The Negative Effects of Overpressurization on Hydraulic Components

Blog | November 4th, 2019

A hydraulic pump is designed to run at a specific flow and pressure level, and so, bumping up the pressure level of the pump can cause negative effects on its internal components. This phenomenon, known as overpressurization, can degrade the overall quality of the hydraulic pump and will eventually cause its permanent failure.

Effects of Overpressurization

The power of a hydraulic pump relies on the product of its ability to produce or absorb flow and its maximum pressure rating. Exceeding the optimal pressure to keep the hydraulic pump from running smoothly can, unfortunately, cause three main effects on its components.

  • Loss of Lubrication

In a hydraulic pump, some of its components’ surfaces are separated through a cohesive film of lubricant. Also known as the hydrodynamic (full film) lubrication, this effectively prevents wear and tear in moving components of the hydraulic pump, as well as prevents contact between metal parts.

The load on lubricated surfaces is the product of pressure and area. So, by adding unnecessary operating pressure to a hydraulic pump, it will increase the load on lubricated surfaces. This can ultimately cause boundary lubrication and abrasion between the pump’s moving components, which will contribute to the succeeding effects of overpressurization.

  • Components Separation

Hydraulic pumps that operate at higher than normal pressure can also lead to the separation of components. Take axis piston pumps as an example. The cylinder barrel of these pumps is hydrostatically loaded against the valve plate. To maintain hydrodynamic lubrication between these two components, the hydrostatic force that holds them in contact is remunerated by another hydrostatic force that acts to separate them.

The hydrostatic forces that perform the mentioned functions will be highly effective if the operating pressure is high. However, exceeding the pressure limit of the pumps will easily separate the cylinder barrel from the valve plate.

Perfect positioning between opposing hydrostatic forces is prevented by design geometry. On a cylinder barrel, this creates a twisting force or torque that is supported by the drive shaft or centre pin during normal operations. If the operating pressure exceeds the optimal level, the magnitude of torque created causes elastic deformation of the supporting components of torque. This will make the cylinder barrel tilt and separate from the inlet side.

  • Mechanical Damage

The initial displacement and failure of certain components in pumps, cylinders, and valves can affect the whole hydraulic pump in the long run. The overpressurization in pumps and motors puts tension to the piston-ball and slipper-pad socket during intake, causing the piston retaining plate to buckle. Overpressurization can also separate the slipper from the piston and damage the pumps altogether.

Pressure beyond the design limit can also break the radial design motors. The excessive pressure to the motor causes the motor’s pistons to lift off and then hammered back onto the cam, eventually destroying the motor. If the pressure remains high when the motor is stopped, the pistons and cam can make the motor to freewheel, making its movement uncontrollable. To know more about the causes of overpressurization in hydraulic components, and also the ways to avoid them, contact us at Mobile Hydraulics.

Mobile Hydraulic Specialties Pty Ltd

Factory 89, 38-40 Popes Road
Keysborough, Victoria, 3173

Phone: (03) 9798-6511

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