Maintenance Welding for Chemical Plant

[StoneCold]

I work in a small chemical plant in the US. Our piping falls under B31.3 for almost everything. Our larger recent projects are handled by contractors who do the welding and we have 5% x-rayed and if there is no problems then hydro and put into service. My question has to do with welding by our maintenance personnel for smaller projects. What is required to be able to use them on small projects? I believe we need to create weld procedures, and have the maintenance guys tested on them. But then it is a little fuzzy for me. Would we need to x-ray 5% of the piping for a small project or just hydro? What if the project only had 4 welds? Should we x-ray 5% of the welds for that welder per year, since they continue to work for us on small projects? I want to get compliant but contracting every weld is very cost prohibitive. Our guys are probably capable of passing the x-ray test on most things that get done. What are all of you doing?

Thanks
StoneCold

 

[BigInch]

I'd think its more critical to test and stay on top of welders that only do 4 welds per year than it is to test welders that do 4000.

You must have weld procedures for all material and thickness classes and test completed welds for each welder. Both the procedure and the welder will be qualified. Keep the procedure and qualification records and issue the welder a ticket. Welds by your qualified welders must also be checked on each specific job; from each specific welder.

Basically, as you probably already know, the code doesn't care if you do 1 weld or 1000 and the requirement is there for a reason. Besides, do you really need to be taking the personal responsibility for not following the code and perhaps exposing your company and yourself to liabilities for property damages, or worse, resulting from a failed weld. Just product spilled or lost would be enough forms, fines, repair and cleanup expense to convince you not to do it again.

Look on the bright side. While it is true that if you checked only 1 of 4 welds, you'd be at the 25% examination level, rather than the minimum 5%, the cost of the X-rays will amortize much better, if you check all 4 welds. Each X-ray would only cost 1/4 as much than if you checked only one.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[dcasto]

I'd xray 100% and not do a hydrotest for real small maintenance. the cost of xraying 4 welds is $20 more than doing 1 weld.

 

[BigInch]

Good point about not doing a hydro. Treat them all as golden welds.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[StoneCold]

Biginch, dcasto

Thanks for your help and experience on this. This makes me wonder if we should qualify our own guys or just use contractors? Is it your experience to have certified welders on staff and x-ray their work? Is that cost effective? Should we stop pipe welding on site and just do certified structural? As food for thought my total number of pipe welders now is two.

Regards
StoneCold

 

[unclesyd]

Adding a little to the sage advice given above.

Before all this don't let cost interfere with your judgement
If you realized it can't be done safely with acceptable results pull the plug. This not only applies to welding but tightening a nut on a leaking flange.

I don't know extent of your welding requirements from the maintenance end or the small project point of view but having capable welders at arm's length is a very valuable asset. My experience has been if the welder has a sense of ownership he will take more pride in his work.
Our case is somewhat different in that we have large chemical plant sitting along side a synthetic fiber plant as well as powerhouse.
All our on site welders are qualified on pipe to Sect IX for P1-P5 and P8 material. All welding on site is 100% RT. This requirement is flexible in some areas like all our water and air utilities. It can also be modified under extenuating circumstances. The welders cover small projects where there is no time line. The cutoff cost wise use to be $25,000 or where it required off site purchases of materials or where specialty welding such as Titanium was required.
I would advise you to get assistance in setting up your welding program especially in setting up the welding procedures. The procedures should be setup as broad as possible so you don't tie yourself down. You can get an idea of the coverage needed by checking you plant standards. They are also things you can do like using CS pipe welded with SS to cover a lot ground. Watch out on the smaller pipe diameters. All our field welders are qualified for TIG and SMAW, while a subset (6) are also qualified on GMAW and on some of the more esoteric materials like 825, 230, the Hastelloys,etc. One point not mentioned in the above posts is that you can never have enough procedures to cover every contingency, especially on the dark shifts. I would recommend that you also work on getting up to speed on the process of welding especially on repair welding.
Here are a few of the hundreds of incidents concerning welding that I've encountered over many years. Keep in mind that I was working under conditions where time was big money, like in the polymer area where a 30 minute outage was a $200,000 overhaul and in the chemical area an outage had a cost of $30,000/hour. 2:00 AM; We broke a shaft (Vasco Jet 1000) on the finisher pump right at the packing follower, (D-2 Tool Steel) how do we stop the shaft from turning. The available electrodes were Allstate 275, 309, 310. Again in the wee hours of the morning we just broke the foot (unknown casting) on a 1500 Hp motor driving one set of blowers on a nowoven fabric line. Electrodes available: Certainum 889, Cronotron 2210, Mckay Hardalloy. Inconel 182.
It is impossible to cover all contingencies.
All on site welders have to weld at least once every 6 months and the X-ray is on his performance record. We keep maps of all welding on both in house and contract welders. As posted above inspection is cheap insurance.

Hug a welder everyday!

 

[dcasto]

i assumed the welds were on pipe where a hydro test would mean a lot of issues,.

if you build a 6 foot spool with 4 welds and you can tke the spool over and hydro it, that is ok.

but remember under b31.3, the hydrotest is not a strenght test, it's to test joints. So you hydro a spool with two welds and flanges, then take the blinds off and rebolt it in, what good was that hydro, the flanges are the most likely failure point.

 

[rneill]

The 2008 edition of B31.3 has added language (Clause 345.2.3 (a) and (b) ) that indicates it is acceptable to pre-test fabricated spools and then assemble them into the piping system without further testing of the flanged joints. Consequently, despite the test being called a leak test, it seems that the intent is really a strength test since the joints won't end up tested?

However, I would also like to refer to Clause 345.2.3 (c) which indicates "closure welds" can be exempt from hydrotesting. Closure welds aren't clearly defined but I think it can be assumed that closure welds would only include welds connecting new piping and components to existing piping and components or connecting subassemblies. I don't think it would be reasonable to assume that welds connecting individual piping components are "closure welds" for the purposes of avoiding a hydrotest.

Also, the regulatory authority in your jurisdiction may impose requirements more severe than B31.3. I know that the regulatory authority I deal with does not allow the exemption on closure weld hydrotests as provided in B31.3.

 

[BigInch]

Are you opening a question on the invocation of clause 345.2.3 when, shall we say, a designer's sole intent is to avoid hydrotesting the closure weld? IMO intent to avoid a hydro on the completed unit doesn't matter.

The code has already acknowledged that avoiding hydro of a completed unit is reasonable in specific circumstances, stated where it is allowed and prescribed a remedy to assure integrity. While its true that a designer must always consider the intent of the code, the reverse isn't so. As long as the designers somehow manage to adhere to the code's minimum design criteria, the code doesn't care (or for that matter, neither does the pipe) about the designer's intent. We should be able to do a closure weld in accordance with the code anytime its allowed, regardless of our intent.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[unclesyd]

Strange as it may seem our hydrotesting isn't done to satisfy any code requirements. We primarily do it to test the integrity and safety of pipe to be used in the intended service since our episodes with bad SS pipe in the 90's. With our polymer process once on line it is like a rocket ship, it has to go there is no wow button. For a peroid of time we actually tested at 3x to find bad core pipe on existing jacketed SS spools, we did. The core pipe on our CS jacketed spools is hydrotesting flange to flange while we don't hydro the jacket due to heating media being Therminol. We do helium test at 50 psig, the test pressure should be 110 paig. A spool piece is 100% RT to the extent possible and the jacket closure weld is always a butt weld not a fillet weld. They didn't have Sifco Flanges we our plant was built.

The problem with not using exemption from hydrotesting the Golden Weld in our case in two specific areas we have very few valves and fewer flanges. In the majority of cases you would have to test against a control valve or check valve, neither of which we require to be leak tight or use a blank, If you use a blank on both ends of the section of interest you have potential flange leaks when you pull the blanks.
We did check some closure welds on 650 lbs steam line by testing against ice plugs.

I can't recall ever being denied an exemption on testing from the AI and Corporate Safety if the conditions precluded a proper book test.

I agree plan and layout your piping for testing by the book, but on existing pipe sometimes that is impossible to do without compromising the system or creating bigger problems.

In 42 years I never saw a complete failure of a butt weld made on site.

 

[rneill]

What I thought I was suggesting was that if I am in a Fab shop and building a spool, that when I weld a individual component (say and elbow) to another individual component (say a piece of pipe), that would not be a closure weld.

Webster dictionary definition of "closure"

"a closing (e.g., the holiday closure is in August), a conclusion, a bringing to an end (e.g., the closure of a speach)."

 

[BigInch]

Yes, that would be pushing it. But, if you couldn't do it any other way, for instance if there was some adjacent immovable structure hindering access enough to prohibit putting a true closing weld there in the field, I don't see anything in the code that would actually prohibit hydrotesting those components first, welding them together, radiographing, then welding the ends of that assembly into position with 2 more closure welds at each end of the assembly. Even though you could do a hydro on that completed assembly, it would seem to be a minor difference. I'm not saying I would do it that way, just that there seems to be nothing hard written into the code that would specifically prohibit considering it in that manner. Especially considering that if the owner determines its impractical to do any kind of a hydro, not doing a hydro at all is sometimes allowed in certain limited situations when the appropriate extra criteria are meet.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[rneill]

There is no limitation in Code on the number of closure welds and no interpretations that I'm aware of either.

However, as mentioned earlier, the local regulations my take precedence over B31.3 and "closure welds" or "golden welds" may not be allowed without a whole lot more than required by B31.3.

If you want to see one example of the position taken by a regulatory authority, take a look at this ... very onerous ...

http://www.absa.ca/Forms/AB-519 Alternative Test Methods Procedure Requirements.pdf

 

[BigInch]

No doubt. From what I gather, you Canadians are getting worse than GB's HSA.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[Gator]

I think one of the key statements in this thread was:

"My experience has been if the welder has a sense of ownership he will take more pride in his work."

 

[unclesyd]

Something came up this morning that reminded me that I should add a statement to my previous posts.

When you pick your welders make sure you try to find a left handed welder specifically with a slim build.