Hydraulic Cylinder Seal Failure Analysis {7555, 7562} Caterpillar


Hydraulic Cylinder Seal Failure Analysis {7555, 7562}

Usage:

MT700 018

Information for equipment:


HYDRAULIC SYSTEM
CYLINDER GP

Hydraulic Cylinder Repair Process {7562} Hydraulic Cylinder Repair Process {7562}

Testing Hydraulic Cylinders Using the <NOBR>188-3926</NOBR> Caterpillar Cylinder Tester and the <NOBR> 9U-6803</NOBR> Caterpillar Cylinder Tester {0784, 7562} Testing Hydraulic Cylinders Using the 188-3926 Caterpillar Cylinder Tester and the 9U-6803 Caterpillar Cylinder Tester {0784, 7562}
Reuse Guideline for Hydraulic Cylinder Position Sensor {5574, 5736} Reuse Guideline for Hydraulic Cylinder Position Sensor {5574, 5736}
Hydraulic Cylinder Repair Process {7562} Hydraulic Cylinder Repair Process {7562}
Hydraulic Cylinder Seal Failure Analysis {7555, 7562} Hydraulic Cylinder Seal Failure Analysis {7555, 7562}
Inspection and Salvage of Hydraulic Cylinder Components {7562} Inspection and Salvage of Hydraulic Cylinder Components {7562}
Measuring Bores and Installing Seals in Standard and Oversized Hydraulic Cylinders {5100, 7562} Measuring Bores and Installing Seals in Standard and Oversized Hydraulic Cylinders {5100, 7562}
Machining the O-ring Groove into the Face of Oversized Bolted Head Hydraulic Cylinders {0677, 5100, 7562} Machining the O-ring Groove into the Face of Oversized Bolted Head Hydraulic Cylinders {0677, 5100, 7562}

Hydraulic Cylinder Seal Failure Analysis {7555, 7562} Hydraulic Cylinder Seal Failure Analysis {7555, 7562}

Testing Hydraulic Cylinders Using the <NOBR>188-3926</NOBR> Caterpillar Cylinder Tester and the <NOBR> 9U-6803</NOBR> Caterpillar Cylinder Tester {0784, 7562} Testing Hydraulic Cylinders Using the 188-3926 Caterpillar Cylinder Tester and the 9U-6803 Caterpillar Cylinder Tester {0784, 7562}


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Introduction

Table 1
Revision  Summary of Changes in REHS2811 
20  Added new serial number prefixes. 
19  Added new serial number prefixes. 
18  Added new serial number prefixes. 
17  Added new serial number prefixes. 
16  Added new serial number prefixes 

© 2018 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This Reuse and Salvage Guideline contains the necessary information to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Guideline must be used with the latest technical information that is available from Caterpillar.

For questions or additional information concerning this guideline, submit a form for feedback in the Service Information System. To address an urgent issue, use the following resources to communicate your request to Caterpillar Repair Process Engineering:

  • Caterpillar Dealer Technical Communicator

  • Dealer Solution Network

  • Caterpillar Technical Representative

  • Knowledge Network

Canceled Part Numbers and Replaced Part Numbers

This document may include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Summary

This Reuse and Salvage Guideline contains the necessary information to allow a dealer to establish a parts reusability program. This guideline must be used with the recommendations found in the Reuse and Salvage Guideline, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components".

Important Safety Information



Illustration 1g02139237

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method, or operating technique that is not recommended by Caterpillar is used, ensure that the procedure is safe for you and for other people to use. Ensure that the product will not be damaged or be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

------ WARNING! ------

Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death.

Do not operate or perform any lubrication, maintenance or repair on this product, until you have read and understood the operation, lubrication, maintenance and repair information.


Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by the safety alert symbol which is followed by a signal word such as danger, warning, or caution. The "WARNING" safety alert symbol is shown below.



Illustration 2g02825102

This safety alert symbol means:

Pay attention!

Become alert!

Your safety is involved.

The message that appears under the safety alert symbol explains the hazard.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Also, determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

The information, the specifications, and the illustrations that exist in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

Safety

------ WARNING! ------

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.

To prevent possible injury, perform the procedure that follows before testing and adjusting the steering system.


------ WARNING! ------

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.



NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.

Dispose of all fluids according to local regulations and mandates.


References

Table 2
References 
SEBF8072  "Inspection and Salvage of Hydraulic Cylinder Components" 
NENG2500  "Dealer Service Tool Catalog" 

Foreword

Careful inspection of the hydraulic cylinder seals after a failure can give indications of the root cause. Document the complaint of the customer and determine if the problem is drift, leakage, or noise. Leakage can occur at the rod seals between the cylinder head and rod or at the head seals between the head and the tube. Leakage can also occur internally at the piston seals, between the piston and the tube. At disassembly, all seals should be inspected for any change in appearance in comparison to new seals. All scratches, nicks, cuts, foreign particles, dimensional changes, or color changes should be noted. The following sections describe most common problems, indications of the root causes, and remedies.

Cleanliness of hydraulic components during assembly is critical. Before assembly, clean all parts properly. All parts that will be stored prior to assembly must be stored in a way to protect from contamination.

Nomenclature



Illustration 3g01217895
(1) Head O-ring seal
(2) Head seal backup ring
(3) Wear band
(4) Buffer seal
(5) U-cup seal
(6) Wiper seal
(7) Nut
(8) Piston
(9) Head
(10) Rod
(11) Piston seal expander ring
(12) Piston seal ring
(13) Wear band

Illustration 3 shows the position of all the seals, rings, and bands that will be discussed in this document. A bolted head cylinder is shown, but threaded gland and threaded crown cylinders have the same basic seal positioning.

Rod Seal Leakage

Assembly Damage



Illustration 4g01202321
Steel backed PTFE wear band heavily scratched by the edge of the rod.

  1. Assembly Cone Not Used

    Indications

    • A small section of the material is clipped out of the buffer seal, U-cup seal, or wiper seal ID lip.

    • Steel backed PTFE wear ring (used on HEX machines) is heavily scratched in one or more discrete areas. Refer to Illustration 4.

    Possible Root Causes

    A sharp edge, usually at the end of the cylinder rod, has clipped or scratched the seals as the head is pushed over the rod.

    Remedy

    The recommended practice is to use a seal guide when reassembling the head to the rod. Any metal part that comes in contact with a seal during assembly or operation must be free of sharp edges.

    Comments

    The wiper seal is most commonly clipped when a guide is not used. The head lands pilot the head after the wiper goes over the rod. An attempt to assemble the head over the rod in one motion should be made. If a jerking motion is used, there is the possibility for the wiper lip to be caught. The wiper lip will get caught between the edge of the seal guide and the rod chamfer. All burrs and sharp edges should be removed from the end of the rod prior to reassembly.

  2. Wiper Seal Not Installed Properly

    Indications

    • The wiper seal metal shell is dented or deformed.

    • Dirt enters the cylinder through the wiper seal because the lip is not in close contact with the rod.

    • The wiper seal is dislodged from the counterbore.

    • The contacting band of the wiper seal is not uniform in width around the circumference of the seal.

    Possible Root Causes

    The wiper seal was not installed properly or the seal was damaged during installation.

    Remedy

    A piloting, wiper seal driver should be used to install wiper seals that have a metal shell. If necessary, use a rubber mallet to tap around the edges of the seal. The procedure will ensure proper seating of the seal against the counterbore. Do not dent the metal shell.

    Comments

    An uneven contact band on the ID of the wiper indicates that the seal was not properly seated. The contact band should be seated against the back of the counterbore. The uneven contact band could also mean that the rod was bent. Always use bearing adhesive on the OD of the metal shell to aid in retention and eliminate the seal OD as a possible leak path. However, adhesive on any other surface of the seal, rod, or head is not allowed.



    Illustration 5g01202423
    Buffer groove damage by removing a seal with a screwdriver.

  3. Damage to the Head

    Indications

    • Upon removal of the seals, scratches or gouges are found in the seal grooves of the head.

    Possible Root Causes

    The seals were removed in a manner that was too aggressive. Gouges were left in the grooves by screwdrivers, chisels, or other hardened tools. The groove surface finish was degraded beyond the ability of the seals to function properly. Refer to Illustration 5.

    Remedy

    Care should be taken to prevent damage to the groove when removing rod seals. Use a seal pick or other tools of low hardness to remove the seals.

Contamination



    Illustration 6g01202426
    Paint of front face of wiper seals. Paint on the lip edge indicates that the rod was probably painted.


    Illustration 7g01202568
    Strut in which the wiper seal and the rod outboard of the seal was not masked prior to painting.

  1. Paint Contamination

    Indications

    • The front face of the wiper seal is painted to the wiper lip edge. Paint overspray is found on the rod in a location that will enter the seals during operation.

    • Other indications are pieces of paint adhering to the inner diameter of the rod seals. Refer to Illustration 6.

    Possible Root Causes

    The wiper seal and/or rod was not properly masked during painting of the cylinder.

    Remedy

    Before painting, protect the entire front face of the wiper seal and the section of the rod that will contact the seal.

    Comments

    Small paint chips cause leakage by getting between the sealing lip of the U-cup seal and the rod. The U-cup lip edge must be clean of any contaminant to function at maximum efficiency.



    Illustration 8g01202384
    Metallic particles are shown embedded in the piston seal ring. These particles cause leakage by scratching the U-cup sealing lip.


    Illustration 9g03361763
    The scratches in the U-cup lip were caused by metallic contamination.


    Illustration 10g03361764
    Fine scratches are shown on the sealing lip of the U-cup. Small scratches will result in noticeable leakage.

  2. Metallic Contamination

    Indications

    • Small, medium sized axial scratches are found across the sealing lip of the U-cup. Scratches that match are often found on the buffer and wiper seals. Refer to Illustrations 9 and 10.

    • Shiny metal flakes and chips are embedded in the wear bands and in the sides of the plastic piston seal ring. Refer to Illustration 8.

    • The rod is scratched in one or more places. The scratches are straight running the length of the rod stroke.

    Possible Root Causes

    Metal contaminants were not removed from the system before the contaminants migrated to the cylinders. The contaminants may have been the by-product of the manufacturing process, wear, or the result of repairs. The contaminants damage the rod seals.

    Remedy

    Replace wearing components. Always replace the wear bands and piston seal during resealing because these components act as particle traps. The system cleanliness may improve after a cylinder reseal if the contamination was the result of manufacturing cleanliness instead of system wear. Replace any rod with scoring or a nick deep enough to be felt with a fingernail.

    Comments

    There is nothing in the rod seals that can scratch a rod. However, rod seals and wear bands can hold hard particles against the rod resulting in long axial scratches. These scratches may then damage the U-cup seal. A single fine scratch on the ID of the U-cup seal can result in a noticeable leak.



    Illustration 11g03361768
    The cylinder rod was lightly scored by aluminum oxide contaminants that were trapped by the head wear band.

  3. Dirt Contamination

    Indications

    • Heavy scratches or wear is found on the ID of the rod seals.

    • Large amounts of dirt are found between the seals and around the wear bands.

    • The rod is scored to varying degree. Refer to Illustration 11.

    Possible Root Causes

    • The wiper seal was damaged or improperly assembled, and dirt is entering the cylinder.

    • The head was not properly cleaned prior to resealing.

    • Bent cylinder rods cause uneven wear of the wiper seal or a loss of lip to rod contact pressure on one side of the seal.

    • Nonmetallic contaminants were built into the cylinder or other hydraulic components.

    Remedy

    Ensure proper assembly of the wiper seal. Thoroughly clean the head and pay close attention to the inside of the seal grooves prior to resealing. Straighten or replace any bent rod according to the guidelines in the Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components".

    Comments

    A small amount of fine dirt or dust behind the wiper seal is to be expected after long service. The area behind the wiper is dead space and system contamination will not result unless the buildup is heavy. The U-cup or buffer seal may have black oil around the OD after a period of service. This material is a combination of small wear particles from the head wear band and chrome from the rod. This material does not contribute to seal failures.



    Illustration 12g01202682
    Buffer seal destroyed by hydrolysis. Note the leathery "skin" on the outside of the part.


    Illustration 13g01203199
    Head oval seal destroyed by hydrolysis.

  4. Water Contamination (Hydrolysis)

    Indications

    • Any of the rod seals, but especially the buffer, is cracked and brittle.

    • The seal has large pieces missing from the sealing edge.

    • Material can be scratched off the seal with a fingernail.

    Possible Root Causes

    Water or coolant has contaminated the hydraulic oil. Cooler failure is possible if the machine is water to oil cooled. Water can condense on tank walls. Water may also reach higher concentrations around the rod seals. The higher concentration of water is due to low oil flow around the seals.

    Remedy

    If the oil sample indicates water in the oil, change the oil. Use hydrolysis resistant rod seals. Always use special carboxylate nitrile (black) U-cup and wiper seals, and a PTFE step buffer seal when using water/glycol hydraulic fluids.

    Comments

    A small amount of water or coolant can quickly damage rod seals at elevated temperatures. At moderate temperatures, the breakdown occurs more slowly. Refer to Illustrations 12 and 13.

Damage to Mating Iron



    Illustration 14g03361772
    Rod scuffed by poor handling.

  1. Rod Damage

    Indications

    • There may be scratches on the ID of the rod seals and uneven wear patterns on the rod seals and on the wear band.

    • Nicks or scratches on the surface of the cylinder rod that are not straight and axial are other indications.

    • Pits or cracks can be found on the chrome surface of the rod.

    Possible Root Causes

    • The rod is bent.

    • The rod has been scratched or abraded the working environment. Refer to Illustration 14.

    • The chrome surface on the rod is of low quality or was improperly polished.

    Remedy

    Straighten or replace any bent rod according to the guidelines in Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components". Re-chrome, polish, or re-rod any damaged rod according to the guidelines in Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components".



    Illustration 15g01202436
    Step incorrectly machined into the wall of the buffer seal groove.


    Illustration 16g01202760
    U-cup and buffer seal grooves with poor surface finish.

  2. Head Groove Damaged or not Made to Standards

    Indications

    • Seal grooves are corroded and pitted.

    • Tool drag marks are evident. Surface finish does not meet standards. Refer to Illustrations 15 and 16.

    Possible Root Causes

    • Water has entered the head, or the head was left exposed to the environment.

    • The head grooves were not properly machined.

    Remedy

    Obtain a new head. The grooves cannot be machined to a larger diameter to remove pitting or tool marks without reducing the efficiency of the rod seals.

U-cup Extrusion



    Illustration 17g03361776
    A moderately extruded U-cup.


    Illustration 18g03361779
    A heavily extruded U-cup seal.

  1. U-cup Extrusion

    Indications

    • The buffer seal is worn flat or ribbons of material are coming off the back of the seal. Refer to Illustration 17.

    • The ID of the U-cup seal closest to the wiper seal has small chunks removed or has a melted appearance. Refer to Illustration 18.

    • Ribbons of material have flowed in between the rod and the head land behind the U-cup.

    Possible Root Causes

    • High-pressure spikes have occurred in the cylinder.

    • The relief pressure setting may be set too high.

    • The buffer seal has been damaged exposing the U-cup to full system pressure.

    • If extrusion is seen on truck struts, overloading or overcharging may have occurred.

    Remedy

    Use a backup ring behind the U-cup seal that closes the clearance between the land and the rod. Lower pressure relief settings. Replace damaged buffer seals.

    Comments

    Extrusion is not related to melting. The melting temperature of polyurethane is much higher than the temperatures that can be generated in a normal operating hydraulic system.

Heat Damage



    Illustration 19g01203287
    A buffer seal destroyed by oil temperatures higher than the rated operating temperature of the seal material.


    Illustration 20g01203288
    U-cup seal destroyed by hydraulic system temperatures higher than the rated operating temperature of the seal material.

  1. Heat Damage

    Indications

    • The buffer and U-cup seals may appear dark in color.

    • The U-cup has taken a heavy compression set.

    • The seals are cracked and brittle.

    Possible Root Causes

    The hydraulic system temperature is too high for standard rod seals. Standard rod seals are rated to 93 °C (199.4 °F) continuous operating temperature. Refer to Illustrations 19 and 20.

    Remedy

    Check cooling components for efficiency and fix any problems. Modify machine operation to avoid overheating. Use high temperature rod seals. Use appropriate hydraulic oil for the specific operating conditions for good lubricity.

Note: Rod Seal Assembly Tips

  • Push the U-cup to the back of the groove toward the wiper. The U-cup will remain in that position during operation after the first pressure cycle.

  • Lubricate the rod and rod guide lightly before pushing the head over the rod. Do not lubricate the seals excessively. Any oil between the U-cup and wiper seals will leak. The leak will occur during the first hours of operation.

  • For optimum rod seal performance, the rod surface finish should be .40 µm (16 microinch).

Head Seal Leakage

O-ring Seal or Backup Ring clipped during Assembly



Illustration 21g01202471
Head seal Backup Ring Clipped during Assembly.


Illustration 22g01203751
Head seal Backup Rings Clipped during Assembly.

Indications

  • A small section of the O-ring or backup ring appears "bitten" out of the part. This condition is most common of the ends of split backup rings. Refer to Illustration 21 and 22.

Possible Root Causes

The backup ring was in a "sprung out" condition, and the ends of the ring did not remain in the seal groove. The "sprung out" condition prior to the mating of the head with the cylinder tube. The ends of the seal outside the groove were clipped.

Remedy

Make sure that the head seal O-ring and the backup ring grip the head tightly before mating the head with the tube. If the backup ring does not grip the head tightly, assembly compound can be used. Assembly compound is used to prevent the ends from extending outside the seal groove in some cases.

Comments

  • Screw in the threaded gland head slowly to avoid pinching and stretching the O-ring head seal.

  • Lubricate the OD of the seals lightly before assembly.

  • Many threaded gland head seal O-rings have a blue PTFE coating to reduce friction during assembly.

  • The head seal O-ring on the threaded gland cylinder is often cut during disassembly by the threads.

Head Seal and/or Backup Ring Extrusion

Indications

  • Ribbons of material that flowed into the clearance between the head and the cylinder tube are present at disassembly.

  • Large amounts of material are missing on the low-pressure side of the head seal O-ring.

Possible Root Causes

  • Head seal extrusion is caused by oil pressures that are too high.

  • Head seal extrusion failures can also occur if the tube bore is too large. Head seal extrusion failure can also occur if the diameter of the land behind the seal is too small (extrusion gap is too high).

  • Some failures have been attributed to the stretch of head bolts on the bolted cylinders. Threaded gland cylinders have had failures because of the expansion of the tube at high pressures.

Remedy

If the backup ring is extruding use a ring made of a harder material. Reduce the pressure around the head seal if the ring is extruded. Tighten the threaded gland cylinder heads to the proper torque after resealing.

Piston Seal Drift

Dieseling



Illustration 23g03361786
Piston Seal Ring damaged by Dieseling.


Illustration 24g01202479
Piston Seal Ring Damaged by Dieseling at the Step Cut.

Indications

  • The cylinder drifts at a high rate.

  • Oil temperatures are elevated due to flow of oil through small clearances at high pressure.

  • The piston seal ring or rubber expander ring is eroded in a finger-like pattern. The area around the erosion is blackened and sometimes smells burnt.

Possible Root Causes

When air or other entrained gases that are saturated with oil vapors form in the hydraulic oil, dieseling occurs. When these bubbles are compressed, at a high rate the gases ignite due to adiabatic heating. The resulting explosion erodes adjacent components, especially nonmetallic parts. Refer to Illustrations 23 and 24.

Remedy

All efforts should be made to remove air or other entrained combustible gases from the system after resealing a cylinder before using the machine. Extend and retract the cylinders several times before heavy work is done to force air back to the tank.

Explosive Decompression



Illustration 25g01202522
Piston seal expander ring heavily damaged by explosive decompression.

Indications

  • The cylinder drifts at a high rate.

  • The rubber expander ring has large chunks of material missing. Refer to Illustration 25.

  • There is no smell of burning or damage to the seal ring.

Possible Root Causes

Explosive decompression (ED) occurs when gases that have penetrated into a rubber expander ring suddenly expand due to a rapid drop in hydraulic oil pressure. Also when voiding occurs in the cylinder. The rapid expansion of the entrained gas bubble pops a chunk of material out of the rubber ring. If the damage accumulates, the ring can no longer properly seal.

Remedy

All efforts should be made to remove air or other entrained gases from the system after resealing a cylinder before using the machine. Extend and retract the cylinders several times before heavy work is done to force air back to the tank. Refer to the cylinder removal and install procedure for the specific model for more specific instructions. Use dieseling/ED resistant piston seals. These seals are made of a rubber material designed to be less permeable to gases in the hydraulic oil. Use protection piston seal backup rings. These rings reduce the area of the rubber expander ring that is exposed to the oil. Therefore reducing the amount of gas that penetrates the rubber.

Comments

ED and dieseling are similar. The root cause of ED and dieseling is air in the hydraulic system.

Scratched Piston Seal Ring



Illustration 26g03361788
Cylinder heavily scored by metallic contamination.


Illustration 27g03361789
Piston seal ring scored by a cylinder bore with a poor surface finish.

Indications

  • The cylinder drifts slowly.

  • The split plastic seal ring has heavy axial scratches that run from one side of the seal to the other.

Possible Root Causes

  • Bore damage

  • Contamination

Remedy

If a damaged bore is the root cause of a scratched seal ring, lightly hone the bore. If the bore is oversized, remove the damaged areas. Follow the recommendations found in the Special Instruction, SEBF8072, "Guideline for Reusable Parts and Salvage Operations". If contamination is the cause of the scratches, thoroughly wash all components during reseal of the cylinder. Refer to Illustrations 26 and 1.

Note: Other Information

  • Do not apply excessive heat to the cylinder with the seals in place. Heat can be conducted into the seals and the seals may be damaged.

  • Excessively high-pressure spikes will damage the rod seals. PTFE step seals do not last as long as a backed polyurethane buffer seal at pressures above 24 MPa (3500 psi). Any increase in the line relief pressure settings will reduce the life of the rod seals.

  • A head wear band should spring out when in the groove. A piston wear band should grip the piston to avoid damage to the parts. When the head is assembled to the rod, and when the rod assembly is mated with the cylinder assembly.

  • Oversized piston seals and wear bands should be used if the bore is honed 0.25 mm (0.010 inch) past nominal.

Note: Assembly Tips

  • After resealing a cylinder, be sure to torque the piston nut properly. Improperly torqued nuts or bolts may allow cylinder drift due to leakage between the piston and the rod mating surface.

  • The step cut on the piston seal can be slightly open before the rod assembly is mated with the cylinder assembly. The gap will close completely when the assemblies are mated.

  • If the cylinder pressure test shows that cylinder drift occurs, rotate the rod eye while slowly stroking the cylinder. This process will help seat the piston seal in the groove.

  • Slightly scuff the piston seal ring with a fine grit sandpaper or emery cloth in a circumferential direction. This procedure can help seat the ring to the cylinder bore.

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C9 Urban Transit Bus Engine Low Power/Poor or No Response to Throttle
C15 Generator Set Engines Engine Will Not Crank
C32 Petroleum Engines Water Pump - Remove
3600 Heavy Fuel Engines Turbocharger - Inspect - Napier Turbocharger - If Equipped
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