Because unstable detonation arresters are designed and tested under the worst case conditions that any arrester is likely to experience for a given gas-group and initial pressure, the physical location of a device within a piping system relative to the ignition source is not subject to any restrictions (except in locations where endurance burning may occur).
This is not the case for a stable detonation arrester which must be positioned in such a location within a system that it can only ever experience a stable detonation or deflagration event.
In common with North American flame arrester manufacturers, Elmac does not supply the so-called stable detonation arresters (which are available from several European manufacturers) on the grounds that such devices may expose operators to unacceptable levels of risk.
unstable detonation arrester be fitted in systems where
a detonation may be possible, in order to deal with
worst case conditions for the particular piping system.