Preventive maintenance
Preventive maintenance (PM) of a hydraulic system is basic and simple and, if followed properly, can eliminate most hydraulic component failure. PM is a discipline and must be followed as such in order to obtain results. We must view a PM program as performance oriented rather than activity oriented. Many organizations have good PM procedures, but do not require maintenance personnel to follow them or hold the personnel accountable for the proper execution of these procedures. In order to develop an effective preventive maintenance program for your system, you must follow these steps:

• First, identify the system operating condition: Does the system operate 24 hours a day, 7 days a week? Does the system operate at maximum flow and pressure 70 percent or better during operation? Is the system located in a dirty or hot environment?
• Second, what requirements does the equipment manufacturer state for preventive maintenance on the hydraulic system?
• Third, what requirements and operating parameters does the component manufacturer state concerning the hydraulic fluid ISO particulate?
• Fourth, what requirements and operating parameters does the filter company state concerning its filters' ability to meet this requirement?
• Fifth, what equipment history is available to verify the above procedures for the hydraulic system?

As in all PM programs, we must write procedures required for each PM task. These steps or procedures must be accurate and understandable by all maintenance personnel from entry level to master.

PM procedures must be part of the PM job plan that includes tools or special equipment required to perform the task, parts or material required to perform the procedure with store room number, safety precautions for this procedure, and environmental concerns or potential hazards.

Preventive maintenance tasks for a hydraulic system could include the following:

• Change the return or pressure hydraulic filter
• Obtain a hydraulic fluid sample
• Filter hydraulic fluid
• Check hydraulic actuators
• Clean the inside of a hydraulic reservoir
• Clean the outside of a hydraulic reservoir
• Check and record hydraulic pressures
• Check and record pump flow
• Check hydraulic hoses, tubing, and fittings
• Check and record voltage reading to proportional or servo valves
• Check and record vacuum on the suction side of the pump
• Check and record amperage on the main pump motor
• Check machine cycle time and record.

Preventive maintenance is the core support that a hydraulic system must have in order to maximize component and life and reduce system failure. PM procedures that are written properly and followed properly will allow equipment to operate to its full potential and life cycle. The process allows a maintenance department to control a hydraulic system rather than the system controlling the maintenance department. We exercise control by deciding when we will perform maintenance and how much money we will spend. The alternative is breakdown maintenance at a much higher cost.