
44/45
NT 1008-D00 08 18 P BI series e
11. TROUBLESHOOTING (continued)
ABNORMAL NOISES
These noises can be hydraulic or mechanical. They can be distinguished by the fact that only the former
disappear (or at least lessen) when air is allowed into the inlet pipe.
7
HYDRAULIC NOISE
These noises can come from insufficient product being supplied to the pump, or :
7-1
- the rotation speed is too high for the installation conditions (increase of viscosity due to a change of product
or a reduction of temperature, etc.).
7-2
- the suction head is too high or has become too high due to excessive head losses following clogging of
the piping or filter, a change of viscosity of the liquid, etc.
7-3
- an increase of the vapour pressure with a rise of temperature.
8
MECHANICAL NOISES
These can be due to :
8-1
- the bypass valve hitting the seat, the discharge pressure approaching the bypass discharge pressure
(turn the adjuster screw after making sure the electric motor is suitably protected).
8-2
- abnormal stress on the pump : the transmission is pulling on the shaft, pulling on the flanges by the piping.
8-3
- broken material or a foreign body in the pump.
EXCESS POWER CONSUMPTION
9
The most spectacular event occurs when a heat motor stalls or the power to an electric motor is shut off.
9-1
If this incident occurs when closing the discharge line, the cause may be :
a. bypass fitted wrong way around,
b. bypass set too high,
c. motor protection set too low.
9-2
If the incident occurs during operation, the cause could be :
a. an inadequate motor (in this case, the discharge pressure complies with what was expected).
b. higher than expected losses due to viscosity or density higher than initially envisioned (in this case, the
discharge pressure is higher than expected. The pressure can be reduced by loosening the bypass
adjustment screw - the flow is decreased).
c. excessive rotation speed.
d. a fault of the equipment (faulty alignment, deformation of the chassis, stress exerted by the piping on
the flanges, seizing, etc.).
The latter case of excess power consumption can also be due to a poor motor connection (e.g. a 3 phases
motor operating on 2 phases).