HYDRAULIC SYSTEM GRT880 SERVICE MANUAL
2-64
Published 10/19/2017, Control # 618-00
TELESCOPE AND TELE FILL STAGE
SELECT MANIFOLD VALVE
Description
The telescope and tele stage select manifold valve (see
Figure 2-35) is located inside the rear of the boom assembly
and is controlled by the crane control system. Feedback from
the boom proximity sensors and telescope cylinder pressure
transducers enable the crane control system to know when
tele 1 is fully extended and to begin extending tele 2 and tele
3 as well as to know when tele 2 and tele 3 are fully retracted
and to begin retracting tele 1.
The telescope and tele fill stage select valve manifold, the fill
tube pressure regulating valve on the front steer/swing
brake/pilot supply/fill tube manifold valve assembly, and the
two telescope cylinder pressure transducers perform the
following functions:
• prevents the first stage (boom tele sections 2 and 3 from
moving when the second stage (tele section 1) extends
or retracts by maintaining oil pressure in the fill tube of
the first stage.
• prevents the second stage from moving as the first stage
extends or retracts by maintaining oil pressure in the fill
tube of the second stage.
Maintenance
Removal
1. Tag and disconnect electrical connectors to valve.
2. Tag and disconnect hydraulic hoses from valve. Cap or
plug lines and ports.
3. Remove capscrews, lockwashers, and flatwashers
securing valve. Remove valve.
Installation
1. Secure valve with nuts, flatwashers, lockwashers, and
capscrews. Torque capscrews - refer to Fasteners and
Torque Values, page 1-15 for proper torque value.
2. Connect hydraulic hoses to ports on valve as tagged
during removal.
3. Connect electrical connectors to valve as tagged during
removal.
Reference Only
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