With the advancement of hydraulic technology, many people consider hydraulic oil strainers to be a redundant component in the system. The purpose of strainers is to filter out larger contaminants from your oil to prevent them from entering the system. Arguably, your filters should do this work, but many people still insist on using strainers as well. Whether or not you use them in your machinery is your choice, but let’s look at the arguments for and against using strainers from both sides.
Dependng on the hydraulic system you operate, filters generally target and remove contaminants at ten microns or smaller from the fluid. A strainer is also a filter but one that targets contaminants at 75 microns or larger, which is approximately the size of a grain of salt.
Strainers are typically used at pump inlets to filter the liquid before it enters the pump as a first line of defence. There are different types of strainers for large particulates, including mesh strainers and magnetic strainers, which target metal filings.
One of the reasons people prefer not to use strainers is the risk of cavitation occurring in the intake line. Cavitation is where tiny air pockets form in the fluid. Air is also a contaminant, because when the fluid gets put under pressure, these bubbles implode. Cavitation creates shockwaves through machinery and can cause serious damage.
Secondly, strainers, especially if they become clogged with grease, have the potential to cause pressure drops. Loss of pressure puts the system under strain, as it has to work harder to achieve operating pressure. Over time, this will cause significant damage.
Thirdly, there is the argument that strainers are redundant if technicians use clean replacement oil and follow strict filtering guidelines before adding it to the system. Any contaminants in the oil would simply pass through the strainer, as its purpose isn’t to filter out tiny particulates.
Finally, having strainers in the system adds to maintenance. If they aren’t maintained as well as other components, they will cause problems. They are also typically located within the reservoir, so it’s not a simple task to check and replace them. While there are no excuses for careless maintenance, strainers add to the list of parts to check, which adds downtime.
As above, the counterargument for using strainers is to prevent human error when technicians change or replace oil. If a technician doesn’t follow filtration guidelines and large, abrasive debris gets into the system, then the strainer will prevent damage from occurring. Unlike smaller contaminants, which cause damage over time, larger particles like metal filings, gravel and dirt cause immediate, significant damage if allowed to enter the system.
The same applies when machinery gets maintained in unclean environments, such as when it’s necessary to perform maintenance on-site and not back at the workshop. This greatly increases the chance of these larger contaminants making their way into the fluid, where the strainer will catch them before they do any damage.
Technicians who follow thorough maintenance checks will prevent the kinds of contaminants that strainers filter out from entering the system. If you’re confident your maintenance procedures are robust, you may decide against using strainers in your machinery.
Using the same argument, if your maintenance procedures are robust, having strainers in the system shouldn’t cause any issues. For peace of mind, if a large particle of contamination gets into the system, then your strainers will prevent immediate and serious damage and costly downtime and repairs.
At the end of the day, before you make a decision to use or remove your strainers, check the user manual or manufacturer’s recommendations.
