Detonation flame arresters types

An in-line detonation flame arrester must be used whenever there is a possibility of a detonation occurring. This is always a strong possibility in vent manifold (vapor collection) systems, where long pipe runs provide sufficient run-up distances for a deflagration-to-detonation transition to occur. Figure 3-3 shows the installation of in-line arresters of the detonation type in a vent manifold system. 

FIGURE 3-7. Various types of detonation flame arresters. (Sources Protectoseal Company, NAO, Inc., and Westech Industrial, Ltd.)... 

Dry type deflagration and detonation flame arresters have an internal arrester element (sometimes called a matrix) that quenches the flame and cools the products of combustion. A great number of arrester elements have been developed and used. The most common types currently available are as follows ... 

Other types of deflagration and detonation flame arresters that do not contain an arrester element (matrix) have been used snccessfnlly in various applications where conventional dry type arresters were not suitable or were very expensive. Among these are ... 

Wliile all the flame arrester types disenssed above have a solid arresting element (matrix), the hydranlic (liqnid seal) flame arrester contains a liqnid, nsnally water, to provide a flame barrier. It operates by breaking np the gas flow into discrete bnbbles by means of an internal device to qnench the flame. A mechanical nonretnrn valve (check valve) is sometimes incorporated to prevent the displacement of liqnid dnring or after a flame event (deflagration or detonation). 

The ranges of mixture composition pins operating temperature and pressure are important. Unless a detonation flame arrester is used, it is essential to ensure that DDT will not occur after a flame enters the system. Even if a detonation flame arrester is used, it is important to use the correct type of arrester for the service. For example, if it is possible for a flame to approach from either direction, a bidirectional flame arrester must be selected. 

Deflagration and detonation flame arresters should be inspected annually until operating experience indicates otherwise. Also, the need for frequent inspection and maintenance may affect the selection of one type of flame arrester over another type for a specific application. For example, a hydraulic (liquid seal) flame arrester may be more suitable than a dry, fixed-element, flame arrester if the latter requires frequent inspecdon and maintenance because of persistent plugging problems. 

A UL Type 1 deflagration flame arrester must undergo an endurance burn test while a UL Type 11 deflagration flame arrester must be subjected to a continuous flame test. The test conditions for the endurance burn test and the continuous flame test for a deflagration flame arrester are the same as for a detonation flame arrester. 

It also contains specific requirements for testing of flame arresters in equipment such as compressors, blowers, fans, and vacuum pumps. Procedures are presented for deflagration, detonation, and burning tests for all the flame arrester types in the standard. 

In certain exceptional cases, a specially designed deflagration arrester may be mounted in-line without regard to run-up distance. This can be done only where the system is known to be incapable of detonation. An example is the decomposition flames of ethylene, which are briefly discussed under Special Arrester Types and Alternatives. ... 

This book covers many aspects of DBA design, selection, specification, installadon, and maintenance. It explains how varions types of flame arresters differ, how they are constrncted, and how they work, ft also describes when a flame arrester is an effective solntion for mitigation of deflagrations and detonations, and other means of protection (e.g., oxidant concentration rednction) that may be nsed. It also briefly covers some aspects of dnst deflagration protection. 

Fabiano et al. (1999) describe an explosion in the loading section of an Italian acetylene production plant in which the installed flame arresters did not stop a detonation. The arresters were deflagration type and the arrester elements were vessels packed with silica gel and aluminum plates (Fabiano 1999). It was concluded that the flame arresters used were not suitable for dealing safely with the excess pressures resulting from an acetylene decomposition, and may not have been in the proper location to stop the detonation. 

As mentioned earlier, flame arresters can be classified as either deflagration or detonation type. Deflagration flame arresters on tanks are designed to stop a flame from propagating into a tank from an unconfined atmo-... 

It is emphasized that the system shown in Figure 5-13 represents only a simplification of actual plant installations, which may he more complex. If it is not obvious at which point ignition is likely to occur, a flame arrester installed in an actual plant may have to he selected to face a comhination of the conditions shown in Figure 5-13. Therefore, for manifolded vent systems, the arrester should he a hidirectional, detonation type, and hoth sides of the arrester element should he provided with thermocouples to detect a stable flame. 

Dry type flame arresters with small apertures, especially detonation arresters, should not be used in services where dust is present as the arresters will probably plug. 

Acetylene may propagate decomposition flames in the absence of any oxidant above certain minimum conditions of pressure, temperature, and pipe diameter. Acetylene, unlike most other gases, can decompose in a detonative manner. Among the different types of flame arresters that have proven successful in stopping acetylene decomposition flames are hydraulic (liquid seal) flame arresters, packed beds, sintered metal, and metallic balls (metal shot). 

The Canadian Standards Association Standard Z343 (CSA 1998) presents test methods for in-line and firebox flame arresters. In this standard in-line flame arresters are limited to only detonation types and firebox flame arresters are defined as flame arresters installed in an enclosnre, or system of enclosnres, where the mn-np distance is less than 1.5 meters and open to the atmosphere. Firebox flame arresters are commonly nsed on eqnip-ment designed to heat flnids in prodnction operations snch as indirect heaters, emnlsion treaters, and glycol dehydrators. The development history of this standard is presented in Section 2.3.2. 

Underwriters Laboratories Inc. (UL) and Factory Mntnal Research (FM) will condnct tests for flame arrester mannfactnrers to ascertain if a designated flame arrester (deflagration or detonation type) will prevent passage of a flame of a specific gas. Both UL and FM test procednres also inclnde tests for endnrance bnrning, and in the case of UL tests, also for continnons flames. 

FM will condnct tests at their own test facilities nsnally only for deflagration flame arresters, following their Class 6061 test procednre. They will also observe and approve tests done at a hame arrester mannfactnrer s own test facility for both dehagration and detonation type hame arresters. For detonation hame arresters FM will accept tests that are done in accor-... 

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