Manitowoc Grove RT770E, Service Maintenance Manual

Page: 101 / 357

2-61
GROVE
RT770E HYDRAULIC SYSTEM
2
Published 11/26/2014, Control # 447-05
CYLINDERS
General
This subsection provides descriptive information for all the
hydraulic cylinders used on this crane. The description of the
cylinder given here is for the cylinder itself. For information
on how the cylinder functions in the individual circuits, refer
to the Description and Operation of that circuit.
Maintenance
General
There must be a gap between the ends of each wear ring
when it is installed onto the piston (as applicable) or head. In
addition, each wear ring gap is to be located as follows:
Divide 360 degrees by the number of wear rings on the
component. The resulting value is the number of degrees
each wear ring gap is to be located with respect to each
other.
The approximate wear ring gaps are as follows:
Table 2-4
Wear Ring Gap
Surface Protection For Cylinder Rods
Steel cylinder rods include a thin layer of chrome plating on
their surfaces to protect them from corroding. However,
chrome plating inherently has cracks in its structure which
can allow moisture to corrode the underlying steel. At typical
ambient temperatures, hydraulic oil is too thick to penetrate
these cracks. Normal hydraulic operating temperatures will
allow hydraulic oil to warm sufficiently to penetrate these
cracks and if machines are operated daily, protect the rods.
Machines that are stored, transported, or used in a corrosive
environment (high moisture, rain, snow, or coastline
conditions) need to have the exposed rods protected more
frequently by applying a protectant. Unless the machine is
operated daily, exposed rod surfaces will corrode. Some
cylinders will have rods exposed even when completely
retracted. Assume all cylinders have exposed rods, as
corrosion on the end of the rod can ruin the cylinder.
It is recommended that all exposed cylinder rods be
protected using Boeshield® T-9 Premium Metal Protectant.
Manitowoc Crane Care has Boeshield® T-9 Premium Metal
Protectant available in 12 oz. aerosol cans by ordering part
number 9999101803.
Leakage Check
A hydraulic cylinder should not be disassembled unless it is
essential. The following checks will provide a means of
determining if a cylinder has a faulty or leaking piston seal.
1. Extend the rod to its maximum stroke. Remove the
retract hose from the cylinder. Cap the retract hose.
2. Apply hydraulic pressure to the piston side of the
cylinder and observe the open cylinder port for leakage.
If leakage is observed, the seals in the cylinder must be
replaced.
3. Fully retract the cylinder rod (except the telescope
cylinder). Remove the extend hose from the cylinder.
Cap the extend hose.
Head (or Piston) Size Wear Ring Gap
Inch mm Inch mm
1 to 4.75 25.4 to 120.7 0.125 3.18
5 to 10.0 127.0 to 254.0 0.187 4.75
greater than 10.0 greater than 254.0 0.250 6.35
CAUTION
Cylinder operation and inclement weather will remove the
Boeshield® protectant; therefore, inspect machines once
a week and reapply Boeshield® to unprotected rods.
DANGER
Ensure pressure is applied to the piston side of the
cylinder only and the retract hose is capped.
DANGER
Ensure pressure is applied to the retract (rod) side of the
cylinder only and the extend hose is capped.