38
A.0500.751 – IM-TGBLOC/01.00 EN (10/2020)
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 3.17 Installation.
Air leak in suction line
2 • Repair leak.
Very low viscosity
3 • Increase pump speed and reduce axial clearance
(see section 3.20 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 3.17 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 3.17 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 3.17 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.
3.19 Trouble shooting