This valve is designed to relieve excessive over pressure or under vacuum of cargo tanks during cargo loading, discharging, ballasting and thermal variations. It is also designed for devices to prevent the passage of flame into cargo tanks in tankers. Approved for crude oil, products and IMO type or chemical tankers carrying dangerous flammable cargoes of a Maximum Experimental Safe Gap(MESG) with 0.65mm and 0.9mm Features, 1. Reliable operations reduces vapor losses 2. Suitable and compact design ensures long-term maintenance free life cycle 3. Meet new IMO requirements for cargo vapor flammability 4. Non-oscillating performance 5. Full lifting and high flow capacity Standard: IMO.MSC.1/Circ.1324