Nowadays, many breweries like to use hot water to clean fermentation tanks or use steam to sterilize them, which is actually very dangerous.
Under normal pressure, the weight of 1M3 steam is 560g, but the weight of 1M3 water is 1 ton. If steam is condensed, its volume will be reduced to 1/1786 of its original size. this may cause negative pressure and make the tank dangerous.
In addition, if the discharge rate is much faster than the air inflow rate; or when the fermenter is flushed by hot caustic lye, the carbon dioxide is absorbed by the caustic lye and causes volume contraction; or the tank is flushed by cold water just after being drenched by hot liquid, etc. All these operations can cause negative pressure inside the tank. So the temperature of cleaning the fermenter should preferably not exceed 40°C.