Hydraulic Preventive Maintenance

A guide to hydraulic preventive maintenance

The importance of hydraulic preventive maintenance reaches well beyond just keeping one machine running. If that machine is on a production line or part of an extraction process then an unplanned stoppage can bring everything to a halt.

A sudden and unpredicted failure of any machine component can be more than inconvenient, it can be catastrophic.

The load bearing nature of most hydraulic systems means that sudden unexpected failure can be highly damaging.

Despite this reality being well known, lack of hydraulic cylinders maintenance is still the leading source of hydraulic system failure.

A well planned and implemented hydraulic preventive maintenance schedule with associated procedures is a good investment and will pay for itself many times over during the life of the equipment.

Defining Hydraulic Preventive Maintenance

Hydraulic Preventive Maintenance does not have to be complex, but it does have to be regularly carried out.

Regular means having defined time spans between each maintenance activity. It also means clearly defining what needs to be checked, adjusted or changed during the maintenance activity.

The best way to define what will be done and when is by writing everything down in procedure documents. The procedure documents should also say who is responsible for carrying out the work and who is supervising the maintenance.

A good tip when drawing up procedures is to use job titles instead of people's names. This approach means the procedure does not have to be re-written and re-issued every time someone changes jobs.

Organisations with a formal quality management system (QMS) such as ISO 9000, will already have the necessary  procedural structure in place. However it is still important to review frequency of use and checks to make sure everything is correct and being carried out.

If your organisation does not have a formal QMS then procedures will need to be written from scratch and so the following can be used as a guide.

Creating a Preventive Maintenance Schedule

The first thing to do when creating a new preventive maintenance schedule is to review the machinery to be maintained. This review needs to consider both how the machine is used and the environment it operates in.

There are 4 stages to this as follows:

Stage 1 – Usage and environment

Assess the operating hours of the hydraulic system. How long does the equipment operate on a daily or weekly basis? For example, does it operate over 24 hours for 7 days per week or more like 16 hours per day for 5 days per week?

Next, assess the flow and pressure of the hydraulic system during its operations. Take a look at how close it operates to its operational limits. You should be able to find out its limits in the operating manual. If not, then you may need to contact the original manufacturer for clarification.

Finally, assess the environment the machine operates in. For example, is it in an exceptionally hot or dirty location, or perhaps exposed to salt water.

With this information we can assess the overall demands on the equipment. We can then make an estimate on the level and frequency of checks. So more problematic environments like those exposed to salt water will have more frequent and detailed checks.

Stage 2 – Original Equipment Manufacturer’s Recommendations

Look at the machine manufacturer's recommendations for preventive maintenance. Note the detail of the recommended checks and the frequency.

Check what the recommendations are from the hydraulic assembly manufacturer regarding particulates in the hydraulic fluid. This can be separate information to the machine overall and can make a big difference to the frequency of checks required.

Manufactures should normally provide advice on the level and frequency of checks. This can be adjusted according to the information gleaned from Stage 1 and any additional information you may have about the hydraulic system(s) in particular.

Stage 3 - Component Manufacturer’s Recommendations

Check the filter manufacture's documentation to ensure the particulate requirement discovered in stage 2 can be met.

This stage is especially critical if the filter has been changed in the past and is no longer the one supplied by the original equipment manufacturer.

This information may require you to further adjust the frequency, or detail of checks established at stage 2.

Your procedure should make an allowance for review and possible frequency or detail changes if a component is introduced from a new manufacturer.

Stage 4 – Maintenance History

Check the past maintenance history on this equipment. If breakdown maintenance has been undertaken more than once then this information may provide a clue as to the maximum interval for preventive routines.

If you find that past breakdown frequency is greater than the preventive maintenance schedule estimated in the earlier stages then you may need to carry out checks and adjustments more frequently.

For example, if the procedure defines checks and adjustments every 6 months, but the machine is breaking down every 4 months, then checks and adjustments should be set at 3 months.

If you find that the preventive maintenance frequency you end up with is much greater than that recommended by the machinery manufacturer then it is possible the machine is doing more than it was designed for. 

It is also possible the machine or assembly is approaching the end of its life. If this is the case you should consider a potential exchange, or upgrade. Please get in touch and we can run through some options with you.

Detailing the Procedures

hydraulic maintenanceHow preventive maintenance in your organisation is managed and carried out should be detailed in your Quality Management System (QMS). 

If a QMS does not exist then a procedure will need to be established that details how the maintenance is scheduled and monitored.

For each individual piece of equipment or machinery, a separate standard operating procedure will be required for the preventive maintenance.

Each of these procedures should contain the following basic information:

Title of the procedure

A short description of what the procedure covers.

Objective of the Procedure

A brief overview of why the procedure exists and what it is trying to achieve.

Responsibility for undertaking the procedure

The job title(s) responsible for ensuring the procedure is carried out correctly as scheduled. This can be who is doing the procedure as well as who is supervising. Avoid using personal names as people can move on.

Authorised responsibility for the content and date

The authorised responsibility is the person who checked the content of the procedure and gave permission that it can be issued and used. 

Here a name can be used in conjunction with job title as, even if the person moves on, we still need to know specifically who originally made the authorisation.

Ideally this person who authorises the procedure should be in a role above those responsible for carrying out the procedure. It is possible to compromise in smaller businesses without a defined management structure.

Authorisation should be confirmed with a signature and date showing when the authorisation was made.

Identity reference and version number

A unique identity or reference number for this document. This must be combined with a clear indication of the version number.

It should be possible to trace the identifier back to a record in the QMS for the whole organisation. This record should show document revisions, details of changes (ie what, when and who) and the correct current version.

This information is vital so that anyone carrying out the procedure can check that it is the most up-to-date authorised version.


This information should define the minimum frequency with which the procedure should be undertaken. For example, once every 6 months.

It will still be possible to schedule the procedure more frequently (eg once every 4 months) as long as the minimum frequency is complied with.

Tools or special equipment

Defining all of the tools and equipment required to carry out the procedure is useful to make sure that everything is available before work begins. 

Having all the tools and equipment needed at the start reduces time wasted during the procedure. It will keep down time to the minimum and reduce the risk of accidental damage from using the wrong tools or equipment.

Parts or materiel required

As with the tools and equipment, identifying all parts or materiel required to be on hand at the start reduces the down time needed.

Identifying the storage location or source of replacement materiel also reduces the preparation time needed.

Safety precautions

Safety precautions should be highlighted at the start of the procedure. However, additional notes of caution should also be added into the procedure at the appropriate stages.

All risks associated with the undertaking of the procedure should be identified. This applies to the maintenance personnel and anyone else who could be at risk indirectly.

Steps should be included in the procedure to reduce all clear risks. These should take into account when deciding who will undertake the procedure – see detailed steps below.

Environmental concerns

Environmental concerns include such things as disposal of waste following a fluid change. These concerns may also form some of the risks – see above.

Detailed steps to be undertaken

This is the detailed step by step procedure.

It is possible to overdo this and so a general rule of thumb is that the more inexperienced the person likely to undertake the procedure, then the more detail it should contain.

It is also worth defining at the start a minimum skill, or experience required to undertake the procedure.

This approach means the procedure can be very brief if the personnel carrying it out are 'always' highly skilled and experienced.

Additional reference material

If good quality maintenance information is contained in the original equipment manufacturer’s manual then it will make more sense to reference it than try to reproduce it.

For example, when detailing a maintenance step it may be possible to say 'see page 97 of the machine operating manual'.

Reference may also be made to the overarching maintenance plan, or schedule and any smaller sub-procedures that may exist for highly detailed steps.

More Information

Please see our technical section for more information on hydraulic troubleshooting and other resources to support your hydraulic preventive maintenance.


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