Repair Vessel 3

[fuady]

I have case about repair pressure Vessel in our factory. Our vessel have area of shell have thickness corroded and the thickness less than minimum design thickness. Area of corroded area just 36 cm2 (3.9 x 9 cm) that is a small area than whole of shell body, to reduce the cost, we want to change that’s area only. I want to ask you, is not possible or not? What is that role or anything in ASME that arrange about it? If ASME is not recommended, what is reason?
I will be appreciated for your assistance.
Thank you

 

[weldtek]

A flush patch can be installed in a vessel per the rules in NBIC. Any firm that holds a valid 'R' stamp will be familiar with the rules, and can complete such a repair.

 

[metengr]

weldtek is correct, the National Board Inspection Code (NBIC) would be the standard recommended for in-service repair of pressure retaining items. The ASME B&PV code is for new construction.

A second option under NBIC rules would be an internal weld overlay of the corroded area, if it is accessible.

 

[jte]

fuady-

As weldtek and metengr pointed out, you're in NBIC territory with a repair of a corroded shell section. The above two posts presented two options: Cut out the section and replace with a flush patch or, assuming you have not corroded beyond the corrosion allowance, a weld overlay (the term "overlay" being used to describe welding a less corrosion prone material such as stainless over a more corrosion prone material such as carbon steel). A third option is a weld buildup which would be adding thickness to the corroded area by welding with the same type of material (carbon steel weld on a carbon steel shell).

Depending on your specific situation, any of these three options can be good repairs. If you have enough base metal left and the corrosion is localized due to some known reason (inlet impinging, internals, etc) then a weld overlay which will stop the corrosion makes a lot of sense. For a small area, a weld buildup usually beats a flush patch. Either a buildup or flush patch can also be overlayed to slow or stop future corrosion.

jt

 

[valero]

What is the wall loss mechanism? If it is erosion you have a few other sacrificial steps to consider. Weld an impingement plate to the shell after restoration. This sacrificial element is seen often on heat exchanger bundles. If it is a dry particulate you could weld hex anchors to the shell and ram pack them with Resco AA-22s refractory. If it is corrosion a sacrificial impingement plate would still work, but you may want to alloy up. What is the service of the vessel?

 

[fuady]

If the role for repair vessel inside NBIC, what is the exact code/role number? I want to repair by my self, so I want to know about this role. Maybe all of you can inform me everything code that relationship with this case.
Thanks

fuady

 

[weldtek]

I'm not exactly sure if this answers your question, but, if you have a vessel with a 'U' stamp on the nameplate, and you want to maintain 'Code' status, welded repairs can only be performed by a firm holding a valid 'R' stamp, under the supervision of an 'Authorized Inspector'. If your company holds such a stamp, someone in the QC department will be familiar with the rules, if not, you will need to contract the repair work to a company that holds a valid 'R' stamp.

 

[GenB]

Here:
If your the "State" AI allows it, you can repair it,
your first option is to ask the AI.
If not an R stamp holder will need to do the repairs.
A replacement pc or patch is a normal procedure in repairing a vessel.
if the rest of the vessel integrity is okay you are okay,
you will have to proove to the AI that the rest is accetable.
ER

 

[TD2K]

Fuady, where are you located? I get the feeling you aren't in the US.

 

[SJones]

The penny may have dropped - Fuady is, most probably, not in the US and, I would guess, not subject to NBIC jurisdiction. I would recommend that API 510 be consulted in this instance.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[fuady]

That's correct SJones, I'm not in US, but Indonesia - South Easth Asia. That case appear, because I want repair my vessel, but autority inspection not approved if the vessel is repaired like that. So I want to show him code or rule that arrange about repair vessel.

Fuady

 

[LSThill]

fuady (Mechanical)

You may want to contact Mr. Suhermin (TQM),Technical Inspection, PT Dimensi Barumas Perdana,

http://www.dbp.co.id.

 

[SJones]

API 510

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[chicopee]

IF WALL THICKNESS HAS DETERIOATED MORE THAN 50% THAN IT MUST BE CUT FOR REPLACEMENT PER ESTABLISHED NBIC PROCEDURES-

 

[metengr]

chicopee;
Where did you get this information? It is not in the NBIC. Weld build-up of wasted areas can be performed on any remaining wall thickness of the pressure retaining item as long as the material remaining can be welded. There is no 50% wall thickness limitation.

 

[abmech]

please check if you can take advantage of ASME Sec VIII Div.1 appendix 32. It permits LTA (Local Thin area) in cylindrical shell for vessels.
What is the baisc cause of corrosion? One need to know this before recommending the solution.

 

[Daytona955i]

Tut tut, not a single mention of API RP 579.

Faudy, to maximise economic benefit to you, you need to first apply this code to determine if you really do need to effect a repair.

 

[SJones]

API 510 refers to API RP 579.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[jte]

Daytona955i-

Welcome to the forum! How about clicking on the "personal profile" link and adding a few lines of background for yourself. Helps for people to know a bit about you. You can see mine by clicking on the "jte" at the top of this post.

You are, of course, right: We all assumed that the vessel was already out of service and a repair would be relatively easy. My preference is to use API-579 to get us to the next scheduled outage and then repair the vessel (others might argue that a repair is not necessary provided the 579 calc's show adequate remaining strength). Naturally, if this thin spot was found during and inservice inspection by external UT's or some other NDE method then applying a local thin area calc per API-579 would be appropriate.

jt

 

[chicopee]

Reply to metengr:
NBIC 1972 paragraphs RE30 for stayed surfaces and RE31 for manholes and handhole openings; RE32 regarding unstayed shells, drums and headers has no thickness restrictions provided the AI judges strength has not been compromised.
Now my NBIC 1987 is more elusive to the 50% rule and leaves the degree of repair to the AI, however, many AI's that I knew used that rule of thumb particularly w/ fired pressure vessels until I left this discipline in 1989. From that time to the present new generations of AI's may not be aware of this past rule and may be more liberal in their approach.