XVII. Boom Circuit
(continued)
57
FIGURE 64
BOOM CONTROL VALVE SECTION
The boom valve has two port reliefs, a section compensator and compensator regulator.
See Figure 62
Fluid flows
from the rear port when the end cap is pressurized. When the joystick is actuated, the pilot signal shifts the valve
spool and the compensator meters fluid to spool. The spool then routes fluid to the boom cylinder. The valve load
sense system controls compensator shift and signals the pump load sense system. Boom speed is controlled by
spool stroke limiters. When the circuit is bottomed in the retracted position, the regulator opens and allows the
compensator to shift, cutting off fluid to the boom circuit until pressure drops below the regulator setting. The rear
port relief protects against external loads; the front port relief controls boom-out pressure. When the rear end cap is
pressurized for boom-out, the spool immediately shifts to full regeneration. In regeneration, both sides of the cylinder
run at or near equal pressure. Oil does not return to the reservoir during boom-out operation. The maximum flow
rate out of the A (front) port is 48 GPM (pump) + 54.7 regenerative flow; the maximum flow rate out of the B
(rear) port is 42 GPM. The boom valve has stroke limiters on both end caps. These limit how far the valve spool can
be shifted to keep boom speed correct.
Appendix B (XL 4200) or Appendix C (5200)
for boom cycle time.
Do not run the boom faster than the cycle times shown in appendices. Overheating and
poor performance of other hydraulic functions will occur.
NOTE!
Spool
B Port
A Port
Port Relief
Anti-Cav
Valve
Stroke
Limiter
Section
Regulator
Spring
Compensator
Stroke
Limiter
XL 4200/XL 5200 HYDRAULIC SYSTEM OPERATIONS MANUAL
Form No. 29704
Содержание XL4000
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Страница 305: ...GRADALL h y d r a u l i c e x c a v a t o r s XL 4000 5000 CENTER PIN REBUILD Form No 20026 Part No 2460 4164 ...