Gas holder
A gasometer, or gas-holder, is a large container where natural gas or town gas is stored near atmospheric pressure at ambient temperatures. The volume of the container follows the quantity of stored gas, with pressure coming from the weight of a movable cap. Typical volumes for large gasometers are about 50,000 m³, with 60 m diameter structures.
Gasometers tend to be used for balancing purposes (making sure gas pipes can be operate within a safe range of pressures) rather than for actually storing gas for later use. Gas is nowadays stored in large underground reservoirs such as salt caverns. Nowadays however line-packing is the prefered method. Often gas is stored in the summer when it is cheap and sold in the winter when the price goes up.
Throughout the 1960s and 1970s it was thought that gasholders could be replaced with high pressure bullets. However, regulations brought in meant that all new bullets must be built several miles out of towns and cities and the security of storing large amounts of high pressure natural gas above ground made them unpopular with local people and councils. Bullets are gradually being decomissioned. It is also posible to store natural gas in a liquid form and is widely practiced throughout the world.
Gasholders hold a large advantage over other methods of storage. They are the only storage method which keeps the gas at district pressure. Once the District Low Pressure Switch falls and the booser fans come on, the gas in these holders can be at homes, being used in a very short space of time. Gas is stored in these throughout the day when little gas is being used. At about 5pm there is a great demand for gas and the holder will come down, supplying the district.
There are two types of gasholders. The earlier column guided variations were built in Victorian times and have a frame, visible at all times. Spriral guided gasholders were built in the UK up until 1983. These have no frame and each lift is guided by the one below, rotating as it goes up.
Gasometers are often a major part of the skylines of low-rise British cities, due to their large distinctive shape and central location. The pollution associated with gasworks and gas storage makes the land difficult to reclaim for other purposes, but some gasometers, notably in Vienna, have been converted into living space and shopping mall.
Most British cities will have several gasholders. London, Manchester, Sheffield, Leeds, Newcastle and Glasgow are noted for having many gasholders. In the past holder stations would have an operator living on site controlling their movement. However with the process control systems now used on these sites, such an operator is obsolete.
The term gasometer was originally coined by William Murdoch, the inventor of gas lighting, in the early 1800s. Despite the objections of his associates that his so-called "gazometer" was not a meter but a container, the name was retained and came into general use. The word is also used to describe a meter for measuring the amount of gas flowing through a particular pipe.
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