Thrust block and surge
Thrust block and surge
(OP)
I am busy with the design of a pumped main. Regarding the design of thrust blocks: What is the accepted practice with respect to the pressure considered. I see three alternatives:
1) Normal duty point and flow
2) Pump maximum pressure (potentially zero flow, but not nessarily)
3) Surge pressure.....what flow?
I am sure no 3 will govern, but may be excessive!
Also the restriant factors involved in the resistance will be different: if soil resistance, the surge pressures will invoke passive resistance which will be significantly larger, whereas under normal operation a bearing capacity calculations is more appropriate.
My specific situation is the flanged steel bends leading upto the approach of a steel pipe bridge ( VJ expansion joints on steel pipe on bridge and PVC leading upto it, so non continuous piping.) I am not able to make much use of soil resistance and must provide a mass of concrete on these bends. The question of surge pressure now becomes much more important
Any comments?
1) Normal duty point and flow
2) Pump maximum pressure (potentially zero flow, but not nessarily)
3) Surge pressure.....what flow?
I am sure no 3 will govern, but may be excessive!
Also the restriant factors involved in the resistance will be different: if soil resistance, the surge pressures will invoke passive resistance which will be significantly larger, whereas under normal operation a bearing capacity calculations is more appropriate.
My specific situation is the flanged steel bends leading upto the approach of a steel pipe bridge ( VJ expansion joints on steel pipe on bridge and PVC leading upto it, so non continuous piping.) I am not able to make much use of soil resistance and must provide a mass of concrete on these bends. The question of surge pressure now becomes much more important
Any comments?





RE: Thrust block and surge
I think you've answered your question.
You have to design for the worst case. That is a surge produced by an event such as pumps starting against closed valves or the like.
I think a mass of concrete and mechanical joints in the critical areas will be needed.
Alternatively, surge supression, like a surge tank may be applicable, but I'm not an expert on those systems.