Periodically the chains will have to be removed from
the truck for cleaning, inspection and re-lubrication
by immersion in oil. Cleaning must allow thorough
visual inspection and must be aimed at the removal
of wear particles and used oil at pin contact area.
Maintaining the Presence of Oil
Insufficient lubrication permanently damages the
smooth contact area between chain pin and inner
plates. Re-lubricating a damaged contact area
afterwards, will not restore the smooth finish of the
contact area. A damaged contact area causes
accelerated wear and increased friction.
Increased friction may allow the inner plates to
rotate the pin in the outer plates. Once the pin has
rotated in outer plate, integrity of the chain
structure is lost. Rotation of a pin in the outer plate
is visible when the beveled end of a pin no longer
runs parallel to the length of chain. A chain must be
replaced if a pin is at an angle or if a pin has
protruded.
Sufficient lubrication is particularly important for
new chains, which require a breaking in of the
contact area. Proper breaking in also requires low
load conditions during initial lifting and lowering.
At least avoid lifting high capacity loads initially.
Corrosion Protection
Link pins and chain leaves are made of a steel type
that is vulnerable to corrosion. Corrosion causes pits
which are the starting point for fatigue fractures.
Corrosion preventing coatings, e.g. paint or grease,
cannot be applied to the chain as these would
obstruct the penetration of oil for re-lubrication.
Therefore, the applied lubricating oil must also
serve as a protection against corrosion. This outside
oil film must always remain intact to make sure
that humidity does not reach the components of the
chain, and certainly not the contact area between
pin and plate.
Circumstances like temperature, dust and rain will
dictate the frequency of re-application of oil to the
chain to restore a protecting film. Re-apply oil
before the oil film is interrupted.
Requirements for Chain Lubricant
The chain lubricant must be a mineral or synthetic
engine oil. Oil viscosity must match the ambient
temperature, so that the oil remains viscous and can
penetrate to the contact area between link pin and
intermediate link.
• Use SAE 20W to 30W oil in ambient
temperatures of −30 to 5°C (−22 to 41°F).
• Use SAE 40 oil in ambient temperatures of 5
to 45°C (41 to 113°F).
• Use SAE 50 oil in ambient temperatures
above 45°C (113°F).
DO NOT use the following lubricant types:
• Lubrication products that contain solids such
as graphite or molybdenum disulfide. Solids
will not penetrate between the plates, and
over time, they will form a barrier that
prevents oil penetration.
• Grease or lubrication products that stiffen or
form a greasy film. Stiffening products do not
penetrate sufficiently. Grease does not
penetrate at all. Stiffening products and
grease form a barrier that prevents
penetration of oil for re-lubrication. Without
proper lubrication, the service life of a lift
chain is minimized.
• Penetrating fluid Penetrating fluids or aerosol
spray lubricants containing penetrating fluids
do not provide adequate lubricity, adhesion or
corrosion protection, and they do not form a
film.
NOTE:
If an aerosol spray lubricant is used, always
check that it deposits an engine oil equivalent, with
the minimum viscosity as listed under Viscosity,
after the dispersing agent has evaporated.
Load Rollers
Movement of the inner mast within the outer mast,
and movement of the carriage in the inner mast are
guided by load rollers, which reduce friction. The
load on the carriage causes forces on the load rollers
in different directions. The lower load rollers are
pushed against the rear of the mast channels. The
upper load rollers are pushed against the front of
the mast channels. See Figure 11.
When the mast is tilted completely backward and
the carriage is raised, it is possible that the upper
load rollers of the inner mast travel from the front
to the rear of the outer mast channel. To reduce the
related backward movement of the inner mast
inside the outer mast, two mast support pads are
installed at the top of the outer mast. See Figure 10.
Description And Operation
4000 SRM 1664
8
