Flame Arrester Ignition Location
Where a single tank vent system employs an end-of-line deflagration flame arrester, only flames entering from outside the system need to be considered. Obviously, if a flame is propagating from the protected tank side, arrester performance is already academic. In selecting a deflagration arrester, it is necessary to (1) ensure that DDT cannot occur between the atmospheric ignition source (for example an external flame) and the arrester, and (2) test the arrester under the configuration and conditions to be encountered in practice.
In systems where tanks have a common collection system there should be one arrester protecting each tank (see Figure 13-3). When evaluating ignition sources in manifolded tank systems, the individual tanks must be considered potential ignition sources within the system. In order to provide protection from tank-to-tank, detonation flame arresters should be installed not only on the main header but on the collection line to each tank. Wherever sufficient run-up distance exists in both directions for DDT to occur, the detonation flame arrester must be bidirectional.