1 reply to this topic

[Satyajit]

Hi,

We are getting level in annular space of doubled walled atmospheric ammonia storage tank in one of our plants. The increase in level is slow but always there. When the inner tank level is low, the increase of level in annular space is quite slow. As you know that high level in annular space of a double wall tank can be be very dangerous, the inner tank can roll over when ammonia from inner tank is pulled out and the level the annular space remains high. Therefore, the tanks are provided with trip interlock to stop ammonia export from the tank when the annular space level is high.

I am trying to find out root cause of this problem.

Obviously, if it is not due to leak from the inner tank,it must be from the condensation of ammonia vapor in the annular space itself. When the rate of condensation of ammonia vapor in the annular space is higher than rate of boil off liquid ammonia in the annular space, the level in annular space will increase.In some design, the level in annular space is drained to flare, in other design the liquid in annular space is vaporized using hot vapour from BOG compressor discharge, in few other designs there are nothing provided except a drain.

  Did you have any such incident in your ammonia storage tanks (or cryogenic tanks). Please share if you have any such experiences in your plant and how did you resolve the issue.

Appreciate your time.

Kind regards,

Satyajit

[shadyothman]

I have the same problem in Butane storage tank.

Did you identified the reason for that?