PUMPS - HOW TO CHECK THE CLEARENCE OF IMPELLER IN SINGLE STAGE PUMPS

 HOW TO CHECK THE CLEARENCE OF IMPELLER IN PUMPS AND COMPRESSORS

WHAT IS PUMP CLEARENCE?

• All centrifugal pump must have clearance between the stationary pump casing and the rotating element. in single stage pumps this clearance is limited to the clearance between the impeller surfaces and the casing, and the clearance between the seal cavity (stuffing box) throat bushing and the shaft.

TYPES:

In this clearance are classified into two types these are,

1. IMPELLER FRONT CLEARANCE
2. IMPELLER BACK CLEARANCE 

1. IMPELLER BACK CLEARANCE:

• The clearance between the backside of the impeller (shroud) and the stuffing box or crown (wear) plate.

• actually this clearance standardize the stuffing box pressure and should be strictly followed incase of depressurizing vanes  on impeller and semi open impellers.

HOW DO CHECK IMPELLER BACK CLEARANCE?

• By the use of feeler gauge and with dial indicator as possible.

HOW DO YOU ADJUST IMPELLER BACK CLEARANCE?

• Add or shims removed behind the stuffing box

• changing the position of the rotor depends clearance if possible

• machining of impeller hub if there is no another way.

2. IMPELLER FRONT CLEARANCE:

• The clearance between the frontside of the impeller (crown) and the casing or wear plate.

• This clearance should be strictly followed incase of semi open impellers.

HOW DO CHECK IMPELLER FRONT CLEARANCE?

• By the use of feeler gauge and with dial indicator as possible.

HOW DO YOU ADJUST IMPELLER FRONT CLEARANCE?

• Add or remove casing gasket thickness