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A.0500.551 – IM-TGMAG/02.00 EN (02/2008)
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 and correct circulation pump insert).
Magnetic coupling is slipping 7 • Check/correct assembly of rotor shaft and bear-
ings and magnetic coupling
• Check start-up conditions for the magnetic cou-
pling in combination with applied electrical motor
if necessary add fly-wheel or apply soft start.
• Check operating parameters against break-away
torque of the magnetic coupling.
• Check if the pump is blocked, remove blockage.
Irregular flow Liquid level in suction tank falls too low 8 • Correct liquid supply
• Provide a liquid level switch
Output too high 9 • Reduce pump speed/or install a smaller pump.
• Install by-pass line with check-valve.
Air sucking 10 • Repair leak in suction line.
Cavitation 11 • 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)
12 • Check temperature.
• Check vapour pressure of liquid.
• Reduce pump speed. If necessary install a larger
pump.
Not enough capacity Pump speed too low 13 • Increase pump speed. Attention! Do not exceed
maximum speed and check NPSHr.
Air sucking 14 • Repair leak in suction line.
Cavitation 15 • 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 16 • Check discharge pipe.
• Increase pipe diameter.
• Reduce working pressure.
• Check accessories (filter, heat exchanger, etc.).
Safety relief valve set too low 17 • Correct pressure setting.
Viscosity too low 18 • Increase pump speed. Attention! Do not exceed
maximum speed and check NPSHr.
• If necessary, install a larger pump.
Axial clearance 19 • Check axial clearance and correct.
See section 3.21 Maintenance instructions.
Gases come free 20 • Increase pump speed. Attention! Do not exceed
maximum speed and check NPSHr.
• Install a larger pump
3.20 Trouble shooting