A rainscreen is an exterior wall detail where the siding stands off from the moisture-resistant surface of an air barrier applied to the sheathing to create a capillary break and to allow drainage and evaporation. The rain screen is the siding itself but the term rainscreen implies a system of building. Ideally the rain screen prevents the wall air/moisture barrier on sheathing from getting wet. In some cases a rainscreen wall is called a pressure-equalized rainscreen wall where the ventilation openings are large enough for the air pressure to nearly equalize on both sides of the rain screen, but this name has been criticized as being redundant and is only useful to scientists and engineers. A screen in general terms is a barrier; the rainscreen in a wall is sometimes defined as the first layer of material on the wall, the siding itself. Rainscreen is defined as the entire system of the siding, drainage plane and a moisture/air barrier. A veneer that does not stand off from the wall sheathing to create a cavity is not a rainscreen.
However, a masonry veneer can be a rainscreen wall. Many terms have been applied to rain screen walls including basic, conventional, pressure-equalized, pressure-moderated rainscreen systems or assemblies; these terms have caused confusion as to what a rain screen is but all reflect the rainscreen principle of a primary and secondary line of defense. One technical difference is between a plane, a gap of 3⁄8 inch or less and a channel, a gap of more than 3⁄8 inch. In general terms a rainscreen wall may be called a drained wall; the two other basic types of exterior walls in terms of water resistance are barrier walls which rely on the one exterior surface to prevent ingress and mass walls which allow but absorb some leakage. In the early 1960s research was conducted in Norway on rain penetration of windows and walls, Øivind Birkeland published a treatise referring to a "rain barrier". In 1963 the Canadian National Research Counsel published a pamphlet titled "Rain Penetration and its Control" using the term "open rain screen".
Rainscreen cladding is a kind of double-wall construction that utilizes a surface to help keep the rain out, as well as an inner layer to offer thermal insulation, prevent excessive air leakage and carry wind loading. The surface breathes. For water to enter a wall first the water must get onto the wall and the wall must have openings. Water can enter the wall by capillary action, gravity and air pressure; the rainscreen system provides for two lines of defense against the water intrusion into the walls: The rainscreen and a means to dissipate leakage referred to as a channel. In a rainscreen the air gap allows the circulation of air on the moisture barrier.. This helps direct water away from the main exterior wall. Keeping the insulation dry helps prevent problems such as mold formation and water leakage; the vapour-permeable air/weather barrier prevents water molecules from entering the insulated cavity but allows the passage of vapour, thus reducing the trapping of moisture within the main wall assembly.
The air gap can be created in several ways. One method is to use furring fastened vertically to the wall. Ventilation openings are made at the bottom and top of the wall so air can rise through the cavity. Wall penetrations including windows and doors require special care to maintain the ventilation. In the pressure-equalized system the ventilation openings must be large enough to allow air-flow to equalize the pressure on both sides of the cladding. A ratio of 10:1 cladding leakage area to ventilation area has been suggested. A water/air resistant membrane is placed between the furring and the sheathing to prevent rain water from entering the wall structure; the membrane directs water away and toward special drip edge flashings which protect other parts of the building. Insulation may be provided beneath the membrane; the thickness of insulation is determined by building code requirements as well as performance requirements set out by the architect. The system is a form of double-wall construction that uses an outer layer to keep out the rain and an inner layer to provide thermal insulation, prevent excessive air leakage and carry wind loading.
The outer layer breathes like a skin. The structural frame of the building is kept dry, as water never reaches it or the thermal insulation. Evaporation and drainage in the cavity removes water. Water droplets are not driven through the panel joints or openings because the rainscreen principle means that wind pressure acting on the outer face of the panel is equalized in the cavity. Therefore, there is no significant pressure differential to drive the rain through joints. During extreme weather, a minimal amount of water may penetrate the outer cladding. This, will run as droplets down the back of the cladding sheets and be dissipated through evaporation and drainage. A rainscreen drainage plane is a separation between the veneer and the weather resistant barrier of a rainscreen, it provides predictable, unobstructed path drainage for liquid moisture to drain from a high point of the wall to a low point of the wall the wall detail. The drainage plane must move the water out of the wall system to prevent absorption and consequential rot and structural degradation.
A drainage plane is designed to shed bulk rainwater and/or condensation downward and o
Cladding is the bonding together of dissimilar metals. It is different from fusion welding or gluing as a method to fasten the metals together. Cladding is achieved by extruding two metals through a die as well as pressing or rolling sheets together under high pressure; the United States Mint uses cladding to manufacture coins from different metals. This allows a cheaper metal to be used as a filler. In roll bonding, two or more layers of different metals are cleaned and passed through a pair of rollers under sufficient pressure to bond the layers; the pressure is high enough to deform the metals and reduce the combined thickness of the clad material. Heat may be applied when metals are not ductile enough; as an example of application, bonding of the sheets can be controlled by painting a pattern on one sheet. This is used to make heat exchangers for refrigeration equipment. In explosive welding, the pressure to bond the two layers is provided by detonation of a sheet of chemical explosive. No heat-affected zone is produced in the bond between metals.
The explosion propagates across the sheet, which tends to expel impurities and oxides from between the sheets. Pieces up to 4 x 16 metres can be manufactured; the process is useful for cladding metal sheets with a corrosion-resistant layer. Laser cladding is a method of depositing material by which a powdered or wire feedstock material is melted and consolidated by use of a laser in order to coat part of a substrate or fabricate a near-net shape part, it is used to improve mechanical properties or increase corrosion resistance, repair worn out parts, fabricate metal matrix composites. Surface material may be laser cladded directly onto a stressed component, i.e. to make a self-lubricating surface. However, such a modification requires further industrialization of the cladding process to adapt it for efficient mass production. Further research on the detailed effects from surface topography, material composition of the laser cladded material and the composition of the additive package in the lubricants on the tribological properties and performance are preferably studied with tribometric testing.
The powder used in laser cladding is of a metallic nature, is injected into the system by either coaxial or lateral nozzles. The interaction of the metallic powder stream and the laser causes melting to occur, is known as the melt pool; this is deposited onto a substrate. This is the most common technique, however some processes involve moving the laser/nozzle assembly over a stationary substrate to produce solidified tracks; the motion of the substrate is guided by a CAD system which interpolates solid objects into a set of tracks, thus producing the desired part at the end of the trajectory. A great deal of research is now being concentrated on developing automatic laser cladding machines. Many of the process parameters must be manually set, such as laser power, laser focal point, substrate velocity, powder injection rate, etc. and thus require the attention of a specialized technician to ensure proper results. However, many groups are focusing their attention on developing sensors to measure the process online.
Such sensors monitor the clad's geometry, metallurgical properties, temperature information of both the immediate melt pool and its surrounding areas. With such sensors, control strategies are being designed such that constant observation from a technician is no longer required to produce a final product. Further research has been directed to forward processing where system parameters are developed around specific metallurgical properties for user defined applications. Best technique for coating any shape => increase life-time of wearing parts. Particular dispositions for repairing parts. Most suited technique for graded material application. Well adapted for near-net-shape manufacturing. Low dilution between track and substrate (unlike other welding processes and strong metallurgical bond. Low deformation of the substrate and small heat affected zone. High cooling rate => fine microstructure. A lot of material flexibility. Built part is free of porosity. Compact technology. Additive manufacturing All-Clad Copper-clad aluminum wire Copper-clad steel http://apollomachine.com/services/apollo-clad/ https://web.archive.org/web/20150720051133/http://www.beam-machines.fr/uk/innovation/techology.html https://web.archive.org/web/20101207085306/http://www.ccl.fraunhofer.org/download/cladding_titanium.pdf http://www.lasercladding.com/index.html http://www.designforlasermanufacture.com/ https://web.archive.org/web/20110926224642/http://www.alspi.com/lasercladding.htm http://www.laserweldingsolutions.com/ https://web.archive.org/web/20100311075620/http://www.fwgartner.com/fwgts_prodserv_qa_laser.htm http://www.laserline-inc.com/diode-laser-cladding-coating-laser-repair-welding.php http://www.optoiq.com/index/lasers-for-manufacturing/laser-surface-treatment/laser-cladding.html http://www.swansonindustries.com/lasercladding.php http://www.precoinc.com/capabilities/clad.html http://www.neotechservices.com/lens.html https://archive.is/20130116124148/http://www.additive3d.com/lens.htm http://www.darron-sbo.com/ http://www.vectorautomationinc.com/systems/robo
Glossary of boiler terms
Boilers for generating steam or hot water have been designed in countless shapes and configurations. An extensive terminology has evolved to describe their common features; this glossary provides definitions for these terms. Terms which relate to boilers used for space heating or generating hot water are identified by. Ashpan A container beneath the furnace, catching ash and clinker that falls through the firebars; this may be made of steel sheet for a locomotive. Ashpans are the location of the damper, they may be shaped into hoppers, for easy cleaning during disposal. Blastpipe Part of the exhaust system that discharges exhaust steam from the cylinders into the smokebox beneath the chimney in order to increase the draught through the fire. Blow-down Periodic venting of water from the boiler; this water contains the most concentrated precursors for sludge build-up, so by venting it whilst still dissolved, the build-up is reduced. When early marine boilers were fed with salt water, they would be blown-down several times an hour.
Blow-down cock A valve mounted low-down on the boiler around the foundation ring, used for blow down. Blower The blower provides a forced draught on the fire, it consists of a hollow ring mounted either on top of the blastpipe. Holes are drilled in the top of the blower ring, when steam is fed into the ring, the steam jets out of the holes and up the chimney, stimulating draught, much like a blastpipe. Boiler A pressure vessel for the creation of hot water or steam, for residential or commercial use. Boilersmith A craftsman skilled in the techniques required for the construction and repair of boilers - not to be confused with at boilermaker. A boilermaker is a skilled metalworker the member of a union of the same name, skilled in platework or welding. A boilermaker may not be a boilersmith. A boilersmith may be a member of another trade, such as a plumber or pipeworker, so may not be a boilermaker. Boiler stay A structural element inside a boiler which supports surfaces under pressure by tying them together.
Boiler suit Heavy-duty one-piece protective clothing, worn when inspecting the inside of a firebox for steam leaks, for which task it is necessary to crawl through the firehole door. Boiler ticket The safety certificate issued for a steam boiler on passing a formal inspection after a major rebuild, covering a period of ten years (eight years on the mainline. Additional annual safety inspections must be undertaken, which may result in the locomotive being withdrawn from service if the boiler requires work; when the ticket "expires" the locomotive cannot be used until the boiler has been overhauled or replaced, a new ticket obtained. Boiler water treatment Removal or chemical modification of boiler feedwater impurities to avoid scale, corrosion, or foaming. Brick arch A horizontal baffle of firebrick within the furnace of a locomotive boiler; this forces combustion gases from the front of the furnace to flow further, back over the rest of the furnace, encouraging efficient combustion. The invention of the brick arch, along with the blastpipe and forced draught, was a major factor in allowing early locomotives to begin to burn coal, rather than coke.
Bridge clamp Carryover the damaging condition where water droplets are carried out of the boiler along with the dry steam. These can cause scouring in hydraulic lock in cylinders; the risk is accentuated by dirty feedwater. See priming. Check valve or clack valve, from the noise it makes. A non-return valve where the feedwater enters the boiler drum, they are mounted halfway along the boiler drum, or else as a top feed, but away from the firebox, so as to avoid stressing it with the shock of cold water. Cladding The layer of insulation and outer wrapping around a boiler shell that of a steam locomotive. In early practice this was wooden strips held by brass bands, and modern practice is to use asbestos insulation matting covered with rolled steel sheets. The outer shape of the cladding is a simplification of the underlying boiler shell. Termed "clothing" in LMS practice. Crinolines The framework of hoops used to support cladding over a boiler. Named from the similar hoops under a crinoline skirt. Crown sheet The upper sheet of the inner firebox on a locomotive boiler.
It is the hottest part of the firebox, sometimes at risk of boiler explosion, should the water level drop and the crown sheet be exposed and thus allowed to overheat. Supported from above by complex stays. Damper An adjustable flap controlling the air admitted beneath the fire-bed. Part of the ashpan. Disposal The cleanup process at the end of the working day involving dropping the fire and blowing down the boiler. Dome a raised location on the top of the main boiler drum, providing a high point from which to collect dry steam, reducing the risk of priming. Downcomer large external pipes in many water-tube boilers, carrying unheated cold water from the steam drum down to the water drum as part of the circulation path. Drowned tube Either a fire-tube or water-tube, below the water-level of the operating boiler; as corrosion and scaling is most active in the region of the water-level, this reduces wear and maintenance requirements. Exhaust injector a feedwater injector that economizes on steam consumption by using waste steam, such as engine exhaust.
Feedwater Feedwater pump Field-tube A form of water-tube where the water tubes are single-ended, similar to a thimble water tube with an internal tube to encourage circulation. Firebar Replaceable cast-iron bars that form the base of the fur
There are four main techniques used today in the UK and mainland Europe for copper cladding a building: Seamed-cladding: max 600mm by 4000mm'seam centres'. Shingle-cladding: max 600mm by 4000mm'seam centres'. Slot-in panels: max 350mm wide for 1.0mm, by nominal 4 m length. Cassettes: largest-format cladding elements, more subframing is needed: can be 900mm x nominal 4000mm length; when selecting size of a cladding element, take wind-loadings into account, consider the standard sizes available of the sheet pre-material, to minimise material wastage through off-cuts. This helps to reduce costs; the choice of which system to use depends on the aesthetic effect required, building geometry can have an influence on the choice. Copper cladding is durable, lightweight compared to other materials and techniques, at the end of the building life is 100% recyclable. Depending on metal prices, copper may be a cost-effective cladding and roofing material. With good building design, materials choice and craftsmanship, copper roofing or facade cladding may be cheaper than slates or concrete tiles when one takes into account the lasting colour, maintenance-free and lightweight nature of the cladding.
Because the UK code of practice for "hard metal" cladding is quite old - CP143: part 12 - the major manufacturers have to provide detailed technical advice and information for architects and builders, cultivate skilled installers with years of experience to draw on. An installer of hard metal roofing and cladding must put in around 8–10 years on-the-job in order to achieve a respectable experience on a work site. Copper in architecture: Wall cladding
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created. Most nuclear fuels contain heavy fissile actinide elements that are capable of undergoing and sustaining nuclear fission; the three most relevant fissile isotopes are Uranium-233, Uranium-235 and Plutonium-239. When the unstable nuclei of these atoms are hit by a slow-moving neutron, they split, creating two daughter nuclei and two or three more neutrons; these neutrons go on to split more nuclei. This creates a self-sustaining chain reaction, controlled in a nuclear reactor, or uncontrolled in a nuclear weapon; the processes involved in mining, purifying and disposing of nuclear fuel are collectively known as the nuclear fuel cycle. Not all types of nuclear fuels create power from nuclear fission. Nuclear fuel has the highest energy density of all practical fuel sources. For fission reactors, the fuel is based on the metal oxide. Uranium dioxide is a black semiconducting solid, it can be made by reacting uranyl nitrate with a base to form a solid.
It is heated to form U3O8 that can be converted by heating in an argon / hydrogen mixture to form UO2. The UO2 is mixed with an organic binder and pressed into pellets, these pellets are fired at a much higher temperature to sinter the solid; the aim is to form a dense solid. The thermal conductivity of uranium dioxide is low compared with that of zirconium metal, it goes down as the temperature goes up. Corrosion of uranium dioxide in water is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. Mixed oxide, or MOX fuel, is a blend of plutonium and natural or depleted uranium which behaves to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to low enriched uranium fuel used in the light water reactors which predominate nuclear power generation; some concern has been expressed that used MOX cores will introduce new disposal challenges, though MOX is itself a means to dispose of surplus plutonium by transmutation.
Reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant. As of 2015, MOX fuel is made in France, to a lesser extent in Russia and Japan. China plans to develop fast breeder reactors and reprocessing; the Global Nuclear Energy Partnership, was a U. S. proposal in the George W. Bush Administration to form an international partnership to see spent nuclear fuel reprocessed in a way that renders the plutonium in it usable for nuclear fuel but not for nuclear weapons. Reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations. All of the other reprocessing nations have long had nuclear weapons from military-focused "research"-reactor fuels except for Japan. With the fuel being changed every three years or so, about half of the Pu-239 is'burned' in the reactor, providing about one third of the total energy, it behaves like U-235 and its fission releases a similar amount of energy. The higher the burn-up, the more plutonium in the spent fuel, but the lower the fraction of fissile plutonium.
About one percent of the used fuel discharged from a reactor is plutonium, some two thirds of this is fissile. Worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refueling reactors each year. Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive high temperatures. Metal fuels have a long history of use, stretching from the Clementine reactor in 1946 to many test and research reactors. Metal fuels have the potential for the highest fissile atom density. Metal fuels are alloyed, but some metal fuels have been made with pure uranium metal. Uranium alloys that have been used include uranium aluminum, uranium zirconium, uranium silicon, uranium molybdenum, uranium zirconium hydride. Any of the aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle. Metal fuels have been used in water reactors and liquid metal fast breeder reactors, such as EBR-II. TRIGA fuel is used in TRIGA reactors.
The TRIGA reactor uses UZrH fuel, which has a prompt negative fuel temperature coefficient of reactivity, meaning that as the temperature of the core increases, the reactivity decreases—so it is unlikely for a meltdown to occur. Most cores that use this fuel are "high leakage" cores where the excess leaked neutrons can be utilized for research. TRIGA fuel was designed to use enriched uranium, however in 1978 the U. S. Department of Energy launched its Reduced Enrichment for Research Test Reactors program, which promoted reactor conversion to low-enriched uranium fuel. A total of 35 TRIGA reactors have been installed at locations across the USA. A further 35 reactors have been installed in other countries. In a fast neutron reactor, the minor actinides produced by neutron capture of uranium and plutonium can be used as fuel. Metal actinide fuel is an alloy of zirconium, pluto