Figure 3-43. - End fittings and hose fittings.

Reusable hose fittings are pushed on, screwed on, or clamped onto the hose. When the hose wears out, the fittings can be removed and used on a new hose that is cut from stock. Many fittings can be converted to another thread type by changing the nipple in the socket.

NOTE

If hoses and fittings are matched incorrectly, the results can be pinhole leaks, ruptures, heat build ups, pressure drops, cavitation, and other failures.

QUICK-DISCONNECT COUPLERS. - Quick disconnect couplers are used where oil lines must be connected or disconnected frequently. They are self- sealing devices and do the work of two shutoff valves and a tube coupler.

These couplers are fast, easy to use, and keep oil loss at aminimum. More importantly, there is no need to drain or bleed the system every time a hookup is required.

However, dust plugs must be used when the coupler is disconnected.

Sealing Materials and Devices

No hydraulic circuit can operate without the proper seals to hold the fluid under pressure in the system. Seals also keep dirt and other foreign materials out of the system.

Hydraulic seals appear to be simple objects when held in the hand but, in use, they are highly complex; precision parts must be treated carefully if they are to do their job properly.

Hydraulic seals are used in the following two main applications:

1. Static seals are used to seal fixed parts. Static seals are usually gaskets, but also may be O- rings or packings.