Hazards Associated With Dispensing Small Quantities of Flammable Materials
Many companies receive flammable liquids in metal drums or IBCs, and then fill smaller containers from them. While there are different types of small containers that can be used, the use of safety cans is recommended for safer handling of flammable liquids.
Using unsuitable containers such as open cans, buckets or pails is a dangerous practice as the escape of flammable vapours cannot be prevented. In general, the use of glass containers is not advised as these are easily breakable and will increase the chance of a serious spill.
The use of non-reusable glass or plastic containers is acceptable only in special cases where the required liquid purity (e.g., analytical reagent grade or higher) is affected by storage within a metal container, or if the liquid causes excessive corrosion of the metal container.
Metal Drum
Fully-filled metal drums can be very heavy and trying to move one by hand can be difficult, dangerous and bad for your back. Always use a mechanical aid (e.g., a specially designed drum cradle or trolley) for moving individual drums around. Note that drums used for storage of flammable liquids will require venting to relieve pressure build-up (e.g., due to exposure to heat) and prevent the creation of a vacuum (e.g., when liquid is being dispensed). As either pressure or vacuum can cause failure of the metal drum, the use of metal drums with automatic pressure- and vacuum-relief is essential.
Each drum vent should also be fitted with a flame arrester for protection against flashback from external ignition sources.
Dispensing from Metal Drum to Safety Can
A flammable liquid transfer pump with antistatic flexible hose may be used to facilitate safe transfer from a metal drum to a safety can. As static build-up can occur during the transfer of flammable materials from one metal container to another, bonding and grounding (earthing) is necessary before transferring to prevent the generation of electrostatic sparks and possible vapour ignition. The use of antistatic flexible cables/ wires and spring-loaded clamps may be used to achieve an effective onsite bonding and grounding solution.
Bonding both containers and grounding one of them basically “drains off” static charges and prevents the discharge of sparks. All grounding and bonding connections must be from bare metal to bare metal. It is therefore critical that all dirt, paint, rust or corrosion is removed from every electrical contact point.
Safety Can
Portable safety cans are recommended for carrying, storing and dispensing small quantities of flammable liquids. They are available in different shapes and in capacities ranging from 0.5 to 25 litres. Safety cans are usually made of metal or very low conductivity plastic.
The special feature of safety cans is that they have spring-loaded self-closing spout caps. These caps automatically open when the vapour pressure builds up inside, allowing vapours to escape and preventing rupture of the can (e.g., when exposed to fire).
The cap-operating mechanism of a safety can also cause the spout cap to automatically close once pouring is complete, or if the can is dropped. This instant cut-off capability allows onehanded control for safer dispensing without spills. Flexible metal safety hoses can be threaded into the spout cap of the safety can for added control.
Safety cans also typically house a wire mesh flame arrester screen inside its cap spout. These serve to prevent a flashback (from an external ignition source) from reaching the flammable liquid inside the cans.
Note that while this is a safety feature, it could create a hazard under some conditions. Do not store a safety can in a warm, enclosed space (such as in a vehicle) as vapours venting from a safety can may accumulate to within the flammable range and all it would take is a spark to cause a fire. For transporting small amounts of flammable liquid, use a pressure-resistant and non-venting container instead of a safety can.
Never use any safety can that is damaged. If repairs using approved replacement parts cannot restore the damaged can to a safe condition, it should be discarded once it has been properly cleaned.
Health Considerations
As flammable materials may also be toxic (i.e., harmful to human health), it is important to also take the necessary precautionary measures to minimise exposure and protect one’s health when working with a flammable material.
Check out Workplace Safety and Health (WSH) Guidelines on flammable materials which provide practical guidance on risk control measures that can be implemented to ensure the safety and health of workers who work with flammable materials daily. This Guidelines covers all industry sectors where flammable materials are used in smaller quantities.
