Usage:
Reference: IRM, HYD 86-4, "Oversize And Standard Hyd. Cylinder Seal Kits". Special Instruction, Form SEHS8630, "Installing Seals In Oversize Hydraulic Cylinders".
Seal kits are available for hydraulic cylinders with bore sizes from 76.2 mm (3.00") to 235.0 mm (9.25"). When honing a cylinder tube bore for an oversized seal, add either 0.76 mm (.030") or 1.52 mm (.060") to the nominal bore size. Then hone to that dimension +0.13 mm to -0.05 mm (+.005" to -.002"). After honing oversize, the surface finish of the bore must be 0.80 micrometers (32 microinches) or less.
Taper in the bottom of the cylinder bore can be a problem. A 0.76 mm (.030") taper on the diameter is allowable in the last 38 mm (1.5") of the bore. To help control taper, stop the stroking action of the hone and allow the stones to dwell in the bottom of the bore. Another solution is to cut the cap from the tube, hone the tube, then weld the cap back on as described in "Guideline For Reusable Parts", Form SEBF8072.
After the cylinder tube is honed oversize, mark it for future identification. Use 1/4" steel stamps to mark the outside of the tube 152 mm (6.0") from the open end either "76 (030) OS" or "152 (060) OS". If possible, locate the stamping so that it can be read after the cylinder is installed on the machine. A red stripe around the tube will help flag the tube as oversize for later service work.
On standard and threaded crown cylinders, the oversized head seal DOES NOT locate in the head seal groove. It locates in the lead-in chamfer of the cylinder bore. See Illustration 1. The chamfer must be concentric with the bore and free from nicks and burrs. After honing, make sure the chamfer meets the specifications given in Illustration 2. Chamfers that do not meet specifications WILL CAUSE LEAKS. Generally, deburring after honing is all that is necessary. If the chamfer is too deep, up to 3.18 mm (.125") can be removed from the face of the cylinder flange.
These seals offer good value to competitive tube owners also. Conversion information is being developed and will be published as it becomes available.
A value-priced repair alternative to honing cylinder tubes in your own shop is to source Remanufactured Cylinders from Caterpillar. These honed cylinders are available on an exchange basis for a broad range of Caterpillar product. They are priced at approximately 25 to 50% of new cost. For application data, core acceptance criteria and other details, refer to IRM REM86-26.
Illustration 2. Chamfer specifications.
Illustration 1. Location of oversize head seal.