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.
If hoses and fittings are matched
incorrectly, the results can be pinhole leaks,
ruptures, heat build ups, pressure drops,
cavitation, and other failures.
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
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
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
1. Static seals are used to seal fixed parts. Static
seals are usually gaskets, but also may be O-
rings or packings.