What are the operational precautions for plunger pumps?

A plunger pump operates by the reciprocating motion of plungers within the cylinder block, which changes the volume of the sealed working chamber to achieve oil suction and delivery. Plunger pumps are characterized by their high rated pressure. Below, we will outline the operational precautions for this type of plunger pump, hoping it will be helpful to you.

When operating a plunger pump, it is essential to regularly check the liquid level in the reservoir. Also, inspect the oil levels in the crankcase and the lubricator; if they are low, replenish the oil promptly. Verify that all components of the drive system are functioning properly—ensure that couplings are securely connected and belt tension is appropriate. Check the disc-type pump for any abnormal jamming or excessive noise. Confirm that the nitrogen pressure in the nitrogen accumulator is within the specified allowable range. Then, start the supply pump. Once these checks have confirmed that everything is in order, open the pump’s inlet valve to bleed air from the pump, and then open the relief valve. Next, verify that the supply voltage is correct. Inspect the pump base, plungers, clamps, stuffing boxes, valve covers, and other components for tightness and proper fastening. Adjust the limit settings on the automatic control panel and verify that the overload protection device is reliable. Start the lubrication oil pump to build up oil pressure, and manually operate the lubricator to ensure adequate lubrication of the plungers. Check the insulation and grounding of the main motor, and perform a jog start to confirm that the motor is rotating in the correct direction. Of course, care must also be taken to prevent foreign matter from entering the system. Oil contamination can cause malfunctions in the plunger pump and reduce its service life. Therefore, strict control of oil contamination is crucial; the contamination level should be maintained at or below NAS 10. Install an oil tank filter with a minimum rating of 100 μm at the suction port, and install a pipeline filter with a rating of less than 10 μm in the return line.

During installation, the oil-fill port of the plunger pump shall be oriented upward. If the pump is installed above the liquid level, the suction pipe and its strainer must not extend higher than the pump’s inlet connection to prevent air from entering the suction line. Piping considerations: When steel tubing is used for the suction or discharge ports, the additional load imposed on the pump by the piping can generate noise. To avoid such extra loading, rubber hoses are recommended. Another important consideration is shaft alignment; it is advised to use flexible couplings whenever possible to prevent stress caused by bending or axial thrust. The permissible misalignment should be less than 0.1 mm in radial deviation and less than 0.2° in angular deviation. Attention should also be paid to the suction pressure: in practice, the suction pressure at the plunger pump inlet typically ranges from –16.7 to 50 kPa, and at speeds above 1,800 r/min, it ranges from 0 to 50 kPa. The diameter of the suction pipeline must match the specified flange diameter of the pipeline. The pump’s suction inlet should be no more than 1 m above the oil tank’s liquid level. The drain line must ensure that the pressure within the pump chamber remains below the normal operating pressure of 0.1 MPa, with peak pressure spikes kept under 0.5 MPa. The length of the drain line should be less than 1 m, and it must be installed separately—do not combine it with the return line. The end of the drain line should be immersed in the oil.

The above article has outlined the operational precautions for plunger pumps. We will continue to share additional relevant knowledge in future issues, and we hope it will provide you with practical assistance. We also welcome long-term partnerships with colleagues from across the country.