Clark GEX20 - Page 339

Group 34, Uprights
SM 765, Nov ’06 Troubleshooting • 34-2-3
• Internal leakage in primary lift cylinder; perform
cylinder checks listed under “Load cannot be lifted
to maximum height.”
• Damaged primary lift cylinder causing binding in
the cylinder; inspect and repair or replace cylinder.
• Defective velocity fuse; remove fuse from cylinder
hydraulic port, clean and recheck for proper opera-
tion.
Upright mis-staging (TSU lowering)
• Debris in upright roller area or tie bar area; check
and clean.
• Bent or broken carriage or inner rail; replace part -
do not try to repair by welding.
• Damaged or binding roller on upright; check con-
dition of roller and replace if necessary.
• Carriage and upright roller shimming or thrust
roller out of adjustment; perform roller checks on
upright and/or carriage and make adjustments as
necessary.
• Damaged or kinked lift cylinder hose; check condi-
tion of hose, repair or replace as necessary.
• Lift cylinder chain or chain sheave binding or dam-
aged; inspect and repair.
• Bent cylinder rod; inspect and replace rod and/or
cylinder as necessary.
• Internal leakage in piston-type cylinders; perform
cylinder checks listed under “Load cannot be lifted
to maximum height.”
• Damaged lift cylinder causing binding in the cylin-
der; inspect and repair or replace cylinder.
• Defective velocity fuse; remove fuse from cylinder
hydraulic port, clean and recheck for proper opera-
tion.
Upright mis-staging (Standard and Hi-Lo
upright lowering)
• Damaged or binding roller on upright; check con-
dition of roller and replace if necessary.
• Top carriage roller retaining cap screw loose;
check and replace cap screw.
• Lift cylinder chain or chain sheave binding or dam-
aged; inspect and repair.
• Debris in upright roller area or tie bar area; check
and clean.
• Bent or broken carriage or inner rail; replace part -
do not try to repair by welding.
• Carriage and upright roller shimming or thrust
roller out of adjustment; perform roller checks on
upright and/or carriage and make adjustments as
necessary.
• Defective velocity fuse; remove fuse from cylinder
hydraulic port, clean and recheck for proper opera-
tion.
External leakage on primary cylinder
• Gland loose; check and tighten primary cylinder
gland to 588 N⋅m (432 ft-lb) and glands on lift
(secondary) cylinders to 392 N⋅m (289 ft-lb).
• Cracked cylinder tube; replace tube.
• Rod seal damage; replace seals and check for:
− Damaged rod seal groove in gland; check for
damage to groove and replace seal or gland if
necessary
− Scored cylinder wall; repair or replace cylinder
tube if necessary
− Leaking check valve; clean and replace if nec-
essary
− Leaking O-ring seal on check valve; replace
check valve.
• Gland static seals (O-rings and back-up ring) dam-
aged; replace back-up ring.
• Gland static seals sealing surface damaged; check
groove and bore and repair or replace as necessary.
External leakage on lift (Standard) and
secondary cylinder (TSUs and Hi-Lo)
• Gland loose; check and tighten gland on cylinders
to 392 N⋅m (289 ft-lb).
• Cracked cylinder tube; inspect and replace tube.
• Seal damage in piston-type cylinders; replace pis-
ton seals and rod seals.
• Damaged seal groove, piston-type cylinders; check
for scratches, nicks, or burrs and repair or replace
rod and piston.
• Scored cylinder wall, TSU piston-type cylinders;
replace tube and all seals.
• Scored or damaged rod; replace rod and all seals.
• Damaged gland back-up seal; inspect and replace
seal.