Exterior corrosion in unused fluid lines

[MedicineEng]

Dear All:
Last week I had a problem with one exterior hot fluid line. I was conducting some heating tests in a branch of the system that was idle for about 4 years and after some hours heating, I started to have leaks everywhere. The pipe is thermally insulated with rockwool.
When I opened it, I realized that the holes that appeared in the pipe were done from the exterior towards the interior of the pipe and all appeared in the lower half of the pipe. I believe that this fits in my theory that what happened was since this line was not used for some years, the rain infiltrated/soaked the rockwool and stayed there until it dry out or drip into the floor by gravity. In the other lines this doesn't happen since the rain that gets into the pipe most probably is evaporated due to the high temperature.
My questions are the following:
-Is there any way to avoid this problem?
-If not, what do you recomend to avoid drastic failures of the pipes?
This time I got lucky because this was just a test, but if we are in production, stopping the line because of this might not be feasible.

Thanks a lot

 

[EdStainless]

1. Use insulation with less leachable corrodants.
2. Use better weather shields
3. Coat the piping before applying the insulation

Your case is not uncommon. A few of guys here could share some real stories.

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