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A.0500.501 – IM-TGGS/05.01 EN (03/2013)
Symptom Cause Remedy
No flow
Pump not priming
Suction lift too high 1 • Reduce difference between
pump and suction tank level.
• Increase suction pipe diameter.
• Reduce length and simplify suction pipe (use as
few elbows and other fittings as possible).
Also see section 3.18 Installation.
Air leak in suction line 2 • Repair leak.
Very low viscosity 3 • Increase pump speed and reduce axial clearance
(see section 3.21 Maintenance instructions).
Suction strainer or filter clogged 4 • Clear suction strainer or filter.
Pump casing incorrectly installed
after repair
5 • Install pump casing correctly.
See section 3.18 Installation.
Wrong direction of rotation of motor 6 • For 3-phase drivers change 2 connections.
• Change suction and discharge opening.
(Attention! Check the location of the safety relief
valve).
Pump stalls or
irregular flow
Liquid level in suction tank falls too low 7 • Correct liquid supply
• Provide a level switch
Output too high 8 • Reduce pump speed/or install a smaller pump.
• Install by-pass line with check-valve.
Air sucking 9 • Repair leak in suction line.
• Check or replace shaft seal.
• Check/provide quench on shaft seal.
• Connect plug Bb to the pump discharge in order
to increase the pressure in the sealing box.
Cavitation 10 • Reduce difference between pump and suction
tank level.
• Increase suction pipe diameter.
• Reduce length and simplify suction pipe (use as
few elbows and other fittings as possible).
Also see chapter 3.18 Installation.
Liquid vaporises in pump
(e.g. by heating up)
11 • Check temperature.
• Check vapour pressure of liquid.
• Reduce pump speed. If necessary install a larger
pump.
Not enough capacity Pump speed too low 12 • Increase pump speed. Attention! Do not exceed
maximum speed and check NPSHr.
Air sucking 13 • Repair leak in suction line.
• Check or replace shaft seal.
• Check/provide a quench in the shaft seal.
• Connect plug Bb to the pump discharge in order
to increase the pressure in the sealing box.
Cavitation 14 • Reduce difference between pump and suction
tank level.
• Increase suction pipe diameter.
• Reduce length and simplify suction pipe (use as
few elbows and other fittings as possible).
Also see section 3.18 Installation.
Back pressure too high 15 • Check discharge pipe.
• Increase pipe diameter.
• Reduce working pressure.
• Check accessories (filter, heat exchanger, etc.).
Safety relief valve set too low 16 • Correct pressure setting.
3.20 Trouble shooting
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