A gas holder is a large container where natural gas

Natural gas

Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

 or town gas is stored

Natural gas storage

Natural gas, like many other commodities, can be stored for an indefinite period of time in natural gas storage facilities for later consumption.- Usage :...

 near atmospheric pressure

Atmospheric pressure

Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

 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 gasholders are about 50,000 cubic metres, with 60 metre diameter structures.
Gasholders tend to be used nowadays for balancing purposes (making sure gas pipes can be operated within a safe range of pressures) rather than for actually storing gas for later use.

Other storage systems

Gas more recently was stored in large underground reservoirs such as salt caverns. In modern times however line-packing is the preferred method.

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

Committee

A committee is a type of small deliberative assembly that is usually intended to remain subordinate to another, larger deliberative assembly—which when organized so that action on committee requires a vote by all its entitled members, is called the "Committee of the Whole"...

. Bullets are gradually being decommissioned. It is also possible to store natural gas in liquid form

Liquefied natural gas

Liquefied natural gas or LNG is natural gas that has been converted temporarily to liquid form for ease of storage or transport....

 and this is widely practiced throughout the world.

Advantage of gas holders

Gasholders hold a large advantage over other methods of storage. They are the only storage method which keeps the gas at district pressure (the pressure required in local gas mains). Once the District Low Pressure Switch falls, and the booster 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 the holder throughout the day, when little gas is being used. At about 5 p.m. there is a great demand for gas and the holder will come down, supplying the district.

Gas holder types

There are two basic types of gasholder, rigid waterless and telescoping. Rigid waterless gas holders were a very early design which showed no sign of expansion or contraction. There are modern versions of the waterless gas holder, e.g., oil-sealed, grease-sealed and "dry seal" (membrane) types.

Telescoping holders fall into two subcategories. The earlier of the telescoping variety were column guided variations and were built in Victorian times. To guide the telescoping walls, or "lifts", they have an external fixed frame, visible at a fixed height at all times. Spiral 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 as dictated by helical runners.

Both telescoping types use the manometric property of water to provide a seal. The whole tank floats in a circular or annular water reservoir, held up by the roughly constant pressure of a varying volume of gas, the pressure determined by the weight of the structure, and the water providing the seal for the gas within the moving walls. Besides storing the gas, the tank's design serves to establish the pressure of the gas system. With telescoping (multiple lift) tanks, the innermost tank has a ~1ft wide by 2ft high lip around the outside of the bottom edge, called a cup, which picks up water as it rises above the reservoir water level. This immediately engages a downward lip on the inner rim of the next outer lift, called a grip, and as this grip sinks into the cup, it preserves the water seal as the inner tank continues to rise until the grip grounds on the cup, whereupon further injection of gas will start to raise that lift as well. Holders were built with as many as four lifts.

Europe

Gasholders are often a major part of the skylines of low-rise British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 cities, due to their large distinctive shape and central location. The pollution associated with gasworks

Gasworks

A gasworks or gas house is a factory for the manufacture of gas. The use of natural gas has made many redundant in the developed world, however they are often still used for storage.- Early gasworks :...

 and gas storage makes the land difficult to reclaim

Land reclamation

Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

 for other purposes, but some gasholders, notably in Vienna

Vienna

Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

, have been converted into other uses such as living space and a shopping mall

Shopping mall

A shopping mall, shopping centre, shopping arcade, shopping precinct or simply mall is one or more buildings forming a complex of shops representing merchandisers, with interconnecting walkways enabling visitors to easily walk from unit to unit, along with a parking area — a modern, indoor version...

 and historical archives for the city. Many sites however were never used for the production of 'town gas', therefore the land contamination is relatively low.

Most British cities will have several gasholders. London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, Birmingham

Birmingham

Birmingham is a city and metropolitan borough in the West Midlands of England. It is the most populous British city outside the capital London, with a population of 1,036,900 , and lies at the heart of the West Midlands conurbation, the second most populous urban area in the United Kingdom with a...

, Manchester

Manchester

Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...

, Sheffield

Sheffield

Sheffield is a city and metropolitan borough of South Yorkshire, England. Its name derives from the River Sheaf, which runs through the city. Historically a part of the West Riding of Yorkshire, and with some of its southern suburbs annexed from Derbyshire, the city has grown from its largely...

, Leeds

Leeds

Leeds is a city and metropolitan borough in West Yorkshire, England. In 2001 Leeds' main urban subdivision had a population of 443,247, while the entire city has a population of 798,800 , making it the 30th-most populous city in the European Union.Leeds is the cultural, financial and commercial...

, Newcastle

Newcastle upon Tyne

Newcastle upon Tyne is a city and metropolitan borough of Tyne and Wear, in North East England. Historically a part of Northumberland, it is situated on the north bank of the River Tyne...

 and Glasgow

Glasgow

Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

 (which has the largest gasometers

Provan Gas Works

Provan Gas Works is an industrial gas holding plant in the city of Glasgow, Scotland. The plant is in the Provanmill area of the city, and was built by Glasgow Corporation between 1900 and 1904...

 in the UK) are noted for having many gasholders. Some of these gasholders have become listed buildings.

A gasworks in South Lotts

South Lotts

South Lotts is a small area to the south of the river Liffey in Dublin 4, 1 km east of Dublin City Centre, Ireland. It was created following the embankment of the River Liffey in 1711 between the city and Ringsend, thereby reclaiming the North and South Lotts...

, Dublin, Ireland was converted into apartments.

In the past, holder stations would have an operator living on site controlling their movement. However with the process control

Process control

Process control is a statistics and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range...

 systems now used on these sites, such an operator is obsolete. The tallest gasometer in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 is 117 metres (383.9 ft) tall and is located in Oberhausen

Oberhausen

Oberhausen is a city on the river Emscher in the Ruhr Area, Germany, located between Duisburg and Essen . The city hosts the International Short Film Festival Oberhausen and its Gasometer Oberhausen is an anchor point of the European Route of Industrial Heritage. It is also well known for the...

.

United States

Gasometers are comparatively rare in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The most notable of these were erected in St. Louis

St. Louis, Missouri

St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...

 by the Laclede Gas Light Company in the early 20th century. These Gasometers remained in use until the early first decade of the 21st century when the last one was decommissioned and abandoned in place. The most recently used gasometer in the United States is on the southeast side of Indianapolis

Indianapolis

Indianapolis is the capital of the U.S. state of Indiana, and the county seat of Marion County, Indiana. As of the 2010 United States Census, the city's population is 839,489. It is by far Indiana's largest city and, as of the 2010 U.S...

 but it is to be demolished along with the Citizens Energy Group coke plant

Coker unit

A coker or coker unit is an oil refinery processing unit that converts the residual oil from the vacuum distillation column or the atmospheric distillation column into low molecular weight hydrocarbon gases, naphtha, light and heavy gas oils, and petroleum coke...

. Another pair of holders at the Newtown Holder Station, in Elmhurst, Queens, in New York City, was a popular landmark for traffic reporters until the holders were demolished in 1996.

Origin of the name

The term gasometer was originally coined by William Murdoch

William Murdoch

William Murdoch was a Scottish engineer and long-term inventor.Murdoch was employed by the firm of Boulton and Watt and worked for them in Cornwall, as a steam engine erector for ten years, spending most of the rest of his life in Birmingham, England.He was the inventor of the oscillating steam...

, the inventor of gas lighting

Gas lighting

Gas lighting is production of artificial light from combustion of a gaseous fuel, including hydrogen, methane, carbon monoxide, propane, butane, acetylene, ethylene, or natural gas. Before electricity became sufficiently widespread and economical to allow for general public use, gas was the most...

, in the early 19th century. Despite the objections of his associates that his so-called "gazometer" was not a meter

Measuring instrument

In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item...

 but a container, the name was retained and came into general use. The word is also used to describe a gas meter

Gas meter

A gas meter is used to measure the volume of fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly...

 (a meter for measuring the amount of gas flowing through a particular pipe). The term "gasometer" is discouraged for use in technical circles where the term "gasholder" is preferred.

Dry seal Wiggins type gasholder

A dry-seal gasholder can be designed to have a gross (geometric) volume ranging from 200 cubic metre, whilst having a working pressure range between 15 and 150 mbar (1.5 and 15 kPa). The dry-seal gasholder is finished with an anti-corrosive treatment to counteract local climatic conditions and also any chemical attack from the stored medium. This anti-corrosive treatment is fully compatible with the sealing membrane and also the environment.

Main elements

The dry seal gasholder has four major elements — the foundation; the main tank; the piston; the sealing membrane. Each of these elements can be divided into various sub-elements and associated accessories.

Foundation

A concrete and hardcore base designed to withstand the weight of the steel gasholder structure constructed upon it and to withstand dynamic climatic conditions acting upon the gasholder etc.

Main tank

The main tank is designed to accommodate the design requirements laid down by the customer and climatic conditions There are three main sub-elements to the tank:

Tank bottom

The tank bottom forms a gas tight seal against the foundation and is "coned up" to facilitate drainage to the periphery. The bottom is covered with steel plates. The outer annular plates are butt welded against backing strips, whilst the infill plates are lap welded on the top side only. Welded to the bottom infill plates is the:

Piston support structure

When the piston is depressurised it rests on a steel framework which is welded to the bottom plates.

Tank shell

The shell of the tank is designed to accommodate the imposed loads and the general data supplied by the client. The shell is of butt-welded design and is gas tight for approximately 40% of its lower vertical height (known as the gas space) at which point the seal angle is located. The remaining upper 60% (known as the air space) of the shell has in it various apertures for access and ventilation. Attached to the shell are various accessories:

Staircase tower

For external access to the roof of the gasholder and also incorporates access to the inside of the gasholder via the shell access doors. A locked safety gate is usually located at the base of the staircase to prevent any unauthorised access to the gasholder.

Shell access doors

Doors located at pertinent points allowing access into the gasholder from the external staircase tower.

Shell vents

Allow air to be displaced from the inside of the gasholder as the piston rises.

Inlet nozzle

The connection nozzle allowing the stored gas to enter the gasholder from the supply gas main.

Outlet nozzle

For the export of the stored gas, this nozzle comes complete with an anti-vacuum grid to protect the sealing membrane during depressurisation. Depending on the operational process the inlet and outlet nozzles maybe a shared connection.

Shell drains

Allow condensates within the gasholder gas space to drain away in seal pots. The seal pots are designed to maintain the pressure with the gasholder.

Shell manways

Used for maintenance access into the gas space – only used whilst the gasholder is out of service.

Earthing bosses

To ensure that the gasholder is safe during electrical storms etc.

Volume relief pipes

Essential fail-safe system to protect the gasholder from over-pressurisation. Once actuated, by the piston fender, the volume relief valves allow the stored gas to escape to atmosphere at a safe height above the gasholder roof. As the volume relief valves open they actuate a limit switch.

Volume relief limit switches

Used to send signals to the control room to confirm the status of the volume relief valves.

Level weight system

A mechanical counter balance system to ensure that the pistons moments are kept in equilibrium. The level weights, which run up and down tracks located on the gasholder shell, also actuate limit switches to signal when the gasholder volume has reached pre-defined settings.

Level weight limit switches

Used to send signals to the control room to operate import and export valves etc.

Contents scale

On the gasholder shell is a painted scale displaying the volume of gas stored within the gasholder. An arrow painted on an adjacent level weight indicates the current status. Also painted on the scale is the location of the piston in relation to the shell access doors.

Seal angle

Welded to the inside of the shell this angular section is where the sealing membrane attaches to the shell.

Tank roof

The roof is designed to withstand the local climatic conditions and the possibilities of additional loads, such as snow and dust. The roof of the gasholder is of thrust rafter radial construction and has a covering of single sided lap welded steel plates. The roof has various accessories attached including:

Centre vent

Allows air to enter and exit the gasholder as the storage volume changes.

Roof vents

Small nozzle around the periphery used for the installation of the seal.

Roof manways

Allows access down to the piston fender when the gasholder is full.

Circumferential handrailing

Safety handrailing around the outside of the roof.

Radial walkway

For access from the staircase to the centre vent etc.

Volume relief valve actuators

Mechanical arms that operate the volume relief valves once the piston fender reaches a certain level.

Level weight pulley structures

Steel structures mounting the level weight rope pulleys and rope separators.

Load cell nozzles

For maintenance access to the load cell instrumentation used for volume recording purposes.

Radar nozzles

For maintenance access to the radar instrumentation used for volume recording purposes and piston level readings.

Roof interior lighting nozzles

For maintenance access to the gasholders interior lights.

Piston

The gasholder piston moves up and down the inside of the shell as gas enters and exits the gasholder.
The weight of the piston (less the weight of the level weights) produces the pressure at which the gasholder will operate. The piston is designed to apply an equally distributed weight to ensure that the piston remains level at all times. The piston made up of the following sub-elements:

Piston deck

The outer annular area is formed from butt welded steel plates resting on steel section rest blocks. Lap welded steel infill plates form a dome profile to withstand the gas pressure in the gas space beneath it. For higher pressure gasholders the infill plates are lap welded on both sides, whereas, low pressure gasholders are only welded on the top side. The fully welded piston deck forms a gas tight surface, which rests on the piston support structure when the gasholder is depressurised. The following ancillary items can be found on the piston deck:

Piston manway

Used for maintenance access below the piston into the gas space – only used whilst the gasholder is out of service.

Load cell chain receptacle

A receptacle for gathering up the load cell chains as the piston rises.

Piston seal angle

Welded to the outer top side of the annular plates, this angular section is where the sealing membrane attaches to the piston.

Level weight rope anchors

Equally spaced around the periphery of the piston deck are the connections to which the level weight ropes are fixed.

Piston fender

The fender is a steel frame structure that is fixed to the piston deck annular plates and acts as a support structure for the abutment plates. Access can be gained to the top of the piston fender from either the shell access doors or roof manways depending on the gasholder volume. Attached to the piston fender are the following items:

Piston walkway

A platform around the top of the piston fender equipped with safety handrailing, used for inspection purposes.

Piston ladders

Rung ladders complete with safety loops for access to the piston deck from the piston walkway.

Radar reflector plates

Used to bounce the radar signal back to the radar instrument for volume indication recording and piston level readings.

Abutment plates

Fixed to the outside of the piston fender to form a circumferential surface for the sealing membrane to roll against whilst the piston moves during operation.

Piston torsion ring

Around the base of the piston fender is a torsion ring which helps keep the piston shape during pressurisation. Concrete ballast can be added to the torsion ring to increase the weight of the piston and subsequently be a cost effective way to increase the pressure of the gasholder to the required level.

Sealing membrane

The seal of the gasholder is designed to operate in the conditions specified by the client and to suit the stored medium. The seal rolls from the shell to the abutment surface of the piston and vice versa providing the piston with a frictionless self-centering facility. During depressurisation the seal also provides a gas tight facility that protects the holder from vacuum damage by blocking the gas outlet nozzle. During commissioning of the gasholder the sealing membrane is set into an operating condition. This setting must be carried out every time the gasholder is depressurised, otherwise known as "popping" the seal.

See also

• Gasometer Oberhausen
• Gasometer, Vienna
  Gasometer, Vienna
  The Gasometers in Vienna are four former gas tanks, each of 90,000 m³ storage capacity, built as part of the Vienna municipal gas works Gaswerk Simmering in 1896–1899. They are located in the 11th district, Simmering. They were used from 1899 to 1984 as gas storage tanks...
  
  
• Natural gas storage
  Natural gas storage
  Natural gas, like many other commodities, can be stored for an indefinite period of time in natural gas storage facilities for later consumption.- Usage :...
  
  
• Water tower
  Water tower
  A water tower or elevated water tower is a large elevated drinking water storage container constructed to hold a water supply at a height sufficient to pressurize a water distribution system....
  
  , similar utility storage structures
• Gasværket
  Gasværket
  Østre Gasværk Teater is a theatre in the Østerbro district of Copenhagen, Denmark, located in an abandoned gasometer of the former Øster Gasværk . The theatre is constructed within the masonry shell that used to house the gas holder proper...
  
  - a theatre in Copenhagen which was formerly a huge gas holder

External links

• Use of gasometers in Oil & Gas industry
• Condemned: The great gasometer from BBC News, January 28, 1999
• Gasometer Augsburg in Germany and a list of many Gasometers in Europe
• Gasometer Oberhausen, Germany
• Gasometer Vienna, Austria
• Gasometer Schlieren, Switzerland
• Gasworks, Dublin, Ireland
• The rise and fall of gasometers Extrageographic magazine
• Modern Low Pressure Dry Seal Type Gasholders
• Gasholders and their tanks