Manitowoc Grove RT880E User Manual

Grove Published 11-10-2014, Control # 524-00 2-7
RT880E SERVICE MANUAL HYDRAULIC SYSTEM
2
morning. Telescoping OUT may cause air to be forced
back into a cylinder.
Entrapped air may be removed from cylinders having
wet rods by cycling. On certain cylinders, a plugged port
is provided on the rod end to bleed off entrapped air.
In the event that air entrapment should persist, bleeding
of air by loosening various clamp and screw type fittings
may become necessary.
If the above procedures fail to eliminate air entrapment,
contact your authorized Grove Distributor.
Parts Replacement
Parts found damaged or out of tolerance when maintenance
is being performed should be replaced. Refer to the
Manitowoc Crane Care Parts Catalog for proper replacement
parts.
Directional Control Valves
The control valves that control the crane functions are
installed on the right side on the outside of the superstructure
side plate, and between the left and right superstructure side
plates under the main hoist.
Inspection
Inspect the control valves for visible damage, binding spools,
and evidence of leakage. If excessive internal leakage is
suspected during operation with a spool in its center position,
it is possible that the area between the spool and working
section bore of the valve body is worn beyond serviceable
limits. If this condition exists, the spool and body must be
replaced as an assembly.
Valve Leakage
Dripping hydraulic oil indicates some type of external
leakage. The machine should be removed from service for
immediate repairs. External leaks sometimes develop at
fittings and seals. Spool seals are susceptible since they are
subject to wear. Seals may be damaged by temperatures
that are too high, or by dirt or paint accumulation on the
spool. Damaged or torn seals must be replaced.
A component functioning at reduced efficiency may indicate
that the control valve for that component is leaking internally.
If preliminary check-out reveals that adequate volume is
being supplied to the affected valve bank, relief valves are
properly adjusted, and the component is not at fault, check
the valve for scored or worn parts. Scoring is a sign of the
number one problem in hydraulics - contamination (external
contamination by dust or internal contamination by debris
from deteriorating components or oxidized hydraulic oil).
Scored or severely worn valve components must be
replaced.
Check valves in the control valves are designed to permit a
flow of hydraulic oil in one direction only. If a piece of dirt or
rust has worked its way into the check valve and lodges
between the poppet and seat, it will keep the valve open and
allow a return flow of hydraulic oil. The remedy is to clean the
valve, but it is also a good idea to follow through and ensure
the hydraulic system filter is still serviceable.
Binding Spools
Some of the most common causes for stiff spool movement
or jammed spool action are system overheating, excessive
pressure, contaminated or deteriorated hydraulic oil, or
warped mountings. When scorched, deteriorated hydraulic
oil or contamination is the cause, flushing the system and
replenishing with clean hydraulic oil may solve the problem.
If the spool bores are badly scored or galled, the valve must
be removed for servicing.
Warping occurs when mounting plates are not level or they
become distorted from machine damage. As mentioned
previously, the valve can be shimmed level.
Also, check the valve for rust. Rust or dirt collecting on the
valves can prevent free movement of the spool, and keep it
from the true center position. Excessive system pressure
can create both internal and external leaks in valves that are
otherwise sound. Only qualified technicians using the correct
equipment should make pressure adjustments when
pressure adjustments are needed.
Visual Inspection of Hoses and Fittings
Visually inspect hoses and fittings once a month or every 250
hours for the following:
• Leaks at hose fitting or in hose
• Damaged, cut, or abraded cover
WARNING
Extreme care must be used when removing any plugs or
restrictions from a hydraulic system suspected to have
entrapped air that may be pressurized.
WARNING
Do not attempt to loosen fittings in pressurized lines or
while the hydraulic pumps are in operation.
CAUTION
Ensure that the hydraulic hose is depressurized before
loosening the connections.

Manitowoc Grove RT880E Specifications

General

Brand	Manitowoc
Model	Grove RT880E
Category	Construction Equipment
Language	English