Installation and selection of flame arrestors

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A flame arrester is a device that allows gas to pass through, and it is made of a material with many small channels or gaps. When the flame enters the flame arrester, it is divided into many small flame streams by the arrester elements; due to heat transfer effects (the gas being cooled) and wall effects, these flame streams are extinguished. 1. Classification of flame arrestors 1.1 Based on performance, they can be divided into flame arrestors designed to prevent the spread of flames traveling at subsonic speeds, and those designed to prevent the spread of flames traveling at sonic and supersonic speeds. 1.2 Classified by application location, they can be divided into vent flame arresters, end-of-pipe flame arresters, and standard flame arresters. 1.3 Classified by structure, they can be divided into 5 categories: packed type flame arresters, plate type flame arresters, metal mesh type flame arresters, liquid seal type flame arresters, and corrugated type flame arresters. 2. Installation of flame arresters 2.1 Installation of vent flame arresters a. The installation of flame arresters in oil storage tanks shall be carried out in accordance with the provisions of the \"Code for Design of Oil Depots\" (GBJ74-84). b. For storage tanks (and tank trucks) of chemical oils with a flash point ≤ 43°C, a flame arrester shall be installed on their direct venting pipes (including venting pipes equipped with breather valves). c. When the maximum operating temperature of the material in the storage tank (and tank truck) is greater than or equal to its flash point, a flame arrester shall be installed on its direct vent pipe (including the vent pipe equipped with a breather valve). The maximum operating temperature must take into account factors such as changes in ambient temperature, sunlight exposure, and uncontrolled heating elements. d. A flame arrester should be installed on the vent collection pipe of the online combustible gas analysis equipment. e. Install flame arresters on the exhaust pipe of internal combustion engines entering explosive hazardous areas. f, other situations where it is necessary to install a flame arrester. 2.2 Installation of pipe flame arresters: a. In pipes that transport explosive mixtures capable of undergoing deflagration or detonation (taking possible accident scenarios into account), pipe flame arresters should be installed at the inlet to the receiving equipment. b. Pipes for transporting gaseous materials that can decompose explosively on their own and cause flame spread (such as acetylene) shall be equipped with pipe flame arresters at the inlet to the receiving equipment or at the location determined through testing to be most effective in preventing explosions. c. A flame arrester or flame suppression device should be installed before the flue gases from the torch enter the torch tip. d. Other situations where pipe flame arresters should be installed. 3. Selection of flame arrestors – Steps for selecting flame arrestors: 3.1 Determine whether to use an exhaust flame arrestor or a pipeline flame arrestor based on the location of use. 3.2 Determine whether to use an explosion suppression type flame arrester or an explosion deflagration type flame arrester. 3.3 Select a flame arrester of appropriate specification based on the MESG value of the medium under actual operating conditions. 3.4 Determining the flame arrester based on the flame velocity of the medium. Flame velocity refers to the velocity at the inlet of the flame arrester; it is influenced by the medium and operating conditions such as temperature, pressure, pipe diameter, pipe length and shape, as well as installation location. If this value cannot be found in available data, actual testing is required. 4. Precautions for installing flame arrestors 4.1 Flame arrestors should be installed near the ignition source. 4.2 The vent flame arrester should be installed as close as possible to the end of the pipeline, while also taking into account ease of maintenance. Generally, a pipe-end type vent flame arrester is selected; if a regular type vent flame arrester is chosen, it is necessary to take into account the impact of the piping length and shape of the pipes connected downstream from the flame arrester on the selection of its performance characteristics (whether it should prevent deflagration or detonation), and the specifications of the regular type vent flame arrester should be determined based on the properties of the medium and the installation conditions. 4.3 When installing pipe blast and detonation arrestors, care should be taken to ensure that their \"detonation wave absorbers\" are oriented toward the direction where detonations may occur; otherwise, they will lose their ability to prevent detonations. 4.4 The connection between the flame arrester and the pipeline is generally by flange, while smaller-diameter pipelines use threaded connections. 5. Maintenance and anti-freezing of flame arresters 5.1 Maintenance of flame arresters To ensure the performance of flame arresters and enable their safe use, they should be inspected and cleaned regularly, and any blocked, deformed, or corroded components should be replaced promptly. A weatherproof cap should be installed on the vent end of the vent flame arrester to prevent dust and rainwater from entering the flame arrestment element. 5.2 Anti-freezing of flame arresters: Flame arresters have the ability to generate heat, and their temperature drops as a result of cooling when materials pass through them. For materials with a high freezing point or that tend to crystallize, solidification and crystallization may occur when they pass through the flame arrester, thereby increasing the resistance of the flame arrester ； If the material contains water (vapor), it may freeze in cold regions or during winter, thereby blocking the flame arrester. Therefore, in situations where such possibilities exist, anti-freezing or thawing measures should be employed, such as electric heating, steam coils, jacket heating, and regular steam purging. For water-sealed flame arresters, continuous flowing water overflow or the addition of antifreeze to the water can be used.