Hydraulic filtration is an important element in any hydraulic system; without it, contamination can occur and the whole system can, at best, underperform or, in the worst-case scenario, it can cause complete system failure. Contamination is considered the cause of 85% of hydraulic system failures!
Before we discuss hydraulic filtration and the different types of hydraulic filters and the roles that they play let's discuss contamination.
Types of Hydraulic Fluid Contamination
Initial Contamination - this is caused by the introduction of contaminated fluid into the hydraulic system. For example; introducing new oil that is not clean.
Progressive Contamination - this is caused by the operation of the system; such as metal surface wear, oxidisation or cavitation.
Solid Contamination - such as rust, metal particles entering the hydraulic system or additives.
Liquid Contamination - the presence of water within the hydraulic system due to condensation.
Gaseous Contamination - the presence of air due to inadequate oil volume in the tank.
Any one type of the above contamination, or a combination of several, can cause significant problems for any hydraulic system.
The best way to prevent problems occurring and minimising contamination is to use the correct type of hydraulic filter and to change the filter before it becomes blocked.
Types of hydraulic filters and their roles
Suction Filters - these are positioned before the hydraulic pump and are responsible for protecting the pump from outside contaminants.
Pressure Filters - these are positioned between the pump and hydraulic components such as servo valves or proportional valves. They are designed to ensure the class of contamination filtration required by the components - some hydraulic components require a finer level of filtration than others.
Return Filters - these are positioned on the return line to the hydraulic tank and are responsible for filtering contaminants that may have entered the system i.e. wear of components within the hydraulic system.
How to choose the correct filter
When selecting the correct type of filter, the following considerations need to be made;
Where in the hydraulic system does it need to be?
What is the working pressure?
What is the flow rate?
How does it need to be mounted?
What hydraulic fluid is being used and at what temperature?
What micron rating is required for the element?
Not sure on the answer to any, or all, of the above? And require technical assistance in choosing the correct filter for your hydraulic system? Then call HES - our filtration experts will be more than happy to help you choose the correct hydraulic filter.
When should you change a hydraulic filter?
The simple answer to this is, there is no simple answer!
A filter element needs to be changed before it becomes blocked. Once it is blocked, it is no longer protecting the hydraulic system effectively.
The rate at which the hydraulic filter becomes blocked will vary depending on the application, for example: if the oil is extremely dirty then the element will become blocked quicker than a system that uses clean/pre-filtered hydraulic oil and has good preventative practices in place.
The easiest way to tell when a hydraulic filter element should be changed is by using an indicator. These come in various types; visual, electrical and both visual and electrical.
The indicator is designed to trip and alert the user before the hydraulic filter goes into bypass, warning that the element has a limited contamination holding capacity remaining. When the indicator trips and alerts the user, now is the time to change the hydraulic filter element.
What accessories need to be used with the hydraulic tank to help prevent contamination
Filler Breathers - filler caps and breathers perform a dual function; they filter the air at the hydraulic tank inlet and allow for pre-filtration of the fluid using the strainer, which should catch any large contaminants that may be present when the oil is put into the tank.
Air Breathers - the function of an air breather is to intercept any environmental contamination, for example: dust. Using an air breather can help to extend the life of the filter elements in the hydraulic circuit as it has already captured some of the contaminant before it has entered the system.
Level Gauges - these are suitable for both static and mobile hydraulic applications and offer the ability to track the fluid level in the tank and even monitoring the temperature, if required. HES can also offer electrical gauges that can give a warning on high/low fluid levels.
Suction Strainers - the function of a suction strainer is to offer protection to the downstream pump against cross contamination. HES can offer strainers with and without bypass or with and without magnets.
Float Switches - the function of a float level switch is to detect the falling or increasing oil level in the tank, giving a warning signal when it becomes too high or low. These can be supplied by HES in 500mm or 1000mm rod lengths, which can be cut to a required length.
Inspection Covers - these allow for easy access to the inside of the hydraulic oil tank for inspection and maintenance purposes.
Different hydraulic systems will have different filtration requirements and need different accessories for its tank. But almost all hydraulic systems require filtration to some degree or another.
The best, and often easiest, way to prevent your hydraulic system from failing is to ensure that it has the correct hydraulic filtration in place.
If you require a hydraulic filter, an indicator or any hydraulic oil tank or accessory, or if you need assistance in ensuring you choose the correct filter or accessory for your hydraulic system application then get in touch with our hydraulic filtration experts!
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