Hydraulic Cylinder Repair Process {7562} Caterpillar

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Introduction

© 2018 Caterpillar All Rights Reserved. This guideline is for the use of Caterpillar Dealersonly. 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 guideline enables dealers and dealer customers to benefit from cost reductions made possible through an established parts reusability and salvage program. Every effort has been made to provide the most current information known to Caterpillar Inc. Since the company makes ongoing product changes and product improvements, this guideline must be used with the latest technical information. Using the latest technical information available from Caterpillar ensures that such changes and improvements are incorporated where applicable.

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

• Cat Dealer Technical Communicator

• Global Dealer Solution Network

• Cat 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

The following information explains the repair process for hydraulic cylinders through a repair facility. The steps follow the Caterpillar recommended best practices. Every service shop is different, however, the basic workflow and process still applies to all. Dealer management must decide the extent the process is followed.

The Service Operation Development and Assessment (SODA) Guide should be used to determine your level of compliance. The Service Operation Development and Assessment (SODA) Guide can be downloaded from the www.Dealer.Cat.com website. Under Menu Options select “ Product Support > Service Operations > Service Operations Development and Assessments > Hydraulic Cylinder Rebuilds”.

After the assessment is completed, a development plan can be written based off the findings. SODA will help identify process gaps in your operations. This document also references other supporting documents that cover the various stages of cylinder repair in more detail.

Important Safety Information

Illustration 1	g03399556

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, procedure, work method, or operating technique is used that is not recommended by Caterpillar, ensure that the procedure is safe for you and for other people. Ensure that the product will not be damaged or be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

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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 2	g00008666

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

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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.

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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.

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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, PERJ1017, "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

Workflow

1. Customer or technician drops off the cylinder to a clearly marked receiving area.

2. The Work Order is written.

3. The outside of the cylinder is cleaned.

4. The cylinder is transported to a staging area near the cylinder disassembly clean room or is transported directly to the disassembly area.

5. Cylinder is disassembled.

6. After the rod assembly has been removed from the cylinder assembly, an inspection should be performed. A repair option is decided upon.

7. Send the rod or cylinder to machine shop if re-rodding or a re-tubing is necessary.

8. Order parts and send out rod for resurfacing (chrome, HVOF), if necessary.

9. Clean all reusable parts and store for assembly.

10. Hone the cylinder tube.

11. Wash the cylinder tube.

12. Assemble the cylinder group.

13. Test the assembled group.

14. Paint the cylinder.

15. Transport the cylinder to shipping for pick up.

Receiving

The customer should see a sign for receiving from a frontage road. The sign should indicate hydraulic service receiving. The customer should not have to search for a place to drop off a cylinder.

The customer should be greeted by a dealer employee in the receiving area. The repair technicians should not be the initial contact for the customer. The contact for the customer should be able to unload the component and start the Work Order. The Work Order should be filled out completely, with all available information including, but not limited to, customer complaint and cylinder condition.

The receiving area should have adequate means to unload trucks. An overhead crane inside a large overhead door is ideal. A fork truck should be available to unload pallets from flat bed trucks. The receiving area for cylinders should not be in the cylinder clean room. The receiving area should have a good selection of lifting straps and chains. The lifting devices should be dedicated to the shipping area and should not leave the area.

Once the cylinder is unloaded, the cylinder should be placed directly on an incoming rack. The rack can be a flat drip pan with V-blocks or an A-frame rack with a drip pan below. Many cylinders are strapped to a wood pallet when the cylinder arrives at the dealership. The cylinder should be removed from the pallet. Pallets take up too much floor space and leave contamination. The cylinder should be tagged with the Work Order number and other pertinent information. A tag that can be removed during power wash and then wired back to the cylinder is ideal.

Cylinder should be transported from receiving area to initial cleaning area by a dedicated material handler. The wash bay should be close by, preferably dedicated for components. Plug all open ports to avoid introducing water inside the cylinder. For best results and reduced wash time, the wash water should be high pressure, hot, and with a detergent. Cylinder should be washed by a dedicated wash bay employee or the material handler.

The cylinder should be transported to the cylinder shop on a cylinder cart or fork truck. Once inside the hydraulic shop, cylinder carts or overhead lifting devices should be used exclusively.

Disassembly

The cylinder should be transported into the cylinder repair area on a cart. Fork truck operation is not recommended in a hydraulic clean room. Fork truck tires can drag debris into the shop. If a fork truck is used, the fork truck should only go just inside the clean room door to drop the cylinder.

The cylinder should be placed on an incoming cylinder rack using a hoist. Depending on volume of the shop, the incoming cylinder rack can be shared with the outgoing cylinders. The cylinder should still be tagged for quick identification by the technician.

The Work Order should be placed on a job board. A hanging file folder on the wall works well. The Work Orders should be placed of priority by the supervisor or cylinder lead person for technician quick retrieval.

Hoists can be of the jib crane or overhead variety. Generally, a mix of the two types within the shop works well. Jib hoists work well for localized lifting. Overhead cranes are used when transporting the cylinder from one shop area to another. The same hoist should be able to move the cylinder from the incoming rack to the Disassembly and Assembly bench.

The D&A bench should be able to handle the target market of the dealer for Caterpillar and non-Caterpillar cylinders. Size considerations are extended length of the cylinder and piston nut removal torque capabilities. For recommendations on cylinder D&A bench selection, contact Caterpillar.

If the dealership repairs small cylinders 76.2 mm (3 inch) bore or smaller, a flat workbench with a chain pipe vise can be used. The smaller cylinders can generally be disassembled with a large wrench, chain wrench, or spanner wrench. The flat workbench should also have some means of catching and containing waste oil.

Inspection

After the rod assembly has been removed from the cylinder assembly (tube), an inspection of the individual parts should be performed. The tube should be inspected for any cracks, bulges, or scratches in the cylinder tube to determine reusability.

Measure the inside diameter of the cylinder bore. Measure the diameter of the rod. Check the condition of the chrome. Check the rod for straightness. Inspect the seals and wear rings for damage as an indication of other problems with the cylinder.

Refer to Special Instruction, REHS2811, "Hydraulic Cylinder Seal Failure Analysis" for more information. Refer to Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components" for inspection instructions.

Inspection information can also be found in Special Instruction, REHS2689, "Hydraulic Cylinder Honing".

Now, a repair option decision must be made depending on dealer capability and customer preference. Normal repair options are:

• New

• REMAN

• Dealer Repair

• Dealer Exchange

Parts Ordering

Immediately following inspection, parts should be ordered for all repair options other than "new". Technician should order parts electronically on a terminal in the cylinder shop. The parts list can be generated in SIS web and then ordered on-line. Hydraulic parts list can also be generated by using the Hydraulic Information System (HIS). Placing the parts list in an e-mail and sending to the parts department is acceptable, but not the best option.

The terminal should be next to an aisle not more than one bay away for easy access by all in the cylinder shop. Technicians should not have to walk to the next shop. No more than eight technicians should be assigned to one terminal. Parts delivery to the cylinder shop should be prioritized. The following are for example only.

• 1 = as soon as possible

• 2 = within 30-45 minutes

• 3 = 24 hours

1 = as soon a possible. Priority Level 1 should be used on an exception basis. Only use if the part is holding up the assembly, and the part must be assembled immediately due to customer waiting.

2 = within 30-45 minutes. Priority Level 2 would be a standard amount of time to allow for hone and wash. By the time hone and wash is done, the parts are delivered and the cylinder can then be assembled. Use this status to support branch store repairs and ensures quick turn around for trucking.

3 = 24 hours. Priority Level 3 could be for a customer who keeps a spare unit and turn around time is not critical. Level 3 can also be used for a dealer exchange unit. Level 3 could also be used for cylinders undergoing major rework such as re-tubing or re-rodding.

The key is to manage this depending on your particular dealers needs. There is no one single solution to fit all needs. Parts delivery of ASAP for every order is not realistic. 30 minutes or 45 minutes for a typical cylinder repair is manageable for the parts department.

Another option for some dealers is automatically ordering seal kits and all other 100% replacement parts at the opening of the Work Order. The dealer must trend parts orders to make this work. By determining the percent of seal kits and other high use parts sold for a particular cylinder, an automatic parts order can be generated. Every time the cylinder part number is entered into the system in the receiving area the report will be generated.

If the trend of high use parts is tracked properly, a few returns to the parts department should not be an issue.

Parts Cleaning

Once the cylinder has been disassembled and the parts are determined to be reusable, the parts should be cleaned. An automatic method to wash parts is preferable. A cabinet washer works well for cylinder parts and hardware. The washer should be high pressure, hot, with soap.

Maintenance of the wash water is critical for the cabinet to clean the parts well. Inefficient parts washing is due in large to poor maintenance practices along with improper basket loading. Manual cleaning in a solvent tank is not the best use of technician time. If an automatic method of parts washing is used, the technician can move on to other tasks. When the parts cleaning cycle has completed, the technician can simply blow dry the parts and start assembly.

In-Process Racks/Baskets

In-process racks/baskets should be used only to store disassembled, clean cylinder parts that are not going to be assembled immediately. Typically, an A-frame type rack works well. The racks should be placed very close to the D&A bench. The in-process rack should be able to accommodate tubes and rods as well as small parts.

All small parts should be placed in a contamination free bin or container. The container should be marked with the work order number. The container should be in a separate shelving unit next to the rack or below the rack if room allows.

The tube and/or rod should also be marked with the work order. The rods should be wrapped in plastic while on the in-process rack. The tubes should be capped and plugged.

Dealers who do not effectively use in-process racks commonly have small parts piled on bench tops as well as tubes and rods on the floor. Using in-process racks is more important to high volume dealers operating multiple shifts in the cylinder shop. Inmanycasesthe same person may not assemble the cylinder that disassembled the cylinder.

Re-rodding and Re-tubing

Caterpillar has documents to support re-rodding and re-tubing activities. Refer to Special Instruction, SEBF8072, "Inspection and Salvage of Hydraulic Cylinder Components". Once the decision to replace a rod or tube has been made, the guideline will assist in the steps necessary to replace the damaged parts.

Hone

Caterpillar has documents to support the hone process. Refer to Special Instruction, REHS2689, "Hydraulic Cylinder Honing" for repair process information.

After the cylinder tube has been determined fit to be honed, the tube should be moved to the hone. Movement of the tube should be done with a jib crane or an overhead crane. The same crane should be able to reach the hone and the cylinder D&A bench as well as an in-process rack.

There are several areas of consideration when a tube is honed such as set-up, feed, speed, stone grit selection, and hone oil. All of which are covered in the Special Instruction, REHS2689. In terms of process, the overall objective is the correct bore dimension and correct surface roughness in the least amount of time. How the five items listed above are addressed, can have a negative or positive effect on the results.

The Caterpillar hones are considered light hones and are intended for honing up to 0.25 mm (0.010 inch). Caterpillar hones can bore oversize up to 0.76 mm (0.030 inch). Caterpillar hones should not be used for honing oversize on a regular basis. If oversize boring is a usual occurrence, the dealership should purchase a production hone. A light hone takes too much time to hone oversize and will cause a bottleneck in workflow.

Contact Sunnen Products Company for specific information related to the Sunnen HTA- 4100 Hone and HTA-2100 Hone.

Tube Wash

Wash the cylinder tube after honing. The cylinder washer should be directly next to the hone. An overhead or jib crane should be easily accessible to position the tube for wash. The cylinder tube washer should have rotating brushes, as well as a constant flow of wash fluid. The rotating brushes actually sweep the small metallic pieces from the crosshatches in the tube. The fluid then flushes the metallic pieces out of the tube.

The cylinder washer should also have a means of filtration. A 15 micron bag or paper filter should be used to catch the fluid coming back out of the cylinder tube. A second 5 micron spin on filter should be used before the fluid goes back into the tube. Caterpillar offers the 250-6597 Cylinder Washer. Refer to Tool Operating Manual, NEHS0927, "Procedures for Using the 250-6597 Cylinder Washer Tank Group".

Assembly

The cylinder tube should be positioned back on the D&A bench. Use a crane that will reach from the hone to the D&A bench. New seal installation should be done on a workbench. For most cylinders, the piston and head are easier to work with on a bench. The wear rings, seals, back up rings, O-rings, and wear bands should all be installed at this time.

The workbench should have a protective surface such as plastic or hard rubber to prevent damage to parts. The seals should be lubricated with clean 30 weight hydraulic oil. The head is then installed on the rod. The use of a seal guide should be used to prevent damage to the lip seal. The piston should be installed and torqued to specification.

The rod assembly can now be installed into the tube assembly. The D&A bench should be able to adjust the height of the rod along a horizontal line. This capability is needed to line up the piston in the bore of the tube. Line up rod and tube center lines so the piston will install without damage to the seals on the piston. The bench should be able to push the piston into the tube with the use of hydraulic power. Depending on the type of cylinder, bolt on head, threaded gland, or threaded crown, torque to specification. Refer to the Specifications manual for the specific machine you are working on.

Test

Once the cylinder is fully assembled, the cylinder should be tested. Refer to Special Instruction, REHS1765, "Testing Hydraulic Cylinders Using the 188-3926 Caterpillar Cylinder Tester and the 9U-6803 Caterpillar Cylinder Tester" for the procedure to test cylinders. Caterpillar offers the 188-3926 Cylinder Tester. Refer to Tool Operating Manual, NEHS0595.

The best place to test is on the D&A bench immediately after assembly. Testing a cylinder verifies the quality of the build. This benefit should be communicated to the customer.

Various fittings should be on hand and organized for quick retrieval. The fittings should be stored in a contamination free bin, rack, or cabinet. The fittings should be organized by type of fitting or grouped for specific cylinder types. The cabinet might need to be mobile for use at multiple benches.

The tester should also be mobile for use at several benches. If the tester is not mobile, the hoses should be long enough to reach the benches easily.

Paint

All rebuilt cylinders should be painted to show pride in workmanship and quality. After the cylinder is tested, the ports should be plugged. Repair technicians should not be involved in cleaning or painting after test.

If the initial wash bay and paint booth are in the same building, a cylinder cart works well for transport. If a cart cannot be used, a fork truck can be used outside the cylinder area.

The cylinder should be cleaned before painting. Hot, soapy, high-pressure water works well and will dry faster. Once the cylinder is in the paint booth, the cylinder should be prepped for paint by a person dedicated to the paint booth.

The ports should be capped or plugged. Machined surfaces and bearings should be protected with tape or grease. The rod wiper seal should be taped off, also.

The cylinder should be allowed to dry after painting before handling. Dealer stickers should be attached to the cylinder for marketing reasons for future repairs. To track the cylinder better, a tag can be attached to the cylinder with the date and Work Order number.

Shipping

The cylinder should be transported to the shipping area to be placed on an outgoing rack ready for pickup. Keeping the incoming cylinders separate from the outgoing cylinders is recommended. The cylinder should be tagged for quick retrieval. The shipping area should have a large overhead door with an overhead hoist for loading duties. Various lifting devices should be dedicated to the area.