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The LPG System

The Supply of LPG to Consumers

Unlike natural gas, which is piped to the consumer, LPG is transported by road or rail and is stored in the liquid phase at ambient temperature and is carried in specially designed pressure vessels.

The distribution chain for LPG starts from primary storage at oil refineries or shore terminals. Supplies are transported by road tanker or, in some cases, by railcars, to secondary or intermediate distribution depots at strategic locations around the UK.

Intermediate LPG storage depots usually consist of one or more horizontal pressure storage vessels, either above ground, or buried below ground level, or "mounded" for environmental reasons. Buried or mounded vessels are a storage method now being used for small domestic storage.

Intermediate storage depots usually have road tanker loading facilities for deliveries to consumers, and often a cylinder filling plant from which LPG dealers and stockists are supplied.

Propane/Butane

It is normal practice in the UK to use LPG propane gas, supplied and stored in liquid form to serve fixed dwellings, where the use of gas is preferred and the natural gas network is not available. LPG butane is often restricted to individual appliances such as mobile cabinet heaters and barbecues. The installation requirements differ very little for LPG in the home to those of domestic natural gas and, as such, LPG is a practical alternative.

The supply of LPG to the home for central heating normally consists of a bulk storage vessel positioned or buried in a suitable position connected by service pipework to the internal gas installation. The installation of bulk storage vessels on site can be made almost invisible given the different methods of vessel positioning and buried pipework completes a hidden supply.

In the case of a single cooker, or other small usage situations, the supply of LPG may be from an individual cylinder or a number of cylinders coupled by an automatic changeover device - for continuation of supply. The storage vessel/cylinders will require filling / replacing. Consumers using LPG are aware of little differences to natural gas usage.

The Storage and Use of LPG

The storage of LPG, in both bulk storage vessels and cylinders, is covered by Codes of Practice published by UKLPG.

Most bulk LPG installations use storage vessels that are the property of the LPG supply company, who also ensure that they are installed and subsequently maintained in accordance with the regulations.

Special legal considerations apply when the total storage reaches 25 tonnes and 50 tonnes but these are not typically used for domestic applications. These include notification to, and consultation with, the Health and Safety Executive to ensure that the activity is not only operated in a safe manner, but is located in an area where it will not cause problems to the adjoining premises or other activities in the vicinity.

LPG Controls

Because of high storage pressures (6.9 bar at 15°C), certain safety controls are required with LPG bulk storage vessels and will be fitted directly to the storage vessel or certain components may be fitted at the supply entry to the dwelling.

Controls consist of a pressure relief valve, service valve, a 1st stage pressure regulator, under pressure shut off/over pressure shut off (UPSO/OPSO) valve, 2nd stage regulator and an ECV.

In most cases, the only control on view will be the ECV.

Gas Emergency Control

A suitably labelled gas emergency control valve (ECV) is required adjacent to where the gas supply enters the property. With LPG, the ECV is often located outside the property in a specially designed compartment that may also contain the gas meter and / or regulator.

For a cylinder installation, where two or more cylinders are connected together through an automatic changeover valve (ACV), the ECV will be positioned at a point downstream of the ACV.

For a single cylinder installation, the outlet valve of the cylinder also acts as an ECV.

LPG Emergency Service Providers (ESPs)

LPG Emergency Service Providers (ESPs) appointed by the individual gas supplier, attend reported escapes of gas or "fumes". Their prime duty is to make pipeline systems and gas installations safe. Their telephone number can usually be found on the bulk storage vessel or cylinder. If no such details exist, information can be found under GAS in the local telephone directory. Consumers may be required to seek remedial work from a Gas Safe Registered operative who has skills appropriate to the installation involved.

LPG Pipework

Properties, materials and pressure testing of LPG require specific normative documents to be followed. These include BS 5482-1 downstream of the ECV, COP22 and for larger installations.

Buried pipework should be protected and will require specific depth and cover dependant upon circumstances.

Pipe sizing should be calculated for a maximum 2.5 mbar pressure drop across the system from the outlet of the final regulator to each appliance.

 

 

 

 

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