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NT 1008-D00 08 18 P BI series e
11. TROUBLESHOOTING (continued)
3
MEASURING THE VACUUM PRESSURE
(as close as possible to the pump inlet, inlet side).
3-1
If the vacuum is high, e.g. higher than or equal to 6 to 7 meters WC (about 45 or 50 cm of mercury), this
can result in pump noise because :
3-1-1
The suction head is too high, or :
a. the suction lift is too high (reduce it by taking the pump down closer to the level of the liquid)
b. that the dynamic suction losses are too high :
1. cf 2-2-1 b
2. the inlet piping orifice is too close to the bottom of the tank.
3-1-2 The inlet piping is completely blocked (valve, tap, filter, cloth, full seal forgotten, etc.).
3-1-3
The vapor tension of the liquid is too high (or has become so as a result of a change in temperature, for
example. Bring the pump closer to the level of the liquid, install the pump closer to the feed or cool the liquid
to reduce the vapour pressure.
3-2
If the vacuum is low, for example, less than 3 meters WC (i.e. about 20 cm of mercury), isolate the pump
from the inlet piping (by closing the valve nearest the pump or by inserting a full flange seal) and measuring
the vacuum once again.
3-2-1
If the vacuum is high, e.g. higher than or equal to 6 or 7 meters WC (i.e. about 45 to 50 cm of mercury), the
pump is not the cause :
a. air must be entering upstream of the pump isolating valve.
b. the vapor tension of the liquid is to high or has become so as a result of a change in temperature
(cf. 3-1-3).
3-2-2
If the vacuum is low or zero, this may be because :
a. the bypass valve is not closing properly, due to dirt on the valve seat.
b. air is entering the pump (check the front cover seals, flanges, etc.)
c. the pump is worn and the internal tightness is out of specification (broken shaft).
ABNORMAL HEATING OF BEARINGS
4
This heating may be due to :
4-1
- excessive pulling on the pump flanges by the piping (in this case, it must have been necessary to force
the piping into position to connect it to the pump).
4-2
- poor alignment of the pump - due for example to 4-1 (the pump is partially or totally uncoupled, the pump
shaft and drive shaft are not aligned with each other).
4-3
- inadequate anchoring of the pump unit leading to deformation of the chassis (make sure that the chassis
is clear of the ground except for the 3 anchoring points).
4-4
- seizing of the bushings (cured product preventing lubrication and cooling, excess power, etc.).
LEAKING SHAFT SEALS
5
The seal :
a. was damaged during assembly (scratches on friction surfaces, etc.)
b. is not suitable for the product (chemical attach, mechanical damage - abrasion - to seals and counter-
parts)
c. is showing normal wear.
6
The shaft is worn at the seal or does not rotate correctly due to poor alignment, excessive tension on the
transmission belts, chains, etc.