| Operation Manual C 2213 |
35
Back stop / back-pressure valve
It is an experience that even the best ejector non-return valve may become untight sometime because of
impurities. Therefore the installation of an additional back stop is prescribed by law in some countries. Its
function is to prevent water from entering the chlorinators even in the case of a failure. So that these devices
are not damaged.
The backstop has a second safety function. It requires a small differential pressure to open. The value of this
differential pressure has been chosen so that it slightly exceeds the minimum repsonse pressure of the safety
valve. Even in the case of creeping chlorine leakage at the full-vacuum chlorinator, the safety blowdown valve
responds exactly thus avoiding the development of excessive pressure in the vacuum system.
Safety Shutoff Valve
The safety shutoff valve is required according to DIN 19606, if the injector is situated outside of the chlorine
gas area. Often the use of a valve is required which opens only, if the ejector is under vacuum and which is
completely closed during system standstill. The safety shutoff valve ensures this function. It is installed instead
of the back stop.
