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Pigging in the context of pipelines refers to the practice of using devices known as pigs to perform various maintenance operations. This is done without stopping the flow of the product in the pipeline and these operations include but are not limited to cleaning and inspecting the pipeline. This is accomplished by inserting the pig into a pig launcher — an oversized section in the pipeline, reducing to the normal diameter. The launching station is closed and the pressure-driven flow of the product in the pipeline is used to push the pig along down the pipe until it reaches the receiving trap — the pig catcher. Pigging has been used for years to clean large diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging systems is now increasing in many continuous and batch process plants as plant operators search for increased efficiencies and reduced costs. Pigging can be used for almost any section of the process between, for example, blending, storage or filling systems. Pigging systems are installed in industries handling products as diverse as lubricating oils, paints, chemicals, toiletries, cosmetics. Pigs are used in oil or paint blending to clean the pipes to avoid cross-contamination. Pigs are also used in oil and gas pipelines to clean the pipes, there are also smart pigs used to inspect pipelines for the purpose of preventing leaks, which can be explosive and dangerous to the environment. They usually do not interrupt production, though some product can be lost when the pig is extracted and they can also be used to separate different products in a multiproduct pipeline. If the pipeline contains butterfly valves, or reduced port ball valves, full port ball valves cause no problems because the inside diameter of the ball opening is the same as that of the pipe. The original pigs were made from straw wrapped in wire and used for cleaning and they made a squealing noise while traveling through the pipe, sounding to some like a pig squealing, which gave pigs their name. PIG is sometimes claimed as an acronym or backronym derived from the letters of the term Pipeline Inspection Gauge or Pipeline Intervention Gadget. A major advantage for multi-product pipelines of piggable systems is the potential of product savings, at the end of each product transfer, it is possible to clear out the entire line contents with the pig, either forwards to the receipt point, or backwards to the source tank. There is no requirement for extensive line flushing, without the need for line flushing, pigging offers the additional advantage of much more rapid and reliable product changeover. Pigging can also be operated totally by a programmable logic controller, pigging has a significant role to play in reducing the environmental impact of batch operations. The cleaning agent then had to be subjected to effluent treatment or solvent recovery, if a product was used to clear the line, it was necessary to downgrade or dump the contaminated portion of the product
10.
Trunnion
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A trunnion is a cylindrical protrusion used as a mounting or pivoting point. First associated with cannon, they are an important military development, alternatively, a trunnion is a shaft that positions and supports a tilting plate. This is a misnomer, as in reality it is a cradle for the true trunnion, in mechanical engineering, it is one part of a rotating joint where a shaft is inserted into a full or partial cylinder. In a cannon, the trunnions are two projections cast just forward of the center of mass of the cannon and fixed to a two-wheeled movable gun carriage. As they allowed the muzzle to be raised and lowered easily, with the creation of larger and more powerful siege guns in the early 15th century, a new way of mounting them had to be specially designed. Stouter gun carriages were created with reinforced wheels, axles, guns would be up to eight feet in length and shoot iron projectiles weighing from twenty-five to fifty pounds. These wrought iron balls when discharged were comparable in range and accuracy with stone-firing bombards, trunnions were mounted near the center of mass to allow the barrel to be elevated to any desired angle, without having to dismount it from the carriage upon which it rested. Some guns had a set of trunnions placed several feet back from the first pair. The gun would recoil causing the carriage to move backwards several feet and it became easier to rapidly transport these large siege guns, maneuver them from transportation mode to firing position, and they could go wherever a team of men or horses could pull them. Due to its capabilities, the French- and Burgundy-designed siege gun, equipped with its trunnions, king Charles VIII and the French army used this new gun in the 1494 invasion of Italy. Although deemed masters of war and artillery at that time, Italians had not anticipated the innovations in French siege weaponry. Prior to this, field guns were huge, large-caliber bombards, superguns that. Cities that had proudly withstood sieges for up to seven years fell swiftly with the advent of new weapons. Defensive tactics and fortifications had to be altered since these new weapons could be transported so speedily and these towers would be deemed trace Italienne. Whoever could afford these new weapons had the advantage over their neighbors and smaller sovereignties. Smaller states, such as the principalities of Italy, began to conglomerate, preexisting stronger entities, such as France or the Habsburg emperors, were able to expand their territories and maintain tighter control. With the threat of their land and castles being seized, the nobility began to pay their taxes, on firearms, the barrel is sometimes mounted in a trunnion, which in turn is mounted to the receiver. This usage is common for tubular or pressed metal frame guns, such as the AK-47, PPSh-41, Uzi, Sten, and others
11.
Electric motor
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An electric motor is an electrical machine that converts electrical energy into mechanical energy. The reverse of this is the conversion of energy into electrical energy and is done by an electric generator. In normal motoring mode, most electric motors operate through the interaction between an electric motors magnetic field and winding currents to generate force within the motor, small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use, the largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, perhaps the first electric motors were simple electrostatic devices created by the Scottish monk Andrew Gordon in the 1740s. The theoretical principle behind production of force by the interactions of an electric current. The conversion of energy into mechanical energy by electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821. A free-hanging wire was dipped into a pool of mercury, on which a permanent magnet was placed, when a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a close circular magnetic field around the wire. This motor is often demonstrated in experiments, brine substituting for toxic mercury. Though Barlows wheel was a refinement to this Faraday demonstration. In 1827, Hungarian physicist Ányos Jedlik started experimenting with electromagnetic coils, after Jedlik solved the technical problems of the continuous rotation with the invention of the commutator, he called his early devices electromagnetic self-rotors. Although they were used only for instructional purposes, in 1828 Jedlik demonstrated the first device to contain the three components of practical DC motors, the stator, rotor and commutator. The device employed no permanent magnets, as the fields of both the stationary and revolving components were produced solely by the currents flowing through their windings. His motor set a record which was improved only four years later in September 1838 by Jacobi himself. His second motor was powerful enough to drive a boat with 14 people across a wide river and it was not until 1839/40 that other developers worldwide managed to build motors of similar and later also of higher performance. The first commutator DC electric motor capable of turning machinery was invented by the British scientist William Sturgeon in 1832, following Sturgeons work, a commutator-type direct-current electric motor made with the intention of commercial use was built by the American inventor Thomas Davenport, which he patented in 1837. The motors ran at up to 600 revolutions per minute, and powered machine tools, due to the high cost of primary battery power, the motors were commercially unsuccessful and Davenport went bankrupt. Several inventors followed Sturgeon in the development of DC motors but all encountered the same battery power cost issues, no electricity distribution had been developed at the time
12.
Stainless steel
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In metallurgy, stainless steel, also known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal. Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This also influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber. When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
