How to manage gas cylinder safety

Gas cylinder safety requires management of exposure to heat, impacts, and other risks. Since they are semi-portable, handling raises many risks.

How to move gas cylinders safely
[] Valve closed, as when not in use.
[] Regulators removed. These may remain in place on a cylinder truck. Regulators may break off if bumped hard or handled hard.
[] Valve cover in place and secure. Never use this cover to lift the cylinder.
[] Move cylinders by a firm grip, with clean hands, slightly tilting and rolling them on the bottom edges. Do not drop or strike other cylinders or objects.
[] Never use choker slings or magnets to hoist cylinders.
[] Hoist cylinders by a cradle or pallet, after securing.
[] Study the properties and Material Safety Data Sheets for the type of gas, either oxy-acetylene, or various LPG mixtures.
[] See the relevant SANS standards (an extract appears below), assess site risks, and include relevant measures in site procedures and training.

How to protect gas cylinders against heat exposure

If gas cylinders, also named ‘gas bottles’, are close to welding or cutting operations, place a fire resistant shield between the cylinders and the work to keep sparks, hot slag or flames away.

To keep standing cylinders from being knocked over, chain or tie them to a column or to something secure. This applies also to empty cylinders. Even an empty cylinder can cause a lot of damage or injury.

Take the same precautions when handling empty cylinders that you would with full ones. A cylinder you may think is empty could be full.

Inspect cylinders regularly, and after every movement or attachment, to ensure that the equipment matches, that the cylinders are not damaged, and that exposure to sources of heat or energy, such as impacts, toppling over, or electrical installations, are not introduced by the new position.

When using different types of gas, separate the types. If handled or stored incorrectly, a cylinder could go off like a rocket, with lethal force in both directions, since the back-blast is highly energetic.

Gas explosion incidents

Two men have sustained serious injuries after a gas cylinder exploded at a restaurant in New Germany two years ago.

Paramedics found the two occupants outside of the building and injured by burns to their backs, arms, chest and face.

Burns shields were placed on the patients and Advanced Life Support intervention was performed on the patients to help with the pain. They were transported to hospital for further medical care.

It is believed that the two men were changing the cylinder when the explosion occurred. The relevant authorities were on the scene to investigate the incident.

A man died and another was seriously injured after an explosion at a scrapyard in Mosselbay three years ago. Two men were cutting a cylinder when an unknown gas ignited causing an explosion.

The two men working on the cylinder were thrown off of their feet. ER24 paramedics said one man had sustained severe injuries in the form of facial trauma and an amputated leg. He was declared dead while being transported to the hospital.

The second man had sustained severe injury to his leg and was treated on the scene before being transported to hospital.

Three other workers who witnessed the explosion received on-scene treatment for psychological shock, before being transported to a medical facility.

SANS 10087-7 extract

Some extracts from the SA standard for the handling, storage, distribution and maintenance of liquefied petroleum gas in domestic, commercial and industrial installations, are posted below.

Reference to “relevant national legislation” means the Occupational Health and Safety Act, Mine Health and Safety Act, and Electronic Machinery in Hazardous Locations Regulation.

Relevant standards are;
EN 671-1, Fixed fire fighting systems – Hose systems – Part 1: Hose reels with semi-rigid hose.
SANS 543, Fire hose reels (with semi-rigid hose).
SANS 1186-1, Symbolic safety signs – Part 1: Standard signs and general requirements.
SANS 1825, Gas cylinder test stations – General requirements for periodic inspection and testing of portable and transportable refillable gas pressure receptacles.
SANS 1910, Portable refillable fire extinguishers.
SANS 10019, Transportable containers for compressed, dissolved and liquefied gases – Basic design, manufacture, use and maintenance.
SANS 10086-1, The installation, inspection and maintenance of equipment used in explosive atmospheres – Part 1: Installations including surface installations on mines.

LPG properties

Leakage, especially of liquid, will release large volumes of highly flammable gas. LPG vapours become flammable when mixed with air. Gas-air mixtures that contain approximately 1.5 % to 10 % of LPG are flammable.

If a large enough volume of gas is so dispersed in the atmosphere as to reach flammable proportions throughout, ignition of the mixture will result in a rate of combustion of near-explosive intensity, and an explosion will occur when such gas-air mixtures are ignited while contained in a confined space.

LPG is heavier than air and will flow along the ground or through drains. It can be ignited at a considerable distance from the source of leakage, therefore low-level ventilation shall be provided.

LPG is non-toxic, but since it can induce headaches and dizziness when inhaled, inhalation of
LPG should be avoided whenever possible.

LPG, by its rapid vaporization and consequent lowering of the temperature, can cause severe cold burns when it comes into contact with the skin. Appropriate protective clothing, such as gloves, goggles, aprons and boots etc., shall be worn when there is any possibility of contact with the skin.

A container that has held LPG and has been “emptied” is still considered dangerous. In this state, the internal pressure is approximately atmospheric and, if the valve leaks or is left open, air can diffuse into the container and form a flammable or explosive mixture.

Even an “empty” container that does not yield gas when the valve is opened, might in fact not be quite empty. In cold weather, the heavier fractions of the liquid might not vaporize and will therefore remain in the container. Therefore a container that is empty or appears to be empty shall be handled with the same care as a full container.

Cylinder inspection by LPG suppliers

Before any container is filled, the supplier should inspect it to ensure that the following markings are clearly visible and legible:
a) in permanent stamping (stamped on the foot ring or, when relevant, the valve guard or shroud):
1) letters “LPG “;
2) tare mass (TM), in kilograms;
3) applicable standard approved for use in South Africa (for example, SANS 4706);
4) year of manufacture;
5) test pressure, in kilopascals;
6) water capacity, in litres; and
7) normalisation symbol (N);
b) in printed markings (applied by permanent labelling on all privately owned containers, i.e. containers of capacity 9 kg and less):
1) a warning that the container shall not be placed on stoves or hot plates and shall be used in the upright position; and
2) the maximum mass of gas, in kilograms, that the container is allowed to contain.

The following are regarded as defects:
a) corrosion or pitting;
b) illegible stamping;
c) a container that was manufactured before 1969 without the normalization symbol;
d) fire damage;
e) cutting/gouging;
f) defective fittings;
g) unacceptable modifications;
h) bulging/denting;
i) de-lamination
j) presence of arc/torch burns.
Ensure that container foot rings are in a serviceable condition.

Operation of gas cylinder valves

Check each valve in the following way to ensure that it is still in good operating condition:
a) operate the valve to ensure that it is not too tight to operate, and that it is undamaged and operable;
b) valve outlet threads are clean and undamaged;
c) valve or the valve boss is not tilted;
d) no cracks or flaws in the container neck; and
e) safety-relief valve, if fitted, is free of damage, corrosion, plugging or any other condition that might impair its operation.
Replace any faulty component or return the container to its owner with appropriate advice.

How to respond to a gas cylinder leak

If a leak is detected, immediately empty the container by transferring the liquid contents to another container and by venting any remaining LPG into the atmosphere.

Ensure that a competent person is present, and responsible for the entire venting procedure. This person shall ensure that no source of ignition is brought into the area and that the speed of venting is controlled.

Take wind direction into consideration and carry out the venting procedure in such a way that any prevailing wind will tend to dissipate the escaping gas away from any possible source of ignition.

Keep water (supplied by means of a fire hose reel) or a dry chemical powder fire extinguisher (of capacity at least 9 kg) at hand during the venting procedure.

Open the container valve and allow the gas to escape slowly and to disperse into the air without causing a hazardous concentration of gas. Keep the container in a vertical position. Avoid inhaling the gas. When the container is empty, close the valve securely and return it to its owner.

Handling of LPG containers

Containers shall not be dropped (for example, from lorry tailboards), dragged or rolled on their sides or allowed to skid. Containers that are too large to be carried shall be tilted and rolled on the rims of their foot rings. Containers that cannot be handled by hand, shall be transported by hand trolley.

Filled containers shall always be handled, transported, used and stored in a secured, upright position except for containers that are designed to be handled, transported, used and stored in the horizontal position.

Containers that are empty (or appear to be empty) shall be handled with the same care as a full container, and the distributing plant operator shall ensure that the valves of all empty containers received for filling are closed properly.

Storage of LPG containers

The storage area shall;
a) be approved and be as shown in figures 3 to 11 (see the standard document);

b) not be located inside a building, but in an open, well-ventilated area, and shall be used exclusively for the storage of LPG containers,

c) be so located as to eliminate, as far as possible, exposure of the containers to any excessive rise in temperature, corrosive substances or vapours, other highly flammable substances, physical damage and tampering by unauthorized persons,

d) be kept clean and free from any accumulation of combustible matter, such as paper. Any possible source of ignition shall not be allowed in a storage area. An area of at least 3 m in all directions round the perimeter of the storage area shall be kept clear of grass, weeds and other combustible matter, including any electrical source of ignition that does not comply with the requirements of zone 2 equipment, and

e) be provided with fire-fighting protection as given in table 1, and where this cannot be achieved, a rational design as given in SANS 10400 shall be applied.

Purposely designed containers/structures shall be acceptable, provided that the requirements of 5.2 are complied with.

Potentially dangerous activities, such as the use of open flames, welding and cutting operations, the use of electric grinding tools, and smoking, shall be prohibited in the storage area, and symbolic safety signs shall be permanently displayed.

Note that the above includes extracts from a standard, and not a complete standard. Note that some of properties, risks and measures relevant to LPG and ocy-acetylene systems differ.

• Sources; Buildsafe SA. ER24. SABS.

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