Explosion liquid nitrogen tank

There are a number of other possible utihties which may be provided to a laboratory. Among these are natural gas, compressed air, distilled water, vacuum, steam, refrigerated brine, and other gases. In some instances, there are safety issues, such as limitations on the pressure available from a compressed air hne and the need to incorporate provisions for pressure relief, to ensure that personnel will not be injured by explosions due to excess pressure. Often the quahty of the air is more of a problem. The compressor supplying the system should be capable of supplying air which is clear of oil and moisture. Some facilities which have a large, pressurized liquid nitrogen tank at hand, use the vapors from the tank as a source of ultra clean compressed air to clean woik surfaces. 

A liquid chlorine tank was kept cool by a refrigeration system that used CFCs. In 1976 the local management decided to use ammonia instead. Management w as unaware that ammonia and chlorine react to form explosive nitrogen trichloride. Some of the armnonia leaked into the chlorine, and the nitrogen trichloride that was formed exploded in a pipeline... 

Most liquid feedstock and chemicals such as naphtha or benzene are stored in above ground steel tanks. In order to prevent the formation of explosive mixtures in the tank ullage, some organisations use floating roof tanks, particularly favoured for large tanks in the refining industry, whereas others use inert gas blanket of nitrogen, particularly favoured for small tanks in the chemicals industry. 

A stirred tank containing liquid CS2 solvent had to be cleaned because of solid residue that had accumulated in the stirrer. To avoid a possible fire and explosion, the CS2 was pumped out and the tank blanketed with nitrogen. Then the manhole cover was removed from the top of the tank, and a worker started to remove the solid from the stirrer rod with a scraper. At this point the maintenance worker left for lunch. When he returned to complete the job, a spark caused by the scraper striking the stirrer rod started a flash fire. 

The gas accumulates in a special chamber which is fitted with two float switches, and these operate alarms and trips when the gas accumulates slowly or rushes in during internal explosions. This system is called a Buchholz relay, and is normally used only on transformers fitted with conservator tanks. Transformers below about 1600 kVA are often sealed type liquid-immersed units. Internal explosions are released by using a special blow-off valve. Often the space above the liquid level in this type of unit is filled with an inert gas such as nitrogen. 

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