Troubleshooting Guide

Probable Cause

Incorrect size seal not sealing dynamically or statically.

Possible Solution

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

Probable Cause

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

Possible Solution

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

Probable Cause

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.

Possible Solution

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

Probable Cause

Seal is too tall for groove.

Possible Solution

Remachine seal groove or choose a shorter seal.

Probable Cause

Loose bottom bushing under the seal hits the seal when pressurized.

Possible Solution

Secure and vent the bottom bushing.

Probable Cause

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

Possible Solution

Remove the device if not necessary or rework device to prevent contact with seal lip(s).

Probable Cause

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

Possible Solution

Correct the vacuum condition or secure the seal with a retaining device. Check the seal dimensions and correct appli- cation of piston and rod designed seals.

Probable Cause

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

Possible Solution

Correct inside (“d ₂” dimension) of the
piston cup relative to the diameter of the hold down plate. Provide mechanical stop on the stroke or choose a cup with a shorter lip.

Probable Cause

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

Possible Solution

Rework or replace the gland or bushing to achieve recommended clearance. Use a rigid backup ring.

Probable Cause

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

Possible Solution

Rework or replace the gland or bushing. Replace bearings. Use a backup ring. Check the gland
for centering.

Probable Cause

A1: If extrusion is evident all around the circumference of the outside diameter heel, the piston head-to-bore clearance is excessive. This may be due to the design, wear, or pressure swelling or “ballooning.”

Possible Solution

A1: Rework or replace the piston head or retube to achieve the recom- mended clearance. Use non-metallic bearing band(s) to prevent wear. Check the cylinder integrity relative to maximum pressure. Use backup rings under extreme shock loads.

Probable Cause

A2: If extrusion is evident on half of the circumference of the outside diam- eter heel, the piston is side loading or the cylinder is out-of-round.

Possible Solution

A2: Rework the piston head for non-metallic bearing band thus centering the piston. Check the cylinder bore for possible ovality.

Probable Cause

B: Excessive clearance between the gland and stuffing box bore.

Possible Solution

B: Rework or replace the gland or use a backup ring.

Probable Cause

If splitting or separation is apparent over most or all of the seal’s circumference, the cause is a radial oversizing or incorrect seal size.

Possible Solution

Check the equipment dimensions and compare them to the seal dimensions.

Probable Cause

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

Possible Solution

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

Probable Cause

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

Possible Solution

Chamfer the sharp internal port edges, and alter the stroke or piston design to avoid the port. If damage was caused during installation, use a shim or other- wise protect the seal from sharp edges.

Probable Cause

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

Possible Solution

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

Probable Cause

A1: Excessive wear on the outside diameter indicates an issue with the cylinder bore finish.

Possible Solution

A1: Rework or replace the cylinder tube to a bore finish of 8–24 R.M.S (Ra).

Probable Cause

A2: Excessive wear on the outside diameter indicates abrasive particles in the system.

Possible Solution

A2: Check the condition of the fluid. Filter the system with a portable filtration or drain and flush system.

Probable Cause

B1: Excessive wear on the inside diameter indicates a poor rod finish.

Possible Solution

B1: Rework or replace the rod or ram to achieve a finish of 8–24 R.M.S (Ra).

Probable Cause

B2: Excessive wear on the inside diameter indicates abrasive particles in the system.

Possible Solution

B2: Install a sharp lip, abrasion-resistant wiper. Consider an externally mounted, easily replaceable wiper. It may require a custom wiper in excessively wet/dirty environments.

Probable Cause

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

Possible Solution

Check split, if applicable; check alignment of each ring before installing next ring.

Probable Cause

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

Possible Solution

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

Probable Cause

Misapplication of rod or piston designed seal or wrong seal size.

Possible Solution

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

Probable Cause

A. Excessive side load or side load due to misalignment, mounting and clevis deign or application and design causing bushing and wear ring wear and excessive seal wear.

B. Bushing and wear ring wear increase clearances resulting in possible extrusion.

Possible Solution

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

Probable Cause

Overcompression of the piston cup due to overtightening of the hold- down plate or the base thickness is too great for the available space which causes the heel to squeeze out.

Possible Solution

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

Probable Cause

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

Possible Solution

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

Probable Cause

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

Possible Solution

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

Probable Cause

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

Possible Solution

A: Rework to achieve a static finish of 32–45 R.M.S. (Ra).

Probable Cause

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

Possible Solution

B: Rework to achieve a static finish of 32–45 R.M.S. (Ra).

Probable Cause

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

Possible Solution

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

Probable Cause

Dieseling due to auto ignition of the 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 the compressed air bubbles results in energy released as heat.

Possible Solution

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

Probable Cause

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

Possible Solution

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

Probable Cause

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

Possible Solution

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

Probable Cause

A drastically misshaped seal indicates prolonged exposure to heat or extremely high heat. This may be caused by the continual rolling of the seal in the groove.

Possible Solution

Use a high-temperature seal compound. Check the seal groove dimensions.