TM 5-2350-262-20-3
GENERAL HYDRAULIC SYSTEM REPAIR - CONTINUED
CAUTION
Always clean around fittings before disconnecting or connecting hoses or fittings.
Ensure area is clean before installing hydraulic components. Failure to comply
may result in damage to equipment.
Cover, cap, or plug all openings, ports, and tube or hose ends when they are
disconnected. Failure to comply may result in damage to equipment.
Ensure you mate only fittings designed to be mated with each other. Never depend
on trial and error. Just because two fittings will screw together is no guarantee that
the connection will not leak. See illustrations of fitting types in this chapter. Failure
to comply may result in damage to equipment.
Fittings must be installed and hand-tightened. If a fitting cannot be hand-tightened,
it may be cross-threaded or have damaged threads. Use wrench only for final
tightening. Failure to comply may result in damage to equipment.
Do not use Teflon tape as a sealer on any fittings. It can separate from the fittings
and cause control valves, relief valves, and actuators to become contaminated and
fail.
It is possible to screw a male National Pipe Thread (NPT) into a female straight
thread, but the fitting will leak. Learn to recognize the very slight taper which an
NPT has. Do not attempt to connect NPT and female straight threads.
Do not apply sealant to the first threads of NPT fittings. If sealant enters the
hydraulic system, it may cause components to fail.
When connecting NPTs, care must be exercised. If overtightened, the female pipe
thread will split. Replace it. If a connection leaks, disconnect and apply thread
sealant. Reconnect the threads and snug up with an open-end wrench. Failure to
comply may result in damage to equipment.
Be careful when installing preformed packings. Sharp threads can nick the
packing, causing it to leak. If fitting leaks, check packing for nicks or cuts and
replace if necessary.
Do not overtighten a flareless connection. Observe torque values in appendix for
hydraulic fittings. Overtightening can cause leakage, requiring replacement of
entire tube assembly.
When connecting a hose to a fitting, always use two wrenches. Use one wrench to
turn the swivel nut onto the fitting, and use another wrench to keep the hose from
rotating. If the hose rotates, it can loosen the other end of the hose, or loosen the
fitting at the other end.
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