Usage:950G II AXR
Filter Classifications for Controlling Contamination
There are three different filter design classifications that are used in implement hydraulic systems on mobile equipment. These classifications are listed below:
- Cartridge filter (shown on left) - The filter element fits into a tank or canister with the opening for the filter sealed off by a cap.
- Canister filter (shown in center) - The filter element is built into its own housing that screws onto a permanent filter base. The filter material used in the canister filter can be identical to the filter material that is used in the cartridge filter.
- Screen (shown on right) - A metallic mesh that fits into a tank or canister, similar to the cartridge filter, but with larger openings to trap large contaminants before they enter the system.
Filters clean the hydraulic oil by removing contaminants that can damage component parts. As oil passes through the filter element, contaminants are trapped. Clean oil continues through the system.
Some manufacturer's filter elements are given a rating, micron and beta, according to its tested ability to trap particles. The smaller the micron rating, the smaller the particle that will be trapped by the filter. The larger the beta number for a given micron size, the more of that size particle that will be trapped on the first pass of oil through the filter. These beta ratings are determined by using a certain type of particle in a controlled test.
Some manufacturers overlook the usefulness of these ratings because they are run with constant, controlled flow without surges and do not address the quality or useful life of the elements.
Most cartridge and canister filters are equipped with a filter bypass valve in order to ensure the system flow is never blocked. The bypass valves also protect the filter from tearing or from a collapse. The blockage that could lead to the failure of a filter could be caused by the following items:
- A buildup of contaminates that clogs the filter.
- Cold oil that is too thick to pass through the filter.
When the bypass valve opens, unfiltered oil circulates through the hydraulic system. Unfiltered oil contains contaminants that could cause damage to hydraulic system components. The filter must be replaced in order to close the bypass if the filter is clogged.
The filter bypass valve that opens due to cold oil will normally close as the oil warms. This action again sends the oil through the filter in order to remove the contaminants.
Replace the filters as recommended by the machine manufacturer in order to prevent clogging of the filter, and in order to minimize oil bypassing when the oil is cold.