Hydraulic truck pump
PARKER Hydraulics

FEATURES:
Full Pressure Shaft Seal -- The Parker full pressure input shaft seal is able to withstand full system back pressure up to the pressure rating of the Hydraguide. This enables operation of auxiliary hydraulic functions downstream of steering.
Linear Valve Spool -- The linear valve spool is less subject to stick and damage in the event of system contamination and allows generally better control.
Pressure Dams -- Pressure dams provide a barrier of pressurized system oil between metered oil and return. Pressure dam valving provides more precise steering due to the reduction of lost leakage oil from the metering element.
Vaned Rotor -- The spring biased vanes in the rotor tips reduce leakage between pockets in the metering group. This provides more precise and positive steering.
Pressure Balanced Metering Group -- All Parker designs utilize a pressurized envelope around the metering package (rotor set--commutator) to reduce slippage leakage and provide more precise steering control.
Manual Emergency Steering -- A ball check valve allows manual steering in emergencies when pump flow is interrupted. If the vehicle is large enough to require more than 100 ft.-lb. steering wheel torque in the manual mode, another means of emergency steering is recommended.