Ideal for use in oil supply systems which have from 0 to 60 psi supply line pressures on the inlet side of the valve. Requires a sustained vacuum on the outlet side of the valve for fuel to flow to the burner pump. The OSV series provides automatic shut-off for the oil supply in case the line between the device and the burner is broken. Many state and local codes require such a device and also limits inlet pressure on burner pumps to a maximum of 3 psi. Available in 3/8 and 1/2 NPTF porting. UL listed.