Manitowoc 18000, Service Maintenance Manual, Page: 106 / 316

Reference
Only
HYDRAULIC SYSTEM 18000 SERIVCE/MAINTENANCE MANUAL
2-12
Published 12-05-17, Control # 035-23
TIGHTENING HYDRAULIC CONNECTIONS
• Make sure fittings and O-rings being used are proper
size and style.
• Flush sealing surfaces with clean hydraulic oil to remove
any dirt.
• Carefully inspect threads and sealing surfaces for nicks,
gouges, and other damage. Do not use damaged parts;
they will leak.
• Carefully inspect O-rings for cuts and other damage. Do
not use damaged O-rings: they will leak.
• Always lubricate O-rings when assembling on fittings.
• Be careful not to cut O-rings when assembling them to
fittings. Use thimble as shown in
Figure 2-8 when
assembling O-ring over threads.
Pipe Thread Connection
1. Apply sealant (Loctite 92 or equivalent) to male threads,
never to female threads. Do not apply sealant to first two
male threads.
2. Tighten fittings about 4-1/2 turns by hand and then 3
additional turns with a wrench.
Table 2-2 Pipe Thread Leakages
SAE Straight Thread Connection
This type connection leaks most often because the jam nut
and washer are not backed up before assembly.
When the jam nut and washer are not backed up, there is not
enough room for the O-ring when the squeeze takes place
and the washer cannot seat properly as shown in
Figure 2-9 ,
View A. The compressed rubber between the washer and
the spot face will cold flow out of compression, causing the
fitting to loosen and leak as shown in
Figure 2-9 , View B.
Tighten SAE straight thread connections as follows:
1. Back up jam nut and washer to end of smooth portion on
fitting as shown in
Figure 2-10 , View A.
2. Lubricate O-ring with clean oil, this is very important.
3. Thread fitting into port until washer bottoms against spot
face as shown in
Figure 2-10 , View B.
NOTE: If an elbow is being used, back it out as necessary
to align it with hose.
4. Tighten jam nut. When fitting is properly installed, O-ring
will completely fill seal cavity and washer will be tight
against spot face as shown in
Figure 2-10 , View B.
CAUTION
Hydraulic System Damage!
Do not use FTE-fluorocarbon tape to seal threads; pieces
of tape will enter hydraulic system and cause damage.
Causes Cures
Fitting loose. Tighten.
Fitting too tight causing thread
distortion.
Replace damaged parts.
Threads on fitting/port wrong size. Use proper size threads.
Threads dirty, galled or nicked.
Clean or replace parts.
Straight thread used instead of
tapered thread. Use proper type and
size thread.
Threads expanded from heat. Tighten when hot.
Fitting loosened by vibration. Retighten.
O-Ring
Plastic or Metal
Thimble Covering Threads
FIGURE 2-8
S103
View A
View A
O-Ring
Washer
Jam Nut
FIGURE 2-9
Washer cannot seat properly on
spot face. Compressed rubber
between washer and spot face
will cold flow out of compression,
causing fitting to loosen and leak. When jam nut and washer
are not backed up, there is
not enough room for O-ring
when squeeze takes place.
S107
View B
View B
Washer
Jam Nut
FIGURE 2-10
Nut and washer backed
up to end of smooth
portion on fitting.
S106
Spot Face
O-Ring
View A