The HSP cartridge valve can be used as a pilot operated check valve, directional control valve (one or more cartridges can be used to provide 2-, 3-, or 4-way functions), flow control valve (when used with stroke limiter operation), and as a pressure control valve (when used with appropriate pilot valve).

Opening and closing of the valve is a function of force balances on three areas; diameter "X" (port 3), diameter "X-Y" (port 2), and diameter "Y" (port 1). Pressure in ports 1 and 2 acting on respective are "Y" and effective area "X-Y" tend to open the main spool (poppet). Spring force and pressure (when operative) acting on top of the main spool close the plunger. 

The orifice in the spool allows port 1 pressure to operate on the much larger top area of the spool - thus holding the spool in the closed position unless vented through port 3.

The orifice is available with integral check valve to prevent flow from port 3 thru the orifice to port 1.

If port 3 is vented and pressure is applied to port 1 (spool is imbalanced), the spool rises to allow flow to port 2. If pressure is applied to port 2 and port 3 is vented, pressure on the annular area raises the spool and allows flow to port 1. Closing the port 3 vent and/or applying pressure at port 3 tends to close the poppet valve.

Availability in two (different) ratio poppets (spools) and with several springs provides many "cracking" pressure ratios. A spool stop option permits use as a flow control valve. The valve is constructed of steel parts, operating parts are hardened and ground as required. The cartridge is designed for easy service or field repair.