THEORY OF OPERATION
Removable Kingpin. Two are provided, one is 3.5 inch (88.9 mm), the other is 2 inch (50.8 mm),
for fifth wheel plate and kingpin coupling. For kingpin used with prime mover and placement on fifth
wheel towing device, see WP 0034, Kingpin Placement.
HYDRAULIC FLOW VALVE
Hydraulic Flow Valves Adjustment. Located on hydraulic safety valves on center mast. This
procedure for flow valve adjustment is to be used from 120F to -50F (49 C to -46C). As oil
viscosity varies with temperatures, it will be required to change the hydraulic flow valve for the
boom and mast functions. The adjustment is made at the flow control knobs located on the
hydraulic safety valves located on the front side of the center mast frame. To adjust, turn control
knob COUNTERCLOCKWISE TO LOWER back pressure and CLOCKWISE TO INCREASE back
pressure. System should maintain 300-800 psi back pressure when the boom or mast is operated,
using MAST RETRACT or BOOM EXTEND with no load. The hydraulic flow valves will
need to be adjusted as necessary as temperatures vary or when OHA 5606 is replaced with
standard hydraulic fluid (reference WP 0004, item 7).
END OF WORK PACKAGE