These valves are designed to relieve pressure from pipe lines, equipment, and pumps when a certain pressure rating is exceeded (opens when exceeded and then closes again when back within range). The adjustable top knob can be rotated downwards (clockwise) to increase the set pressure. N5093AP generic adjustable to 115 psi/8 bar, N5093APT Tassalini to 72psi/5 bar (other springs available on special factory request). Temperature Range: -10°C (+15°F) to +95°C (205°F).