Safety Equipment Alert: Liquid Flashback Arrester vs. Dry Flashback Arrester

Flashback arresters are one of the most important safety and hazard prevention tools available. Flashback arresters are used in industries where explosive gases are transferred from one location to another. This safety device is essential in large industrial set-ups as well as during simple welding functions.

When gases are transferred via hoses, pipes, or cylinders, there could be a spark, leak, irregular pressure, or other circumstances that could cause conditions that lead to a fire. In such cases, the fire tends to move in a reverse direction (towards the source), and eventually can lead to an explosion. This is called a flashback. A flashback arrester is a device that allows flow to occur in one direction only. If there is a reverse flow, the arrester quenches the fire with a wet or dry barrier.

Liquid or hydraulic flashback arresters and dry flashback arresters are used in industries to disallow reverse flow and extinguish fire/ sparks. The gas type and process set-up will determine the use of wet or dry flashback arresters.

What are Flashback Arresters?

Flashback arresters are used in conjunction with several machines. They can be mounted on cylinders (most common application method), as well as on torches, oxy-fuel cutting machines, and other gas delivery apparatus. Most flashback arresters are equipped with several safety features like check valves, which don’t allow reverse flow to occur. Another safety feature is a flame arrester, which acts as a shield, and doesn’t allow the flame to reach the gas supply unit. Flashback arresters also feature pressure relief and temperature cut-off valves. These components will be discussed in detail later in the blog.

Flashback arresters should also be leak tested to ensure that they are not defective, and function without any problems. All these safety features provide optimal protection when handling flammable gases, or gases that could mix with air and pose a threat.

Main Types of Flashback Arresters

Two main types of flashback arresters are available in the market:

1. Wet (Hydraulic or Liquid) Flashback Arresters

These flashback arresters use a liquid to extinguish the fire, and keep the reverse flow from reaching the source. They effectively prevent flames from travelling in the pipe or hose. The liquid should be non-flammable and non-absorbing. Generally, ethylene glycol is the liquid used in wet flashback arresters. The gas is bubbled through the liquid, which helps in dousing the fire.

          Application Examples of Wet Flashback Arresters

Wet or liquid flashback arresters come in various sizes and should be sized to the required flow of the application. . These flashback arresters are especially useful in large industrial set-ups and have a long life span.  

2. Dry Flashback Arresters

Dry flashback arresters use dry products like sintered metal or ceramic cartridges to impede the flow of the fire. The sintered material should be porous and powdered. This makes for an effective barrier and diffuser, providing resistance to the flame. A variety of materials like bronze wool, sand, and others can be used for the sintered material. In professional set-ups, sintered metal is the material of choice.

        Application Examples of Dry Flashback Arresters

Dry flashback arresters are used in small portable applications like welding or oxy-fuel cutting. These arresters are smaller and lighter compared to liquid flashback arresters and are typically thrown away after a flash or have a cartridge replacement.

 Variants of Flashback Arresters

The different flashback arresters are available in two variants:

1. External Flashback Arresters

These flashback arresters are fit externally on top on the gas supply unit. These instruments are easier to repair and replace since they are placed on the outside of the machinery. External flashback arresters can feature larger components as well. This makes the arrester long-lasting.

2. Internal Flashback Arresters

As the name suggests, these flashback arresters are fitted inside the machine onto the main gas supply unit.

Flashback Arrester Safety Features

Flashback arresters can be equipped with the following features for safer functioning:

       1. Temperature Cut-off Valve

Many flashback arresters are also equipped with a heat sensitive valve that shuts off the gas flow once the internal temperature of the equipment crosses a pre-defined mark.

      2. Pressure Relief Valve

Dry or wet flashback arresters could face the problem of pressure build up within the internal mechanism of the gas-regulating unit. The pressure could cause serious damage to life and property if not released. Hence, a pressure relief valve is of immense importance in a flashback arrester unit. Most arresters will be equipped with pressure relief valves. Most flashback arresters will feature an integrated pressure relief valve. This is a safety feature within a flashback arrester that must not be overlooked.

Factors to Consider When Purchasing Flashback Arresters

Depending on the equipment, you will need to consider the type of flashback arrester to be used:

1. You will need to consider the type of gas being used.
2. The industrial set-up and the risk of exposure to other materials.
3. You need to consider the equipment specifications like the material of the equipment, the size, and function.
4. The flow capacity of the gas in the main unit should be taken into consideration when choosing the flashback arresters.

Importance of Flashback Arresters

Reverse gas flow is generally caused by human error, faulty equipment, incorrect gas pressures, and other such problems. Flashback arresters are means of safeguarding lives and equipment against gas explosions. The importance of flashback arresters in equipment utilizing explosive gases cannot be overstated.

It is also important for every user to note that personal safety is entirely dependent on one’s ability to follow manufacturer instructions. It is important that as a user, you follow safety protocol when using any equipment. Although, utilization of safety equipment is needed, following safety principles is vital.