Cylinder Trouble Shooting:
Detailed Guide - Stage 1

<< Back to Index

 

About Stage 1

The first step to an effective troubleshooting program is to report what is observed as the actuator is operating. As these observations are made, record the information with the maintenance records. This data is critical to the troubleshooting process and will serve as important background to demonstate that the troubleshooting program is effective when corrective measure have been put in place.

The following is a troubleshooting guide for cylinder performance. Each heading is a description of the type of potentional damage followed by some probable causes and possible solutions.

 

Extrusion of Inside Diameter Heel

Probable CauseSolution

If extrusion is evident all around circumference of inside diameter heel, rod or ram to gland or bushing clearance is excessive for pressure.

Rework or replace gland or bushing to achieve recommended clearance. Use rigid back up ring where necessary.

If extrusion is evident on half of the circumference of the inside diameter heel, rod or ram is side loading. Gland may not be centred or cylinder head may be cocked.

Rework or replace gland or bushing. Replace bearings. Use back up ring. Check gland for centring. Check torque of the rod nuts and alignment of cylinder.

Excessive Abrasion or Grooving of Dynamic Seal Lip

Probable CauseSolution

Excessive wear on inside diameter indicates poor rod finish.

Rework or replace rod or ram to achieve finish of 8-24 R.M.S. (Ra)

Excessive wear on inside diameter indicates lack of effective wiper.

Install sharp lip, abrasion resistant wiper. Consider an externally mounted, easily replaceable wiper. May require a Snap-Lox wiper in excessively wet/dirty environments.

Excessive wear on outside diameter indicates poor bore finish.

Rework or replace cylinder tube to a bore finish of 8-24 R.M.S (Ra)

Excessive wear on outside diameter indicates contaminated fluid.

Check condition of fluid. Filter system with portable filtration or drain and flush system.

U-Cup Split Through Centre of its Cross Section

Probable CauseSolution

If splitting or separation is apparent over most or all of seals circumference, the cause is radial over sizing of incorrect seal size.

Check equipment dimensions and compare to seal dimensions..

C-Cup or Piston Cup Lip is separated from Heel

Probable CauseSolution

If splitting or separation is apparent over a small portion of seals circumference, the cause is a lack of concentricity or ovality of equipment.

Rework or replace bearing support to achieve concentricity of rod or piston. Check stuffing box and cylinder bores for roundness.

Crescent shaped Section missing from Dynamic Sealing Lip

Probable CauseSolution

Piston seal lip is passing over port either during installation or actual use.

Champfer sharp internal port edges, alter stroke or piston design to avoid port. If caused during installation, use shim or otherwise protect seal from sharp edges.

Seal lip was kinked, jammed, or curled back during installation.

Use care when installing. Don’t use sharp tools. Check lip before pushing into bore.

Discoloration, Swelling, Softening or Hardening of Seal Compound

Probable CauseSolution

Fluid incompatibility with hydraulic fluid, lubricating oil, installation grease or cleaning solvent.

Check compatibility of seal compound. Change fluid type or substitute seal compound.

Excessive Wear, Misshaping, Darkening of V-Ring Sets in Stacked Sets

Probable CauseSolution

Under compression of stacked V-Ring set can cause rings to roll or twist and bind causing leakage and excessive friction.

Measure equipment and seal set carefully; shim and adjust properly. Seat each ring completely, check split if applicable, check alignment of each ring before installing next ring.

Over compression of stacked V-Ring set can cause binding and excessive friction due to lack of lubricating barrier and additional drag.

 Measure equipment and seal set carefully; shim and adjust properly. If ram or rod is binding, loosening of load on set may ease binding. May need to remove and repack V-Rings properly.

 Wear on Dynamic heel 360 degree of Seals Circumference

Probable CauseSolution

Miss-application of rod or piston designed seal or wrong seal size.

Use rod seals for rod applications and piston mounted seals on pistons. Check equipment and seal dimensions.

Excessive Wear on Dynamic heel and Lip of 180 degrees of Seals circumference. May also show Extrusion of Dynamic Heel 180 degrees opposite of the Worn Side to the Seal

Probable CauseSolution

Side loading due to misalignment, mounting and clevis design causing bushing and bearing wear and excessive seal wear. Also increases clearances resulting in possible extrusion.

Rework or replace bearing or bushing to achieve concentricity. Check for  misalignment or cause of side loading. Increase bearing area with strong, non metallic bearings. Check diametral clearances for adequate seal support.

Excessive Wear on Heel 360 degrees of Circumference of Piston Cup, often the Seal Lip will not show Wear

Probable CauseSolution

Over Compression of the piston cup. Due to over tightening of the hold down plate or base thickness too great for the available space causes the heel to squeeze out.

Compress flange thickness (H2) 10%. Check base thickness relative to space available. Do not over tighten. Check cup visually after tightening for heel squeeze out.

Black, Tar- Like Deposits and/or Burned Spots, possibly burned completely through The Heel of the Seal. This damage will appear in The Crotch Area between the Seal Lips.

Probable CauseSolution

Dieseling, due to auto ignition of hydraulic fluid causing intense heat at the damaged area. Dieseling results from trapped air bubbles in the fluid rising to settle between the seal lips where, under pressure, the bubbles are compressed.  Rapid decompression of compressed air bubbles results in energy released as heat.

Bleed all air from hydraulic system. Caution should be used to bleed system after any work is done to pump, valves, lines or actuators.

Rolled or Twisted Seal may have Permanent Creases from twisting in Seal Cavity. May be severely rolled.

Probable CauseSolution

A variety of conditions may cause rolling of a seal. Drag due to sizing problem, vacuuming, extrusion or swelling may all cause seals to roll. In addition, side loading and shock loading could be contributing factors.

Check dimensions of seal and equipment. Check system and application for operating condition. Look for other types of damage to help troubleshoot this problem.

 

No visible damage, but leaking

Probable CauseSolution

Incorrect size seal not sealing dynamically or statically.

Check seal and equipment dimensions. Check for additional causes of leak such as static O-Ring or gasket leak.

Hydroplaning due to low sealing pressure with high viscosity fluid and too smooth surface finish.

Check fluid pressure on return to tank cycle. Check dynamic surface finish. Check cycle speed. Consider alternate seal design with higher pre-load.

Extrusion of outside diameter heel

Probable CauseSolution

If extrusion is evident all around circumference of outside diameter heel, piston head-to-bore clearance is excessive. May be due to poor design, wear or pressure swelling or “ballooning.”

Rework or replace piston head or retube to achieve recommended clearance. Use non-metallic bearing Bands to prevent wear. Check cylinder integrity relative to maximum pressure. Use back-up rings under extreme shock loads.

If extrusion is evident on half of the circumference of the outside diameter heel, piston is side loading or cylinder is out-of-round.

Rework piston head for non-metallic bearing band thus entering piston. Check cylinder bore for possible ovality.

Excessive clearance between gland and stuffing box bore.

Rework or replace gland or use back-up ring.

Seal Lips are crushed, crimped or creased

Probable CauseSolution

Seal too tall for groove.

Re machine seal groove or choose shorter seal.

Loose bottom bushing under seal hits seal when pressurised.

Secure and vent bottom bushing.

Seal is being mechanically loaded by a metallic or elastomeric retaining device.

Remove device if not necessary or re-work device to prevent contact with seal lip(s).

Seal is being dragged to bottom of groove or box by vacuum or by miss sizing of seal.

Correct vacuum condition or secure seal with retaining device. Check seal dimensions and correct application of piston and rod designed seals.

Piston cup lip is jammed by hold down plate on piston or is acting as stop at end of stroke.

Correct inside (“d2”dimension) of piston cup relative to diameter of hold down plate. Provide mechanical stop on stroke or choose cup with shorter lip.

Seal is dark or black in colour, has lost flair or is drastically misshaped.

Probable CauseSolution

Darkening of entire seal indicates excessive fluid temperatures or environmental heat exposure.

Protect against environmental heat source. Maintain or utilize cooling system. Use high temperature seal compound.

Darkening of dynamic lip only indicates excessive friction due to speed, lack of lubricity or jamming of dynamic lip or heel.

Check reciprocating or rotating speed. Check lubrication of pneumatic system or lubricity of hydraulic fluid. Look for evidence of jamming of lip or extrusion of heel.

Drastically misshaped seal indicates prolonged exposure to heat or extremely high heat. May be caused by continual rolling of seal in groove.

Use high temperature seal compound. Check seal groove dimensions.

Vertical/Axial scratches on static lip may be associated with other damage

Probable Cause

Solution

Incorrect sizing of rod or piston seal will cause seal to move axially in the seal groove/stuffing box. Axial movement is evident due to scratches on static lip.

Check dimensions of seal groove/stuffing box and rod or bore diameter. Check for seal fit and correct application of rod seal or piston mounted seal.

Vacuuming due to inability of fluid to fill cylinder to make up for increasing volumetric area.

Correct shock-loading if possible. Check system for pipe flow volume. Consider alternate seal design.

Excessive wear or “pock-marked” appearance on outside diameter indicates a poor static finish on bore or seal groove.

Re-work to achieve a static finish 32-45 RMS (Ra)

Excessive wear or “pock-marked” appearance on inside diameter indicated a poor static finish on piston seal groove.

Re-work to achieve a static finish 32-45 RMS (Ra)


<< Back to Introduction Stage 2 >>