A vacuum relief valve should be located before the inlet port if there is any possibility of a
blockage in flow to exist which would exceed the maximum pressure differential -especially
blowers operating with negative inlet pressure.
A pressure relief valve should be located after the discharge port if any possibility of
increased resistance exists to exceed maximum pressure differential - especial blowers
operating with positive discharge pressures.
Be sure that pressure relief valves must be rated for temperatures above expected discharge
temperatures during operation.
Set Point
The set point on the relief valve must correspond to the designed operating pressures and
the range of condition under which the unit will operate.
A pressure relief valve is necessary to be sure that the unit
never exceeds its maximum pressure difference by no more
than 1 psi – positive pressure or vacuum. This includes full
blow- off condition.
The required relief valve flow rate should be equivalent to the maximum flow delivered by
the rotary blower under those inlet and discharge conditions.
The limiting values must be observed.
9.4.2 Check valve
A check valve is necessary to prevent a reversal of flow whenever the rotary blower starts and
stops.
The sizing of the check valve should be rated for the
maximum flow rate and maximum operating pressure
differential.
The check valve must:
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Be located after the discharge port for positive pressure and at the inlet port for
vacuum; and
