(Weight Loaded) The Model 400 Weight-loaded Emergency Relief Vent operates in the last resort when a vessel or storage tank is exposed to a large-scale fire, and the standard pressure relief valve has failed to open or cope with the extreme conditions.

Designed to open in the event of high pressure, the set-pressure should be chosen to be above that of the pressure or pressure-vacuum relief valve. When the set-pressure is reached, the vent cover rises sufficiently to dissipate the pressure in the tank. As the pressure returns to normal, the cover closes and reseals, thereby preventing any further loss of vapour from the tank or vessel.

There is a choice of pressure release settings to enable a selection close to the maximum working pressure of the vessel.

The integrity of the seal is tested for leakage in accordance with API Standard 2521 – Use of Pressure-Vacuum Vent Valves for Atmospheric Loss.

The size of the vent should be calculated in accordance with API Standard 2000 (ISO 28300) – Venting Atmospheric and Low-Pressure Storage Tanks or other international standards.