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Water contamination in hydraulic fluid and how to eliminate it ben lee
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In this week’s blog we look at how water contamination can affect hydraulic fluid, especially with the winter months approaching, where freezing temperatures can interact with system operation causing potential system damage.


If you see a cloudy build up appearing within the oil in your hydraulic power unit, this could point to water contamination and must be investigated immediately, as it shows that water has risen above the typical saturation level when mixed with oil giving a cloudy-like appearance. This saturation level comes at approximately 200 - 300 ppm at 20°C (68°F) for mineral based hydraulic oil.


Ideally, preventative measures should be taken from the outset to remove the chances of water ingress contaminating oil and this is where desiccant breathers come in to the equation. We have covered these in a recent blog and highlighted their benefits in reducing moisture entering a hydraulic power unit. The silicone gel contained within the desiccate breather soaks up any moisture present, thus helping the system to run at optimal efficiency.


Passing dry desiccant air directly through the system to dry the oil is another effective method of filtering out water and this is best carried out at approximately -40°F dew point temperature. Water ingress and moisture is most commonly found entering the system through the reservoir breather cap, so replacing the standard cap with a purpose built breather will help to alleviate this problem.


When monitoring the colour of the hydraulic oil itself to identify any potential water contamination, it is not always a warning sign if the fluid had some discolouration as this could be attributed to such things as thermal stress and oxidation, which can be commonly found in systems but still need to be monitored to rule out any other issues that may arise. This may include increased heat generated through pressure loss and component failure within the system.


It is always best to take a sample of oil and check it fully for contaminant traces so the exact cause of discolouration can be identified, as speculating and guesswork at this stage could prove to be costly.


The environment around the hydraulic power unit can play a big part in the contamination process. For example, cold temperatures and lack of proper ventilation will contribute to moisture building around the system and increase the possibility of it seeping in, so locating the hydraulic system correctly is crucial. Freezing is another big issue because if the liquid is exposed to extremely low temperatures it could cause catastrophic damage to a system, rendering it in-operational as components could seize up and cause the system to malfunction.


At Hydraproducts, we have the facilities to test if contaminants are present in hydraulic fluid; these samples are then sent off to the lab for further analysis where required to pinpoint exactly what is causing the contamination so it can be effectively dealt with. We always test our hydraulic power units fully before they reach our end customer, to ensure that they are in optimal running condition prior to their first use in an application.

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