A common area of disagreement in the field of hydraulics is whether hydraulic pump strainers are necessary to filter out larger contaminants from the system. There are valid arguments for both sides, and many would state that the use of strainers is more of a legacy component than a necessity. The ultimate choice is up to you, but it is important that your choice is based on facts.
What Are Hydraulic Pump Strainers?A hydraulic pump “strainer” typically refers to a mesh strainer used as a filter at a pump inlet. Its purpose is to filter out contaminants as the hydraulic fluid approaches the suction side of a pump.
They are relatively coarse 140-micron filters that are screwed onto the pump intake penetration that is located inside the hydraulic reservoir itself. They prevent larger contaminants from entering into the suction side of the pump, and are sometimes referred to as “trash filters” because of this.
Pros and Cons of Hydraulic Pump Strainers
One of the immediate drawbacks of a having such a filter on the suction side of the pump is the potential for cavitation to occur in the intake line. Cavitation is the formation of bubbles or cavities in liquid, developed in areas of relatively low pressure. When these bubbles collapse or implode, it triggers intense shockwaves inside the pump which can potentially cause significant damage. A strainer can cause a pressure drop even when it is kept very clean and can induce a severe pressure drop when it becomes clogged. This leads to starving the pump and, in turn, major damage.
If the hydraulic reservoir starts out clean and strict cleanliness and filtering procedures are used when adding fresh hydraulic fluid, then any contamination that results would simply not be captured by such a coarse mesh screen. Again, that is assuming that the hydraulic fluid is always filtered before it is added to the reservoir and contamination prevention procedures are followed carefully. The purpose of the hydraulic pump strainer is not to capture finer contaminants, but larger objects that may make their way into the hydraulic system.
If, on the other hand, technicians are careless or maintenance is regularly done in an extremely unclean environment (such as heavy equipment maintained in the field) where debris such as nuts, small rocks, pebbles, or gravel can find their way into the hydraulic reservoir, then the strainer will effectively prevent serious damage to the pump. However, the pump intake line is usually four inches off the bottom of the reservoir if designed and installed correctly; this means that it would be very difficult for something like a piece of rock or gravel to make its way to the intake line. Large, dense objects pose a minimal threat even if they do make their way into the reservoir.
Hydraulic pump strainers can prevent the free and complete filling of a pump’s chambers, reducing its effectiveness and efficiency. This can become a problem when the strainers get clogged, and a common culprit is grease. If grease finds its way into the hydraulic fluid, it will eventually disintegrate and cause minimal problems at most. However, if it encounters a strainer on its path through the system, then it can quickly clog the strainer, starve the pump, and cause severe issues with cavitation. If enough pressure builds up, the strainer can fail and introduce steel mesh particles into the hydraulic fluid. That type of damage can quickly reach catastrophic levels.
The Importance of Hydraulic Pump Strainer Maintenance
Maintenance is another potential problem: it is no small task to check and change these strainers. Hydraulic pump strainers are located within the hydraulic reservoir, which can discourage a careless technician from any attempt to maintain them. If a technician is sloppy enough to let a bolt fall into the hydraulic reservoir, he will not be likely to follow a strict regimen of strainer maintenance. As these strainers get clogged, they increase the chances of cavitation and can result in serious damage to the pump. In short, if a strainer is used, then it must be carefully maintained to ensure that it prevents problems rather than introduces them.
Using Strainers in Hydraulic Pumps
The decision to use or forego a strainer is ultimately up to the owner of the equipment. If you plan to follow an extremely strict regimen of strainer maintenance despite the inherent difficulties in accessing them, then the strainer should introduce few if any problems to your hydraulic system. Strainers can successfully prevent larger objects from making their way into the pump intake and causing devastating damage, even though modern design and installation techniques minimize the chances of such debris ever reaching the pump intake.
Keep in mind that modern hydraulic maintenance techniques work very well to prevent this type of contamination in the first place, causing many pump owners to decide to remove the strainers from their system. However, it might be best to consult the owner’s manual and manufacturer’s documentation before any such steps are taken.
Hydraulic Repair Facility Offering Superior Equipment Maintenance Services
At MAC Hydraulics, we provide customized maintenance plans and on-site services tailored to the maintenance requirements of your equipment. Once a program is in place, our highly trained technicians will implement the latest techniques to keep your equipment running. We can handle it all from fluid analysis to filter changes to hose replacement. In addition, we can help you with decisions about issues such as hydraulic pump strainers, providing up-to-date information and informed opinions that will not only minimize the downtime of your equipment but help your equipment retain its value and efficiency. Our skilled technicians, with extensive experience in hydraulics and a commitment to quality, are waiting to serve all of your company’s hydraulic needs – contact us today!