TM 9-2510-247-13&P
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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 couple only fittings designed to be coupled 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 handtightened,
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 install 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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