24 January, 2021

Top ten tips – oil analysis

21 August, 2015

With between 70 and 80 per cent of all hydraulic failures caused by contaminated oil, effective analysis is vital to ensuring the healthy functioning of machinery. Bosch Rexroth outlines its top ten tips for maintaining oil quality.

1. Monitor

Regular monitoring is essential to ensuring oil integrity, as a minimum oil should be sampled on a quarterly basis.

2. Identify

There are three types of contamination and identifying them correctly will impact treatment:

• Solid - likely to be dirt or dust particles and can cause jamming and wear to components

• Liquid - which can lead to corrosion and impair viscosity and lubricant properties

• Gaseous - resulting in foaming in the oil sequences, inaccurate valve responses and damage to pumps

3. Locate the source

Identifying the source of the contamination will help to prevent or offset further occurrences. These could include built in contamination as a result of the component manufacturing process, external such as air borne contamination ingress, and contamination generated by the functioning of the machine itself.

4. Neutralise

Neutralising the cause of the contamination could include a thorough oil transfusion, installing additional air filters and replacing worn or damaged components.

5. Benchmark

ISO 4406 is the code that almost all industrial oil analysis reports are based, with the benchmark being determined by the application.

6. Filter

Effective filtration can significantly offset, or in some cases prevent, oil contamination. Identifying flow rates, viscosity and pressure are all essential to specifying the right filtration system.

7. Analyse

Effective oil analysis requires in-depth inspection. This could be in a laboratory environment through microscopic particle count and gravimetric test, or through a mobile particle counter installed on the machine.

8. Predict

Recording and plotting results will enable maintenance engineers to identify trends and predict future risks. This is essential for minimising, and in some cases eradicating, unplanned machinery downtime.

9. Prevent

There are a number of simple steps that can be taken that can help prevent contamination:

• Ensure all oil is filtered, whether it’s new or old.

• Change oil filters at least every 12 weeks or by use of filter indication (mechanical/electrical).

• Take oil samples at least every 12 weeks to identify if filters are achieving correct cleanliness level.

• Install air breathers to minimise contaminant ingress.

10. Invest

Oil analysis does come with a small cost of approximately £15 per machine. However, when you consider that the cost of replacing an average sized pump can be anywhere been £3000 and £5000 and that a typical hydraulic system can feature five or more pumps all fed from the same oil reservoir, the financial argument really starts to stack up.


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