Goulds Pumps AF (Axial Flow) (42"/1200mm/54/60"/66") LM/LMR Bearings - IOM" - Manual (Page 37)

AF (42-66) IOM 37
Listed below are some causes for circulation loss.
Keep in mind that operation at reduced capacities can
cause damage to the pump.
1. Increase in TDH against which pump operates
could be caused by:
a) Heat exchanger tubes partially plugged.
b) Too many heat exchanger tubes blanked off.
c) Improperly sized or partially plugged strainer.
2. Viscosity of slurry higher than it should be.
3. Pump speed low. V-belt drive may be slipping and
operating pump below design speed.
4. Pump throttled on suction side. This could be
caused by:
a) rubber lining pulling away from the suction pipe
and partially collapsing,
b) large solids dropping into the suction, or
c) by an improperly sized or-plugged strainer in
the suction pipe.
5. Pump partially plugged by large solid jammed
between two impeller blades. This will also cause
rough operation with excessive vibration.
6. Incorrect pump rotation. When changing motors
for any reason or after any electrical system
changes or modifications, always check motors for
correct direction of rotation.
7. Worn pump impeller and/or casing. On a new
pump, clearance between tip of impeller blade and
casing is carefully determined. As this clearance
increases, pump performance decreases.
It is not practical to predict performance at any given
clearance without running a test at this clearance. On
small pumps, this effect is magnified as the
percentage of impeller blade area lost from wear and
corrosion is higher.
Other pump conditions and possible causes
are:
HIGH HP DEMAND
1. Increased head or viscosity
2. Pump speed too high
3. Specific-gravity of slurry higher-than normal
4. Packing gland pulled up too tight
5. Impeller rubbing in casing
NOISY OR ROUGH OPERATION
1. Throttled suction or plugging
2. Impeller rubbing in casing
DAMAGE OCCURS FROM:
1. Increased vibration levels - Affects bearings,
stuffing box seal chamber, and mechanical seals.
2. Heat build up - Vaporization causing rotating parts
to score or seize.
3. Cavitation - Damage to internal surfaces of pump.
4. Loose impeller
5. Broken impeller blade
6. Bearings not properly lubricated
7. Bent shaft
8. Impeller out of balance.
Operating under freezing conditions
Exposure to freezing conditions, while pump is idle,
could cause liquid to freeze and damage the pump.
Liquid inside pump should be drained.
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