U20-3, U25-3 WSM General
I-10
c. Piping
(1) General precautions
• Tightening the pipe socket to the specified torque. If too tight, the socket itself or a hydraulic
component may get damaged. It too loose, an oil leak may result.
• In connecting a new hose or pipe, tighten its nut first to the specified torque and then turn it back
(about 45°). Then tighten it again to the specified torque. (Do not this to the sealing tape-applied
hose or pipe.)
• When disconnecting a vertical hose or pipe, separate its bottom connection first.
• In disconnecting and reconnecting the hose and pipe, be sure to use two wrenches. With one
wrench, restrain the mating part to allow no twist.
• Check the mating connector’s sleeve and the hose’s taper for dust deposits and scratches.
• When the pipe socket has been tightened up, wipe the joint clean. Apply the maximum operating
pressure 2 or 3 times to make sure there is no oil leak.
(2) Hydraulic hose
Check the hydraulic hose for too tight a connect or twist.
*Excessively tight contact
Let’s suppose that a hose is in contact with another hose or other part. If the hose is pulled away by a
force of 2 kg but still in contact, it means the contact is too tight.
(3) Precautions in tightening the bolts and nuts
• Use bolts of specified length.
• Do not over tighten the bolts: Its threads may get deformed or the fixed part may get damaged. Do
not undertighten the bolt either: It may get loose.
• In other words, tighten the bolt to the specified torque.
• Tighten the bolts and nuts diagonally for even tightness.
R (Tapered thread)
G (Straight thread)
Nut
Sleeve
Steel pipe Union nut
Tapered thread
Joint body
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