Sawsan311
Chemical
- Jun 21, 2019
- 303
Dear all,
I am going through the estimation of the design pressure of the pumping system along with its associated inlet and discharge piping based on shut off pressure calculations. During the design stage when the vendor pump curves are not available to get the shut off head, I seek your interpretations of the best descriptive analysis for estimating the shut off pressure considering API 610 section 6.3 recommendations on allowing tolerances for performance hydrotests as well as maximum speed, maximum density and potential future impeller upgrades :
SOP-scenario 1 = suction system design pressure (PSV set point) + maximum sucion static height considering LAHH+ 1.2-1.3 maximum density* g * H rated--> where Hrated is at the rated point and the multiplier represents the rise to shut off for fixed speed to variable speed.
SOP Scenario 2: Maximum suction operating pressure + 1.2 -1.3 rated differential pressure + maximum static height considering LAHH
SOP Scenario 3: Suction design pressure (PSV set point) + rated differential pressure + maximum static height considering LAHH
Do you think above scenario 1 is although conservative but possible since it captures the level increase in section vessel with overfill and triggering of the suction vessel PSV set point along with the associated increase in speed in case pump is operating under VSD control action.
In the case we have available pump performance curve and hence we know the shut off head of the pump at zero flow (even for the maximum impeller which is greater than the rated impeller in service), which of the below scenarios you find practically technically optimum:
Scenario 1: Maximum suction pressure + maximum static head+ maximum density*g*shut off head from curve
Scenario 2: Suction PSV set point + maximum static head + maximum density* g* rated differential head
In my opinion and for this case when the curve is available the shut off pressure shall be:
Scenario 3: PSV set point + maximum static head+ maximum density*g*shut off head from curve
Therefore, do you agree that all shut off pressure calculations need not consider the suction system PSV set point although the above explanation provides the system's reaction following a pump's blocked in scenario.
API 610 also states that a 10% margin to be applied on the estimated shut off because of the performance test tolerences leading to exceeding the shut off head on the curve.
Appreciate your views.
Regards.
I am going through the estimation of the design pressure of the pumping system along with its associated inlet and discharge piping based on shut off pressure calculations. During the design stage when the vendor pump curves are not available to get the shut off head, I seek your interpretations of the best descriptive analysis for estimating the shut off pressure considering API 610 section 6.3 recommendations on allowing tolerances for performance hydrotests as well as maximum speed, maximum density and potential future impeller upgrades :
SOP-scenario 1 = suction system design pressure (PSV set point) + maximum sucion static height considering LAHH+ 1.2-1.3 maximum density* g * H rated--> where Hrated is at the rated point and the multiplier represents the rise to shut off for fixed speed to variable speed.
SOP Scenario 2: Maximum suction operating pressure + 1.2 -1.3 rated differential pressure + maximum static height considering LAHH
SOP Scenario 3: Suction design pressure (PSV set point) + rated differential pressure + maximum static height considering LAHH
Do you think above scenario 1 is although conservative but possible since it captures the level increase in section vessel with overfill and triggering of the suction vessel PSV set point along with the associated increase in speed in case pump is operating under VSD control action.
In the case we have available pump performance curve and hence we know the shut off head of the pump at zero flow (even for the maximum impeller which is greater than the rated impeller in service), which of the below scenarios you find practically technically optimum:
Scenario 1: Maximum suction pressure + maximum static head+ maximum density*g*shut off head from curve
Scenario 2: Suction PSV set point + maximum static head + maximum density* g* rated differential head
In my opinion and for this case when the curve is available the shut off pressure shall be:
Scenario 3: PSV set point + maximum static head+ maximum density*g*shut off head from curve
Therefore, do you agree that all shut off pressure calculations need not consider the suction system PSV set point although the above explanation provides the system's reaction following a pump's blocked in scenario.
API 610 also states that a 10% margin to be applied on the estimated shut off because of the performance test tolerences leading to exceeding the shut off head on the curve.
Appreciate your views.
Regards.
