Measuring Bores and Installing Seals in Standard and Oversized Hydraulic Cylinders {5100, 7562} Caterpillar

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Introduction

Table 1

Revision	Summary of Changes in SEHS8630
24	Updated Effectivity
23	Updated Effectivity
22	Updated Effectivity
21	Updated Effectivity

© 2019 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 not 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 instruction provides the necessary procedure for measuring the cylinder bore to determine if the dimension is inch or metric. This instruction helps decide whether the bore requires standard or oversize seals and the procedure for installing the seals.

Since there is the possibility that the cylinder bore could have been honed oversized, determine a tube bore size prior to installing new seals. Also, many cylinders from Caterpillar and other suppliers are designed using metric dimensions. Knowing if the bore is inch or metric, new, standard, or oversize when selecting and installing seals is important.

If you are not certain of the bore size, examine the tube for one or more of the following:

• A plate attached to the OD of the tube near the open end. The plate will have raised characters indicating the oversize amount along with an "0R" part number.

• Characters stamped into the casting at the closed end of the tube that indicates the oversize amount.

You will have to measure the bore of the cylinder if the previous two methods of identification are not present.

Important Safety Information

Illustration 1	g02139237

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.

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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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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, 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

Table 2

Media Number	Title
NENG2500	“Dealer Service Tool Catalog”

Tooling and Equipment

Table 3

Part Number	Part Description
6V-1541	Quick Cure Primer (PUMP BOTTLE)
7M-7456	Bearing Mount Compound (50-ML TUBE)

Determining the Bore Size

First measure the cylinder bore and convert the measured diameter to inches or metric. This procedure will help you to determine whether the bore is inch or metric, or if the cylinder is using standard or oversized seals. Refer to Table 4 and the following process for determining bore sizes.

English (Inch) Cylinders

• The bore diameters of English (inch) cylinders increase in size by nominal values of 0.250 inch. (Examples: 7 inch, 7.25 inch, 7.5 inch, 7.750 inch)

• New English (inch) cylinders from the factory have bores that are no larger than 0.005 inches larger than the nominal size. (Examples: 7.005 inches, 7.255 inches, 7.505 inches, 7.755 inches)

• New English (inch) cylinders can be honed up to 0.010 inches over the new (nominal) size and still use standard-size seals. (Examples: 7.010 inches, 7.260 inches, 7.510 inches, 7.760 inches)

• English (inch) size cylinders can be honed 0.030 inches over the standard nominal size and be resealed by using oversized seals. (Examples: 7.030 inches, 7.280 inches, 7.530 inches, 7.780 inches)

• Once the cylinder has been honed 0.030 inches over the standard nominal size, the cylinder can be honed an additional 0.010 inches and use oversized seals. Once the bore size has reached 0.040 inches over the standard nominal size, the cylinder must be retubed or replaced.

Note: Check the availability of oversized seal kits before honing your cylinder bore oversized.

Metric Cylinders

• The bore diameters of metric cylinders increase in size by nominal values of 5 mm or 10 mm. (Examples: 115 mm, 120 mm, 130 mm, 140 mm)

• New metric cylinders from the factory have bores that are no larger than 0.10 mm larger than the nominal size. (Examples: 115.10 mm, 120.10 mm, 130.10 mm, 140.10 mm)

• New metric cylinders can be honed up to 0.254 mm over the new (nominal) size and still use standard-size seals. (Examples: 115.254 mm, 120.254 mm, 130.254 mm, 140.254 mm)

• Metric size cylinders can be honed 0.762 mm over the standard nominal size and be resealed by using oversized seals. (Examples: 115.762 mm, 120.762 mm, 130.762 mm, 140.762 mm)

Note: Check the availability of oversized seal kits before honing your cylinder bore oversized.

Bore Sizes Chart

Table 4

Inch and Metric Bore Sizes
Inch Bore Size	Metric Bore Size	0.25 mm (0.010 inch) Oversized Bore Dimension	0.76 mm (0.030 inch) Oversized Bore Dimension
2.250 inches	-	57.40 mm (2.260 inch)	57.91 mm (2.280 inch)
2.500 inches	-	63.75 mm (2.510 inch)	57.22 mm (2.253 inch)
2.750 inches	-	70.10 mm (2.760 inch)	70.61 mm (2.780 inch)
3.000 inches	-	76.45 mm (3.010 inch)	76.96 mm (3.030 inch)
-	80 mm	80.25 mm (3.159 inch)	80.76 mm (3.180 inch)
3.250 inches	-	82.80 mm (3.260 inch)	83.31 mm (3.280 inch)
3.500 inches	-	89.15 mm (3.510 inch)	89.66 mm (3.530 inch)
-	90 mm	90.25 mm (3.553 inch)	90.76 mm (3.573 inch)
3.750 inches	-	95.50 mm (3.760 inch)	96.01 mm (3.780 inch)
-	100 mm	100.25 mm (3.947 inch)	100.76 mm (3.967 inch)
4.000 inches	-	101.85 mm (4.010 inch)	102.36 mm (4.030 inch)
4.250 inches	-	108.20 mm (4.260 inch)	108.71 mm (4.280 inch)
-	110 mm	110.25 mm (4.340 inch)	110.76 mm (4.360 inch)
4.500 inches	-	114.55 mm (4.510 inch)	115.06 mm (4.530 inch)
-	115 mm	115.25 mm (4.537 inch)	115.76 mm (4.557 inch)
-	120 mm	120.25 mm (4.734 inch)	120.76 mm (4.754 inch)
4.750 inches	-	120.90 mm (4.760 inch)	121.41 mm (4.780 inch)
-	125 mm	125.25 mm (4.931 inch)	125.76 mm (4.951 inch)
5.000 inches	-	127.25 mm (5.010 inch)	127.76 mm (5.030 inch)
-	130 mm	130.25 mm (5.128 inch)	130.76 mm (5.148 inch)
5.250 inches	-	133.60 mm (5.260 inch)	134.11 mm (5.280 inch)
5.500 inches	-	139.95 mm (5.510 inch)	140.46 mm (5.530 inch)
-	140 mm	140.25 mm (5.521 inch)	140.76 mm (5.541 inch)
-	150 mm	150.25 mm (5.916 inch)	150.76 mm (5.935 inch)
6.000 inches	-	152.65 mm (6.010 inch)	153.16 mm (6.030 inch)
6.250 inches	-	159.00 mm (6.260 inch)	159.51 mm (6.280 inch)
-	160 mm	160.25 mm (6.309 inch)	160.76 mm (6.329 inch)
6.500 inches	-	165.35 mm (6.510 inch)	165.86 mm (6.530 inch)
-	170 mm	170.25 mm (6.703 inch)	170.76 mm (6.723 inch)
7.000 inches	-	178.05 mm (7.010 inch)	178.56 mm (7.030 inch)
-	180 mm	180.25 mm (7.097 inch)	180.76 mm (7.116 inch)
7.250 inches	-	184.40 mm (7.260 inch)	184.91 mm (7.280 inch)
7.500 inches	-	190.75 mm (7.510 inch)	191.26 mm (7.530 inch)
-	190 mm	190.25 mm (7.490 inch)	190.76 mm (7.510 inch)
7.750 inches	-	197.10 mm (7.760 inch)	197.61 mm (7.780 inch)
-	200 mm	200.25 mm (7.884 inch)	200.76 mm (7.904 inch)
8.250 inches	-	209.80 mm (8.260 inch)	210.31 mm (8.280 inch)
-	210 mm	210.25 mm (8.278 inch)	210.76 mm (8.298 inch)
8.500 inches	-	216.15 mm (8.510 inch)	216.66 mm (8.530 inch)
-	220 mm	220.25 mm (8.671 inch)	220.76 mm (8.691 inch)
9.250 inches	-	235.20 mm (9.260 inch)	235.71 mm (9.280 inch)
10.00 inches	-	254.25 mm (10.010 inch)	254.76 mm (10.030 inch)
10.250 inches	-	260.60 mm (10.260 inch)	261.11 mm (10.280 inch)
10.500 inches	-	266.95 mm (10.510 inch)	267.46 mm (10.530 inch)
11.000 inches	-	279.65 mm (11.010 inch)	280.16 mm (11.030 inch)
11.500 inches	-	292.35 mm (11.510 inch)	292.86 mm (11.530 inch)
12.250 inches	-	311.40 mm (12.260 inch)	311.91 mm (12.280 inch)
12.500 inches	-	317.75 mm (12.510 inch)	318.26 mm (12.530 inch)
13.000 inches	-	330.45 mm (13.010 inch)	330.96 mm (13.030 inch)
13.250 inches	-	336.80 mm (13.260 inch)	337.31 mm (13.280 inch)
14.250 inches	-	362.20 mm (14.260 inch)	362.71 mm (14.280 inch)
14.750 inches	-	374.90 mm (14.76 inch)	375.41 mm (14.78 inch)
16.750 inches	-	425.70 mm (16.760 inch)	426.21 mm (16.780 inch)

Measuring Examples

• The measured bore size is 158.93 mm (6.257 inch) in diameter. This bore is not metric because this measurement is not close to the standard or oversized metric diameter as found in the chart. This cylinder is English (inch) with a standard bore size of 6.250 inches. The bore is oversized 0.007 inches and the cylinder is not new because the bore is more than 0.005 inches larger than the standard (nominal) size. This cylinder can still be honed up to 0.003 inches more in diameter and use the standard seals.

• The measured bore size is 165.86 mm (6.530 inch).This bore is not metric because this measurement is not close to the standard or oversized metric diameter as found in the chart. This cylinder is English (inch) with a standard bore size of 6.500 inch cylinder that has been honed exactly 0.030 inches oversized. This cylinder will still use the oversized seals.

• The measured bore size is 120.76 mm (4.754 inch). This bore could be metric because the bore is exactly 0.76 mm (0.030 inch) oversized for a metric cylinder. However, this bore is a new English (inch) bore. The bore is less than 0.005 inches larger than the standard nominal bore size of 4.750 inches. This bore can be honed up to 4.760 inches and still use standard seals.

• The measured bore size is 160.02 mm (6.300 inch). This bore is metric because the bore diameter is too large to be an oversized English (inch) cylinder and too small to be a new English (inch) cylinder. Also, this bore is less than 0.10 mm larger than the standard (nominal) 160 mm bore.

Head Seal Locations

Illustration 3	g01640536
Threaded gland with standard head seal

The head seal for the oversize threaded gland cylinder is the standard O-ring and back-up ring (1).

Illustration 4	g01640543
Threaded crown with oval seal

The head seal for the oversize threaded-crown cylinder is an oval cross-section seal (2). The seal is located in the lead-in chamfer at the open end of the cylinder. The O-ring and back-up ring groove (A) in the head is left empty

Illustration 5	g01640566
Bolted-Head Cylinder

Formerly, the head seal for the oversize bolted-head cylinder was the same oval seal (6) that is used in an oversize threaded-crown cylinder. The oversize bolted-head cylinder is now sealed at the head joint (3) by an O-ring (4). This O-ring (4) provides a more effective seal than the oval head seal. The groove (5) for the stock seal is left empty.

Seal Installation Information

Rod Seal Installation

Illustration 6	g01644830

1. Install buffer seal (2) by hand. The sealing lip of the buffer seal should face the pressure side of the cylinder. The seal will take on a kidney shape during installation. Then, install the back-up ring (3). The backup ring should be installed closest to the rod eye end. Make sure that you do not twist the back-up ring.

2. Next, install the U-cup seal (6) next. Install the U-cup seal by hand. The "U" of the U-cupped seal should face toward the piston.

3. The head wear ring (1) is rigid and the wear ring is split to aid in assembly. Compress head wear ring (1) and slide the head wear ring down into position until the wear ring snaps into place.

   1. Use the following procedure to install wiper seal (8).

      Note: The wiper seal (8) can be a press-in style that uses a metal shell or the wiper seal can be a snap-in style. The snap-in style does not require the use of bearing mount compound.

   2. Scuff the surface of the counterbore in the head as well as the outside diameter of the wiper seal's (8) metal shell with emery cloth.

   3. Clean the counterbore in the head and the outside diameter of the wiper seal metal shell with 6V-1541 Quick Cure Primer. Clean the counterbore and the metal shell until neither of the components discolor a clean white towel.

      Note: The metal shell of the wiper seal is coated with a corrosion inhibitor. This coating may prevent proper bonding of the wiper seal to the cylinder head if the inhibitor is not removed. After cleaning, do not touch the counterbore or the metal shell because the oil from your fingers may prevent a good bond. Handle the seal by the lip only.

   4. Apply 6V-1541 Quick Cure Primer on the counterbore and the metal shell. Allow the primer to dry. The primer will dry in approximately 30 seconds.

   5. Apply 7M-7456 Bearing Mount Compound evenly, but do not apply the Bearing Mount Compound excessively. Apply Bearing Mount Compound to the counterbore and to the metal shell. Do NOT allow the Bearing Mount Compound to contact the sealing lip.

   6. Press wiper seal (8) into the cylinder head. Make sure that the marking "THIS SIDE OUT" on the seal (8) is toward the rod end. Ensure that the seal is firmly seated against the bottom of the counterbore. Wipe away any excess Bearing Mount Compound. Allow Bearing Mount Compound to dry for 15 minutes before assembling the hydraulic cylinder.

4. Assemble the oval seal (7) or the O-ring (4) and back-up ring (5), depending on the application.

   Note: The O-ring (4) should always face the pressure side of the cylinder and back-up ring (5) should be located on the rod eye side.

Piston Seal Installation

Illustration 7	g01646458

1. Install expander ring (3) first. Do not twist the expander ring during installation. Use a small screwdriver to work the expander ring around piston (2) and into the groove.

2. Install piston seal ring (4) on top of expander ring (3). Seal ring (4) is split and can be installed by hand.

3. The piston wear ring (1) is rigid and is split to aid in assembly. Expand wear ring (1) and slide over piston (2) until wear ring (1) snaps into position.

Installation of the Head onto the Rod

Illustration 8	g01646675

1. Lubricate the rod (1) and the seals with clean hydraulic oil.

2. Install a seal guide (2). The seal guide (2) is a cone shaped tool that is used to open the seals that are located in the head. The seal guide ensures that the seals will slide onto the rod without damage. The seal guide also serves to align the seals.

3. Push the head (3) over the rod by using one quick motion.