Starting; Operating Problems; The Pump Does Not Prime - VARISCO V6 Instructions Pour L'utilisation Et L'entretien

8

STARTING

During pump start up, particular attention should be paid to the following points to avoid costly mistakes.
Before starting the pump, check the following:
❑ Check the alignment of the pump, gear box (if fitted) and motor
❑ Check that the filter and pipework are free of welding scale and metal shreds
❑ Check that the flanges are well tightened.
The pipework does not weigh too heavily on the pump casing. See the maximum permitted nozzle loads in the (MTV1) Technical
Manual. If the liquid can reach high temperatures, check that expansion joints are fitted in the pipework.
Verify the electrical connections and rating of the motor and check its direction of rotation.
❑ Check that the direction of rotation of the pump is correct (see MTV1 Technical Manual).
❑ The by-pass relief valve, if fitted, must be correctly mounted (see MTV1 Technical Manual).
❑ Check that the pump shaft is free to rotate.
❑ The inside of the pump should not be dry, especially if it must self-prime. Fill or wet the internal parts with oil, the liquid to be pumped
or with a liquid compatible with the pumped liquid.
❑ During assembly, the pumps are protected with a passivating oily liquid. If the liquid inside the pump is not compatible with the
pumped liquid, the pump must be disassembled and cleaned (see paragraph 7.1)
❑ Fit the connections for pressure and vacuum gauges.
❑ Check that the mechanical seal quench is full of oil.
❑ Do not test V series pumps with water.
❑ Before pumping liquids other than that for which the pump was sold, consult Varisco S.p.A.
❑ Check that all valves are open.
❑ If the pump is powered by an internal combustion engine, start the engine with the clutch disengaged.
After starting the pump, check that liquid has entered it and that the pump is operating correctly. If after one minute the pump is still
running dry, stop the pump and check pump and pipework as described under paragraph 9.1.
9

OPERATING PROBLEMS

If operating problems are edxperienced, either on start up or after the pump has run for some time, proceed as follows before opening
the pump:
❑ Check that the liquid inside the pump is not under pressure
❑ Ensure that the pump does not start up by mistake or through automatic controls (disconnect the motor power supply)
❑ Read the following instructions carefully
9.1

The pump does not prime

❑ Wrong direction of rotation
❑ No liquid in the pump to create a seal between the gears and the casing. The suction gauge hardly moves or else oscillates. If the
pump is required to self-prime at every start up and has difficulty in priming, it is advisable to fit a "goose neck" or a foot valve in the
suction line to ensure that there is always liquid in the pump.
❑ Suction valve closed, suction line or filter clogged. The vacuum gauge reading is high.
❑ Air leaks in the suction line : check gaskets, threads and welds. Attention: It is not easy to trace air leaks in the suction pipework.
Listen for the characteristic hiss of air leaks near the joints.
❑ The pump cannot expel the air through the discharge line. Check that all the valves are open; if necessary, bleed the delivery pipe.
❑ Excessive suction lift, especially when pumping liquids with high vapour pressure. Install the pump on flooded suction.
❑ Low rotation speed.
❑ By-pass relief valve blocked in the open position by impurities.
❑ Suction tank empty.
❑ Pump cover installed in the wrong position.
9.2 Low capacity
❑ Rotation speed too low for the required capacity.
❑ Suction line or filter clogged or valve closed.
❑ The vacuum gauge reading is high. Metallic cavitation noise.
❑ Air leaks in the suction line. The vacuum and pressure gauges oscillates. Check the suction line.
Attention: It is not easy to trace air leaks in the suction pipework. Listen for the characteristic hiss of air leaks near the joints.
❑ The by-pass relief valve is set at too low a pressure causing some of the liquid to recirculate inside the pump. Tighten the regulation
screw (see paragraph 10.5); the pressure gauge will show a higher pressure.
❑ Air pockets may have been formed in the suction line, especially if the pipework includes vertical bends.
❑ The liquid vaporizes before entering the pump, especially when trying to pump liquefied gases or liquids with high vapour pressure on
suction lift. The static suction lift is too high.
❑ The suction pipe is not sufficiently immersed in the liquid allowing air to enter the suction line. The vacuum gauge oscillates. The pipe
must be immersed in the liquid to a depth of at least twice the diameter.
❑ The liquid is too viscous for the rotation speed of the pump. The vacuum gauge reading is very high and a metallic noise comes from
inside the pump. Reduce the liquid viscosity by heating, reduce the rotation speed of the pump or increase the diameter of the pipework.
❑ The pump cover is mounted in the wrong position.
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INSTRUCTIONS FOR THE USE AND MAINTENANCE - V