Parker PVP Piston Pump Noise: How to Identify the Cause

When a Parker PVP piston pump becomes noisy, record the operating condition. Noise that fades as oil warms points in a different direction from noise accompanied by slower hot operation. Foaming after hose replacement and vibration after motor replacement also suggest different checks.

Inlet supply, entrained air, internal leakage, mechanical alignment and compensation control can all contribute. Relate the sound to temperature, flow and pressure changes before deciding to dismantle the pump.

Noisy when cold, quieter when warm

Cold oil increases resistance in suction lines, bends and strainers. At large displacement the pump needs more inlet flow. Inadequate supply lowers inlet pressure and can cause gas release or cavitation.

The PVP catalogue gives an inlet limit of 0.17 bar vacuum at 1800 r/min with petroleum-based hydraulic fluid. This is pressure below atmosphere, not absolute pressure. Permitted inlet conditions at other speeds depend on the relevant model curve.

Suppose cold-start noise diminishes after warming. If inlet vacuum is greater when cold at the same flow, check viscosity, suction-line diameter, bends and strainer restriction. Restore inlet conditions and reassess before opening the pump to investigate wear.

Speed can magnify the problem. At a full displacement of 33 cm³/rev, theoretical intake flow is 39.6 L/min at 1200 r/min and 59.4 L/min at 1800 r/min. A 50% speed increase raises intake demand by 50%.

A line adequate at low speed may have excessive pressure drop at the higher speed. Destoking reduces intake demand, so record displacement or movement state as well as noise.

Foam appears after a suction-hose replacement

A poorly sealed suction connection can admit air when its internal pressure is below atmosphere without leaking oil externally. A dry connection is not proof of an airtight joint.

If noise and foam begin after hose replacement with unchanged speed and pressure, inspect the new connections, flange O-rings and hose suitability for vacuum service. A damaged seal can admit air; a collapsed inner liner increases restriction. Both faults can occur together.

Low-level vortexing, excessive return agitation or aerated return oil entering too close to the suction point can also introduce air. Observe oil level, return location and when foam appears.

Fluid condition affects foaming too. Interpret it together with inlet pressure and seal checks. Inspect or dismantle hoses and joints only after stopping and isolating the equipment; retain temperature, level and operating records from running conditions.

Hot operation is noisier and the cylinder slows down

Wear can enlarge internal clearances. As hot oil becomes less viscous, internal leakage may become more pronounced. Slower hot movement together with increased case-drain flow at the same pressure warrants a pump performance check.

For example, a stroke that previously took similar time cold and warm now takes longer when hot. If speed, outlet pressure and displacement state match, and hot case flow has increased relative to a healthy record, investigate internal leakage.

PVP case flow also includes control and lubrication-related flow. Oil leaving the case drain is normal. Assess changes under comparable conditions rather than applying one arbitrary flow limit to every pump size.

Keep the case-drain path unrestricted and use suitable measuring equipment. Blocking it or fitting an undersized temporary hose raises case pressure and can affect pump operation.

Normal pressure with insufficient flow can also mean the variable-displacement control has destroked the pump. See PVP normal pressure but slow cylinder movement.

Vibration starts after motor replacement

If noise starts after replacing the motor or coupling, or moving the pump unit, and changes little with load, inspect the drive connection.

Coupling misalignment, incorrect axial installation, loose fasteners and inadequate base stiffness transmit vibration into the housing and piping. After shutdown and isolation, inspect the flexible element, alignment, fasteners and base. A shaft that turns freely is not proof of correct alignment.

Parker specifies alignment, rigid mounting and coupling installation requirements for PVP pumps. Correct mechanical installation faults before assessing the remaining internal pump noise.

Noise and pressure oscillate together during holding

A PVP reduces displacement when pressure reaches its setting. Periodic noise accompanied by pressure fluctuations during holding calls for checking compensation control, control lines, relief circuitry and changing oil demand.

If high-flow movement is smooth but periodic noise starts only at the holding position, investigate pressure control. Observe whether the pump repeatedly strokes and destrokes and whether another valve unloads oil at the same time.

The article on PVP flow reduction at the pressure setting explains the difference between normal destroking and repeated loading and unloading.

Useful records without a flowmeter

Stop further trial operation if noise accompanies pressure loss, severe vibration or visible metal debris. These indicate damage or abnormal operation that continued running can aggravate.

Conclusion

Cold high-flow noise calls for checking inlet supply. Air after hose replacement calls for checking suction seals and hoses. Hot slowing with increased case flow calls for investigating leakage. Check alignment after motor replacement, and compensation when holding noise tracks pressure oscillation. The operating condition determines which check is most useful.