Removal of rust inside improperly stored 6" steel piping 1

[PagoMitch]

Did a search and could not get an apropos result.
I'm assisting a US based facility on an island, and a Contractor has had a half dozen nominal 20' sticks of S40 A53B 6" grooved piping sitting outside in his storage yard. For years. It is to be used in a chilled water distribution system (40F at about 70' head). The exterior of the piping is, as would be expected, rough. Rust craters maybe 1/16"+ deep. Wire brushed and painted it looks...like old rusty piping that has been wire brushed and painted...

The interior is not much better - best comparison would be an inconsistent 30-40 grit sandpaper - with some areas at 20 grit and fewer at 60.
In my honest opinion, this material is now suitable for fenceposts or the scrap dealer...

See pics below.

I have advised the owner to reject this piping, and make the Contractor purchase new. As would be expected, the Contractor is pushing back. "It's not too bad, it will clean up nice, etc."

As can be seen by the pics above, the outside (after wire brushing and painting)is ...fair, with some wall thickness loss. But the inside is still cr@p. I know of no way to de-rust the inside of half a dozen sticks of 20' steel piping. If they were to build a giant bathtub and use a chemical rust remover, I would think that might work; but with another reduction in wall thickness.

Is there anything I am missing? The owners are kind-of trying to find a middle ground. This seems like such a no-brainer decision to me - "No." That said, it is really hard to get materials here. Think a once-a-month ship, and whatever you want on the ship needs to be at the dock 2 weeks in advance. It makes construction projects really drag out, and they are under pressure from politicos above to get this project completed. My final recommendation to the owner's staff has been "you do not want to accept compromised material for a system that will be in service for literally decades."

Note that a response of "Are u nuts?" would not be entirely un-expected.

TIA.

Edit - Seems I now need to manually post a link to each pic. Don't remember doing this previously.

https://files.engineering.com/getfile.aspx?folder=9b5fe8b7-9876-47c8-81b7-3f14f9570a2a&file=1.jpg

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[LittleInch]

Attachments only load one file. Images you can load many and are normally preferred to stop everyone downloading them all.

Like this.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

A bit of a recipe for disaster alright if not done properly.

Wire brushing is the worst thing possible when it comes to good adhesion for paint, but then you also need proper primer and decent paint, not what looks like stuff you would paint your house with.

Any chance of a decent grit blaster available? Sometimes places like car repair shops have them or you could fly one in with an internal spray nozzle? And some bags of proper grit, not sand of the beach.

I've seen worse but it needs to be taken back to proper bare metal, not "polished" with a wire brush which just removes all the required roughness for the paint to stick on.

And get some two pack epoxy and some primer on the plane while you're bringing in the grit blasting machine. Compressed air you should have available?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[PagoMitch]

LittleInch - Thanks. I did indeed add attachments - not images. Appreciate your loading the images.

 

[LittleInch]

No problem.

Sometimes you do get into what I call Appollo 13 engineering and just need to use what's in front of you with the tools you have.

But throw the wire brushes away and redo those pipes which have been painted. They wouldn't last 12 months.

Are you welding these or using the vuctaulic connectors?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[PagoMitch]

A grit blaster is a great idea - as long as it could be put on an extension that is appx 10 feet in length to reach the halfway point. Air compressor should be no problem.

I am more than a little concerned about the degradation of the cut groove that the gasket fits in. This is/was literally the weak point in the piping - even before this rust issue. Thoughts on this in particular?

"Not sand from the beach". LOL. I have seen more than a few concrete failures from using beach sand in the concrete mix. The good news is that it usually takes awhile... awhile defined as low single digit years - before failure.

 

[PagoMitch]

LitleInch - seems our posts passed each other.
We are using VIC couplings; too hard to get reliable welders around here. VIC also provides some...flexibility... in piping systems during seismic events. This place is rated about the same as Los Angeles and San Fran for seismic concerns.

 

[LittleInch]

The grooves should be OK, just make sure they use new elastomers not ones which have been sitting there as long as the pipe has...

Yes, a job I did in the desert once they took the term "ssnd blasting" a bit too literally and turned up with bags of sand they had filled from outside, complete with rocks, stones, leaves and insects. Then I started to only use the word "grit"....

You want something like this for the inside, but search pipe internal grit blasting for alternatives

https://www.corrotech.com/en/produc...hot-blasting-machine-for-internal-pipe-parts/

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

Build a trough and fill it with phosphoric acid. Immerse the pipes in the acid. Most of the rust will dissolve. The rest will convert to a black compound called iron phosphate which adheres well and can be painted over. This process also etches the metal which provides better paint adhesion.

 

[EdStainless]

And if the coating is meant to actually protect the piping then there needs to be Zn rich primer, a protection layer, and a sealant.
It needs to go onto a clean surface of the correct profile.
The thicknesses need to be according to the manufacture.
And the cure is important.
The real problem is the amount of Cl down in the pits.
Acid cleaning would be best.
Then decide if the pipe even still meets the specification.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

As suggested use zinc rich primer for best results but if you want to get the best results from a zinc rich primer you'll want to remove all color from the metal. This requires some nitric acid to be added to the solution. These processes are laid out for picking carbon steel hydraulic pipes. Don't forget to incline the pipe so you don't get trapped bubbles.

Painting over the corrosion in your pictures is not different than painting over mill scale. Your process is simply missing a step.

 

[EdStainless]

If you want the pipe rejected, then tell them to clean it back to white metal (grit blast and/or pickle) and then you will inspect it.
They won't want to put work into it knowing that they still risk rejection.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[PagoMitch]

Thanks gents for the knowledgeable comments. I have advised the Owners Rep I am dealing with that while there are a few ways to remediate this, all involving considerable time and expense, and the result will still not be equal to new pipe. You paid for new pipe; not refurbished pipe that may - or may not - have the same longevity as new pipe.

 

[LittleInch]

Low Cost, Fast schedule, High quality.

You only ever get two....



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

Keep in mind that new pipe is still going to require the same surface prep as the rusty pipe if you expect your coating to have a chance at adhering. Mill scale and rust both pose the same problem for coatings.

 

[racookpe1978]

As concerning as the external (visible) general rust and untreated corrosion is,

- and the near-certain probability that "several specific points" with the internal corrosion on the salt-water "puddles" deep in the bottom and the sagging middle of the three or more of these pipes have locally deep, very penetrating corrosion points,

- and the widely spread general dirt and corrosion products internally that will foul and plug up heat exchangers and the "equipment" that this chilled water system will serve,

is the pitting and rough surfaces of each of the "sealing areas" inside and across the surfaces of the notches/ring-contact surfaces in the sealing areas for each rubber washer.

 

[PagoMitch]

All,

It was indeed the pic of the o-ring sealing surface that finally convinced the Manager to say...NO.
Thanks again all.