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What do I need to consider when installing a pressure relief valve and a back pressure control valve on a LPG pumping system?

I’m designing a liquid LPG mixing system and need to consider how to control the back pressure at the discharge of the propane and butane pumps. In the current design, a pressure relief valve is installed at the discharge of the pump to relief excessive head pressure by recirculating the LPG back to the suction of the pump. Since the pressure at the suction of the pump is near to the vapor pressure of LPG, doesn’t this cause LPG to flash due to the pressure drop across the pressure relief valve?

If I install a back pressure control valve next to the pressure relief valve to recirculate the LPG back to the top of the storage tank, I envision I can install a pressure relief valve at the end of the piping (top of the tank) to provide a back pressure at P2 of the control valve to prevent cavitation from happening and the LPG would just flash off at the top of the tank as the LPG discharges from the pressure relief valve. Would this work?

1 Reply

  • Eric: I am with Emerson Regulator Technologies, LPG Equipment in McKinney, TX. We may be able to assist as we provide a good deal of valves, relief valves, etc. in to LPG & butane applications. If you can send us a schematic of your application; we would be happy to provide you some options. Michael.hiefner@emerson.com