The PDB12PZ pilot-operated, spool type proportional pressure relief valve is zinc-plated and corrosion-proof. If pressure at port 1 exceeds the setting defined by the electrical signal, the pilot poppet opens and oil flows from behind the main spool to tank port 2. The resulting pressure differential causes the main spool to lift against the return spring and allows flow from port 1 to port 2.
As a function of the electrical signal, the relief pressure at port 1 can be changed steplessly. With decreasing control current, the pilot poppet closes, the main stage follows the pilot stage, and a counter-pressure is created at port 1—to drive a fan moto, for example.
The maximum pressure can be pre-set mechanically. The valve offers good stability across the whole pressure and flow range, as well as hardened and ground internal components ensuring minimal wear and extended service life.
Image courtesy of Hydac International