| 摘要 |
A large portable liquid mixing tank has a top wall with a large access opening that is sealingly closed with a manhole cover and also when the manhole cover is removed and a liquid mixer is installed. In either case, the pressure of any air trapped in the tank increases with rising ambient temperature and can be of a magnitude that blows off the manhole cover or mixer when released from the tank. A universal pressure relief bung is adapted to be threaded in a bung flange in the manhole cover, mixer and the tank top wall and is operable with a strategic vent hole arrangement to completely relieve any air pressure in the tank on only one turn of the bung within the shortest of the minimum times required to remove the liquid mixer, the manhole cover and the bung itself.
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