Derime of air sepration unit

[airseperator]

Question on deriming an air separation cryogneic unit. When a unit is shut down for a period of time, do you have to derime before coming back up? Is there a certain amount of time you can be down before having to derime the unit?

 

[cryotechnic]

Dear airseperator,

Most important thing when shutting down the ASU is to purge the liquid which can contain hydrocarbons. So what we do when we shut down an ASU for a period of time we drain the lox from the main condensor and we drain the enriched air.
At an standstill, there will be an enrichtment of hydrocarbons due to evaporation of the liquids.

When we have to shut down the ASU for more then a week we drain all the liquid an do a complete deriming procedure.

Thing is, when leaving the ASU stand-by in a cold situation, it is possible that moisture enters the installation. (even when pressure is maintained etc).

We have some small ASU's (max 1000m3 N2) which we have to stop for the weekend every week. In history we also stopped large ASU's (30000m3 GOX) for a few days.

regards,
Cryotechnic

"Math is the ruler of your potential succes...."