The HSTV valve is a low torque, fast acting, non-compensated, adjustable orifice (port 2 to 1) used to meter-in, meter-out, or bleed-off circuits to control fluid flow volume.

The adjustable screw is separate from the main spool. Turning the screw outward connects the upper area of the spool to the low pressure port 1 and allows port 2 pressure (flow) to acton the annular area of the main spool and raise it until the point of the screw seals a passage to port 1 drilled thru the spool. Port 2 is also connected thru a balancing orifice and another drilled passage to the area above the spool. Therefore, fluid pressure is the same (balanced) on both ends of the spool. When the screw is turned inward to reduce flow, only the sliding friction of the spool in the body has to be overcome. Unadjustable flow from port 1 to 2 is possible under some circumstances.

The valve is hydraulically balanced and can be adjusted, even at 5000 psi, in either direction with finger tip ease. The cartridge valve is constructed of steel parts, operating parts are hardened and ground as required. The cartridge is designed for easy service or field repairs. A stepping motor drive can be added for open or closed loop control.