8
9.3
Excessive pump noise
❑
Not enough liquid reaches the pump because the viscosity is too high. Reduce the rotation speed, increase the diameter of the suction
pipework, reduce the friction losses in the suction line.
❑
The pump cavitates because the liquid is too volatile. Increase the diameter and/or reduce the length of the suction line. Raise the level of
the liquid in the suction tank; if necessary mount the pump on flooded suction.
❑
Check the alignment of the flexible couplings.
❑
The by-pass relief valve vibrates: tighten the regulation screw.
❑
Check the anchorage of the base plate and the pipework supports.
❑
Foreign bodies in the pump.
❑
The cover is mounted at 180 degrees compared with the correct position.
9.4
Motor overload
❑
High rotation speed.
❑
High viscosity: reduce the rotation speed as shown in the performance tables or heat the liquid.
❑
High pressure: increase the diameter of the delivery line and check that all valves are open and that the pipe is not clogged. Do not exceed
the pressure shown in the table.
❑
Packing too tight. Loosen the gland screws until the correct drip rate is reached.
❑
Check the pump alignment. (If this the problem, noise will also be generated).
❑
Tolerance too tight for the liquid to be pumped. The bushes overheat and seize, and the extremity of the idler pin on the cover heats to over
80 degrees C. Stop the pump and increase the tolerances as indicated by Varisco.
9.5
The pump wears out quickly
Rapid wear of the pump causes a sudden drop in performance. The following are the main causes and how to put them right.
❑
The liquid is abrasive or contains solids. Grooves are present on the surfaces, the bushes wear out rapidly, the clearances increase and
the surfaces are irregular.
❑
Clean all the pipework throughly and install a suction filter. If the liquid is abrasive, reduce the rotation speed. Reduce the delivery pres-
sure. Use the AT version.
❑
Corrosion, shown by the formation of rust, porosity or pitting on the surfaces and damage to elastomers.
❑
Check that the materials used are those best suited to the application and check that the liquid has not been contaminated in such a way
as to become corrosive. Check that the concentration has not changed and/or that the liquid temperature is within the permitted range.
❑
The operating limits have been exceeded. This is shown by excessive, broken bushes, bent or broken shaft vibrations etc. Use a larger
pump chosen from the catalogue.
❑
Tight tolerances.This is shown by pump seizure, overheating, breakage of or damage to bushes, and motor overheating, breakage of or
damage to bushes, and motor overload. Increase the clearances after consulting Varisco and giving full details on the application and duty.
❑
Lack of lubrification causing noise, heating and rapid wear of the external pedestal bearing and wear of the oil seal, or noise in the gear
box. Ensure that the ball bearing is lubricated as directed in paragraph 11.1. Ensure that the gear box is lubricated as instructed.
❑
Misalignment. This is shown by non uniform wear (wae on one side of the casing, of the packing or of the cover). The possible causes are
deformation of the casing due to the weight of the pipework, misaligned flexlible coupling, excessive belt tightening or base plate out of
plane.
❑
Check the alignment of the pump and drive under conditions as near as possible to those of operation. Support the pipework and check
the type of belts.
❑
Dry running and pump seizure due to the deformation of internal components, overheating and colour changes caused by excessive heat.
❑
Ensure that liquid is present, mount a foot valve when starting the pump or install an adequate alarm system or motor cut out when the
pump runs dry.
10
ROUTINE MAINTENANCE
10.1 Lubrication
The external pedestal bearing has a grease nipple. Lubricate the bearing with suit-
able grease (MOBILUX EP2, AGIP GR MU EP2, IP ATHESIA EP2 or equivalent)
every 500 hours of operation or every two months, or more frequently if the pump
duty so requires. Do not use excessive quantities of grease.
10.2 Packed gland seal
If the drip from the gland is excessive, tighten the gland screws gradually without
overtightening.
During operation, liquid must leak through the packing for lubrification and cool-
ing. If the leak is excessive, replace the packing or use another type of packing. If
the loss of liquid is too dangerous because of corrosion or fire hazard, a mechan-
ical seal must be fitted.
grease
nipple
fig. 6
packing rings
gland
screw
fig. 7
