Flame Arrestor & Flame Arrestor Element Process Guide

Flame Arrestor
  • Significance

    Flame arrestors are important safety accessories in storage and transportation systems of petroleum tanks and combustible gas pipelines, and play an important role in preventing disasters such as explosions and fires.

  • Executive Standards
    • National standards: GB5908 Flame Arresters for Petroleum Tanks; GB13347 The Quenching Ability of Flame Arrester And Its Test Method For Petroleum Gas Piping Systems.
    • European standards: EN12874 Flame Arresters – Performance Requirements, Test Methods And Limits For Use
    • International standards: ISO16852 lame Arresters – Performance Requirements, Test Methods And Limits For Use
  • Working Principle

    Flame arrestor divides the cross-section of a gas pipeline into multiple sections with small enough diameters. After a flame passing through these small channels, it will turn into several small flames and will be extinguished after moving a certain distance. This is called "quenching". There are currently two main views on the principle of flame quenching. One is that heat transfer is the main reason for achieving fire resistance, while the other is that the wall effect has a great influence on flame quenching.

A horizontally placed red flame arrestor
Flame Arrestor Category
  • Category
    • By installation site, it is divided into storage tank flame arrestor and pipeline flame arrestor. The former is often installed at the top of storage tanks and the latter is often installed in the middle or at the end of conveying pipeline.
    • By the speed of stopping flame propagation, it is divided into deflagration flame arrestor and detonation flame arrestor. The former is generally installed at the end of pipeline and near the middle of the pipeline or at the top of the storage tank to prevent flames that propagate and spread at subsonic speeds; The latter is typically installed at a far distance from the end of the pipeline or at the end of a closed pipeline system connected to a storage tank to prevent flames that propagate and spread at supersonic or near-sonic speeds.
    • Common accessory inside the flame arrestor: Stainless steel corrugated flame arrestor element.
A hand is putting next to a stainless steel corrugated flame arrestor element.

Stainless steel corrugated flame arrestor element

Flame Arrestor Installation

  • By position.

    The installation site influences the selection of flame arrestor. That's because the distance between the ignition source and the flame arrestor varies and causes the difference in flame propagation speed, which in turn affects the selection of flame arrestor.

    Storage tank flame arrestor is only suitable for installation on the short pipe for storage tank ventilation. It can be used separately or matching with a breathing valve. However, the distance between the flame arrestor and the flashback point shall not exceed 5 times of the selected pipe diameter. Besides, it can only be used in environments where flammable gases are present but there is no open flame. Storage stank flame arrestor can only prevent flames with a speed of no more than 45 m/s from passing through, so its fire retardance cannot meet the requirements of pipeline flame arrestor. Therefore, storage tank flame arrestor cannot be used as an alternative to pipeline flame arrestor.

  • By function.

    When a combustible gas delivery pipeline is connected to a burner without other anti-backfire facilities, a flame arrestor should be installed.

    • Deflagration flame arrestors shall be used to prevent flames that that propagate and spread at subsonic speeds and be installed near the source of ignition;
    • Detonation flame arrestors are adopted to prevent flames that propagate and spread at supersonic or near-sonic speeds and be installed far away from the source of ignition;
    • For detonation flame arrestors with different nominal diameter, the required minimum installation distances from the source of ignition are shown in the table below.
    The Required Pipeline Length of Detonation Flame Arrestors with Different Nominal Diameters
    Pipe nominal diameter (DN) 15 20 25 32 40 50 65 80 100 125 150 200
    Minimum installation distance (L/m) 0.5 1 1.5 2 3 4 6 8 10 10 10 10

    Notes:

    • For flame arrestor used in cold areas, part or the whole housing with a heating jacket should be selected, and other heating tracing methods can also be used;
    • In special circumstances, flame arrestors with flushing pipes, pressure gauges, thermometers, drain outlets, and other interfaces can be selected as needed.
    • For flame arrestors installed at the end of the pipeline, threaded connections should be used when the nominal diameter is less than DN50, and flange connections should be used when the nominal diameter is greater than or equal to DN50;
    • For flame arrestors installed in the pipeline, flange connections should be used;
    • For flame arrestors installed at the end of the pipeline, it should be equipped with a rainproof and ventilated cover that can open automatically;
    • For flame arrestors installed on all branches of gas connecting pipes between storage tanks, detonation flame arrestors should be selected;
    • For oil and gas discharge pipes at the top of the storage tank, detonation flame arrestors should be selected and installed at the connection with the tank;
    • For protective gas and oil and gas discharge pipes at the top of the storage tank, detonation flame arrestors should be selected and an emergency emptying pipe should be installed.

Flame Arrestor Design

  • Material. It is generally made of stainless steel materials and features high melting point, large heat conductivity coefficient, corrosion resistance and not easy to deform. If it is made of aluminum or copper plate, it deforms easily and even becomes broken when subject to strong flashback pressure, and cannot play the role of flame-arresting.
  • Flame Arrestor Element Specification Description
    • D: The maximum diameter of flame arrestor element. The sum of all unit void area of the flame arrestor element shall be greater than or equal to the cross section are of the connecting pipes at both ends.
    • l: The thickness of flame arrestor element, that is, the length of the flame arrestor element.
    • t: The thickness of the metal sheet. The metal sheet for flame arrestor element should be made as thin as possible under processing conditions and allowable strength to fully reduce the flow resistance loss of the flame arrestor.
    • h: The height of a regular triangle, that is, the peak height of the triangle.

    Notes:

    • The larger the contact area between the flame arrestor element and the flame, the more sufficient the heat exchange, and the better the fire retardance effect. In other words, the smaller the triangular unit and the longer the channel, the higher the cooling efficiency.
    • Reducing the height h of the triangular unit can correspondingly shorten the length l of the triangular channel. But if the h is too small, it will increase the flow resistance of gases, and too small l will weaken the fire-arresting ability of the flame arrestor element. Therefore, when designing a flame arrestor, the selection of l and h values should be considered comprehensively.
Flame arrestor housing structure with remarks

Flame arrestor element maximum diameter

Flame arrestor structure marked with symbols

Flame arrestor element structure

A caliper is used to check the thickness of flame arrestor element.

Flame arrestor element thickness inspection

A caliper is used to check the regular triangle height of flame arrestor element.

Flame arrestor element regular triangle height inspection

A vertically placed flame arrestor element

Flame arrestor element

2 horizontally placed and 3 vertically placed flame arrestor elements

Flame arrestor elements seen from different angles