PA VS80/150 280 400 Safety Relief Valves. Body and internal parts made of stainless steel AISI316. Atex Directive CEE \94\9 (DNV 0575 CERTIFICATION) complianT. The valve limits the maximum pressure of the system. In the event of over-pressure, this relief valve will open to allow the liquid to by-pass. During normal system operation, a shutter driven by a spring will keep the bypass opening close. The set valve pressure can be regulated by adjusting the spring load by means of the dedicated adjusting screw.