C7110 - Pressure
The main application of the pressure reducing valve
is to prevent reliquefaction of chlorine gas so that
destruction of PVC parts is avoided.
Some explanations: The main disinfectant used in water
treatment is chlorine. It is normally stored as a liquid
in steel tanks. Elementary liquid chlorine does not
at all attack plain steel.
However, PVC is strongly attacked and loses its original
shape. As most chlorinators are made of PVC, it is essential
to prevent liquid chlorine from entering the components
of the unit.
How to avoid chlorine reliquefaction
The above mentioned energy loss could be compensated
for by means of a heater block.
Such device is available but requires heating energy
all the time (electrical current).
It is more reasonable to install a pressure reducing
valve because it doesn't need any auxiliary energy.
It lowers the pressure to that extent that the chlorine
only would reliquefy at a temperature far below 0°C.
Such temperatures are normally not to be expected in
normal plants. It is an advantage that it is not important
how accurately the pressure is controlled or at which
pressure the set-point is adjusted. The main point is
that the pressure is by far lower than the pressure
in the liquid chlorine tank.