REED B50HPG, Technical Manual, Page: 19 / 235

OPERATION and MAINTENANCE
Rev 1.2 18 of 80
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The power for operation of the concrete pump is provided by the engine, which drives
the hydraulic pumps.
All functions for operation of the concrete pump can be accomplished from the local
controls mounted on the side of the unit. Optional hand-held cable or radio remotes
enable the pump to be operated away from a remote distance.
HYDRAULIC SYSTEM DESCRIPTION
The hydraulic system of the concrete pump consists of three separate circuits and
although integrated, each is designed to perform a particular function within the
operation of the concrete pump. The three circuits utilized are:
• Main Pump Circuit
Controls operation of the hydraulic drive cylinders.
•
S-Tube Shift Circuit
Controls operation of shifting the s-tube from one material cylinder to the other.
•
Auxiliary Circuit
Controls the operation of the agitator and other auxiliary equipment.
For the purpose of making the operation of each circuit easier to understand, they are
being described separately.
MAIN PUMP CIRCUIT
The main hydraulic pump is a variable displacement axial piston pump of swashplate
design. The pistons run along the swashplate which is capable of being tilted. This tilting
changes the angle of the swashplate and thus the stroke length of the pistons, which in
turn varies the displacement of fluid. The larger the angle of the swashplate, the greater
the flow. The angle of the swashplate is varied by the volume control that works in
conjunction with the load sense feature of this pump.
The main hydraulic pump is driven directly by the engine or electric motor. When the
engine is running, PUMP switch in the OFF position and the VOLUME control minimized,
there is no demand placed on the pump. This is referred to as the pump being de-stroked,
meaning, it is only producing a minimal amount of flow to enable the lubrication of the
pump. This lubrication exists regardless of whether the engine is at idle or maximum RPM.
The main pump circuit is equipped with a manifold that is drilled and ported to
accommodate the relief valve, check valve, flow control and the pilot operated
directional valve. The cycle valve is a directional spool valve with electrohydraulic