Predictive or Planned Maintenance for Hydraulics

08 April 2020 by Mike Retford

For many years the planned maintenance route for hydraulics has been adopted; changing hydraulic filters, breathers, replacing hoses and fixing leaks. Also the system oil may need changing.

What about the pump, instrumentation, hydraulic valves and coolers?

Nobody is going to remove a hydraulic pump and strip it down to look at wear, likewise nobody is going to do that with hydraulic valves, unless there is a problem. Predictive maintenance, utilising modern plant condition monitoring can reduce plant failures and redcue the cost of ownership of hydraulic systems. There are techniques to determine the condition of the above components;

1. Hydraulic pumps -  flow meters inserted into the main pressure line can determine peak flow rates, or installed in the case drain line to measure the flow being lost.

2. Instrumentation -  this can be difficult without removing the instruments for calibration. Using thermal imaging can show up any hot spots and problem connections.

3. Hydraulic valves - the operation of the valves and speed of operation can be determined by data logging. Pressures of hydraulic pressure relief and reducing valves can also be confirmed.

4. Coolers - a thermal imaging camera can show the temperature difference between inlet and outlet. A flow meter in the oil or water will detail the flow. A calculation can be perfomed to determine the heat dissipation. Air blast coolers can always benefit with a good clean of the matrix.

Filters should have blockage indicators and should be changed when they are blocked, else there is a risk of wasting money. Oil analysis has been around for a number of years and is an important part of a predictive maintenance system.  Planned and predictive mainteance are not mutually exclusive, when related to hydraulic maintenance. A good mix of both is cost effective and reliable.

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