SHUT OFF TEST OF A PUMP

WHAT CAN SAY THE SHUT OFF TEST?

AT WHAT HEAD THE REAL H-Q CURVE STARTS?
AT WHAT POWER THE REAL P-Q CURVE STARTS? 

Confirm the diameter of the impeller.
Confirm the speed of rotation.
Confirm the direction of rotation.
Validate the measurements at other operating points.

Shut off test is a very useful approach for validation of field measurements.
Very often characteristics of pumps differ from the curve in the catalog or initial after a long time of operation.
Trimming of the impeller can be made before and the new curve is not known.
Pump model can be unknown 

WHAT IS THE MAIN ADVANTAGE OF SHUT OFF TEST? 
FLOW RATE OF PUMP IS KNOWN

Q= 0

PERFORMING A SHUT OFF TEST OF PUMPS 

What is necessary to know before!!!

  • The Shut off test can be used only during a limited period !!!

  • For centrifugal pumps, not more than 3 minutes!!! 

  • Otherwise, there is a risk of a pump overheating.

NEVER USE IT FOR POSITIVE-DISPLACEMENT PUMPS !!!

PERFORMING A SHUT OFF TEST OF PUMPS 
During the shut-off test we measure the following parameters  
Pinlet  - inlet pressure
Pdisch  - discharge pressure
IA, IB, IC  - current of three phases 
SOT_pic.png

The idea of SOT is to measure pump parameters when the discharge valve is closed and the pump operates at zero flow.

CONDUCTION A SHUT OFF TEST OF PUMPS 
SOT_CURVE.png

When you close the valve on the discharge pipeline And the operating point will come to the position with zero flow.

VALIDATION OF MEASURED PARAMETERS 
How Shut Off test allows users to validate measured parameters?
Two results can be achieved:
1. Shut off point coincide with the curve 
2. Shut off point standoff the point on the curve.
SOT_Pump Curve.png
Conclusion:
The H-Q curve is close to the original.
We can define the flow by measuring pump Head 
Conclusion:
The H-Q curve is NOT close to the original curve.
Impeller was trimmed either at the factory or further. 
The elements of a pump are worn out.  
SOT_pump curve_1.png