Reason for sandblasting of the cryogenic tank during this air separation unit shutdown

You’d better explain it more clearly – where exactly, and so on. Was it caused by your improper parking method, which led to high pressure in the nitrogen pipeline and thus excessive inflation of the cryogenic tank, or was it due to a broken pipeline?

A beginner’s analysis: When parking, it is necessary to purge and heat the entire system. The reason is simple – thermal expansion and contraction. This problem occurs when the opening of the purge valve is too large, as it leads to excessive expansion in an instant, causing the cold box to bulge and resulting in sand leakage. That was exactly the reason for the sand leakage in our factory’s cold box last time

There are some relevant papers on the specifics of sandblasting in cold boxes; the original poster can take a look at articles on this topic!

It’s possible that cracks have formed in certain pipes, allowing high-pressure liquids or gases to leak out; this results in the pressure inside the cold box being higher than atmospheric pressure. When you open the cold box, this pressure is released, causing a spray of fluid

Thank you all for your valuable suggestions. Besides the suggestions above, what other reasons are there? This post was last edited by chc1125 on 2008-12-2 10:06.]

OP, could you describe the scene of what happened? That way it will be easier to make some guesses~

1. Leakage in the pressure pipes inside the cryogenic tank is the most common cause of sandblasting in the cryogenic tank； 2. During the initial operation of the cryogenic tank, air was used as the sealing gas for an extended period; the switch to another gas was not made in time, resulting in partial liquefaction of the air. When the cryogenic tank was heated, this liquefied air vaporized, causing sanding to occur within the tank.

I think it’s very likely that there was a leak in the liquid pipeline; the liquid that leaked out while you were parking the vehicle to carry out heating and purging vaporized rapidly, causing sand spraying. It is recommended to conduct an analysis to determine the gas composition inside the box. :) :)

In my opinion, there are the following points: 1) After the air separation unit was shut down, the cooling tank inflation system was not deactivated in a timely manner (or the design of the cooling tank sealing system was inadequate)； 2) During the parking process, excessive valve movement causes significant stress on the liquid (gas) pipelines, leading to pipeline rupture ； 3) During the cold-state heating of the air separation unit, the pressure increases as the sealed gas inside the cryogenic tank expands due to heat ；

What were the reasons for sandblasting the cryogenic tank during this air separation unit shutdown? The so-called \"sand blasting\" refers to the phenomenon of insulation sand being ejected at the breathing port of the cold box, or at the areas where the cold box cracks, due to the internal pressure within the cold box. There are two reasons for this phenomenon: one is that the pressure of the sealing gas inside the cold box is too high (often dirty nitrogen is used), and the resulting effect is not very significant ； Secondly, sandblasting is caused by excessive pressure inside the cryogenic tank due to leaks in the pipes and valves within it, and this is quite noticeable. Causes of leakage: fractures due to pipeline stress issues, overpressure resulting from the sudden liquefaction of a large volume of liquid in a short period of time, which leads to pipeline rupture; explosions caused by excessive levels of harmful elements; static electricity, etc.