Group 34, Uprights
SM 765, Nov ’06 Upright Inspection • 34-3-5
IMP
RTANT
Never replace a single chain in a set. Always
replace the two chains in a set for consistent
lift operation. Always replace anchor pins
when replacing chains.
1. For example, measure a 305 mm (12 in) segment of
the chain that does not roll over a sheave and count
the number of links in the segment.
2. Find an area of the chain that normally runs over the
sheave. This can usually be identified by wear on the
plate edges that roll over the sheave.
3. If the same number of links measures over 315 mm
(12.36 in) the chain must be replaced.
If using a chain check ruler, see instructions on the ruler.
Chain replacement procedures appear in Section 6.
Chain Length
IMP
RTANT
Perform a chain length check and adjust-
ment every 50-250 hours. Checks and adjust-
ments should also be performed to adjust for
chain stretch and tire wear.
Chain length must be adjusted if:
• The fork-to-ground clearance is less than 5 mm
(.20 in) or more than 25 mm (1.0 in) when the
upright is vertical.
• The center of the bottom carriage roller comes
within 20 mm (0.80 in) of the bottom edge of the
inner rail.
• The carriage safety stop hits the inner rail stop at
full lift height.
• On TSUs and Hi-Lo, the difference between the
bottom of the inner rail and the outer rail is greater
than 10 mm (0.40 in).
See Section 6 for chain length adjustment procedures.
Chain Tension
IMP
RTANT
Center any auxiliary attachments before
beginning tension check
1. Raise the upright enough to put tension on the chains
to be checked.
2. Push the chains forward and pull them backward; the
amount of tension should be equal on both sides.
WARNING
!
Do not reach through the upright to push
chains for tension check.
3. If one chains moves more than the other;
a. Lower the forks to ease tension on the chains.
b. Adjust chain adjustment nuts for equal tension on
both chains. See Section 6 for chain adjustment
procedures
4. Repeat the tension test and make adjustments until
the tension is equal on both chains when the carriage
and upright are raised.
Carriage and Upright Weldments
The carriage and upright should be checked for fatigue
cracks and bent components every 2000 hours or every
year..Fatigue cracks start in areas of stress after a high
number of load cycles. Stress concentrations typically
exist in welded joints, in the area around a welded joint, or
in the corners of parts. Dye penetrant, magnaflux, or other
crack detection methods can be used to find or trace
cracks. If cracks are found in any structural weldment, the
component should be replaced before returning the truck
to service.
• Bent components indicate excessive loading or
high impacts to the weldments. Bent components
are usually structurally damaged and should be
replaced.
• Inspect roller contact patterns on the rail sections.
Roller contact patterns should be smooth and regu-
lar.
− In some applications, it may take up to 500
hours of operation to develop a roller contact
pattern on the flange of the rail.
− In applications where heavy loads are common,
a rail lubricant may be required to allow proper
wear-in on the roller.
• Check rails and carriage for wear due to undesir-
able contact between components. Such contact
can be an indication of broken rollers, loose com-
ponents, foreign objects or debris on the upright, or
a broken weldment.
− If contact or rubbing exists, the condition must
be corrected immediately.
− Rail and carriage weldments with damage
should be replaced.
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