chimney |
truck |
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top 10 words in brain distribution (in article): build wood structure wall design form city type floor construction |
top 10 words in brain distribution (in article): body time steel type term allow modern common size vehicle |
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top 10 words in brain distribution (not in article): material paint size surface window tree frame cell store plastic |
top 10 words in brain distribution (not in article): church bishop cell blade iron head form century pope roman |
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times more probable under chimney 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under truck (words not in the model) | |
| A chimney'" is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney, effect. The space inside a chimney is called a "flue". Chimneys may be found in buildings, steam locomotives and ships. In the US, the term smokestack'" (colloquially, "'stack'") is also used when referring to locomotive chimneys. The term "'funnel'" is generally used for ships' chimneys and sometimes to refer to locomotive chimneys.. Chimneys are tall to increase their draw of air for combustion and to disperse pollutants in the flue gases over a greater area so as to reduce the pollutant concentrations in compliance with regulatory or other limits. History. Romans used tubes inside the walls to draw smoke out of bakeries but real chimneys appeared only in northern Europe in the 12th century. Industrial chimneys became common in the late 18th century. The earliest extant example of an English chimney is at Conisborough Keep in Yorkshire, which dates from 1185 AD. Chimneys have traditionally been built of brick, both in small and large buildings. Early chimneys were of a simple brick construction. Later chimneys were constructed by placing the bricks around tile liners. To control downdrafts venting caps (often called "chimney pots") with a variety of designs are sometimes placed on the top of chimneys. In the eighteenth and nineteenth centuries, the methods used to extract lead from its ore produced large amounts of toxic fumes. In the north of England, long near-horizontal chimneys were built, often more than 3 km (2 mi) long, which typically terminated in a short vertical chimney in a remote location where the fumes would cause less harm. Lead and silver deposits formed on the inside of these long chimneys, and periodically workers would be sent along the chimneys to scrape off these valuable deposits. Construction. Due to brick's limited ability to handle transverse loads, chimneys in houses were often built in a "stack", with a fireplace on each floor of the house sharing a single chimney, often with such a stack at the front and back of the house. Today's central heating systems have made chimney placement less critical, and the use of non-structural gas vent pipe allows a flue gas conduit to be installed around obstructions and through walls. In fact, many modern high-efficiency heating appliances do not require a chimney. Such appliances are typically installed near an outside wall, and a noncombustible wall thimble allows vent pipe to be run directly through the outside wall. Industrial chimneys are commonly referred to as flue gas stacks and are typically external structures, as opposed to being built into the wall of a building. They are generally located adjacent to a steam-generating boiler or industrial furnace and the gases are carried to it with ductwork. Today the use of reinforced concrete has almost entirely replaced brick as a structural component in the construction of industrial chimneys. Refractory bricks are often used as a lining, particularly if the type of fuel being burned generates flue gases containing acids. Modern industrial chimneys sometimes consist of a concrete windshield with a number of flues on the inside. The 300 metre chimney at Sasol Three consists of a 26 metre diameter windshield with four 4.6 metre diameter concrete flues which are lined with refractory bricks built on rings of corbels spaced at 10 metre intervals. The reinforced concrete can be cast by conventional formwork or sliding formwork. The height is to ensure the pollutants are dispersed over a wider area to meet legislative or safety requirements. Chimney tops. A chimney pot is placed on top of the chimney to inexpensively extend the length of the chimney, and to improve the chimney's draft. A chimney with more than one pot on it indicates that there is more than one fireplace on different floors sharing the chimney. A chimney cowl is placed on top of the chimney to prevent birds and squirrels from nesting in the chimney. They often feature a rain guard to keep rain from going down the chimney. A metal wire mesh is often used as a spark arrestor to minimize burning debris from rising out of the chimney and making it onto the roof. Although the masonry inside the chimney can absorb a large amount of moisture which later evaporates, rainwater can collect at the base of the chimney. Sometimes weep holes are placed at the bottom of the chimney to drain out collected water. A chimney cowl or wind directional cap is helmet shaped chimney cap that rotates to align with the wind and prevent a backdraft of smoke and wind back down the chimney. An H-style cap'" (cowl) is a chimney top constructed from chimney pipes shaped like the letter H. It is an age old method to regulate draft in situations where prevailing winds or turbulences cause down draft and backpuffing. Although the "'H cap'" has a distinctive advantage over most other downdraft caps, it fell out of favor because of it bulky looks. It is found mainly in marine use but has been gaining popularity again due to its energy saving functionality. The "'H-cap stabilizes the draft rather than increasing it. Other down draft caps are based on the Venturi effect, solving downdraft problems by increasing the up draft constantly resulting in much higher fuel consumption. A chimney damper is a metal spring door placed at the top of the chimney with a long metal chain that allows you to open and close the chimney from the fireplace. In the late Middle Ages in Western Europe the design of crow-stepped gables arose to allow maintenance access to the chimney top, especially for tall structures such as castles and great manor houses. Chimney draught or draft. When coal, oil, natural gas, wood or any other fuel is combusted in a stove, oven, fireplace, hot water boiler or industrial furnace, the hot combustion product gases that are formed are called flue gases. Those gases are generally exhausted to the ambient outside air through chimneys or industrial flue gas stacks (sometimes referred to as smokestacks). The combustion flue gases inside the chimneys or stacks are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught draft", "natural ventilation", "chimney effect", or "stack effect". The taller the stack, the more draught or draft is created. Designing chimneys and stacks to provide the correct amount of natural draught or draft involves a number design factors, many of which require trial-and-error reiterative methods. As a "first guess" approximation, the following equation can be used to estimate the natural draught draft flow rate by assuming that the molecular mass (i.e., molecular weight) of the flue gas and the external air are equal and that the frictional pressure and heat losses are negligible: Drawbacks. A characteristic problem of chimneys is they develop deposits of creosote on the walls of the structure when used with wood as a fuel. Some types of wood, such as pine, generate more creosote than others. Deposits of this substance can interfere with the airflow and more importantly, they are flammable and can cause dangerous chimney fires if the deposits ignite in the chimney. Thus, it is recommended — and in some countries even mandatory — that chimneys be inspected annually and cleaned on a regular basis to prevent these problems. The workers who perform this task professionally are called chimney sweeps. In the middle ages in some parts of Europe, a crow-stepped gable design was developed, partially to provide access to chimneys without use of ladders. Masonry (brick) chimneys have also proved particularly susceptible to crumbling during earthquakes. Government housing authorities in quake-prone cities like San Francisco and Los Angeles now recommend building new homes with stud-framed chimneys around a metal flue. Bracing or strapping old masonry chimneys has not proved to be very effective in preventing damage or injury from earthquakes. Perhaps predictably, a new industry provides "faux-brick" facades to cover these modern chimney structures. Other problems include "spalling" brick, in which moisture seeps into the brick and then freezes, cracking and flaking the brick and loosening mortar seals. Dual-use chimneys. Some very high chimneys are used for carrying antennas of mobile phone services and low power FM TV-transmitters. Special attention must be paid to possible corrosion problems if these antennas are near the exhaust of the chimney. In some cases the chimneys of power stations are used also as pylons. However this type of construction is not very common, because of corrosion problems of conductor cables. The Dům Dětí a Mládeže v Modřanech in Prague, Czech Republic is equipped with an observation deck. Cooling tower used as an industrial chimney. At some power stations, which are equipped with plants for the removal of sulfur dioxide and nitrogen oxides, it is possible to use the cooling tower as a chimney. Such cooling towers can be seen in Germany at the Power Station Staudinger Grosskrotzenburg and at the Power Station Rostock. At power stations that are not equipped for removing sulfur dioxide, such usage of cooling towers could result in serious corrosion problems. | A truck'" is a type of motor vehicle commonly used for carrying goods and materials. Some light trucks are relatively small, similar in size to a passenger automobile. Commercial transportation or fire trucks can be quite large and can also serve as a platform for specialized equipment. Etymology. The word "truck" possibly derives from the Greek "trochos" (τροχός =wheel). In North America, certain kinds of big wheels were called "trucks". When the gasoline-engine driven trucks came into fashion, these were called "motor trucks." International variance. In the United States and Canada "truck" is usually reserved for commercial vehicles larger than normal cars, and for pickups and other vehicles having an open load bed. In the United Kingdom and the Republic of Ireland, "lorry" is used as well as "truck", but only used for the medium and heavy types (see below); "i.e." a van, a pickup or an off-road four-wheel drive vehicle such as a Jeep would never be regarded as a lorry in these countries, unlike in the United States (it should be noted, however, that the term lorry is not used in the United States). The same applies to the initials "HGV" (for Heavy Goods Vehicle) which is basically synonymous with "lorry". The word "truck" is also accepted in these countries, and can apply to large vans as well as to lorries ("i.e." its scope is slightly wider). In the UK vernacular, "wagon" is still commonly used to describe various larger vehicles. Though the US term station wagon is occasionally used in the UK, it can cause confusion (despite retaining the US definition), so the societal term estate car remains widely popular. "Lorry" is also used in Hong Kong. In South Africa, the word "kombi" is used, based on its Afrikaans equivalent. The word "lorry" is also used in Cambodia, although here it can refer to a train. In Australia and New Zealand, a pickup truck (a relatively small, usually car- or van-derived vehicle, with an open back body) is called a ute'" (short for "utility") and the word "truck" or "lorry" is reserved for larger vehicles. Other languages have loanwords based on these terms, such as the Malay language and the Spanish language in northern Mexico. A commonly understood term for truck across many European countries is "'camion'". Camion is also used in Quebec to identify trucks in French. Additionally, from the German language the initials "PKW" ("'P'"ersonen"'K'"raft"'W'"agen or passenger carrying vehicle) for a car van or small truck) and "LKW" ("'L'"ast"'K'"raft"'W'"agen or cargo load freight carrying vehicle) for larger trucks are understood. In U.S. English the word "truck" is used in the names of particular types of truck, such as a "fire truck" or "tanker truck". Note that in British English these would be a "fire engine" and "tanker" respectively. Driving. In the United States a commercial driver's license is required to drive any type of vehicle weighing 26,001 lbs (11,800 kg) or more. In the United Kingdom there are complex rules; as an overview, to drive a vehicle weighing more than 7,500 kg for commercial purposes requires a specialist license (the type varies depending on the use of the vehicle and number of seats). For licenses first acquired after 1997, that weight was reduced to 3,500 kg, not including trailers. In the Australia a truck driving license is required for any motor vehicle with a GVM exceeding 4500 kg. The motor vehicles classes are further expanded as "'LR/MR'" (Light Medium rigid up to 8000 kg GVM + trailer to maximum GCM 8000 kg), "'HR'" (Heavy Rigid +trailer up to GCM 9000 kg), "'HC'" (Heavy Combination, a typical prime mover +semi trailer combination) and the "'MC'" (Multi Combination e.g B Doubles Road trains). There is also a heavy vehicle transmission condition for a licence class HR, HC or MC in a vehicle fitted with an automatic or synchromesh transmission, driver’s licence will restrict to vehicles of that class fitted with a synchromesh or automatic transmission. To have the condition removed, a person needs to pass a practical driving test in a vehicle with non synchromesh transmission (constant mesh or crash box). Engine. The oldest truck was built in 1896 by Gottlieb Daimler. Small trucks such as SUVs or pickups, and even light medium-duty trucks in North America and Russia will use gasoline engines. Most heavier trucks use four stroke turbo intercooler diesel engines. Huge off-highway trucks use locomotive-type engines such as a V12 Detroit Diesel two stroke engine. North American manufactured highway trucks almost always use an engine built by a third party, such as CAT, Cummins, or Detroit Diesel. The only exceptions to this are Volvo and its subsidiary Mack Trucks, which are available with their own engines. Freightliner Trucks, Sterling Trucks and Western Star, subsidiaries of Daimler AG, are available with Mercedes-Benz and Detroit Diesel engines. Trucks and buses built by Navistar International usually also contain International engines. The Swedish manufacturer Scania claims they stay away from the U.S. market because of this third party tradition. In the European Union all new truck engines must comply with Euro 5 regulations. Drivetrain. Small trucks use the same type of transmissions as almost all cars, having either an automatic transmission or a manual transmission with synchronisers. Bigger trucks often use manual transmissions without synchronisers, saving bulk and weight, although synchromesh transmissions are used in larger trucks as well. Transmissions without synchronizers, known as "crash boxes", require double-clutching for each shift, (which can lead to repetitive motion injuries), or a technique known colloquially as "floating," a method of changing gears which doesn't use the clutch, except for starts and stops, due to the physical effort of double clutching, especially with non power assisted clutches, faster shifts, and less clutch wear. Double-clutching allows the driver to control the engine and transmission revolutions to synchronize, so that a smooth shift can be made, "e.g.," when upshifting, the accelerator pedal is released and the clutch pedal is depressed while the gear lever is moved into neutral, the clutch pedal is then released and quickly pushed down again while the gear lever is moved to the next highest gear. Finally, the clutch pedal is released and the accelerator pedal pushed down to obtain required engine speed. Although this is a relatively fast movement, perhaps a second or so while transmission is in neutral, it allows the engine speed to drop and synchronize engine and transmission revolutions relative to the road speed. Downshifting is performed in a similar fashion, except the engine speed is now required to increase (while transmission is in neutral) just the right amount in order to achieve the synchronization for a smooth, non-collision gear change. "Skip changing" is also widely used; in principle operation is the same as double-clutching, but it requires neutral be held slightly longer than a single gear change. Common North American setups include 9, 10, 13, 15, and 18 speeds. Automatic and semi-automatic transmissions for heavy trucks are becoming more and more common, due to advances both in transmission and engine power. In Europe 8, 10, 12 and 16 gears are common on larger trucks with manual transmission, while automatic or semiautomatic transmissions would have anything from 5 to 12 gears. Almost all heavy truck transmissions are of the "range and split" (double H shift pattern) type, where range change and so-called half gears or splits are air operated and always preselected before the main gear selection. More new trucks in Europe are being sold with automatic or semi-automatic transmissions. This may be due the fuel consumption can be lowered and truck durability improved. The primary reason perhaps is the fact that such transmissions give a driver more time to concentrate on the road and traffic conditions. Frame. A truck frame consists of two parallel boxed (tubular) or C-shaped rails, or beams, held together by crossmembers. These frames are referred to as ladder frames due to their resemblance to a ladder if tipped on end. The rails consist of a tall vertical section (two if boxed) and two shorter horizontal flanges. The height of the vertical section provides opposition to vertical flex when weight is applied to the top of the frame (beam resistance). Though typically flat the whole length on heavy duty trucks, the rails may sometimes be tapered or arched for clearance around the engine or over the axles. The holes in rails are used either for mounting vehicle components and running wires and hoses, or measuring and adjusting the orientation of the rails at the factory or repair shop. Though they may be welded, crossmembers are most often attached to frame rails by bolts or rivets. Crossmembers may be boxed or stamped into a c-shape, but are most commonly boxed on modern vehicles, particularly heavy trucks. The frame is almost always made of steel, but can be made (whole or in part) of aluminum for a lighter weight. A tow bar may be found attached at one or both ends, but heavy trucks almost always make use of a fifth wheel hitch. Environmental effects. Trucks contribute to air, noise, and water pollution similarly to automobiles. Trucks may emit lower air pollution emissions than cars per pound of vehicle mass, although the absolute level per vehicle mile traveled is higher and diesel particulate matter is especially problematic for health. With respect to noise pollution trucks emit considerably higher sound levels at all speeds compared to typical car; this contrast is particularly strong with heavy-duty trucks. There are several aspects of truck operations that contribute to the overall sound that is emitted. Continuous sounds are those from tires rolling on the roadway and the constant hum of their diesel engines at highway speeds. Less frequent noises, but perhaps more noticeable, are things like the repeated sharp whine of a turbocharger on acceleration or the abrupt blare of an exhaust brake when traversing a downgrade. There has been noise regulation put in place to help control where and when the use of engine braking is allowed. Concerns have been raised about the effect of trucking on the environment, particularly as part of the debate on global warming. In the period from 1990 to 2003, carbon dioxide emissions from transportation sources increased by 20%, despite improvements in vehicle fuel efficiency. In 2005, transportation accounted for 27% of U.S. greenhouse gas emission, increasing faster than any other sector. Between 1985 and 2004, in the U.S., energy consumption in freight transportation grew nearly 53%, while the number of ton-miles carried increased only 43%. "Modal shifts account for a nearly a 23% increase in energy consumption over this period. Much of this shift is due to a greater fraction of freight ton-miles being carried via truck and air, as compared to water, rail, and pipelines." According to a 1995 U.S. Government estimate, the energy cost of carrying a ton of freight a distance of one kilometer averages 337 kJ for water, 221 kJ for rail, 2 000 kJ for trucks and nearly 13 000 kJ for air transport. Many environmental organizations favor laws and incentives to encourage the switch from road to rail, especially in Europe. The European Parliament is moving to ensure that charges on heavy-goods vehicles should be based in part on the air and noise pollution they produce and the congestion they cause, according to legislation approved by the Transport Committee The Eurovignette scheme has been proposed whereby new charges would be potentially levied against things such as noise and air pollution and also weight related damages from the lorries themselves Commercial insurance. Primary Liability Insurance coverage protects the truck from damage or injuries to other people as a result of a truck accident. This truck insurance coverage is mandated by U.S. state and federal agencies and proof of coverage is required to be sent to them. Insurance coverage limits range from $35,000 to $1,000,000. Pricing is dependent on region, driving records, and history of the trucking operation. Motor Truck Cargo insurance protects the transporter for his responsibility in the event of damaged or lost freight. The policy is purchased with a maximum load limit per vehicle. Cargo insurance coverage limits can range from $10,000 to $100,000 or more. Pricing for this insurance is mainly dependent on the type of cargo being hauled. Truck shows. In the UK, three truck shows are popular -Shropshire Truck Show in Oswestry Showground during May, The UK Truck Show held in June at Santa Pod Raceway and FIA European Drag Racing Championships from the home of European Drag-Racing. The UK Truck Show features drag-racing with 6-ton trucks from the British Truck Racing Association, plus other diesel-powered entertainment. Truck Shows provide operators with an opportunity to win awards for their trucks. |