Developing Commissioning Procedures for Hydraulic Equipment

Brendan Casey
Tags: hydraulics

Evidence gained through my many years working in the hydraulic repair industry suggests that the failure of maintenance personnel to follow proper procedures when re-commissioning hydraulic systems after carrying out maintenance work, is a significant cause of infant mortality in hydraulic equipment.

Incorrect commissioning during startup can result in damage to hydraulic components through cavitation, aeration and inadequate lubrication. In many cases, this damage will not show itself until the component fails hundreds or even thousands of service hours after component failure.

A common misconception among maintenance personnel with limited training in hydraulics is that because oil circulates through hydraulic components in operation, no special attention is required during installation beyond bolting the component into position and connecting its hoses. This is not the case.

Damage to hydraulic components during initial startup can be prevented by:

  1. Developing commissioning procedures specific to equipment.
  2. Training your maintenance personnel to effectively carry out these procedures.

Depending on the type of equipment in operation, detailed commissioning procedures may be available from the machine manufacturer on request. If this information is not available for a specific piece of equipment, appropriate procedures should be developed. If necessary, consult a fluid power engineer for assistance. The following generic procedure illustrates many of the issues that should be considered.


If the system is down as a result of a major component failure:

When installing pumps and motors, check the drive coupling for fit on the pump or motor shaft. Loose fitting couplings cause accelerated wear of the drive shaft and should be replaced.

On closed-circuit systems (hydrostatic transmissions), inspect the high-pressure hoses or pipes between the pump and motor, and replace any suspect lines. A burst hose or pipe in service can result in the destruction of the pump and/or motor through cavitation.

Cylinders - Before connecting service lines, fill cylinders with clean hydraulic fluid through the service ports. This reduces the risk of air compression within the cylinder (dieseling) on startup, which will result in damage to the cylinder and its seals.

Motors - Fill the case of piston-type motors with clean hydraulic fluid through the highest case-drain port and connect the case-drain line. Failure to do so will result in damage to the motor through inadequate lubrication on startup. Units that are mounted vertically with the shaft up require special attention to ensure that the fluid level in the case is high enough to lubricate the front shaft bearings.

Pumps - After installing the pump(s) and connecting service lines:


Once commissioning procedures for a specific piece of hydraulic equipment have been developed and the necessary training has been provided, from a preventive maintenance perspective, ongoing costs are limited to training of new maintenance employees.