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3.3

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• The suction hydrostatic head exceeds the discharge pressure: Increase the discharge pressure by means of a back

pressure valve. (OBL, series 300).

•

Back pressure valve stuck in open position because of foreing

matters, or pressure setting too low respect to the suction head:

Check

• Pump valves jammed in open position:

Check

SOLUTIONSCAUSES

STARTUP

FLOW RATE IRREGULAR OR HIGHER THAN EXPECTED

• Air entering the suction piping through the fittings:

Check.

• Air trapped inside the pump:

Raise pump flow rate to maximum value, otherwise unscrew

discharge valve housing (pos.14) till the liquid arrives.

• Suction lift too high:

Reduce it.

• The vapour pressure of the fluid is too high:

Increase the hydrostatic head on suction side.

• The viscosity of the liquid is too high:

Install a suction piping having a larger diameter.

Increase the hydrostatic head on suction side.

• Suction piping is clogged or its valves are shut:

Verify.

• Filter on suction side is clogged:

Clean it.

• Pump valves are stuck because of foreign matters

coming from suction side:

Dismantle the valves and clean them carefully.

• Check valves are mis-arranged:

See instructions on page 14

(Pump heads - Dismanting and reassembly ).

FLOW RATE LOWER THAN EXPECTED

POSSIBLE TROUBLES DURING STARTUP

OBL MB Series User Manual

Questions and Answers: