Component Related Documentation

Return line filters are the least expensive filter to install into a system because, unlike pressure line filters, a high pressure rated housing is not required. Return line filters trap particles ingested by the stroking of cylinder rods as well as particulates resulting from system generated wear, capturing the particles before as the fluid returns to the reservoir. Return line filters must be sized to handle the maximum return flow rate from the system resulting from flow intensification rates as differential area cylinders are retracted.

Safety Related Notes

Before working on this machine, perform lockout-tagout procedures per the rules of your plant. Determine the sources of energy on this machine – electrical, pneumatic and hydraulic – and release or vent sources of stored energy – electrical capacitors, air receivers, and hydraulic accumulators. Shut off sources of power – electrical, pneumatic and hydraulic. Safely block mechanical sources of energy such as loaded springs and loaded machine members, or safely position the machine members so they are unloaded and springs are not under tension. Beware of hot hydraulic fluid and hot surfaces which can cause burns. Never “crack a hydraulic or pneumatic fitting” to check for the presence of stored energy. Hydraulic fluid injection injuries, as well as injection injuries from many other fluids, are extremely serious and must be treated immediately by medical personnel familiar with this type of injury. Loss of body parts or death may result from improperly treated fluid injection injuries! Never use your hands to feel for a hydraulic leak! Review the schematics and think before proceeding to work on the machine to ensure you have made the machine safe to work on.

Troubleshooting Document

Probable Cause	Possible Remedy
Restricted return filter	Check for bypass of element. Replace element.
Improper size element	Replace element with proper size.
Restricted suction filter	Check for high vacuum reading. Replace or clean filter element
Restricted pressure	Check for high differential across filter Replace element
Restrictive suction filter (cavitation)	Check for high inlet vacuum. Replace or clean element.
Loose filter housing cover (aeration)	Check for loose mounting bolts on cover.
Low fluid level (aeration)
Improper type of filter element	Determine if the micron rating of element is correct foe application. Check for bypass condition.
Plugged element	Replace o clean element
Filter change interval too long	Increase filter change frequency. Add bypass indicators to filters.
Pressure differential too high	Check for high inlet pressure. Replace element with a high pressure element and housing
Ruptured element	Check for stuck bypass: repair or replace. Replace element Check for high pressure surging.
No element	Install proper element
Fluid viscosity too high.	Check for recommended fluid viscosity.
Broken spring or weak spring	Remove and replace bypass spring.
Plugged element	Replace or clean element
No element installed	Install element
Ruptured element	Replace element. Refer to ruptured element problem
Broken spring	Remove and replace bypass spring.
Too high pressure	Check for pressure surges and correct. Check suitability of element of housing for application.
Shock pressure	Install shock suppressor (accumulator).
Bypass not installed or stuck close	Check housing for installed bypass. Check for broken spring or guide system. Replace bypass
Too high pressure	Check suitability of element for application.
Change interval too long	Decrease time between filter change period. Add bypass indicator to filter application.
Oil viscosity high during cold start up.	Run system until it reaches normal operating temperature.
Highly contaminated system (If new system has not been flushed. It’s common to load a filter with dirt within minutes of initial startup initial startup)	In new systems, flush with low viscosity fluid at high velocities. Replace filter element several times until fluid at high velocity. In existing systems, consult specialist and replace filter element(s)
Filter bypass setting too low relative to filter pressure drop with a clean element installed (for given conditions)	Select a higher bypass setting if available and if circuit conditions will permit. Replace wrong element with correct one.
Wrong element installed (filter media too fine and/or pressure drop too high)	Replace wrong element with correct one.
Filter indicator out of calibration	Clean indicator, most will read ”CLEAN” when system is shut down and there is no flow through filter. Replace or calibrate indicator.