Themanhole covers installed on the top of tank, it has built-in respiration andemergency exhaust function. We can also install the gas collection valve\diphatch\feeler lever etc. on the manhole.The electronic sensor will alarm and cutoff when oil reach the warning position.The built in respiration vavle can be onand off according to gas pressure, it is the valve to keep the gas pressurewithin bounds.Auxiliary openings can install dip hatch\protection againstoverflowing feeler lever\gas collection valve.