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Visual examination of filter element
Many filtration problems can be identified with a simple visual examination of Filter Element.
Significant aspects include the following:filter element components, seals, pleat condition and filter media.
1.Filter element Components
Examine components such as the end caps, center core and outer wrap.
1)If they are damaged, investigate whether damage could have caused the fluid to bypass the filter element. The fluid is not filtered any time fluid bypasses the element.
2)If the components show rust, it is possible that the fluid has water contamination. Water in oil could show up as high, abnormal particle counts. The water will also cause the element go into early bypass, which could result in dirty system oil.
There are various seals on an element. The obvious ones are the elastomeric seals on the outsides of the end caps, an epoxy seal (or similar adhesive) between the endcap and the media and another seal along the longitudinal seam. Missing or improper seals provide a leakage path and may explain the increase in particle count.
A missing elastomeric seal is a big concern because if left in the housing, it could affect the sealing performance of the next and all future elements. One must examine the housing to make sure seals are not piling up. Take corrective action to prevent any leakage paths created by improper sealing.
Upon changing an element, the operator must make sure that the seals on replacement elements and spent elements match. If there are any missing parts, check the parts manual to ensure that the replacement part matches the drawing. After verifying that the replacement is correct, check the housing for the missing part.
Most new elements have properly defined pleat shapes. Pleats should be longitudinal and evenly spaced. Compare the new and used element. Are the pleats straight? If they are wavy or bunched up, it may indicate that the element was subjected to high differential pressure or the flow was fluctuating frequently. In most hydraulic systems, fluctuation in flow is a normal phenomenon. A properly sized filter should not be affected by flow fluctuation. Either condition (high differential pressure drop or flow fluctuation) could allow the housing bypass valve to open frequently and cause the oil to bypass the element, resulting in high particle counts.
Observe the media to identify the amount of dirt on its surface. If the entire surface is full of contaminant, the filter element was most likely in bypass and the fluid was not filtered.
Another sign of trouble can be revealed with an inspection of the media texture. If the old media is appreciably softer than the new media then it is possible that excessive heat or water is present in the system. As explained earlier, water may cause bypass conditions to occur and account for the higher particle counts. The water must be removed to improve the filter life and also to prevent future damage to system components.
If the element was subjected to high temperatures, the media may not show obvious signs of degradation but the oil properties may have changed. Oil may have oxidized and particle counts may have risen.
From Machinery Lubrication