If you are purifying HFO or Lube oil this can happen when the oil in the discharge line is cold and highly viscous causing excessive back pressure. If this may be the case make sure that you recirculate the oil through the heater until it is at the correct purifying temperature, 98 C for HFO, 95 C for 4 stroke L.O. and 90 C for 2 stroke L.O. before admitting any oil to the purifier, if you can manually regulate the flow, reduce it until the entire length of the discharge pipe has become hot, and/or open the back pressure regulating valve to keep the back pressure down to the correct level. Then as the back pressure drops increase the flow rate gradually until it is the full rated flow rate and then slowly shut in the back pressure regulating (throttle) valve until the temperatures, flow rate and back pressure have all stabilised and you have the correct back pressure.
This is a common problem where there is a long discharge pipe from the purifier. Hope this helps.
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