A flashback retainer or flash holder is the most commonly used gas security device in oxy-fuel welding and cutting to stop flame or backflow of gas back into equipment or supply lines. It protects users and equipment from damage or explosion. This device is mainly used in industrial processes where oxy-fuel gas mixtures are handled and used. The flashback retainer as a security product is essential to secure the workplace and work environment. In the past wet flashback arrestor was also used. Currently the industry standard is to use a dry flashback antidote with at least two security elements.
Video Flashback arrestor
Dry type
Dry flashback arrestors typically use a combination of security elements to stop flashbacks or gas backflow. This type is usually found in cutting and welding applications worldwide. They work equally effectively in all orientations, and require very little maintenance. In many countries or territories they shall be installed in a gas regulator or gas outlet/tapping point. Depending on the application they are also often used on the torch side as an additional security device.
Flashback holder helps prevent:
- Further gas flow in terms of shock pressure.
- Entrance of air or oxygen to a single distribution or cylinder.
- Flashback which is a quick propagation from flame to hose.
- Further gas flow in case of burnback.
According to EN 730-1/ISO 5175 norm they include at least two security elements:
The non-turning gas valve (NV), which:
- prevent harmful gas mixtures.
- ensuring the gas only flows in the intended direction.
and flame arrestor (FA), which:
- cools the fire down the ignition temperature of the gas or gas mixture.
- prevent flashback.
In addition to these two basic safety functions, flashback retention can also have:
Thermal cut-off valve (TV), which:
- prevent excessive temperatures.
- automatically shuts down at a certain temperature and cuts off the gas flow long before the ignition temperature of the gas mixture is reached.
and a pressure-pressure cut-off valve (PV), which stops the gas flow in case of pressure shocks
The flashback arrester is suitable for most technical gases (fuel gas) such as acetylene, hydrogen, methane, propane, propylene and butane and oxygen and compressed air.
Flashback holds should be tested for non-return gas, for gas tightness and flow by a qualified person depending on country-specific regulations.
Maps Flashback arrestor
Wet type
The seal fire barrier is a liquid barrier following the siphon principle in which the liquid stops entering deflagration and/or detonation and extinguishes the flame, they work by inflating the gas through a non-flammable liquid and ideally not absorbing the gas, which is usually water. They stop the flame by preventing it from reaching the submerged intake.
These devices are usually very effective at stopping flashbacks from reaching the protected side of the system. They have losses only work in one orientation and tend to be much larger than the dry type catcher. This makes them particularly suitable only for large or fixed installations and fluid levels need to be constantly checked.
In smaller units that have pressure relief valves to prevent the unit from exploding under severe flashbacks, the level of fluid should be monitored to always above the intake and not so high that the liquid can splash or overflow into an outlet.
External links
- Video and flashback retainer description with four security elements
- Flash Back And Flame Arrestor (with diagram)
- "Saffire 36ec Flashback Internal Arrestor (with cut-away images)" (PDF) . Archived from the original (PDF) on 2010-10-09.
Source of the article : Wikipedia
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