ChemEng33
Chemical
- Jul 2, 2017
- 5
A new centrifugal pump has been installed which is capable of exceeding the pipework's design pressure when the discharge is blocked. The client would like a relief valve to be installed on the discharge of the pump which relieves to the suction side of the pump. I am trying to determine what the required relieving rate would be and would be very grateful for your thoughts.
From my understanding, as the discharge valve is closed the pressure will increase along the pump curve until the relief valve starts to lift (relief valve set pressure - pump suction pressure). The further the discharge valve is closed the more flow is bypassed across the relief valve. As the discharge valve is fully closed all the flow is bypassed across the relief valve and the pump suction pressure becomes the discharge pressure - frictional losses. The pressure will fall along the pump curve and flow will increase.
My questions therefore are firstly, is my understanding correct and how do you determine the point at which maximum flow through the relief valve would occur?
If I assume that the only pressure losses are through the orifice of the relief valve, would you calculate the pressure drop across the relief valve with incremental increases in flow until a point on the pump curve was found?
Thanks in advance
From my understanding, as the discharge valve is closed the pressure will increase along the pump curve until the relief valve starts to lift (relief valve set pressure - pump suction pressure). The further the discharge valve is closed the more flow is bypassed across the relief valve. As the discharge valve is fully closed all the flow is bypassed across the relief valve and the pump suction pressure becomes the discharge pressure - frictional losses. The pressure will fall along the pump curve and flow will increase.
My questions therefore are firstly, is my understanding correct and how do you determine the point at which maximum flow through the relief valve would occur?
If I assume that the only pressure losses are through the orifice of the relief valve, would you calculate the pressure drop across the relief valve with incremental increases in flow until a point on the pump curve was found?
Thanks in advance