LOCK 4E3897 - Caterpillar

All LocationsReference: Service Magazine; December 9, 1985, Page 2; "New Ratchet Wrenches Available For Tube Fittings".Reference: Caterpillar Service Technology Group promotional ad, "Ratchet Wrenches for Tube Fittings", NEDG5005. Torque Specifications, SENR3130, for all Service Manuals.Face-type seals and connectors for tubes and hoses that carry fluids are being phased into many existing systems, and are already used in most new products. Several million of these seals and connectors will be used each year in Caterpillar products, and most servicemen, if not already, will be servicing these seals and their fittings.
Some face-type seals have leaked because of incorrect assembly. Also, difficulties in assembling of these joints have been reported. This article provides brief features of the seal and joint design, new recommendations for assembly, and tools available from Caterpillar to use on these fittings. The correct use and assembly of these fittings provides a reliable leak-free joint and will be more economical than other fittings in the long run.
Seal And Joint Design
The face-type seal and joint combination provide a reliable, leak-free seal at higher operating pressures than the metal-to-metal JIC (Joint Industry Council) 37° flare-type fittings. When a JIC fitting is retightened to stop a leak or seepage, the metal-to-metal surface is slightly deformed because of overtightening, and the leak probably will resume later. In some cases, the leak may be cause by an irregularity (scratch, nick, etc.) in the sealing surface. Retightening in this case will not cure the problem. Illustration 1 compares the flare-type joint to the face-type seal joint.
Illustration 1. Comparison of the face-type seal joint with the former flare-type joint commonly used by Caterpillar.The face seal joints can endure higher pressure spikes and vibration forces. Service problems, downtime, and oil and fuel leaks are minimized.
Some other advantages of the face-type seal are:
... Sealing up to 41 250 kPa (6000 psi). JIC fittings are not recommended for pressures above 20 625 kPa (3000 psi).
... Connections can be made and broken without disturbing nearby plumbing.
... Reduces problems of misalignment during reassembly.
... Retightening to stop leaks is not required.
... Less sensitive to overtightening.
... If not damaged when the joint is disconnected and reconnected, the metal parts have unlimited reuse.
As shown in Illustrations 1 and 2, the O-ring seal fits in an annular groove in one end face of the connector (or fitting). When the nut on the mating part is tightened on the connector (or fitting), the two mating faces come together and the O-ring seal is retained tightly in its groove.
Illustration 2. Face-type seal joint for a hose or tube.Face-type seals on machines in the field can be either an O-ring or a square section type. See Illustration 3. (Only the O-ring seals are now used in production.) Either seal will work, provided the seal is the right size for the groove. Be sure you use the seal identified by the part number in the Parts Book. Do not be confused by the descriptions of the seals, because in some cases a square seal installed as the original