Usage:
All Caterpillar Products So Equipped
- SUPPLEMENT: 02/08/82
SERVICE MAGAZINE, NOVEMBER 30, 1981, PAGE 1. In the article "New Duo-Cone Seals Use Seal Rings Made Of Steel Instead Of Cast Iron" that starts on Page 1, change the subtitle to read "Some Caterpillar Product Applications".
This change is made because the new seals will not be used in all applications at the present time. Generally, the first applications will be for compartments where there is little or no pressure.
For example, these seals are not used in the rear wheels of off-highway trucks. New nickel-chrome seals have been released for this application.
Also, while the steel seals will be used in some other applications, there are no plans to change track roller seals or bogie cartridge pin seals.
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Description of Change: New Duo-Cone seals use seal rings made from sheet steel instead of the cast iron formerly used. The new steel seal rings are heat treated, and the flange is through-hardened to Rockwell C62 minimum hardness. The rings are coated (treated) with manganese phosphate, then the seal face is machined to a very smooth surface. The manganese phosphate gives the rings a black color (except on the seal face) in comparison with the gray color of the former cast iron rings. The black color and the thinner cross section of the steel rings permits easy identification of the new seals. See Illustration 1.
The new steel rings are more flexible than the former cast iron rings. Because of this characteristic, the seal contact face will be wider during machine operation, with more surface contact area. As the rings wear during machine operation, the contact surface becomes wider, until it extends completely across the ring flange. This amount of wear is the normal maximum service life for the former iron rings, but not for the new steel rings. The total thickness of the flange is usable wear material on the steel rings, and good seal performance can generally be expected until the flange is completely worn away.
Illustration 1. Cross section comparison of new and former Duo-Cone seals.
With the new rings, the measurement used to check the remainder of seal service life is the flange thickness at the outer edge. See Illustration 2. As shown in the illustration, the measurement must be made carefully because of the shoulder, which is only 1.52 mm (.060") from the edge of the flange. Also, before the flange is measured, it must be inspected for a wear lip around the outer edge as shown in Illustration 3. The development of a wear lip at the outer edge is a normal condition any time the edges of the two ring flanges are not exactly even when the seal is installed. A wear lip in this location does not damage the seal ring, and has no effect on seal performance, but it must be carefully ground off before the flange thickness is measured and/or before the seal is installed again. If any type of wear lip is found around the inner edge of the seal face (see Illustration 3), or if the seal face has any scratches or other damage, a new seal must be installed. The seal face must be flat and smooth.
Illustration 2. Measurement of flange thickness on hardened steel rings.
Illustration 3. Location of wear lip on seal ring.
Estimates of expected seal life are difficult because of the many differences in machine applications, job conditions, maintenance and other factors which have an effect on seal service life. The chart that follows can be used as a guide to make an estimate of the remainder of seal service life, according to flange thickness.
Adaptable As: Direct replacement. Specific part numbers and applications are not shown here because some groups are not yet available, but each of the new seal groups can be used as a direct replacement for the respective former group.
Seal Storage and Hand Contact: Protection from rust and corrosion, expecially on the machined seal face, is very important. The new seals, like existing seals and many other parts, need protection from moisture (water) and/or mechanical damage (scratches, bend stresses, etc.). Damage can also be caused by hand contact because of moisture and salt from the person's body. Be sure seal rings are thoroughly cleaned and have an application of heavy oil before storage. This needs to be done for storage intervals as short as one or two days during service work on the machine.
Installation And Tools
... Use correct tools for seal installation, which are made specifically for this purpose. The same tools are used for the new steel rings which were used for the former cast iron rings.
... Be sure the toric ring is not twisted when it is installed on the seal ring.
... During installation of used parts, keep the same two seal rings together which have "worn in" together. When two rings have been used together, they must be installed as a "set".
... Never mix new and used metal seal rings.
... During seal installation, be sure the toric rings and the ramps (tapers) on both the seal retainers and the seal rings are clean and dry, with no oil or other lubricant on them. Lubrication can permit the rings to slip (slide), and possibly cause leakage.
... Just before the seal faces are put together during assembly, wipe (clean) the faces with a lint-free paper (tissue). Then put oil on a piece of tissue, and again wipe the seal faces. This will make sure the seal faces are clean and have lubrication.
... During installation of a used seal, be sure to check for a wear lip (see Illustration 3) which must be removed before the seal in installed.