Useful tips on how to troubleshoot a positive displacement rotary pump

If you have a positive displacement pump, it is important to know how to troubleshoot common problems. For example, if the pump isn’t primed, you need to prime it from the side of the outlet by keeping the outlet vent for air open until the liquid comes out of the vent. Another common problem is having the rotating unit turning in the wrong direction or when the valves are closed or there is an obstruction in the outlet or inlet line. In such a case, you should check the flange gaskets and ensure they have their Centre cut out. If the end of the inlet isn’t submerged, you can either raise the level in the tank or increase the length of your inlet pipe into the fluid level. Other common problems include a stuck valve, a clogged filter, a net inlet pressure that is too low, an open bypass valve, a leakage of air in the inlet line, the stuffing box being under negative pressure, the pump is worn, a broken component and when there is no power to the pump. All these issues are minor issues that can be fixed without the intervention of a professional. Here are some useful tips for rotary pumps.

A low capacity from the pump

You should check if the internal clearances of the pump have increased. If this is the case then it is time to change some parts. If the net inlet pressure is too low, you should know that the pump is cavitating. Low capacity could also be due to a filter or strainer being partially clogged in most submersible pumps rental If the low capacity is due to the speed of the pump being too low, you should check the voltage and ensure there is no problem with the power supply. The bypass line could also be open or the relief valve could be stuck partially open. The piping could be damaged due to someone running over it. You should also check the inlet piping because this could be due to a corrosion-resistant liner collapsing in the piping. Another potential cause could be due to air leaking through the packing and if this is the case then you should go to a mechanical seal.

Your pump losing its prime after it has been functioning for a while

This could be due to an exhausted supply of the liquid. You should therefore check the tank level and see whether the float is stuck. It could also be due to the liquid vaporizing at the inlet of the pump or a bypass line heating the income liquid. Another potential cause could be a leak developing in the suction piping.

PD pump using too much power

If your positive displacement pump is using too much power, you should check the speed and ensure it is not too high. Maybe the velocity of the liquid is higher than normal and the discharge pressure may also be higher than calculated.

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