A screw is a type of fastener, in some ways similar to a bolt made of metal, characterized by a helical ridge, known as a male thread. Screws are used to fasten materials by digging in and wedging into a material when turned, while the thread cuts grooves in the fastened material that may help pull fastened materials together and prevent pull-out. There are many screws for a variety of materials. A screw is a combination of simple machines—it is in essence an inclined plane wrapped around a central shaft, but the inclined plane comes to a sharp edge around the outside, which acts a wedge as it pushes into the fastened material, the shaft and helix form a wedge in the form of the point; some screw threads are designed to mate with a complementary thread, known as a female thread in the form of a nut, or object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted; the most common uses of screws are to hold objects together and to position objects.
A screw will 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 wrenches; the head is 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. There are exceptions; 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"; the majority of screws are tightened by clockwise rotation, termed a right-hand thread. If the fingers of the right hand are curled around a right-hand thread, it will move in the direction of the thumb when turned in the same direction as the fingers are curled. Screws with left-hand threads are used in exceptional cases, where loads would tend to loosen a right handed fastener, or when non-interchangeability with right-hand fasteners is required. For example, when the screw will be subject to counterclockwise torque, a left-hand-threaded screw would be an appropriate choice.
The left side pedal of a bicycle has a left-hand thread. More screw may mean any helical device, such as a clamp, a micrometer, a ship's propeller, or an Archimedes' screw water pump. There is no universally accepted distinction between a bolt. A simple distinction, true, although not always, is that a bolt passes through a substrate and takes a nut on the other side, whereas a screw takes no nut because it threads directly into the substrate. So, as a general rule, when buying a packet of "screws" nuts would not be expected to be included, but bolts are sold with matching nuts. Part of the confusion over this is due to regional or dialectical differences. Machinery's Handbook describes the distinction as follows: A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, is intended to be tightened or released by torquing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, of being tightened or released by torquing the head.
An externally threaded fastener, prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt. 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 bolt. The issue of what is a screw and what is a bolt is not resolved with Machinery's Handbook distinction, because of confounding terms, the ambiguous nature of some parts of the distinction, usage variations; some of these issues are discussed below: Early wood screws were made by hand, with a series of files and other cutting tools, these can be spotted by noting the irregular spacing and shape of the threads, as well as file marks remaining on the head of the screw and in the area between threads. Many of these screws had a blunt end lacking the sharp tapered point on nearly all modern wood screws. Lathes were used to manufacture wood screws, with the earliest patent being recorded in 1760 in England.
During the 1850s swaging tools were developed to provide a more consistent thread. Screws made with these tools have rounded valleys with rough threads; some wood screws were made with cutting dies as early as the late 1700s. Once screw turning machines were in common use, most commercially available wood screws were produced with this method; these cut wood screws are invariably tapered, when the tapered shank is not obvious, they can b
A fire hydrant called a fireplug, fire pump, jockey pump, or pump, is a connection point by which firefighters can tap into a water supply. It is a component of active fire protection; the user attaches a hose to the fire hydrant opens a valve on the hydrant to provide a powerful flow of water, on the order of 350 kPa. This user can attach this hose to a fire engine, which can use a powerful pump to boost the water pressure and split it into multiple streams. One may connect the hose with a threaded connection, instantaneous "quick connector" or a Storz connector. A user should take care not to open or close a fire hydrant too as this can cause a water hammer, which can damage nearby pipes and equipment; the water inside a charged hose line causes it to be heavy and high water pressure causes it to be stiff and unable to make a tight turn while pressurized. When a fire hydrant is unobstructed, this is not a problem, as there is enough room to adequately position the hose. Most fire hydrant valves are not designed to throttle the water flow.
The valving arrangement of most dry-barrel hydrants is for the drain valve to be open at anything other than full operation. Usage at partial-opening can result in considerable flow directly into the soil surrounding the hydrant, over time, can cause severe scouring. Gate or butterfly valves can be installed directly onto the hydrant orifices to control individual outputs and allow for changing equipment connections without turning off the flow to other orifices; these valves can be up to 12 inches in diameter to accommodate the large central "steamer" orifices on many US hydrants. It is good practice to install valves on all orifices before using a hydrant as the protective caps are unreliable and can cause major injury if they fail; when operating a hydrant, a firefighter wears appropriate personal protective equipment, such as gloves and a helmet with face shield worn. High-pressure water coursing through a aging and corroding hydrant could cause a failure, injuring the firefighter operating the hydrant or bystanders.
In most jurisdictions it is illegal to park a car within a certain distance of a fire hydrant. In North America the distances are 3 to 5 m or 10 to 15 ft indicated by yellow or red paint on the curb; the rationale behind these laws is that hydrants need to be accessible in an emergency. To prevent casual use or misuse, the hydrant requires special tools to be opened a large wrench with a pentagonal socket. Vandals sometimes cause monetary loss by wasting water; such vandalism can reduce municipal water pressure and impair firefighters' efforts to extinguish fires. Sometimes those seeking to play in the water remove the caps and open the valve, providing residents a place to play and cool off in summer. However, this is discouraged as residents have been struck by passing automobiles while playing in the street in the water spray. In spite of this, some US communities provide low flow sprinkler heads to enable residents to use the hydrants to cool off during hot weather, while gaining some control on water usage.
Most fire hydrants in Australia are protected by a silver-coloured cover with a red top, secured to the ground with bolts to protect the hydrant from vandalism and unauthorized use. The cover must be removed before use. In most areas of the United States, contractors who need temporary water may purchase permits to use hydrants; the permit will require a hydrant meter, a gate valve and sometimes a clapper valve to prevent back-flow into the hydrant. Additionally, residents who wish to use the hydrant to fill their in-ground swimming pool are permitted to do so, provided they pay for the water and agree to allow firefighters to draft from their pool in the case of an emergency. Municipal services, such as street sweepers and tank trucks, may be allowed to use hydrants to fill their water tanks. Sewer maintenance trucks need water to flush out sewerage lines, fill their tanks on site from a hydrant. If necessary, the municipal workers will use a meter. Since fire hydrants are one of the most accessible parts of a water distribution system, they are used for attaching pressure gauges or loggers or monitor system water pressure.
Automatic flushing devices are attached to hydrants to maintain chlorination levels in areas of low usage. Hydrants are used as an easy above-ground access point by leak detection devices to locate leaks from the sound they make. Fire hydrants may be used to supply water to riot control vehicles; these vehicles use a high pressure water cannon to discourage rioting. In areas subject to freezing temperatures, at most, only a portion of the hydrant is above ground; the valve is connected by a riser to the above-ground portion. A valve rod extends from the valve up through a seal at the top of the hydrant, where it can be operated with the proper wrench; this design is known as a "dry barrel" hydrant, in that the barrel, or vertical body of the hydrant, is dry. A drain valve underground opens when the water valve is closed. In warm areas, hydrants are used with one or more valves in the above-ground portion. Unlike with cold-weather hydrants, it is possible to turn the water supply off to each port.
This style is known as a "wet barrel" hydr
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. In early days, electricity was considered as being not related to magnetism. On, many experimental results and the development of Maxwell's equations indicated that both electricity and magnetism are from a single phenomenon: electromagnetism. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others; the presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges produces a magnetic field; when a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to move, the electric field would be doing work on the electric charge, thus we can speak of electric potential at a certain point in space, equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is measured in volts.
Electricity is at the heart of many modern technologies, being used for: electric power where electric current is used to energise equipment. Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. Practical applications for electricity were few, it would not be until the late nineteenth century that electrical engineers were able to put it to industrial and residential use; the rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an limitless set of applications which include transport, lighting and computation. Electrical power is now the backbone of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", described them as the "protectors" of all other fish.
Electric fish were again reported millennia by ancient Greek and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and electric rays, knew that such shocks could travel along conducting objects. Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them; the earliest and nearest approach to the discovery of the identity of lightning, electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning ra‘ad applied to the electric ray. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.
Thales was incorrect in believing the attraction was due to a magnetic effect, but science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber, he coined the New Latin word electricus to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay.
In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature, he explained the paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines used; the recognition of electromagnetism, the unity of electric
Gaz de France
Gaz de France was a French company which produced and sold natural gas around the world in France, its main market. The company was particularly active in Belgium, the United Kingdom and other European countries. Through its part-owned Belgian subsidiary SPE it was involved in nuclear power generation; the company conducted a merger of equals with fellow utility company Suez on 22 July 2008 to form GDF Suez. Its head office was located in the 17th arrondissement of Paris. Gaz de France was created with its sister company Électricité de France in 1946 by the French Government. After the liberalisation of Europe’s energy markets, Gaz de France entered into the electricity sector, having developed combined natural gas-electricity offerings. With part-privatisation EDF and Gaz de France latterly became two separate entities, with each controlling a distribution subsidiary responsible for running its distribution system. For Gaz de France, this was the Gaz de France Distributor. Together, these two distributors managed a joint department, “EDF Gaz de France Distribution” called “EDF GDF Services, responsible for field-based activities.
In January 2008 EDF Gaz de France Distribution was split into two entities: ErDF, 100% owned by EDF, GrDF, wholly owned by Gaz de France. The company's capital was floated on the Paris Stock Exchange in July 2005, raising €2.5 billion for the State of France. The government continued to hold an approximate 80% stake in the company until the 2008 merger with Suez; the French state now holds 35.7% of GDF Suez. On 25 February 2006 French Prime minister Dominique de Villepin announced the merger of Suez and GDF, which would make the world's largest liquefied natural gas company. Since the French state owned over 80% of Gaz de France, it was necessary to pass a new law in order to make the merger possible; the merger was overseen by R N Sons Investment Bank. On 3 September 2007, Gaz de France and Suez announced agreed terms of merger, on the basis of an exchange of 21 Gaz de France shares for 22 Suez shares via the absorption of Suez by Gaz de France; the French state would hold more than 35 % of shares of GDF Suez.
Whilst Nicolas Sarkozy was for several months opposed to the Villepin government’s plans for a merger of the two companies, he subsequently accepted the government proposal. This plan for a merger between Gaz de France and Suez came under fire from the whole of the political left, which feared the loss of one of the last ways of preventing the price rises experienced over the previous three years, by the social Gaullists and trade unions. In retaliation, the opposition submitted 137,449 amendments to the plan. Under normal parliamentary procedure, parliament would have been required to vote on the amendments, which would have taken 10 years; the French Constitution does give the government options to bypass such a filibuster, but in the end these were not used. Law No. 2006-1537 of 7 December 2006 on the energy sector authorised the privatisation of Gaz de France. On 2 September 2007 the boards of directors of Gaz de France and Suez approved the new framework for the planned merger between the companies.
The newly created company, GDF Suez, came into existence on 22 July 2008. Robert Hirsch: 1970-1975 Pierre Alby: 1979-1986 Jacques Fournier: 1986-1988 Françis Gutmann: 1988-1993 Loïk Le Floch-Prigent: 1993-1996 Pierre Gadonneix: 1996-2004 Jean-François Cirelli: 2004-2008 Yves Colliou – Deputy CEO. Jean-Marie Dauger – Deputy CEO. Stéphane Brimont – CFO. Emmanuel Hedde – General Secretary. Pierre Clavel – Head of International branch. Henri Ducré - CEO Energie France. Philippe Saimpert - Head of Human Resources. Raphaële Rabatel - Communications manager. Jean-Michel Carboni - Head of Central and Eastern Europe. Jean-Paul George - President of Cofathec group. Gaz de France's head office was located in the 17th arrondissement of Paris; the company took possession of the building, built in the late 1950s, in the early 1960s. Dirigisme Official website of Gaz de France / English website English website English website English website Official website of GDF Suez
A nut is a type of fastener with a threaded hole. Nuts are always used in conjunction with a mating bolt to fasten multiple parts together; the two partners are kept together by a combination of their threads' friction, a slight stretching of the bolt, compression of the parts to be held together. In applications where vibration or rotation may work a nut loose, various locking mechanisms may be employed: lock washers, jam nuts, specialist adhesive thread-locking fluid such as Loctite, safety pins or lockwire in conjunction with castellated nuts, nylon inserts, or oval-shaped threads. Square nuts, as well as bolt heads, were the first shape made and used to be the most common because they were much easier to manufacture by hand. While rare today due to the reasons stated below for the preference of hexagonal nuts, they are used in some situations when a maximum amount of torque and grip is needed for a given size: the greater length of each side allows a spanner to be applied with a larger surface area and more leverage at the nut.
The most common shape today is hexagonal, for similar reasons as the bolt head: six sides give a good granularity of angles for a tool to approach from, but more corners would be vulnerable to being rounded off. It takes only one sixth of a rotation to obtain the next side of the grip is optimal. However, polygons with more than six sides do not give the requisite grip and polygons with fewer than six sides take more time to be given a complete rotation. Other specialized shapes exist for certain needs, such as wingnuts for finger adjustment and captive nuts for inaccessible areas. A wide variety of nuts exists, from household hardware versions to specialized industry-specific designs that are engineered to meet various technical standards. Fasteners used in automotive and industrial applications need to be tightened to a specific torque setting, using a torque wrench. Nuts are graded with strength ratings compatible with their respective bolts. An SAE class 5 nut can support the proof load of an SAE class 5 bolt, so on.
Castellated nut Distorted thread locknut Centerlock nut Elliptical offset locknut Toplock nut Interfering thread nut Tapered thread nut Jam nut Jet nut Keps nut with a star-type lock washer Nyloc plate nut Polymer insert nut Security locknut Serrated face nut Serrated flange nut Speed nut Split beam nut BINX nut Note that flat sizes differ between industry standards. For example, wrench sizes of fastener used in Japanese built cars comply with JIS automotive standard. In normal use, a nut-and-bolt joint holds together because the bolt is under a constant tensile stress called the preload; the preload pulls the nut threads against the bolt threads, the nut face against the bearing surface, with a constant force, so that the nut cannot rotate without overcoming the friction between these surfaces. If the joint is subjected to vibration, the preload increases and decreases with each cycle of movement. If the minimum preload during the vibration cycle is not enough to hold the nut in contact with the bolt and the bearing surface the nut is to become loose.
Specialized locking nuts exist to prevent this problem, but sometimes it is sufficient to add a second nut. For this technique to be reliable, each nut must be tightened to the correct torque; the inner nut is tightened to about a quarter to a half of the torque of the outer nut. It is held in place by a wrench while the outer nut is tightened on top using the full torque; this arrangement causes the two nuts to push on each other, creating a tensile stress in the short section of the bolt that lies between them. When the main joint is vibrated, the stress between the two nuts remains constant, thus holding the nut threads in constant contact with the bolt threads and preventing self-loosening; when the joint is assembled the outer nut bears the full tension of the joint. The inner nut functions to add a small additional force to the outer nut and does not need to be as strong, so a thin nut can be used. Bickford, John H..
A dry riser is a empty pipe that can be externally connected to a pressurized water source by firefighters. It is a vertical pipe intended to distribute water to multiple levels of a building or structure as a component of the fire suppression systems. Most buildings have a "wet riser" or "wet standpipe" system where the pipes are kept full of water for manual or automatic fire fighting operations. Dry risers are used when the water pressure of a building wouldn't be enough for fire suppression and in unheated buildings where the pipes could freeze. Dry risers must allow fire engine access within 18 m of the dry riser inlet box. Dry risers in occupied buildings must be within a fire-resistant shaft one of a building's fire escape staircase enclosures; the riser is where the gauges and alarm devices are located. Depending on regional nomenclature, the term "dry riser" may refer to a standpipe, intended to provide water to fire hose connections, or a vertical main pipe in an automatic dry pipe fire sprinkler system.
A dry standpipe has an external fire department connection at ground level, such as a Storz coupling, through which water can be pumped from the fire engine pump to the fire hose attachments on each floor. A dry pipe fire sprinkler system is a network of pipes connected to fixed sprinklers inside a building, full of air until one of the sprinklers is triggered. Roger Greeno. Building Services Handbook. Routledge. Pp. 642–. ISBN 978-1-317-61721-1. V. K. Jain. Fire Safety In Buildings. Taylor & Francis. Pp. 193–. ISBN 978-81-224-1035-8. Fire fighting Fire sprinkler Siamese connection Standpipe