Interactions in the Explosion Isolation of Series-Connected Flame Arresters
For explosion isolation in piping systems for recovery and exhaust air purification systems, up to three independent measures are required according to TRGS 724 and NFPA 67, depending on the probability of an explosive atmosphere occurring. In addition to the independent measures, the standards also provide recommendations for the installation location and design of piping sections.
National and international standards do not currently provide any recommendations regarding the arrangement of series-connected flame arresters (FARs). The approach for pipe constrictions, with a constriction distance L/D = 120, is often used for series-connected detonation flame arresters. In practice, this requirement cannot be met in many cases, raising a wide range of safety-related questions. In order to provide operators with recommendations for action and to answers the questions that arise in practice, these experimental studies thoroughly investigated combined measures for the explosion-technical decoupling of pipe explosions using detonation flame arresters, and examined potential interactions and mutual influences. Due to the high complexity of explosion-technical processes, various test series are essential to derive safety-relevant recommendations for practical action.
For the test gas mixture of explosion group IIB3 used in a setup with two detonation flame arresters, it was found that no negative influence could be detected on detonation flame arresters installed closely together. Similar tests with a flame initiation in the deflagration range also showed no negative influence.
In further experimental studies, the upstream detonation flame arresters were deliberately forced to ignite through overload or mechanical manipulation. This provoked flame penetration of the first FDS, the measured flame speeds and explosion pressures after the FDS showed an accelerated reaction start, which led to a renewed transition from deflagration to detonation within a very short run-up time/distance.
In our presentation, the various experimental investigations will be presented in detail and practical recommendations will be derived.