Before the installation of a new flareless-tube connector, the end of the tubing must be square, concentric, and free from burrs. For the connection to be effective, the cutting edge of the sleeve or ferrule must bite into the external surface of the tube.

Permanent hose fittings are discarded with the hose when the hose is damaged or defective. They are either crimped or swedged onto the hose. A crimping machine that may be found in most shops does crimping of the fitting. The crimping machine is either powered by hand. an air pump, or a hydraulic pump.

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.