SLURRY PUMP IMPELLER ADJUSTMENT
1.Initial Adjustment
With a Gland Seal assembly fitted,both Rubber and Metal Lined Slurry Pumps should be adjusted to operate with the Impeller having minimum axial clearance with the front casing liner(Throatbush or Cover Plate Liner).This is most important with High Efficiency Impellers.Adjustment of Impeller front-end clearance is carried out as follows:
(a)Rotate the Shaft clockwise(as viewed from the drive end)by hand,and move the Bearing Assembly forward(towards the pump intake)by adjusting the rear nut on the ADJUSTING SCREW until the Impeller rubs on the front Liner.
(b)Unscrew the rear nut by one sixth of a turn,and move the Bearing
Assembly back by adjustment of the front nut on the Adjusting Screw until the plug on the Bearing Assembly contacts the rear nut.Fully tighten the front nut to secure the Bearing Assembly in position.
(c)Ensure that the Shaft can now rotate freely without contact of the Impeller with the front Liner.
If contact occurs,repeat step(b).
NOTE:After each Impeller adjustment is completed,the BEARING HOUSING CLAMP BOLTS must be tightened to torque values indicated in(Ref.2),below.If a torque wrench,or equivalent device is not available,bolts should be tightened as Ref.3.
With a Centrifugal Seal or Super Seal assembly fitted,the pump should be adjusted to operate with the Impeller having approximately equal axial clearance with the front and rear casing liners.
If leakage occurs from the Centrifugal or Super Seal during slurry pump operation,the Impeller should be adjusted rearwards to minimize axial clearance between the Impeller and rear casing liner.
If seal leakage persists after Impeller adjustment,this indicates that the intake pressure is excessive for the Impeller fitted.Leakage may be prevented by fitting of an alternative Impeller having improved intake pressure sealing characteristics.This may require fitting of a differential Impeller.
(2)Periodic Adjustment
Periodic adjustment of Impeller clearance over its operating life is an important factor in maximizing wear life of both Impeller and front Liner.Extensive field experience has shown that an increase in wear life of up to 50 percent can be achieved by regular Impeller adjustment,compared with pumps not subject to initial or ongoing adjustment.Regular Impeller adjustment has shown an increase in wear life of typically 20 percent compared with pumps subjected only to initial adjustment.
The recommended procedure for periodic Impeller adjustment is as follows:
(a)At initial pump assembly,adjust Impeller to“just clear”the Throatbush or front Liner,as described in(1).
(b)After 50 to 100 hours of slurry pump operation,re-adjust Impeller front-end clearance.
(c)Re-adjust Impeller front-end clearance a further two or three times at regular intervals over its wear life.This may coincide with regular pump maintenance intervals,typically 500 hours.
NOTE:After each Impeller adjustment is completed,the BEARING HOUSING CLAMP BOLTS must be tightened to torque values indicated in(Ref.2),below.If a torque wrench,or equivalent device is not available,bolts should be tightened as Ref.3
TIGHTENING TORQUE(Ref.2)
For CLAMP BOLTS on the bearing housing
Ref. 3
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Frame Size
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Minimum Torque(N m)
|
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A & B
|
10 |
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C & D
|
45 |
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E & F
|
185 |
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G
|
325 |
Ref. 3
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Bolt Size(mm)
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Shank Length Between Load Faces of Bolt and Nut(mm)
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Final Torsion Displacement Between Bolt and Nut (turns)
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||
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M16-M22
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>120
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0.75
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||
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M24-M36
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>160
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0.75
|
||
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M38-M64
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>200
|
0.75
|
