Flammable liquid stores

Flammable liquids are used extensively in industry and commerce and their storage is strictly controlled by local authority and national legislation.

Storage requirements are primarily based on the flammability of the substance, which for the purpose of this article, is defined as a substance that has a closed-cup flash point below 55ºC.  The flash point is the lowest temperature at which the application of a small flame causes the vapour above the liquid to ignite momentarily when it is heated or cooled under prescribed conditions in a closed container.

Classification of liquids

Flammable liquids are classified according to their flash points and these classifications determine the quantities of liquids which may be kept on any premises without providing a flammable liquid store as described in this document. There is some variance in the requirements of local authorities, particularly with regard to the classifications and it is recommended that these be checked with the local fire brigade to ensure compliance.

SABS 0400 – The Application of the National Building Regulations

The South African Bureau of Standards Code of Practice for the Petroleum Industry Part 1: The Handling, Storage and Distribution of Petroleum Products in Bulk Depots (SABS 089 Part 1- 1999), classifies flammable liquids as follows:

Class 1A : Liquids with a closed-cup flash point below 23ºC and a boiling point below 35°C
Class 1B : Liquids with a closed-cup flash point below 23ºC and a boiling point above 35ºC
Class 1C : Liquids with a closed-cup flash point at or above 23ºC but below 38ºC
Class 11 : Liquids with a closed-cup flash point at or above 38ºC but below 60, 5ºC
Class 111A : Liquids with a closed-cup flash point at or above 60, 5ºC but below 93ºC
Class 111B : Liquids with a closed-cup flash point at or above 93ºC

Construction of stores

The requirements listed below are general. It is imperative that the local authority fire brigade be consulted to ensure compliance with the regulations.

Positioning

The store should not be positioned where it will impede the escape of persons from any building, or endanger any building. The store may under certain circumstances be constructed of non-combustible material, which is not fire-resistant if it has no building nearer to it than 30m and it is surrounded by a bund (retaining) wall. The purpose of the bund is to ensure that burning flammable liquids are contained in the vicinity of the storage area.

Walls

These should be of brick, or other impervious material having similar stability characteristics. The material used should be capable of withstanding the effects of fire for 240 minutes in the case of a store attached to a building. In the case of free-standing stores and when permitted by the chief fire officer, the fire resistance rating of the walls may be reduced to 120 minutes.

Doors

The door to the store should be at least a Class B-rated door and frame assembly as defined by the SABS. Such a door achieves a minimum tested rating of 120 minutes stability, 60 minutes integrity and 60 minutes insulation.

In the case of attached stores, any door communicating with any other part of the building should be a Class D door. These doors achieve a minimum tested rating of 120 minutes for stability, integrity and insulation and will have been subjected to an impact test.

Doors should open outwards and be kept locked when the store is not in use. When the total floor area exceeds 10m2, two doors in opposite walls, should be provided. The additional door is intended as an escape door and should be accessible and securely closed with a device that permits easy and quick operation from the inside.

Windows

In the case of stores attached to other buildings, windows are only permitted on external walls. The windows should have metal frames and not be able to be opened. Glazing should be of wire-woven glass with panes not exceeding 450mm by 450mm.

Floor

The floor should be of concrete or a suitable impervious material and should be constructed in such a manner that the liquid kept in the store will be confined in the event of leakage. It could be recessed below the door threshold or incorporate a sill. The well so formed should have sufficient capacity to contain the maximum registered liquid capacity plus 10% thereof as a safety factor.

Ventilation

Ventilation should be provided to ensure that vapour accumulation is prevented. Where circumstances permit, natural cross-flow ventilation through terracotta airbricks, protected by non-corrodible wire gauze having a mesh not exceeding 600 micrometers, can be provided. The bricks are usually spaced 450mm apart on all free walls to provide ventilation openings at 0,15m2 per 5m2 of floor area.

Where natural ventilation is not practicable, or when the well is of greater depth than 300mm, mechanical ventilation through an exhaust fan providing 30 air changes per hour should be provided. The fan extraction point should be at threshold height and should discharge through vertical metal ducting terminating at least 1m above the roof or at least 3,65m above ground level.

The wall opposite the exhaust fan(s) should have a row of airbricks installed at threshold height and spaced 225mm apart.

Ducting external to the store, but in communication with other working areas, should be enclosed in 100mm brick or any other fire-resistant coating/plaster with an equivalent rating. Ducts should be as short as possible and not have sharp bends.
The exhaust fan(s) should be operated by means of a courtesy switch fitted to the door to ensure that ventilation is continuous while the door is open.

Lighting

If electric lighting is required, it should be of the flameproof type with wiring enclosed in seamless screwed metal conduit or of armoured cable design.

Switches, junction boxes, fuses and other electrical equipment should be outside the store.

Fire protection

At least one 9kg dry powder extinguisher should be provided. The extinguisher should be mounted on a bracket outside the store.

Notices

Suitable signage, in accordance with SABS 1186 indicating “No Smoking” and “No Open Flames”, needs to be provided.

General

• In local authority controlled areas, stores may be required to be registered with that authority. The registration certificate will normally state the class of liquid and maximum quantity of flammable liquid permitted to be kept therein. Plans of the store are usually required to be submitted and these should include a site plan, ground plan, wall elevation showing ventilation provisions and a section through the store showing the roof and floor well details.
• Combustible shelving, packaging or any other combustible material other than flammable liquids, are not permitted within the store.
• The store should not be used for any other purpose than for the storage of flammable liquids.
• People should not be permitted to work in the store unless the doors are fully open and kept unobstructed.

References:

Various municipal regulations relating to the storage, use and handling of flammable liquids and substances.

Published by
Fire Protection Association of Southern Africa
(Incorporated Association not for Gain)
(Reg.No. 73/00022/08)
P O Box 15467
Impala Park
1472

Flammable Liquid Stores.pdf

People in Risk