Component Related Documentation

Cylinders are linear actuators. Their output force, or motion, is in a straight line. Their function is to convert hydraulic power into linear mechanical power. Their work applications may include pushing, pulling, tilting, and pressing. Cylinder type and design are based on specific applications. Welded-type cylinders are very robust, and are suitable for extreme applications. These applications can include mobile equipment, cranes, civil engineering, and OEM equipment. Both cylinder ends of a welded cylinder are welded into the cylinder tubes. Typically, a plug is held into the cap end by a retainer to allow disassembly of the cylinder for repair.

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
Cylinder leaks internally	Repair and/or replace parts and seals. Check fluid viscosity using a visgage or through oil analysis. Compare to equipment manufacturer’s specification Check for contamination. Flush, clean & refill system.
Aeration of system	Bleed the system of air Check pump intake with vacuum gage. Fix any leaks Check for low fluid level Check for fluid return line in tank above fluid level. Extend return line.
Directional valve not shifting completely	Disassemble and clean Reassemble. Check pilot pressure, too low Check for system aeration. Check for contamination and wear.
Low pilot pressure	Check choke control (if so equipped) for proper adjustment Check source pressure. Adjust as needed. Disassemble and clean valve passages
Cylinder binding or sticking	Disassemble and inspect for probable cause of sticking; clean and reassemble. Readjust rod gland seal packing Realign linkage Check rod for bending. If necessary, check for proper rod size and if a stop tube is needed.
Nicked, worn and/or scored rod and seals	Check rod for damage: replace Check for normal seal wear with a .002 feeler between seals and rod. Should be tight
Loose retainer or brushing	Adjust retainer until leakage stops (V-packing) Remove & replace V-packing
Hard and brittle	Check for excessive operating temperature Remove & replace with heat tolerant seals.
Mushy or soft	Check compatibily of seals and fluid. Replace with compatible seals
Extreme back pressure	Check flow control adjustment and correct if necessary. Check internal cushion adjustment and correct if necessary.
Soft or mushy seals	Check compatibility of seals and fluid. Replace with compatible seals
Hard and brittle	Check for excessive operating temperature. Remove and replace with heart tolerant seals.
Improper installation	Disassemble and turn seals to proper position.
Excessive wear	Remove and replace seals. Flush, clean & refill system Replace with more durable seals.
Hard and/or brittle	Check for excessive operating temperatures.
Pressure too high	Pressure should be lower, o adjusted rated limit. Measure pressure inside cylinder during cushioning. Use external shock absorbing device.
Crushed or extruded seal	Remove and replace seal Lubricate seal before installation Retorque tie rods properly. Check manufacturer specifications.
Mushy or soft seals	Check seal and fluid compatibility. Replace with seal that is compatible with fluid
Improperly torqued tie rods.	Retorque tie rods properly. Check manufacturer specification
Wear or flat spots on seal inner and/or outer diameter.	Check for side loading or for other causes of wear. Replace seals.
Binding of linkage arrangement	Check linkage for proper alignment.
Piston rod bent or broken	Disassemble & replace seals
Piston seal(s) leak	Check & adjust system pressure.
Pressure too low	Recalculate cylinder size and load requirements
Cylinder to small	Recalculate cylinder
Contamination	Replace all worn and scored parts. Flush, clean & refill system.
Piston seal(s)	Disassemble & replace seals
Directional control valve	Refer to section on directional control valve maintenance.
Sufficiently high return line back pressure (Single acting cylinder)	Check for restricted line. Remove and replace return line filter.
Common occurrence with center directional valve in neutral or center position and pump under load.	Change to tandem spool type valve. Check for proper mounting alignment