II. Hydraulic System - General
Hydraulic System:
The XL 4200 and XL 5200 Hydraulic System is designed for efficient operation with a minimum amount of wear to
related system components. Air from an electric compressor and from the engine intake manifold pressurizes the
hydraulic system to 6-8 PSI. A 120 PSI backpressure valve is located in the main control valve banks return line.
These features ensure fluid is always present to components when required.
DO NOT OPEN
the hydraulic reservoir
without relieving air pressure. Serious injury could result from being sprayed with hot hydraulic fluid. Hydraulic fluid
temperature is controlled by a cooler circuit which maintains the fluid temperature approximately 100° above
ambient temperature. Individual hydraulic components and circuitry will be explained in this Manual.
The primary circuits of the GRADALL XL Series Crawler -Mounted Excavator are as follows:
Main pump: Work circuits whose fluid is supplied by the main hydraulic pumps
Pilot Pump: Control circuits whose fluid is supplied by the pilot pump
Recirculating Pump: Cooling circuit directing a constant flow of fluid through the cooler
Swing Pump: Closed loop circuit separate from the main pump circuit
Hydraulic fluid:
Use only specified hydraulic fluid. Use of fluids other than those which meet specifications will
seriously damage the hydraulic components, resulting in expensive failure or machine
downtime. Approved fluids are:
Hydraulic Oil: M
bilfluid
®
424
or Citgo Tractor Hyd. Fluid #33310.
Fire-Resistant Fluid:
Quaker Chemical Quintolubric 822-300.
Do Not
use any other fluid
without first receiving
approval from your GRADALL Distributor or the GRADALL factory. Fluid specifications are listed in the lubrication chart
on your machine and the decal on the fluid reservoir of the upperstructure.
Add additional fluid through the main reservoir return filter when topping off the system. If the reservoir has been
drained, follow START-UP PROCEDURE.
See Section V11, Main Hydraulic Pump.
Hydraulic System logic is determined by the following: Load Sense Control which regulates standby pressure. High
Pressure Cutoff which senses pressure above 500 PSI then reduces pressure by destroking the pump. Horsepower
Control which does not let the engine draw down below 1900 RPM when all circuits are activated at the same time.
If repairs or adjustments to the hydraulic system become necessary, we recommend you contact GRADALL distributor
to have this work done by a qualified GRADALL technician.
See Appendix B & Appendix C for circuit operating times.
XL 4200/XL 5200 HYDRAULIC SYTEM OPERATIONS MANUAL
Form No. 29704
3
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