What is a flashback arrestor?
When using oxy-fuel gas equipment, if insufficient gas is being fed through to the flame, it will seek more fuel by burning back into the nozzle, which means that the burning velocity of the flame is higher than the exit velocity of the gas.
If a large amount of energy is generated when this occurs, then the flame (and a subsequent pressure wave) can travel back up the hose(s) towards the gas cylinders.
A flashback arrestor is a device which stops the flame from travelling into the regulator and the cylinder.
Do I have to fit flashback arrestors if I’m using oxy-fuel gas equipment?
Yes.
When acetylene is the fuel gas, a flame arrestor, a non-return valve and a quick-acting shut-off device is mandatory in compliance with the Acetylene Safety (England and Wales and Scotland) Regulations.
For all other applications which use fuel gases with compressed oxygen (including compressed air), BCGA CP7 states that a flashback arrestor (commonly known as a composite safety device) shall (must) be fitted to prevent a flashback, therefore protecting the gas source from a potential ignition.
If I’m only using a single cylinder of propane, do I need to fit a flashback arrestor?
Your risk assessment will identify the hazards when using propane for your application, as well as the control measures required to reduce the level of risk.
Some flashback arrestors are thermally activated, so if they are involved in a fire situation, they will trip and stop the flow of gas from the cylinder.
So, it’s probably a good idea to fit one.
I’ve seen some flashback arrestors that are large and ‘chunky’ and others which are narrow and slim...what’s the difference between them?
As a rule of thumb, the larger flashback arrestors are resettable.
This means that when the unit activates, a lever or a ‘button’ either pops up or pops out to indicate that a flashback has occurred and that the gas supply has stopped.
After the operator has shut the system down, inspected the equipment for damage, and replaced any damaged items, the lever or button can be reset and the unit (if not damaged) can be reused.
Some slim flashback arrestors will only activate once to stop a flashback and then must be replaced, whilst others contain an internal reset device which activates when the unit has stopped a flashback and then subsequently cools down.
Please check with your supplier as to whether your unit(s) are resettable.
Does my flashback arrestor need to be labelled with any specific information?
Yes, your flashback arrestor should be labelled with the following information:
- Gas name(s)…some fuel gas arrestors are designed to be used with multiple flammable gases;
- Maximum inlet pressure;
- An arrow indicating the direction of flow;
- The name or trademark of the manufacturer and/or distributor;
- A date mark showing either the date of manufacture or a date when the arrestor is to be replaced or refurbished.
What’s the lifespan of a flashback arrestor?
Most gas components, such as flashback arrestors, are given a service life.
Most manufacturers stamp their arrestors with either an expiry date or a code which relates to an expiry date. Most manufacturers state that the life of their arrestors is five years from the date of manufacture.
BCGA CP47 states that where no date is able to be determined, then typically the life of the component (arrestor) should be limited to 5 years from the date of purchase from the supplier.
How often do I need to inspect my arrestor?
Flashback arrestors should receive a visual inspection each time prior to use.
If any damage or contamination is found, then the unit must not be used and should be replaced immediately.
Arrestors should receive a full inspection, which includes functional tests, at least annually, or more frequently if identified in your risk assessment.
This inspection should be undertaken by a competent person, and written records should be kept.
