A HSN-90 valve is used to open (or close) one portion of the circuit to (or from) flow from another portion. Flow can be in either direction (bi-directional).

There are ports drilled thru the body and the main spool. Rotating the handle 90 degrees counter-clockwise aligns the ports and allows the flow between ports 1 and 2. Rotating the handle clockwise shuts off flow.

The valve handle's position can be re-set in any position, after the valve has been installed, by simply lifting, rotating, and releasing the handle. The design incorporates a roller thrust bearing to ensure flow rotational torque to adjust the valve.

The valve is constructed of steel parts, and all operating parts are hardened and ground. The cartridge is designed for easy service and field repair.