Working with fuel gasses such as propane by properly trained personnel, a dangerous situation could develop if it is used incorrectly. Fuel gasses should not be used unless the proper training is followed and safety devices are in place. Does propane need a flashback arrestor?
A flashback arrestor will contain a flashback and prevent the flashback from traveling up the hose and reaching the source of propane. If the flashback is not suppressed it can travel into the regulators and cause a dangerous situation or explosion.
Below we will take a closer look at flashback arrestors and their use on propane systems.
What is Flashback and What Makes it Dangerous?
Flashback is when the flame of a torch or cutting equipment burns rapidly up the hose of the torch. It is generally accompanied by a loud explosion.
If it is not stopped it can travel to the regulator and into the gas bottle supply. The flashback can be triggered by improper cylinder pressure, improper maintenance of the equipment, or operator error.
Flashback can become a dangerous situation and cause slight damage to your equipment up to a serious explosion that can cause the loss of life and major property damage.
It is impossible to control the severity of the damage which makes it necessary to reduce the chance of a flashback.
What is a Flashback Arrestor and How Does it Work?
The flash arrestor is designed to stop the flashback and prevent it from reaching the regulators or propane supply.
It consists of three major parts, the non-return valve, the Thermal Activated Cut-Off Valve, and the Sintered Flame Filter.
The non-return valve stops the reverse flow of the gas with a spring-loaded actuator that only allows the gas to flow in a single direction.
The middle of the flashback arrestor is hollowed out and filled with stainless steel. This design can extinguish any leak back in a few fractions of seconds by causing the flames to flow through a filter depleting its energy.
The thermal-activated cut-off valve is the last safety feature. In the event of continuous or repeated flashbacks, the flashback arrestor will overheat and melt the plastic seal contained in the flashback arrestor. Once the plastic seal is melted, a valve will close and shut off the supply of propane completely.
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Why is a Flashback Arrestor Important for Propane Systems?
The main reasons for flashbacks or backfires are faulty torches or the gas operating at the wrong pressure.
When a backfire occurs the flame will travel into the torch and cause a cracking sound to be heard. This will cause the flame to become extinguished or will reignite at the torch opening.
If the backfire continues it can reach the mixing point for the propane and produce a whistling sound.
The gas mixture in the hoses when combined with a backfire will cause a flashback. This will burn the mixture at a higher rate than the gas is flowing out.
When a flashback occurs the results can be dangerous. It can result in the burning and bursting of the gas hose, the pressure regulator catching on fire, or even the explosion of the propane cylinder.
Flash arrestors in the propane system will eliminate this dangerous occurrence and eliminate the risk of a fire or explosion in the propane fueling system.
It is recommended that two flashback arrestors are attached to the propane supply lines. One should be added after the pressure regulator, and the second should be added before the torch. These devices can suppress any backfire or flashback situation before they become dangerous.
Regulations and Codes for Flashback Arrestors in Propane
Section 19 of the Occupational Safety and Health Act 1984 states that all employers must provide a safe working environment for employees. Regulation 3.98(1) states that a flashback arrestor should be connected to the supply hose after the regulator. It further states that it is not required on gas cylinders that mix with atmospheric air.
Since most propane tanks are designed to mix with atmospheric air, they are not required to have a flashback arrestor installed. They are an added step of safety, but should not be used instead of proper safety practices and maintenance procedures.
Types of Flashback Arrestors Available for Propane Systems
There are two types of flashback arrestors available, wet and dry flashback arrestors. The wet flashback arrestors contain a liquid that keeps the reverse flow of the flashback from reaching the supply of gas. The main liquid used in these wet flashback arrestors is ethylene glycol. They are generally used for large industrial setups.
The dry flashback arrestors use sintered metal or a ceramic cartridge to stop the flashback. These are normally used in smaller portable applications.
They are much smaller and lighter than wet arrestors and can be easily replaced after they have been used.
Proper Installation and Maintenance of a Flashback Arrestor in a Propane System
Flashback regulators require regular inspection and must be tested at regular intervals not to exceed every six months.
They need to be checked for gas leaks and gas reverse flow. Repairs are only to be carried out by the manufacturer. The dust filter, however, can be cleaned and changed by the user.
Proper maintenance and training will prevent the most dangerous situations involving the usage of welding and propane gasses. The installation of flashback arrestors is an extra safety precaution designed to advertise a dangerous condition when a flashback does occur.
The flashback arrestor will prevent a fire in the propane regulator or even a possible explosion of the propane tank that could cause property damage or loss of life. It is recommended that two flashback regulators are installed in the supply line. One should be installed after the regulator and the other before the torch assembly.
The installation of flashback regulators is not required in propane systems that mix with the atmospheric air. They are recommended to prevent a serious incident or explosion should a flashback occur.