Liebherr Mining Equipment Co.
Product Support Division
HUSCO SPLIT SPOOL SYSTEM
Liebherr Mining Equip. Co
4100 Chestnut Ave.
Newport News, VA.
23607
Technical Training Department
Telephone = 757-928-2503
The term split spool describes the spool section of the main valve. The spool section
encloses two spools and its components. Each spool is equivalent to one-half the spool in
a conventional valve. The spool operates in synchronization with or in opposition to its
mate. Each section is basically two 2-position / 3-way diverting valves. This feature
allows control and circuit flexibility.
The hydraulic schematic section depicted above will be utilized to describe specific
components and functions of the Husco Split Spool Valve.
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The hydraulic schematic section depicted above will be utilized to describe specific
components and functions of the Split Spool Pilot Valve and the Pilot Control Valve.
The Inlet Section of the Main Dump Control Valve consists of a Flow Control Valve,
Main Relief Valve, Low Pressure Relief Valve, Load Check Valve, and an Anti-Void
Poppet. Take note of this particular diagram depicting the Husco 6500 Series, which has
two inlet sections to accommodate the T-282s dual pump system.
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Hydraulic flow for the split spool system can range from 90 GPM to 500 GPM. The 500
GPM is possible by using the 6500s paralleled inlet section.
Some of the working features of the Main Dump Control Valve are as follows:
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Complete pressure control is provided by a main relief valve.
The large capacity flow control in the inlet section of the split spool, allows a low
neutral pressure drop.
A great degree of mounting flexibility is possible, which allows the pilot valve to
be located as to simplify controls and minimize line connections.
The Pilot Spool Valve is spring centered to the neutral position. The center passage is
open and pilot flow from the main valve is unobstructed. As depicted here, the Pilot
Spool Valve is actuated by a Pilot Control Valve.
When the Pilot Control Valve directs flow to either end of the Split Spool, this will
overcome the spring bias, and the flow control poppet opens and the pump flow is
directed to the outlet.
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Main Dump Valve Component Descriptions and Operations:
1. INLET = the port connection(s) for the system pump lines.
2. OUTLET = the port connection for the line(s) that directs return flow to the
reservoir.
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3. HIGH PRESSURE CORE = the passage which is common to the inlet section and
the spool section of the main valve and directs pump flow to the spool sections.
4. DRAIN PASSAGE = the passage which allows portions of the surface area
between main valve sections to bleed-off directly to the outlet.
5. FLOW CONTROL = the inlet section component between the inlet and outlet ports.
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5. MAIN RELIEF VALVE = the element located inside of the flow control poppet.
It is a pilot operated (compound) relief valve, and has the capacity to limit the
working pressure at full pump flow.
6. LOW PRESSURE RELIEF VALVE = the assembly located between the low
pressure core and the outlet, and provides a controlled back pressure in the low
pressure core when oil is returning from an actuator.
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7. LOAD CHECK POPPET = the check valve that allows free flow from the inlet to
the high pressure core and prevents flow from the high pressure core to the inlet.
8. ANTI-VOID POPPET = the check valve that allows free flow from the low
pressure core and prevents flow from the high pressure core from entering the low
pressure core.
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9. PILOT SUPPLY ORIFICE = the orifice that is located between the inlet and the
spring side of the flow control valve. It is in conjunction with the flow control
spring, which regulates the amount of pilot flow to the pilot valve.
10. PILOT SUPPLY PORT = the port connection for directing flow from the pilot
supply orifice to the pilot valve inlet. (See drawings above and below for
reference)
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11. FLOW CONTROL or DAMPENING POPPET = this is an orifice / check valve
arrangement located between the pilot supply orifice and the spring side of the
flow control. This arrangement regulates the filling or exhausting of the volume
of oil behind the flow control. The orifice slows the movement of the flow
control and prevents sudden changes in the direction of the pump flow, and
thereby reduces shocks or surges.
12. WORK PORT or WORKING PORT = the port connection on the main valve
spool section for a working line to be connected to one side of an actuator.
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13. LONG HOLE = this term relates to the cross drilled hole in the spool section,
which covers and provides a passage for flow from the low pressure core to its
corresponding main spool.
14. MAIN SPOOL = There are one main spool for each work port and they are spring
biased at both ends. This is to block the work port from the high and low pressure
cores when there is no flow through the spool cross-holes. When there is flow
from the pilot valve to the main valve work port (through the cross-holes) a
positive differential pressure at the top of the spool will overcome the bottom
spring bias and the spool will overcome the top spring bias and the spool will shift
to connect the work port to the low pressure core.
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15. RESTRICTOR POPPETS = these check valves are located in the main spools and
are identified as DAMPENING POPPETS in the above diagram. They permit
free flow from the work port to the pilot port and restrict flow from the pilot port
to the work port. They are also used to control spool response and / or spool
movement during void conditions.
16. PILOT VALVE INLET SECTION = the port connection for receiving pilot flow
from the main valve pilot supply port.
17. PILOT VALVE OUTLET = connection for return to tank.
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18. CENTER PASSAGE = the passage that directs pilot flow from the inlet to the
outlet of the pilot valve when the spool is centered or in the float position.
19. BRIDGE CORE = this passage directs flow from the center passage to a control
port when the pilot valve spool is shifted.
20. PILOT SPOOL = the element in the system which is controlled directly by the
operator of the unit. The pilot spool transforms the small pilot flow from the main
valve into control signals which cause the main valve to direct the large working
flow.
21. LOAD CHECK = the valve that allows free flow from the center passage to the
bridge core and prevents flow from the bridge core to the center passage.
22. SOLENOID VALVES = located on the pilot control valve, which when activated
by an operators selector will shift the flow of pilot pressure to the Split Spool
Pilot Valve.
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