6.2.1 Approved storage containers shall not be buried underground/mounded unless written permission has first been granted by the relevant authority.
6.2.2 Container design pressure
The minimum design pressure of underground/mounded storage containers shall be 1 750 kPa (gauge).
6.2.3 Lifting lugs
All underground storage containers shall be provided with lifting lugs or other approved means for lowering the container into position without damage to the container or to the corrosion resistant coating provided in accordance with 6.2.4. Any damage shall be repaired in accordance with 6.2.4.
NOTE. Underground containers should have a liquid evacuation pipe running down into a shallow well (e.g. a short piece of 75 mm diameter pipe, blanked off) in the base of the container for cleaning out purposes.
6.2.4 Corrosion control
6.2.4.1 General
Each underground/mounded container shall be provided with a corrosion resistant coating and with cathodic protection.
6.2.4.2 Surface preparation
Before application of coating material, the external surfaces of the container shall be suitably prepared by grit blasting or chemical treatment.
For Public Comment
6.2.4.3 Coating material
The external surfaces of the container shall be covered with a corrosion-resistant coating which will provide an electrical insulator between the containers and earth. The coating material shall be strongly bonded to all external surfaces of the containers and shall be inert, non-absorbent to moisture, of high dielectric strength and of adequate mechanical strength to resist damage during handling of the container or from its burial in soil. The preparation of the surface and the handling and application of the material shall be in accordance with the codes approved by the relevant authority (see Annex A).
6.2.4.4 Testing of coating
After coating of the container is completed, the electrical resistance of the coating and its continuity shall be spark tested over the whole surface using a potential suitable for the characteristics of the particular coating, in accordance with the codes approved by the relevant authority (see Annex A). Any flaws detected in this test shall be repaired and retested. Any damage to the coating sustained during handling or installation of the container shall also be repaired and the repair spark tested as above, before burying the container.
6.2.4.5 Cathodic protection
Every underground/mounded container and associated underground/mounded pipe work shall have an adequately designed cathodic protection system.
This system may be of the sacrificial anode or impressed current type but in either case shall be provided with a point at which a test can be made to determine the efficacy of the system.
Tests shall be made every 6 months and records of such tests shall be kept and be available to the relevant authority.
Where there is cathodic protection common to the container and an underground/mounded pipeline as in 6.4.6.1, the insulated joint may be bonded across or omitted.
6.3 Container location and safety distances
6.3.1 General requirements
6.3.1.1 Underground/mounded storage containers shall not be placed inside building or in open pits.
6.3.1.2 Storage containers shall not be located beneath the bunded area of flammable or combustible liquid storages.
6.3.1.3 Storage containers shall not be installed one above the other. An underground container shall not be directly below any aboveground container.
6.3.1.4 An underground/mounded LPG container shall not be less than 3 m from an underground container containing flammable and combustible liquids.
For Public Comment
6.3.1.5 Underground containers shall be protected from aboveground loading due to vehicular traffic or other cause, either by fencing off the area under which the containers are buried, or by reinforced concrete slab or other adequate cover to prevent the weight imposing concentrated direct loads on the container shell. If the container area is not fenced off, the container manhole cover and the container fittings shall be protected against damage and tampering. The perimeter of the area under which containers are buried shall be permanently marked.
6.3.2 Safety distances
6.3.2.1 The safety distances refer to the horizontal distance in plan between the nearest point on the storage container and a specified feature (e.g. an adjacent storage container building, property boundary).
6.3.2.2 The number of underground/mounded storage containers in any one group shall not exceed six. Any container in one group shall be at least 7.5 m from the nearest storage container in another group.
6.3.2.3 Safety distances for underground/mounded storage containers in various locations shall comply with the requirements in 6.3.2.4 and 6.3.2.5.
6.3.2.4 Bulk storage at consumers' premises
This applies to commercial and industrial consumers' premises such as industrial plants and hotels where there is bulk storage of LPG. Location of underground/mounded storage containers in these premises shall comply with the minimum safety distances given in Figure 5. Location of vaporisers shall comply with 5.2.6.5c). Further requirements for vaporisers are given in 4.3.
6.3.2.5 Automotive LPG dispensing stations
Location of underground/mounded storage containers in automotive LPG dispensing stations shall comply with the minimum safety distances given in Figure 6. Further requirements for automotive LPG dispensing stations are given in Section 13.
6.3.2.6 Refineries and bulk plants
Location of underground/mounded storage containers in refineries and bulk plants shall comply with the minimum safety distance shown in Figure 7.
For Public Comment
Minimum safety distance (m)
Water capacity of individual container
(kl) A B C D G H
Up to 135 1.5 3 3 6 10 See 4.3.3.3 d)
NOTE. For location of indirect-fired vaporisers, see 5.2.6.5 c) and 4.3.1.3 e), f).
Figure 5. Location of underground/mounded containers for bulk storage at consumers’ premises
For Public Comment
Minimum safety distance (m)
Water capacity of individual container
(kl) A B C D J K L M
Up to 70 1.5 3 3 6 3 3 5 6
Figure 6. Location of underground/mounded containers for automotive LPG dispensing stations
For Public Comment
Minimum safety distance (m)
Water capacity of individual container
(kl) A B C D F R S T U
< 135 135 to 265
> 265
2.5 2.5 2.5
15 20 30
3 3 3
6 6 6
7.5 7.5
7.5 See Figure 8 See Figure 8 15 15 15
10 10 10
Figure 7. Location of underground/mounded containers in refineries and bulk plants