MKT V-22/HP-380T4, Operating, Maintenance And Parts Manual, Page: 13 / 73

V. START UP PROCEDURES (CONTINUED)
E. HYDRAULIC CLAMP CYLINDER
Whenever the hydraulic lines of the V-22/HP-380T4 system has been
reconnected,
THE CLAMP CYLINDER CIRCUIT MUST BE BLED OF
ENTRAINED AIR. Lift the V-22 hammer vertically off the ground, switch the
clamp selector switch to the "clamp close" position to close the jaws. Using the
proper tools unscrew the vent valve screw located on the outboard end of the
clamp cylinder.
CAUTION: A STREAM OF FROTHING HYDRAULIC FLUID WILL
SHOOT FROM THE RELIEVED VENT SCREW.
After approximately thirty seconds, close the vent screw. Now switch the clamp
selector switch to the "clamp open" position to open the jaws and repeat the
process at the inboard vent valve screw. Repeat the procedure until an air free
stream of oil comes from each relieved vent screw.
CAUTION: FAILURE TO COMPLETELY BLEED THE CLAMP
CIRCUIT OF AIR MAY IMPAIR CLAMPING FORCE
AND DAMAGE JAWS.
SEE PAGE 28 FOR BLEEDING ILLISTRATION
F. HYDRAULIC CIRCUITRY
The repetitive functions of the V-22 hammer are powered by two pumps
contained within the HP-380T4 power unit. The hammer is first able to clamp
onto a pile, vibrate the pile, stop vibration and unclamp from the pile. Two
different types of hydraulic circuits are used to perform these functions.
The hydraulic clamp assembly is operated by the use of a pressure
compensated piston pump and directional control valve. This pump is bolted to
a mounting pad on the pump drive. Hydraulic fluid from the reservoir first
passes through a suction strainer and then into a suction hose before entering
the clamp pump. The hydraulic fluid leaving the pump is directed to the
directional control valve. The directional control valve is shifted by the use of 12
volt solenoid operators. The pressure compensator on the pump is set at 3,000
PSI. When this pressure has been reached in either the clamp open or clamp
close function, the pressure compensated pump will destroke and maintain itself
in a zero flow condition. If any additional fluid is required the pump will respond
to this need and again send fluid to the clamp open or clamp close function.
There is also a pressure relief valve set at 3,500 PSI contained within the clamp
directional control valve to act as a safety feature in case of a malfunction within
the pressure compensator on the pump. The clamp circuit of the V-22/HP-
380T4 system also has a pilot operated check valve on the clamp cylinder. In
the event of a broken clamp hose or other loss of clamp pressure, the check
valve will maintain clamp pressure on the pile.
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