4.11 Liquefied petroleum gas storage
This guidance deals with non-domestic supply installations where liquefied petroleum gas (LPG) is stored under pressure at ambient temperatures in fixed vessels larger than 75 kg LPG capacity.
Guidance is also given on the storage of LPG within grouped cylinders, when connected to a supply installation.
The intention of the guidance to this standard is to minimise both the risk of fire spreading to the tank and of the contents of the tank forming explosive gas pockets in the vicinity of any LPG storage container.
All persons concerned with the storage and use of LPG should be aware of the following characteristics and potential hazards:
the two forms of liquefied petroleum gases that are generally available in the UK are commercial butane and commercial propane
LPG is stored as a liquid under pressure. It is colourless and its weight as a liquid is approximately half that of the equivalent volume of water
LPG vapour is denser than air, commercial butane being about twice as heavy as air. Therefore the vapour may flow along the ground and into drains, sinking to the lowest level of the surroundings and may therefore be ignited at a considerable distance from the source of the leakage. In still air, vapour will disperse slowly
when mixed with air, LPG can form a flammable mixture
leakage of small quantities of the liquefied gas can give rise to large volumes of vapour/air mixture and thus cause considerable hazard
owing to its rapid vaporisation and consequent lowering of temperature, LPG, particularly in liquid form, can cause severe frost burns if brought into contact with the skin
a container that has held LPG and is ‘empty’ may still contain LPG in vapour form and is thus potentially dangerous.
The type, size and location of an LPG storage installation will determine the factors that should be addressed in the construction of the facility, to comply with health and safety requirements.
The UKLPG produces and maintains Codes of Practice which give guidance on achieving levels of risk appropriate to compliance with health and safety legislation for the design, construction and operation of LPG installations. These Codes have been produced in consultation with the Health and Safety Executive (HSE). http://www.hse.gov.uk/
The operation of properties where LPG is stored or is in use are subject to legislation enforced by both the HSE and by the Local Authority.
A liquefied petroleum gas storage tank, together with any associated pipework connecting the system to a combustion appliance providing space or water heating, or cooking facilities, should be designed, constructed and installed in accordance with the requirements set out in the UKLPG Code of Practice 1: 'Bulk LPG Storage at Fixed Installations'.
Above-ground tanks should be in accordance with Part 1 – ‘Design, Installation and Operation of Vessels Located Above Ground’, as amended.
Below-ground tanks should be in accordance with Part 4 – ‘Buried/Mounded LPG Storage Vessels’, as amended.
For propane installations, above or below-ground, of not more than 2 tonnes (4500 litres) overall capacity, reference may be made to the simplified guidance given in the UKLPG Code of Practice 1: ‘Bulk LPG Storage at Fixed Installations’: Part 2 – ‘Small Bulk Propane Installations for Domestic and Similar Purposes’, as amended.
Guidance given in this clause is relevant for all tanks, though specific criteria are noted for tanks below 4 tonnes (9000 litres) LPG capacity. LPG storage tanks in excess of 4 tonnes LPG capacity are uncommon in domestic applications. Guidance for larger installations is contained within the relevant Part of the Code of Practice.
Every tank should be separated from a building, boundary, or fixed source of ignition, to:
in the event of fire, reduce the risk of fire spreading to the tank and
enable safe dispersal in the event of venting or leaks.
Tanks should be situated outdoors, in a position that will not allow accumulation of vapour at ground level. Ground features such as open drains, manholes, gullies and cellar hatches, within the separation distances given in column (A) of the table below should be sealed or trapped to prevent the passage of LPG vapour.
Tanks should be separated from buildings, boundaries or fixed sources of ignition in accordance with the following table:
Table 4.9. Separation distances for liquefied petroleum gas storage tanks
|Maximum capacity (in tonnes)||Minimum separation distance for above ground tanks (in metres)|
|of any single tank||of any group of tanks||From a building, boundary or fixed source of ignition to the tank||between tanks|
|A - no fire wall ||B - with fire wall |
Fire wall means a wall or screen meeting the guidance for an external wall with a fire resistance of short duration (Section 2, Fire) within 1m of the boundary, and located between 1m and 1.5m from the tank and extending:
longitudinally: so that the distance specified above without the fire wall is maintained when measured around the ends of the fire wall, and
vertically: 2m or the height to the top of the pressure relief valve, whichever is greater.
For vessels up to 1.1 tonnes capacity, the fire wall need be no higher than the top of the pressure relief valve and may form part of the site boundary. For vessels up to 1.1 tonnes capacity located closer to a building than the separation distance in column (A) of the above table, the fire wall should form part of the wall of the building in accordance with the diagram below. Where part of the building is used for residential accommodation (or as a dwelling), such a fire wall should meet the guidance for an external wall with a fire resistance of medium duration (Section 2, Fire).
Where a group of tanks are sited together, the number of tanks in a group should not exceed 6 and the total storage capacity of the group should not be more than that given for any group of tanks in the table above.
Figure 4.13. Separation or shielding of a LPG tank from a building, boundary or fixed source of ignition
Motor vehicles under the control of a site occupier should be parked at least 6m from LPG tanks or the separation distance in column (A) of the table to this clause, whichever is the smaller. This does not apply to the loading/unloading of vehicles. Motor vehicles not under site control (e.g. those belonging to members of the public) should be parked no closer than the separation distance in column (A) of the table to this clause.
Where an LPG storage installation consists of a set of cylinders, the installation should be in accordance with the UKLPG Code of Practice 24: 'Use of LPG cylinders': Part 1 - 'The Use of Propane in Cylinders at Residential Premises'.
Use of cylinders in a domestic installation commonly takes the form of 2 sets of paired cylinders connected to a manifold, with supply provided from one pair of cylinders at any one time. This allows continuous supply to be maintained when changing empty cylinders.
Any installation should enable cylinders to stand upright, secured by straps or chains against a wall outside the building.
Cylinders should be positioned on a firm, level base such as concrete at least 50mm thick or paving slabs bedded on mortar, and located in a well-ventilated position at ground level, so that the cylinder valves will be:
Cylinders should be readily accessible, reasonably protected from physical damage and located where they do not obstruct escape routes from the building.