A flame arrester is a device fitted to the opening of an enclosure or to the connecting pipe work in a system of enclosures and which permits gases or vapours to flow under normal operating conditions but prevents the transmission of a flame should an ignition take place.
A Flame arrestor is a safety device whose principal purpose is to prevent a flame entering or leaving a pipe or vessel or to prevent it travelling further down a pipe. In many cases it is used in conjunction with the components to create a safety system. Failure to stop a flame can result in catastrophic damage to equipment, loss of production, injury to people and even loss of life and potentially large litigation costs.
The dimensions should be at least 4 m circumference, 4 m length and a material wall thickness of 0.05 mm.
In other words flame arrester can be explained as :
A Flame Arrestor is a device which allows gas to pass through it but stops a flame in order to prevent a larger fire or explosion.
Construction of flame arrester
Typically a flame arrester comprises a housing, an element and connection(s) to secure it to pipe work or equipment. The element is the device that quenches the flame and the majority of constructions used incorporate a form of “filter” that provides small apertures through which the process gas will flow but will prevent flame transmission. The flame front is broken down in the “filter” into smaller flamelets which are cooled by the large heat capacity of the element thus extinguishing the flame. Materials used for the “filter” element include crimped metal ribbons, woven wire gauze, sintered materials and honey comb materials. Because of its construction, the element will cause a pressure drop or an obstruction to process flow. In order to mitigate this increased resistance to flow, the element area is usually larger than the cross sectional area of the pipe work. Larger elements also have a greater heat capacity.
Other types of flame arrester include devices which incorporate a small aperture that ensures the velocity of the gas being emitted exceeds the burning velocity of that gas and thus will not transmit the flame. Alternatively, the gas may be bubbled through a liquid or water in a manner that provides a liquid barrier to flame transmission.
Flame screens should be:
- designed in such a manner that they cannot be inserted improperly in the opening;
- securely fitted in openings so that flames cannot circumvent the screen;
- able to meet the requirements of these standards. For flame screens fitted at vacuum inlets through which vapours cannot be vented the test specified , need not be complied with; and
- be protected against mechanical damage.
Types of flame arrester:
- End of line flame arrester.
- In line flame arrester.
- Pre volume flame arrester.
Regulation for flame arrester:
The 1981 and the 1983 amendments to the International Convention for the Safety of Life at Sea, 1974 (SOLAS) include revised requirements for fire safety measures for tankers. Regulation II-2/59 of these amendments contains provisions concerning venting, purging, gas-freeing and ventilation. regulation II-2/59.1.5 states: “The venting system shall be provided with devices to prevent the passage of flame into the cargo tanks. The design, testing and locating of these devices shall comply with the requirements established by the Administration which shall contain at least the Standards adopted by the Organization’’.