Remove liner from LP72

[Conshelf]

PSI certified inspectors are taught not to pass any lined tank. Either get the liner out so the structural metal can be inspected in its entirety or the tank fails, end of story. No partial removal, gee it wasn't pitted so there underlying metal just "shoulda" been fine...

Exact words from Bill Highs book and referenced in the PSI course.The CGA recommends that interior linings be viewed carefully and, whenever corrosion appears to have developed, the liner should be removed and the significance of the corrosion assessed.

The removal of epoxy linings, are in themselves, a problem. Often, only small portions of the epoxy have been loosened by the rust while the remainder is bonded firmly to the metal. Tumbling with aluminum oxide chips or equivalent, for several hours, will usually remove the liner from corroded metal but leave the bonded epoxy intact. Since corrosion has not formed behind firmly bonded liner, over-zealous tumbling may not be necessary.

In other words, the whole liner does not need to be removed to make an assessment. In the end the DOT and Transport Canada inspections are the ones that the government care about. In the US the scuba visual is per the CGA pamphlets written into the CFR so has some merit but the CFR does not exist in Canada. Here we have the Transportation of Dangerous Goods Regulations which does not even require an eddy current test on 6351 aluminum tanks at time of hydro or even at all. Either way, I cannot find any reference in the CGA pamphlets, the DOT, or Transport Canada that says a cylinder cannot be passed with an internal coating. Whether it is a good thing or not or the inspector wishes to reject it is a different story.

 

[Luis H]

Neither the 4th or the 5 edition of the PSI Inspecting Cylinders manual says anything about any requirements to remove all the internal tank liners to pass inspection. The quote above are correct.

A quote from the 5th edition:

Visual inspectors should ensure that all epoxy having corrosion
beneath or adjacent, has been removed in order that the extent of
corrosion may be visually assessed. Intact and firmly adhering epoxy will
cause no harm. Therefore, it is only necessary to tumble the liming for up
to several hours, until all loose material is removed.

There is no requirement to remove any internal coatings if there is no signs of rust.
There is also no requirements from CGA or the CFR to remove the coatings before inspection.

The volume of rust (iron oxide) is many times the volume of the original steel. Due to the volume increase, it is normally very easy to detect any rust that is below a coating. It shows as blisters. If the coating is very smooth and uniform, there is no rust under it.

There are definitely situations were it is difficult to determine if the coating has been compromised with rust, but in 40+ years I haven't seen many (maybe I am lucky).

Note: I am a PSI certified inspector.
I have also worked in the pressure vessel industry and in the past I have provided technical information to PSI/ PCI

 

[klauricella]

Finally got back to pick up my tanks. They passed one so I just set up as a single. Asked guy working on tanks if they had to have liner completly removed and he didn't know Talked to shop owner and asked what it would take to pass inspection and he said that the liner had to come out. He thought the only way to properly do that was sandblasting. But he did say that they get alot off old LP72 that people did what and would let me know, would sell to me for the cost of having it hydo'd and vip. Thought that would be a pretty good deal. Also went to fire safety place where they hydro tanks and that guy had no idea that tanks ever had liners in them, he was going to check with his boss if they could pass with partial liner.

Kevin