Galvanized piping

Date 04-08-2010 21:08

I've written dozens of times in this Forum that it's against Good Engineering Practice to weld galvanized metal. The weld heat burns the zinc coating, resulting in a yellow fume made of zinc oxyde that is dangerous to human health at breathing it. So, welding galvanized metal spoils both the metal and the welder's lungs.
Galvanized piping and fittings should be threaded to make up threaded connections.
The so called "cold galvanizing" is nothing else than a zinc powder rich paint, so when you paint the burnt surface produced by welding you're not galvanizing it again, you're just painting it.
If you want to weld the piping, then use black piping; if you use galvanized piping, you should employ threaded connections.
Giovanni S. Crisi
Sao Paulo - Brazil

By 803056

Date 04-09-2010 15:46

I'll buy that arguement.

Best regards - Al

By rfieldbuilds (**)

Date 04-10-2010 23:33

Minor highjack here. What do you believe is the effect of burning off HDG with an oxy/acetylene torch? I've had welders try and pull that instead of grinding prior to welding.
RF

By Joey

Date 04-11-2010 14:36

Hello Prof Crisi,

If it's against the good engineering practice, then why AWS allows it?

Here what AWS says:

5.7.2 When welding galvanized base metal, one of the
following options shall be met:

5.7.2.1 Option 1. Welding of galvanized base metal,
without prior removal of the coating, shall be performed
in accordance with a WPS qualified to the requirements
of this code. Note that the WPS will normally involve
larger root openings in joints, electrodes with lower silicon
content, and slower welding speeds.

Dangerous to human health? then what AWS says:

5.7.3 When welding galvanized surfaces, suitable ventilation
shall be provided to prevent the concentration of
fumes. See ANSI Z49.1 and Annex D.

So, will welding galvanized metal spoils both the metal and the welder's lungs? Well, I don't think so :) :)

Regards
Joey

By jrw159

Date 04-11-2010 14:49

Joey,
AWS D1.? and what year says this? It sure is not AWS D1.1 2008 5.7.2 - 5.7.2.1 or 5.7.3.

jrw159

By Joey

Date 04-11-2010 15:01

yup! not D1.1.
could not remember....it was long ago, wrote it in my notebook :)

By jrw159

Date 04-11-2010 18:22

Well what AWS D1 did you get this from?

jrw159

By Joey

Date 04-12-2010 02:18

jrw159

The AWS code # was given by my best friend…. but I don’t think you trust the CAWI.

You may want to check it in your library at home. I have mine from smokey mountain.

have a nice day :)

By jrw159

Date 04-12-2010 11:20

Joey,
I am not the one that quoted AWS, you are. I do not have my full library as it is 8.5 hours away. I only have access to a limited amount of AWS code books here in OK. The info you posted is in none of them.

It has absolutely NOTHING to do with a CAWI.

You posted it and I am just interested which AWS code you got this from. Being able to provide that is good practice when quoting AWS codes.

If you are unable to do this, I understand. :-)

jrw159

By 3.2 Inspector (***)

Date 04-12-2010 12:41

Is a CAWI allowed to quote codes?

3.2

By bert lee (**)

Date 04-12-2010 13:42

cwi supervision?

By Lawrence (*****)

Date 04-12-2010 16:32

Joey

Anybody can quote code..

But so far code has not been quoted. Just a bunch of unidentified text.

If you are unable to identify the source doccument how can any authority be granted to the text?

A CAWI is able to converse about anything.. A CAWI's authority is limited in regards to signing off doccuments and also limited in scope of inspections as far as direct supervision. If you are interested in the specifics of that scope I can help to direct you to the appicable code upon request.

By Joey

Date 04-13-2010 03:06

Lawrence

Are you telling me now that you are interested to know the AWS code# because you are convinced that my earlier post is no longer very strange?

I’m actually interested to know whether I can use a threaded connection if my pipe nominal size is 16" sch 80. Can you direct me to the applicable code? I’m interested to know your basis when you said that the “threaded connections are a far better choice”, please note that there were no pipe sizes given in the original poster.

Thanks for your offer to direct me to the aplicable code, but here we are not only using American codes. Are you familiar with BS EN? As an Inspector, if the applicable code is not stated in the project specification, I would rather seek advice from the Project Engineer / or Design Engineer.

Regards
Joey

By Lawrence (*****)

Date 04-13-2010 06:18

Not at all Joey.

Although quoting numbered text without even knowing where it came from other than (AWS) is very strange :)

Yes I am familliar with European Norms.

Seeking advice from the project engineer or designer is the perfect thing to do.

By jrw159

Date 04-12-2010 17:27 Edited 04-12-2010 18:41

Allowed? Of course.

Capable? Well in this particular case that remains to be seen.

jrw159

EDIT: Actually in this case, apparently not.

By Lawrence (*****)

Date 04-11-2010 19:36

Come on Joey...

Read the original post and apply common sense to Prof. Crisi's answer

The Original question focused specifically on fluid piping.

AWS D.1. has nothing to do with fluid piping.. So why quote it?

Burned off galvanized coatings in weld joints *WILL* corrode before the rest of the material, even if supplimentary applications are put to use post weld.

Threaded connections are a far better choice when you are in the design phase of a project such as the one noted by the original poster. Saves time, saves corrosion, saves costs in a dozen different ways...

Your such a sharp guy... very strange post.

By Joey

Date 04-12-2010 02:08 Edited 04-12-2010 03:31

Oh come on Lawrence,

What common sense you are talking? Do you catch the message of Prof Crisi? He said “I've written dozens of times in this Forum that it's against Good Engineering Practice to weld galvanized metal.” Dozens of times – his message could be “in general”.

For those inspector new in construction site, when you just came on board and see some welding works being done on galvanized metal….my suggestion is don’t behave like a smart azz by stopping them….you better ask first if they have supporting documents (i.e. approved WPS, PQR, welder cert) for such work.

http://www.sperkoengineering.com/html/articles/WeldingGalvanized.pdf

Attachment: weldinggalvanizedsteel.pdf (304k)

By Lawrence (*****)

Date 04-12-2010 05:03

Poster needs Galv inside and out..

How exactly do those links help?

By Joey

Date 04-12-2010 09:43

Well, at least it will help to understand that welding a galvanized metal is not against the Good Engineering Practice. You will also noted that there are ways to avoid damage both the metal and the so called welder's lungs.

Can you assure me that your recommended “threaded connections” are always permitted as pipeline assembly joints?

By Lawrence (*****)

Date 04-12-2010 16:42

I cannot assure you about threaded connections always being permitted as pipe assembly joints.

That's way above my paygrade.

I can assure you that many galvanized pipe joints that are welded will no longer be galvanized on the inside of the weld joint and heat affected zone, which presents a problem for assemblies that require coating inside and out.

By Joey

Date 04-13-2010 11:38

Come on Lawrence

You called my post very strange...but you bite the idea of threaded connections without
knowing the pipe nominal size and thickness...I think your's a blunder post.

By Lawrence (*****)

Date 04-13-2010 12:07

You think I have blundered.

How ever will I sleep tonight.

You just keep quoting 5.6.3.8 From some code you can't even identify, then tell everybody else they have problems.

Really Joey I understand you.

By 803056

Date 04-11-2010 19:08

Anyone that has welded galvanized steel recognizes it does not do anything beneficial for the welder's lungs. Anyone that has welded enough galvanized steel to experience metal fume fever is less likely to be as stupid a second time.

I have yet to see anyone actually qualify a welding procedure without removing the HDG from the groove face and adjacent areas first.

At the behest of a contractor I have performed a number of experiments with fillet welds on tee joints. None of the results were encouraging. Each sample had evidence of zinc along the grain boundaries when viewed with low power magnification and the welds exhibited a distinct reduction in ductility. Some of the samples were welded with E6010 and some with E7018. The results were similar.

Welding austenitic stainless steel to HDG carbon steel is the kiss of death.

The only people that favor welding over HDG are the contractor's that are interested in one thing, their bottom line. Their attitude on the subject of welding can be summed up as, "If it doesn't break while I'm still on the project, it's OK."

Those are my thoughts on the subject.

Best regards - Al

By Richman (**)

Date 04-12-2010 10:06

Gentlemen, My questions is; are there any EFFECT on the systems during operations if the galvanized coatings are damaged or remove INSIDE due to welding are not rectify or not return to shop to re-galvanize the damaged portion of the spools?

By 803056

Date 04-12-2010 11:05

Read the report by Walter Sperko. I believe it has the information you are looking for.

Best regards - Al

By G.S.Crisi (****)

Date 04-12-2010 23:12 Edited 04-12-2010 23:24

1st. I recognize I've exaggerated at saying "dozens of times". Actually, they were only six or seven.
2nd. I wouldn't put my nose close to the yellow fumes produced by welding galvanized steel even if there was an exhauster three feets over the weld.
3rd. Before welding galvanized steel it's mandatory to remove the zinc coating, which can be done by burning it with a torch or by grinding it off with a grinding wheel. The removal must be extended as far to the weld as necessary so as to reach a zone in which the zinc won't burn due to the increase of temperature. In practice, a couple of inches, three at the most, are sufficient. Burning is better than grinding, because by grinding you can not guarantee 100% that all of the zinc has been removed.
4th. After welding, the so called "cold galvanizing" must be carried out. This is done either by painting with a zinc powder rich paint, or as joe pirie explained, by spraying the zinc powder with an air gun. Both methods are just remedies, none of them replaces or has the same efficiency than a good hot dip galvanizing.
5th. In pipes, the "cold galvanizing" can be carried out easily on the outside. Does anyone know how to do it by the inside, after the weld is complete?
6th. Is all of this Good Engineering Practice?
7th. I insist. Galvanized pipes were thought to be joined by threading, not welding, that's why the threaded fittings exist. By the way, the largest world manufacturer of galvanized fittings is Brazilian: www.tupy.com.br
Giovanni S. Crisi

By rfieldbuilds (**)

Date 04-13-2010 02:12

Is anyone here familiar with ASTM approved methods of repair to HDG parts??? AGA has a one hour "inspection" webinar which highlights the approved methods of repair to HDG products.
RF

By 803056

Date 04-13-2010 04:20

There are a lot of things done by industry as being "expedient" or because "that's the way we always do it.” Just because we see things done a certain way does not mean it is the right way.

Most of us have been around long enough to see a number of major screw-ups that were life changing. I can list a number of them here in Connecticut that should send shivers up your spine. Men have been killed, but at the time their actions were based on "good engineering judgment", "that's the way we always do it", "getter done,” "do something, even if it's wrong, but don't just stand there!"

Hartford Civic Center
Mianus River Bridge
LaAmbiance
Middletown Power Plant

The list of lesser-known accidents caused by not paying attention to details is long to say the least.

In my humble opinion the welding of galvanized materials without adequate removal is "not good practice.” Welding galvanized pipe, as noted by our good friend Giovanni, is not the best practice. There is a time and place where the use of galvanized pipe makes sense. That would be when threaded fittings are used. Threaded fittings cause the least damage to the galvanized protective coating. HDG will heal itself to a certain extent. It is sacrificial; meaning it useful life is limited. If the galvanized coating is damaged for a good distance from the welded joint, it cannot provide the protection it is intended to.

The designer has to take into consideration several design constrains. The useful life of the system, the nature of the corrosive environment, whether threaded or welded fittings are to be used to name a few of the factors to be considered. If the system has to be welded and where corrosion is a concern, there are other material choices that can be made. "Plastic" pipe, stainless steel, nickel alloys, titanium, etc. are viable alternatives for different reasons and operating conditions. Each has limitations and the cost is always a consideration.

We use the services of the designer to weigh the factors and decide which materials are going to provide the best service for the minimal cost. ASME piping codes do not provide direction when corrosion is a concern. NACE is a good source of information where corrosion control is an issue. A good piping designer has training and utilizes information from both organizations (and others) to determine the best way to optimize the system at the lowest cost to the owner. If the designer selects galvanized steel pipe for a welded application, I would hope that he considered all the ramifications involved.

Would I weld galvanized steel pipe? Sure, for a Farm Code application.

Best regards - Al

By Joey

Date 04-13-2010 08:02

Al,

Thanks for sharing your opinion.

May I know you opinion on these two standards AWS B2.1.003 & B2.1.007? Do you think they belong to your category of “not good practice”.

Speaking on welding galvanized metal regardless of its usage whether it's a pipe, plate or rebar,.... will you consider D1.4 as a farm code? It was stated in this code that the preparation for welding on coated base metal shall preferably be made after coating. Pardon me as I don’t know the meaning of farm code.

Again, thanks for sharing.

Regards
Joey

By 803056

Date 04-13-2010 14:41

Reference to the "Farm Code" is my sarcastic way of throwing a barb at the welding of Hot Dipped Galvanize (HDG) and expecting a "high quality weld."

The welding of sheet steel that has a thin layer of galvanizing is somewhat different than hot dip galvanizing in several ways, the most import to this discussion is the thickness of the zinc layer. The second factor is that sheet steel is not normally used in applications where very high unit stresses are involved. The acceptance criteria for welds made in accordance with Sheet Steel Code are fairly liberal when compared the the structural steel code, i.e., D1.1. Consider the acceptance criteria for porosity and burn through for sheet steel in comparison to the D1.1 Structural Welding Code/Steel or D1.5 Bridge Welding Code.

AWS D1.4 permits welding the reinforcing steel with the galvanize intact if the contractor qualifies the procedure with the HDG intact. Ref clause 5.7.2.1. This requirement would be applicable to both groove and fillet welds. This is a departure from the basic qualification requirements where in fillet welds are prequalified provided the other conditions of D1.4 are met. Notice the next clause, 5.7.2.2, allows the welding of coated reinforcing if the contractor removes the HDG before welding without separate procedure qualification.

I gained considerable experience welding HDG components during my career as a structural ironworker. We did what we could to remove the HDG before welding it to improve the appearance of the weld and to reduce the amount of porosity. The applications did not involve welded joints subject to tension or high unit stresses.

As I mentioned, I have welded a number of sample T-joints with single pass welds on behalf of a client and found the single pass fillet welds did not have the ductility as those fillets deposited on uncoated steel. Low magnification allowed me to see where the zinc or other components of the HDG wetted the grain boundaries near the toe of the fillet weld.

If you have experience welding HDG I am sure you have noticed the first weld bead deposited on HDG parts was less than impressive. It is not unusual to see welders burn in the first bead and then deposit additional weld beads just to make the “crappy” first bead look better. No matter how you cut or dice it, welding over HDG without first removing as much HDG as possible is going to result in welds that do not provide the optimum properties.

Can you weld over HDG? Sure, but I don’t believe it is logical to assume the mechanical properties are as good as welds deposited on clean steel without actually qualifying the welding procedure with the HDG intact. I have yet to see a circumstance where the contractor has spent the money to qualify the procedure with the HDG intact.

By Joey

Date 04-14-2010 07:33

Well to say that the code permits welding on galvanized steel is more than enough to hear.
I can’t tell the contractor that they are doing bad engineering practice when they are not violating the code requirement.

Apologize to Prof Crisi, I realize that you might be explaining it as a professor’s point of view. Anyway, without this argument I may not be able to
learn something new....farm code :) ....I’m a rice eater…I will not dare to use it :)

By jrw159

Date 04-14-2010 12:11

Joey,
You mentioned AWS D1.4 Structural Welding Code - Reinforcing Steel in an earlier post. Then you make this comment....

"Well to say that the code permits welding on galvanized steel is more than enough to hear."

AWS D1.4 may very well have allowances for this (in accordance with a WPS qualified to the requirements
of this code.) However, this particular code is far from being applicable in this particular situation IMHO.

Just because one AWS code may allow something does not mean that all AWS codes allow it.

It has been awhile since I have used any of the piping codes (ASME/API) but I do not recall any of them allowing welding directly over coatings, especially HDG.

So in short, I would absolutely not consider AWS D1.4 a "Farm Code" but I do consider it not even closely applicable to this situation.

Apples and oranges.

jrw159 :-)

By Joey

Date 04-14-2010 13:11

Well I'm very much aware. I did mention this line in my earlier post to Lawrence --"Do you catch the message of Prof Crisi? He said “I've written dozens of times in this Forum that it's against Good Engineering Practice to weld galvanized metal.” Dozens of times – his message could be “in general”. (e.g. piping, plates, rebar etc)

I'm not that stupid not to know apples & orranges, I have API 510, 570 & 653 certs and have read many codes during exam prep. The last digit of my AWS cert is 8 not 1 for your info.

by the way, in smokey mountain we dont see apples and orranges :) ....we see banana and lots of banana :)

have a nice day :)

By jrw159

Date 04-14-2010 13:29

LOL, banana's.... good source of potassium. :-)

jrw159

By ssbn727 (*****)

Date 04-14-2010 13:29

Hola Joey!

Por favor, No te ponga te en mal humor hombre! ;) No necissita a poner se bravo por ningun razon vaquero!!! ;) :) :) Translation roughly; Please do me a favor, Don't put yourself in a state of bad humor Man! ;) No need to get angry for no reason at all Cowboy!!! ;) :) :)

First off, Nobody said that you are stupid, so please get that notion out of your head... John is simply attempting to point some things out to you in general, not to berate you in any way, shape or form. ;) And we know that you have experience from reading some of your other posts...

By the way, what color are the bananas??? Green or yellow??? I like my platano's and overripe yellows - to boil and mash, and the yellows to cut into long strips and fry man!!! ;)
Great source of Potassium... Are you Phillipino by any chance???

Respectfully,
Henry

By Joey

Date 04-15-2010 09:23

Thank you Sir, Yes I'm a Filipino

jrw159 is actually one of my idol. I purposely didn't tell him the D1.4 because I thought he had collection of AWS code books at home.
Sorry jrw159 - I've seen your collection of inspection tools and some code books you've posted here last time. I'm impressed :)

Try those yellow bananas with Del Monte sticker....you'll have the boxing speed of Manny Pacquio :)

Regards
Joey

PS. Mr Henry - I've enjoyed reading manny of your posts. You have an excellent writing skill which is very usefull to stop those people who
like to score points or like to play politics in the office by e-mail :) :)

By Shane Feder (****)

Date 04-15-2010 10:58

Hi Joey,
Magandang hapon po.
Ayos lang po ?
I spent 6 months at the CB&I yard in San Pasqual, Batangas last year whilst working on the Goro Nickel Project.
Still have a lot of pinoy friends from AG&P and EEI who were our contractors in New Caledonia.
Fell in love with Asia so I am now based in Thailand doing another modularisation project for Australia.
Don't worry about bananas - send JW some balut - just in case he has bad knees.
All the best,
Shane

PS. Pac Man for President !!!

By jrw159

Date 04-15-2010 11:25 Edited 04-15-2010 11:30

Joey,
I do have a copy of D1.4 but it is at my home in Colorado. I have a pretty good collection in Colorado but I am currently calling Oklahoma home and only have D1.1, D1.6, and D8.8 with me here. When I posted the pictures you are referring to I was working in Dallas.

I like these....

A slice of wheat toast,
peanut butter (thick layer),
Miracle Whip (thin layer),
sliced banana's.

BIG glass of cold milk.

Mmmnnmmnn. :-)

jrw159

By Shane Feder (****)

Date 04-15-2010 12:42

John West,
Calories maximus !!!!!!!! (Here's me preaching while I reach for my 4th or was it the 5th rum and coke ?) LOL !!

By jrw159

Date 04-15-2010 14:42

LOL, I can relate to that. :-)

jrw159

By Lawrence (*****)

Date 04-14-2010 13:34

Hey Joey

You said:
"The last digit of my AWS cert is 8 not 1 for your info."

For my info... What is the difference between an "8" and a "1" on an AWS cert... And which AWS cert are we referring to?

Maybe after you tell me I can look through my papers and see which numbers I have. Am I a magnificent 8 or a lowly 1... Again, how ever will I sleep :)

By jwright650 (*****)

Date 04-14-2010 14:30

How to interpret the CWI number to determine the level of certification:

The first four digits of the CWI number are the year and month of original certification. For example, 9603xxxx means that the inspector was certified in March of 1996.

The next three digits of the number are unique and the last digit of the CWI number indicates the level of certification. A last digit of ‘8’ means that the individual is a Senior Certified Welding Inspector (SCWI). A last digit of ‘1’ or '3' means that the individual is certified as an AWS Certified Welding Inspector (CWI). A '2' or ‘4’ means that the individual is certified at the level of Certified Associate Welding Inspector (CAWI).

http://www.aws.org/w/a/certification/search.html

By Joey

Date 04-15-2010 09:31

Hi Lawrence,

Actually, I must thank you because some of the reading materials I've used during SCWI exam prep are
supplied by yourself...like those NDT notes you posted here when one of the member asked for help
(i think that was yr2005 or yr2006?). I used them during exam.

Sorry to trouble your sleep :) Peace be with you :)

Regards
Joey

By Lawrence (*****)

Date 04-15-2010 09:58

Glad to help Joey

And Congrats on the SCWI, thats really quite a professional accomplishment.

When I look at the body of knowledge required for that one I loose sleep!

By jrw159

Date 04-15-2010 11:28

I will second the congrats on the SCWI. I have 2 1/2 more years until mine.

jrw159

By 803056

Date 04-20-2010 18:12

Congratulations!

Al

By jrw159

Date 04-20-2010 19:48

Thanks. Plus from what I was told by AWS certification is that I will not need to test because my 80 hours at Hobart covers it. I just have to pay, provide work documentation, documentation of my hours at Hobart and eye exam.

jrw159

By HgTX

Date 04-13-2010 16:59

ASTM A 780 covers repair of damaged or uncoated areas of HDG. They list zinc-based solders, zinc-rich paints (what some call "cold galvanizing"), and sprayed zinc (a.k.a. metallizing). The only part of it that we've taken issue with is the zinc content of the paint--they say "zinc dust in the range of 65 to 69 % or above 92 % in the dried film", which basically means minimum 65% but with that middle range of 70-92% left out because of adhesion problems, while we want minimum 94% zinc. We've found that the lower concentrations don't do so well when applied using typical Farm Code methods. Also keep in mind that's the percentage of zinc in the dry film. Often you'll see some percentage listed on the spray can that's referring to the purity of the zinc itself, not how much zinc is in there.

Hg