Repairing ASME vessel with internal liner

[AMenJr]

Hi folks,
I have a 72"OD x 15's/s @ 125psig horiz. vessel that has internal corrosion at the bottom of the vessel which operates at about 50psig. No vacuum. The bottom 1/3 has the internal corrosion. The corrosion is severe enough to cause leaking. The corrosion type is pitting with pin holes. Instead of replacing the vessel I would like to know if there are any internal coatings or cladding type repair methods that I could consider and still hold lower pressure? If there is, do you have any contacts? Do you know where they are located? My vessel is about 50 miles offshore Gulf of Mexico, USA on a platform. We would also consider re-rating the vessel to a lower pressure and maybe even making it a non-code vessel operating at atmos. pressure. We would then pump the liquids out of the atmos. vessel if we have to. Replacing the vessel would take a least 8 weeks of fab. and more for installation. The facility is shut down due to this vessels leaks.

 

[vesselfab]

the problem with repairing corrosion with pin holes is

""Where do we stop?"""

No matter how much you repair...there are always thin spots right beside where you just welded.

No internal coating or cladding is going to hold pressure...or should I say.....you should rely on it holding pressure.

I wish I could give you a better answere....but


I would replace it

 

[corus]

Here's a site I found

http://www.flaretec.com/clad-lined.html

You'd have to ask the company as to whether it would satisfy the codes.

corus

 

[AMenJr]

I know that this was a long shot, but I had to try just in case there was a repair procedure out there that maybe sprayed hot cladding material that would adhere to the carbon steel internal wall. Thanks for your input.

 

[unclesyd]

Here is one of the several companies that can effect a repair on your vessel. This type repair is done all the time on things like digesters in paper mills. This approach is fairly costly though on the basis of production loss it can be cheap.

http://www.weldingservices.com/services/weld_metal_overlay.asp

 

[chicopee]

replace your entire vessel or the entire bottom in accordance w/NB-ASME procedures.

 

[AMenJr]

Unclesyd, I went to the website you attached. Thanks. Whenever we tackle a unique problem we also consider "New Technology". I'm sure this spray-on method is not new but applying it to our industry in a situation like this would be considered new. I am going to look closer at the vessel internals to see if this type repair would have access to the whole bottom of the vessel corrosion. Thanks Unclesyd and Chicopee for taking the time to consider my vessel.

 

[moltenmetal]

You haven't told us what this is made of...

If the temperature is suitable and the vessel has adequate access, you might be able to Teflon sheet line the thing. The benefit of using Teflon sheet with welded seams is that you won't need to bake the liner to cure it (ie. unlike rubber). If it's really low hazard service, you could get away with something cheaper like polyethylene or polypropylene.

WIth no vacuum, a non-bonded Teflon liner will span holes up to 3/32" in diameter- it has to, as this is the size of the weep holes generally drilled through the shell to prevent material from accumulating between the liner and the shell. The liner would stop the leakage and would take less than 8 weeks to install, though it wouldn't be inexpensive. The liner WILL collapse if you pull ANY vacuum.

One firm that does this is Nisshin Gulf Coast, though there are others.

This also presumes you don't have anything other than pinholes. If you've lost significant wall thickness or have a risk of cracking associated with the nature of this corrosion, then the unit is most likely scrap- as an ASME pressure vessel that is- and not just the corroded portion.

If it's to be converted to an atmospheric non-code tank, there may be even cheaper bladder-type liners that could be installed in it to make it fit for purpose- depending on what it's storing.

 

[MJCronin]

Amen....

You probably already agree with this, but it is worth repeating.... The reason that management should endorse a mechanical integrity inspection program is to save money.

If the tank leaking causes the unit to shut down, what is the actual cost ?

Eight weeks for fabrication sounds a little long for such a small tank (money always talks with fabricators) ....

Is it carbon steel ? What is the operating temperature ?

How about the purchase of a used tank on the salvage equipment market ?

-MJC

 

[AMenJr]

MJCronin, My vessel is made of common carbon steel like SA516-70. This forum effort was to focus on potential repairs. We are exhausting other options like replacement. We have located several potential salvage vessels. The owner should of had a mech. integ. plan in action but they don't in this case. Long story. The operating pressure is between 15 and 30psig and the operating temp. is around 80oF. The vessel fab. shops located in our part of the states are loaded down and currently have long deliveries. We found one shop that needs work and we may choose a salvage vessel and send it to that shop.

Moltenmetal, I plan to look into your option a little. In the past we coated the inside of vessels with a type of plastic to prevent H2S attack and in some other cases the inside was coated with porcelan. It does not restore the vessel pressure rating but it is something to consider. The bottom of the vessel is corroded and there are obstructions on the bottom that make this more complicated also. I like the concept of making it a non-code atmos. vessel operating at atmos. pressure and coating the inside bottom and obstructions with a thick plastic or rubber spray-on layer. First we would have to clean it and sand blast the inside before the coating is applied. One of the water oulet nozzles would have to be enlarged for it to operate properly and pumps used for the oil outlet. Again thanks for the insights so far.

 

[moltenmetal]

Dunno where the other guys are working, but eight weeks sounds totally reasonable for a replacmeent like this!

Don't spray apply any liner to a corroded tank- you WILL get holidays. Once you start blasting, you very likely know when to stop until you're through the wall. Pits are by their nature small at their mouth and cavernous behind. Any liner you spray apply, aside from perhaps a solvent-borne film-forming lining like Placite epoxy etc., will form bubbles at every pit which will lead to holidays in the coating.

Do some research on what's required to get an intact coating also. Sharp edges can't just be broken- they need to be radiused. And I don't know what "obstructions" there are in the bottom of this tank, but if there are too many it may not be feasible to install an intact liner of any kind on a retrofit basis.

The benefit of a sheet-applied liner like PTFE or PE, PP etc. that doesn't need to be baked to cure is that it won't care about the pits themselves. Holidays aren't going to happen, though weld seam leakage is a risk later. The good thing is that you'll know (due to leakage at the weep holes, which you can collect) when your liner has failed.

 

[jte]

I guess from my perspective, as far as delivery times go, here's what I'd expect:
Regular delivery - 20 weeks, 1x price
Expedited delivery - 8 weeks, 3x price
Super-expedited - 3 weeks, 10x price

I've had a carbon steel moderately heavy wall reactor delivered in 4 weeks. I know it can be done if the economic incentive exists. If the normal price is $50,000 but the lost profit opportunity due to being shut down is $250,000 per day (figure an LPO can vary from zero to several million per day), then paying $500,000 to get the vessel delivered in three weeks instead of eight or twenty makes a lot of sense. I've seen photos of ~6' dia x 30' long vessels being unloaded from cargo aircraft. It made economic sense to air-freight them in that case. There have been several times that I've placed an order with a trusted shop and told them to tell me the price in two weeks when they are half way done fabricating it.

The key to getting a quick delivery is not so much shop time/availability (basically, your extra cost is going to "buy out" the already taken shop space), but material availability. If you need 1/2" SA-516-70 plate for the shell, maybe you want to make it clear to the fabricator that you will happily pay for 3/4" plate if that is what he happens to have available. Likewise for other components like the heads (must it be a 2:1 SE or would you be willing to use F&D or some other type) and fittings.

I'd be curious to hear a fabricators perspective on this...

jt

 

[AMenJr]

Thanks jte, I just sent a designer to look at a used vessel located near us in New Iberia, Louisiana. We are in Lafayette, LA. Parellel to this repair option, we have also been trying to locate used or new options in order not to loose valuable time. This vessel, used, is for $7,500. A new vessel mounted on a skid with piping and controls blasted and painted was also located at a fab. yard in New Iberia for $92,000. So far I can see that repairing may not be our best option this time, however I will present all the information you guys mentioned above to management as well, to show due diligence for potentially new technology options. Actually, I was hoping that someone out there finally invented a way to spray-on hot molten metal to quickly build-up corroded carbon steel surfaces and at a competetive price (probably an unrealistic perspective). You know there are ASME Coded fiberglass vessels. Looks like there should be a laminated option for very low pressure vessels. A built up repair of fiberglass on carbon steel lamination, you know, like plywood. Maybe even additionally secured in place with stay-bolts. The ASME Code would have to come up with approved calculations for this method of repair and it's limitations. It would have to be tested over and over again to prove it as an acceptable option. And then maybe I'm just dreaming. There are a lot of aging low pressure vessels out there and it would be beneficial (and green, ha!) to repair these. I'm now wondering if refactory used this way adds potential wall strength. Dreaming again, I guess. Thank folks.

 

[vesselfab]

Currently, most vessel shops on the Gulf Coast are full up to the gills with existing work.

Right now, I am quoting 6-8 weeks just for drawings and calculations with deliveries in 2010.

Now if this was for an existing customer we could probably squeeze it in somewhere....but not for someone new.

plain jane 516-70 plate or normalized is readily available in one day delivery. since you mentioned H2S, Hic quality, Tuff37 trade name, is readily available in small quantities.

Heads of stock sizes are readily available and some head companies stock HIC plate from Europe in extra wide sizes but will take a few weeks to form & trim.

Getting the vessel built is no problem if the shop needs work and does not mind pushing back deliveries to existing clients. We don't do this, but many folks do for MONEY

 

[roca]

Interesting post this and an interesting point made at the end:
“a built up repair of fiberglass on carbon steel lamination, you know, like plywood. Maybe even additionally secured in place with stay-bolts”
For a vessel - I’ve never heard anything like it. Give me a break - why not just wrap some cling film around the whole vessel instead – cheap and cheerful.

The facts are:
1. Wrong initial choice of material – maybe the process conditions / contents properties and corrosiveness were initially wrong or unknown
2. The vessel should have been internally coated
3. Not enough inspection during the life of the vessel

The facility has been out of action now for a while (weeks…?) At what cost? As MJCronin stated an inspection regime should have been in place as this in the long run saves you money.

IMO the only correct way forward is a new vessel and again at $140+ per barrel the cost of a new vessel will be peanuts compared to what has been lost in downtime production.

 

[AMenJr]

OK roca... we're ordering the new one today and will you're right we are internally coating the lower water section. Thanks folks for the exchange of repair options and ideas. Getting a salvage vessel or a new one was always an option. The forum question was to identify current repair possibilities and to maybe locate new existing technologies. Maybe though, this is not the place to stimulate or speculate new uncharted waters? This should be the last thread. Thanks again.

 

[unclesyd]

AMenJr;,

Thanks for the update.

 

[jte]

AMenJr-

Yes, the "laminate" approach is being developed as a repair method, though for now focused on piping. Composite wraps have been used on piping and pipelines for several years, some with good sucess some with failures. I have seen a composite wrap on a VIII Div. 1 vessel boot which worked sucessfully until it was repaired "properly" at the next planned shutdown. I didn't mention this as a repair option to you earlier since I didn't really think it was an appropriate repair method for your situation without knowing more details about the situation (i.e. we work for the same company and I'm working with you directly to deal with the situation) and I'm not sure there is experience in applying this for this large diameters.

For references, get a copy of ASME PCC-2 and take a look at Article 4.1 Nonmetallic Composite Repair Systems for Piping and Pipework: High Risk Applications which I think you may find very interesting. Article 4.2 deals with low risk applications which is probably not appropriate for your situation. These articles are being extensively worked; the nominal (i.e. not known if it will be printed this year) 2008 edition of PCC-2 will have some updates to these Articles and I would expect the edition after that to continue the expansion of these articles.

http://catalog.asme.org/Codes/PrintBook/PCC2_2006_Repair_Pressure.cfm

One example of a commercially available wrap system is

http://www.powerwraplp.com/index.php?view=standard

jt

 

[roca]

Thanks AmenJr - good luck with it all.
Sorry if I sounded a little patronising - didn't mean to...!

:-0)