End-of-line flame arrester

All flame arresters should be located so that they are readily accessible for maintenance. If an end-of-line flame arrester is on a vent pipe from an indoor vessel, the pipe should be routed above the building roof so that flammable vapors are not discharged into the building. Also, the flame arrester should be installed so that the discharge opening is at a minimum height above the roof so that personnel on the roof will not be directly impacted by the vent vapors. Some companies specify the minimum height to be seven to ten feet above the roof. 

FRS. 1985. Evaluation of the Performance of an End-of-Line Flame Arrester When Subjected to Unconfmed Hydrogen-Air Explosions. Report of Investigation FRD 184/03 for IMl Amal Limited. Fire Research Station, Borehamwood, Herts., England. 

Appendix B to Part 154 is a standard specification for tank vent (end-of-line) deflagration flame arresters. It does contain test procedures for these types of flame arresters. An end-of-line flame arrester mnst be able to arrest three atmospheric deflagrations as well as to withstand two honrs of continnons bnrning withont flashback. 

In-line flame arresters for both detonations and deflagrations and end-of-line flame arresters can be tested and approved for atmo-... 

End-of-Line Flame Arrester A deflagration flame arrester that is installed on atmospheric pressnre tank vent nozzles, having only one pipe connection. It is also called a tank vent deflagration flame arrester. 

The element consists of wound corrugated metal strips. The quenching gap size can be adjusted in accordance with the flash-back capability of the explosive mixture. The principle of flame quenching in small gaps is applied in end-of-line flame arresters and in-line flame arresters. 

Deflagration Arresters The two types of deflagration arrester normally considered are the end-of-line arrester (Figs. 26-23 and 26-24) and the tank vent deflagration arrester Neither type of arrester is designed to stop detonations. If mounted sufficiently far from the atmospheric outlet of a piping system, which constitutes the unpro-tec tea side of the arrester, the flame can accelerate sufficiently to cause these arresters to fail. Failure can occur at high flame speeds even without a run-up to detonation. 

Deflagration Arrester Testing For end-of-line and tank vent flame arresters, approval agencies may require manufacturers to provide users with data for flow capacity at operating pressures, proof of success during an endurance burn or continuous flame test, evidence of flashback test results (for end-of-hne arresters) or explosion test results (for in-line or tank vent arrester applications), hydrauhc pressure test results, and results of a corrosion test. 

FIGURE 3-1. End-of-line deflagration flame arrester locations. 

Since gauzes have limited effectiveness in quenching high-velocity flames, they are only used as end-of-line deflagration flame arresters. 

The flame propagation direction affects the type of flame arrester selected. An end-of-line or in-line deflagration flame arrester used for the protection of an individual tank may be of a unidirectional design because the flame will only propagate from the atmosphere towards the tank interior. A bidirectional flame arrester design, however, is needed for an in-line application in a vapor recovery (vent manifold) system because the vapors must be able to flow from the tank interior into the manifold, or from the manifold into the tank interior. Consequently, flame may propagate in either direction. 

Depending on the design, the pressnre drop throngh a crimped metal ribbon flame arrester may exceed that of a parallel plate type of the same size. If a crimped metal ribbon type arrester is nsed for end-of-line service... 

Location and piping configuration must consider the possibility of DDT. For example, for end-of-line and in-line deflagration flame arresters, the location must be identical to the test piping configuration or a DDT may occur. 

Type I Flame arresters acceptable for end-of-line applications. Where a Type I arrester is provided with cowls, weather hoods, or deflectors, etc., it shall be tested in each confignration. 

ASTM published a standard specification F 1273 for tank vent flame arresters (end-of-line deflagration flame arresters) in 1991 (reapproved in... 

The British Standards Institnte standard specification BS 7244 (1990) applies to both deflagradon (end-of-line and in-line) and detonadon flame arresters. For end-of-line deflagradon flame arresters ten tests are reqnired, and for in-line deflagradon flame arresters fifteen tests are reqnired. For detonation flame arresters three tests at increasing lengths of pipe for both deflagration and detonation conditions and ten nnrestricted overdriven detonation tests are reqnired. Endnrance bnrning test procedures are presented, bnt tests are condncted only if specified. 

The IMO standard MSC/Circ. 677 (1994) provides testing procedures for end-of-line deflagration and in-line detonation flame arresters, as well as high velocity vent valves for use on cargo tanks in tanker ships. Its development is discussed in Section 2.3.4. 

The test gas may be propane, hexane, or gasoline vapors. Eor end-of-line deflagration flame arresters, tests shall be performed twice each for three ignition sources, for a total of six tests. Eor in-line detonation flame arresters three detonation tests are required. 

Comparison of Test Parameters of Various Standards for End-of-Line and In-Line Deflagration Flame Arresters (Adapted from Lapp and Werneburg 1999)... 

Example 2—Sizing of an End-of-Line Deflagration Flame Arrester... 

Size an end-of-line deflagration flame arrester for the normal vent nozzle of a 126,000 gallon API-type atmospheric pressure storage tank for the following conditions ... 

Figure 3-1 (page 19) shows where an end-of-line deflagration flame arrester should he located. It preferably should be installed on a nozzle that is near the outer edge of the tank/vessel roof for ease of accessibility for maintenance and removal. 

The length of installed pipe between the ignition source and the flame arrester is critical to the proper performance of end-of-line and in-line deflagration flame arresters. Line lengths greater than those used in the test allow higher flame speeds and pressure to... 

An approved flame arrester should not he misapplied, i.e., an end-of-line arrester should not he installed in an in-line application. 

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