Abandon/interrupt welding

By 803056

Date 07-08-2013 22:23

Is the contractor's responsibility to determine what in necessary.

Al

By Cumminsguy71 (*****)

Date 07-09-2013 03:03

I'll be watching this thread to see the final solution as I have always heard and been taught that you could tack weld and leave it for the next shift, next day but once you started to weld it you needed to finish it. Then again I'm dealing with smaller pipe where your probably dealing with 36", 48" or something.

I'm curious to see the responses.

By Smooth Operator (***)

Date 07-09-2013 05:07

Super....... I would think its the owners call ....Worked for National Fuel out of Buffalo ...New York and root / with hot pass could sit a few days (48 hrs.) I believe it is...... Only thing they seemed concerned over was #1 hot pass in 5 min. Of root finish ....#2 No rain hitting a hot weld no matter what pass.....Then again I worked for another co. That in a COLD PA. winter they had us welding 6" with NO preheat and didn't care how long it was between passes...... So cold they were breaking shanks off on the excavator 1st thing every morning..... Only good thing was it was close to home( W. Pa.) and they paid ON TIME (like clock work) Money was good too.....

By Shane Feder (****)

Date 07-09-2013 14:16

Superflux,
The only critical time as per API 1104 is the time between root and hotpass.
Once the hotpass is in the pipe can sit for a month without completing the weld.
When you think about it - what is the difference between a hotpassed weld that has cooled to ambient for 1 hr, 1 day or 1 month ?
When it is time to fill & cap, heat it up to minimum preheat (if required) and away you go,
Cheers,
Shane

By dbigkahunna (****)

Date 07-10-2013 01:14 Edited 07-10-2013 01:16

Usually the company specifications and the written welding procedure will dictate the time lapse between the bead and hot pass. Usually on X60 and higher it is less than 5 minutes. But the time lapse between the hot pass and fill can be hours or days. If you are on X80 or higher the specifications may give a time between the hot pass and first fill.
The governing documents for welding on pipelines are the company specifications, qualified welding procedures and if referenced, 1104.
If the company specification or welding procedure does not state the time lapse between the bead and hot pass, then it can be days, weeks, months. And if neither specify pre-heating before welding after it has cooled, well good practice would be to pre-heat, but it is not required.
I have seen a welding spec for a gas company recently that the whole welding specification was "Contractor shall follow the requirements of API 1104"
Period. Nothing else. Fortunately it is X42 pipe.
Many years ago came across a 6 inch crude oil pipeline running from Levelland to Sundown TX that was laid in 1944. All that was in it was a bead, bead and hot pass. That's right one joint had a bead, the next had a bead and hot pass. Story was they could not get welding rods and they stretched what they had. Was in service for 60 years. Steady 450 psi with a two big Gasso's keeping the pressure up. Moved many a barrel of oil. Pipeline started leaking not from the welds but too many pipelines with CP interference.

By JTMcC

Date 07-10-2013 01:39

The most common requirements over the last few years, in the west, have been this:

HP within 5 minutes of completion of the bead.

HF required on pipe over say .300W (give or take, depends on the gas/oil company), samo samo, 5, "maybe" 10/15 minutes to allow for the slowing down of the front end in mountanous terrain or lot's of bends. Preheat is a constant tho, gots to have it and inspection carry's heat guns to verify no sluggo helpers are slackin off on preheat, + travel speed/heat input. Meters are seen pretty often in that world and they mark off a foot of pipe with soapstone and click the stopwatch.

Break the time barrier, cut out city ($10K plus, plus ea. jobs are lost : )).

F/C within 24 hours. That one really gets addressed on a case by case basis with significant latitude. Conditions being what they usually are in the firing squad ie weather, terrain, welders thrown in the can last night. Preheat still exists here and is enforced with vigor.

All this is what we commonly see on big bore X60 line pipe west of the Mississipi. YMMV of course.

Go back east and you can run into seriously wierd spec's written by seriously wierd dudes. All bets are off there cause you get what you get and reason no longer applies. But some of those guys are kinda new to big mile big bore transmission lines, especially the larger distribution co's.

J

gas/oil co sets these specs internally, nobody really "tells" them what's all happy, happy. Small companies follow what's been proven in the field by big companies. That's just my observation/opinion.

By Superflux (****)

Date 07-10-2013 11:11 Edited 07-10-2013 11:33

Thanks to all that responded.
I'm constantly amazed at how many CWI's and other certified QC professionals are always telling me "It's in the code!", when it isn't.

By dbigkahunna (****)

Date 07-10-2013 21:34

My other two favorites is "OSHA says" and "Well DOT..."

By Smooth Operator (***)

Date 07-11-2013 03:10

Well this is the way we been doing it since I been here..... :yell:

By MMyers

Date 07-11-2013 14:51

Dumb question. I don't play in the pipeline world, so having time limits between passes is foreign to me. Why are there time limits between root and hot pass? I would generally come to the conclusion of it being an inexpensive way of keeping preheat, but if the job it preheated, then I'm at a loss.

By JTMcC

Date 07-11-2013 17:55

One reason is to prevent cracks, say you leave a joint with a bead only overnight. As the temps drop the pipe contracts (possible a long run) and moves, puts stress on the tiny weld on the big old pipe. Or if skids sink into the ground. Or if a sag or overbend isn't "just right", lot of strain on the pipe.

A fast paced production bead gets a lot of help from the HP & HF. The more heat you keep pounding into the bevels, the better the bead gets.

There's a couple but I'm sure the spec writer has many reasons I'm not aware of.

J

By MMyers

Date 07-11-2013 18:52

Gotcha. It's no so much welding related, it's just all the things that can go wrong to damage a weld.

By JTMcC

Date 07-11-2013 19:53

The second part is all weld related, a salty hooked up production bead goes in very fast, as fast as possible.

I've seen the inside of many beads that were cut outs for other reasons before a HP/HF were put in, say an arc strike or preheat too low or a tractor broke and the 5 minutes went all sideways, pipe bent wrong or whatever. It's just amazing (to me at least) the amount of rejectability some production beads have BEFORE a smoking hot pass and a smoking hot filler are slammed in there.
That same bead is very compliant after those two passes and will shoot anywhere.

Kind of interesting from a welders standpoint. You can watch another welder HP/HF a test set of nipples and see the bead just get better and better every pass. Kind of a magical thing as it glows bright yellow from the inside, smoothes out, humps up, IU just disappears. Internal lumps and bumps and "maybe slightly" low spots stand up proud.

So it seems (to me) to be very weld related.

J

By MMyers

Date 07-11-2013 21:07

Watchin from the inside is cool. First time I saw a purged TIG root melt was one of the more memorable welding moments I've had. Makes sense now that you've explained it - thank you. We see the same type of movements on thick section narrow groove welds (what I'm more involved with, I have alot of time on AMI rotating tungsten narrow groove equipment). The ID gets pulled in tighter by the weld, so anything that was low becomes a nice shallow hump on the ID. If the root purge wasn't perfect and slightly discolored (heat tint), the root will be *silver* after the hot passes.

By 2006strat (***)

Date 07-11-2013 03:09

In my 8yrs of welding, i have always gone by the rule of eathier tack it and leave it, or root and hot pass. Never leave have a root or half hot pass. I haven't ran into any problems that way.

By ozniek

Date 07-16-2013 12:51

Hi Superflux

The fundamental code related requirement for time restrictions between weld runs are normally found in pipeline welding codes, where cellulosic electrodes are often used for root runs. Due to the high hydrogen content of these electrodes, there is a relatively high probability of experiencing hydrogen cracking. (also called delayed cracking or cold cracking) The best (cheapest) way to prevent this is to weld the second pass (hence called the hot pass) as soon as possible, before the hydrogen has time to accumulate and result in hydrogen cracking. The second pass (now being done with a low hydrogen filler) will tend to bake out the hydrogen. For this reason most pipeline welding codes will have the time lapse between root and hot pass as an essential variable. If it was 5 minutes in the PQR test coupon, then that is required during production welding. (In API 1104, paragraph 5.4.2.8, titled "Time between passes", the following is said: "An increase in the maximum time between completion of the root bead and the start of the second bead constitutes an essential variable.")

As mentioned by other people, the second reason is that thermal expansions and other loadings can result in relatively high stresses in an unfilled weld. I am not aware of this effect being addressed in any codes. It is however often addressed within end-user specifications.

There are also issues when welding certain materials that could crack if the pre-heat is lost, (e.g. Thicker Cr-Mo materials) but this is something different, but I think that sometimes people get these issues confused with requirements for carbon steels and finishing welds within certain time periods.

Hope that helps

Niekie

By Superflux (****)

Date 07-16-2013 17:43

Niekie,

I appreciate the response and 1104 reference.

By JTMcC

Date 07-16-2013 18:41

Niekie seems to be from outside the USA. Correct me if I'm wrong there.

A large amount of API welding is done in the US with cellulosic consumables from bead to cap. Preheat is used appropriate to the pipe grade, hydrogen cracking is the smallest issue to deal with. At least in mainline construction, compressor station work, gathering systems and distribution work. I know nothing about the other API applications such as tanks, etc.

The gas/oil company will set their own standards for time between passes, and they are responsible for the end result.

But in the US, in API applications mentioned above, the second pass (HP) is rarely made with a low hydrogen consumable.

The hot pass is called a hot pass (in downhill API/ASME cellulose work in the US) because it's sole reason for being is to melt out wagon tracks left from the bead (and leave a smooth, clean, concave profile for the fillers and help the bead), and to do that it's run at heat closely bordering on burn thru.

J

By Smooth Operator (***)

Date 07-17-2013 02:56

JTMcC, I agree w/you 100% about burning out the wagon tracks......After getting back to work after being off for over 6 months, (broken leg) I decided the best way to practice before taking a test was to go to Lincoln's pipeline class for 2 weeks....In the classroom theory part they talked about time between root/hot passes and they said the cellulose coating becomes harder as it cools and in NO WAY will the heat from the hot pass burn it (wagon tracks ) out !!!!!!!!! ( in its cool state) Also Lincoln recommends (thru their research )hot pass run w/5's at 185-190 amps ( any higher and you get premature coating breakdown .........Unfortnately I have to go now I have to leave the $$$$$$ of pipe welding to chase loser Walmart work with illegal labor......LOL : Some people just shouldn't be in business !!!!!!!!!!!!

By dbigkahunna (****)

Date 07-18-2013 01:27

I respectfully disagree with Lincoln.
In the days of wooden ships and iron men the bead was not ground before the hot pass. It was the hot pass hands job to get the wagon tracks out. There is/was more going on here than just letting the hot pass fill in. You used a stitch motion and 190 was in the low end of where the HP hand ran. The welder pushed the bead in. And 50 feet away from the hot pass crew you could hear the stitch. The helper hit the bead weld with a block brush and what you got, is what you got. On large pipe when the two HP hands got in sync it sounded like a machine gun. And god help the bead hand that left a thin spot in the bead like coming off the tacks on the top. The hot pass would blow the bead. You saw a hot pass hand step back, you had a cut out because the HP hand would drag if you told him he had to fix the blow out.
It was not his fault.
When you watched the hot pass bead progress you could see the wagon tracks open up and disappear. The HP welder had to be sure he was not leaving wagon tracks in the hot pass in the bevel.
With the advent of the higher grades of pipe and understanding what grinding the bead did for the integrity of the weld the front end kept grinding the bead thinner and thinner. Set it on the skids, and "CRACK". Keep the time between the bead and the hot pass close and you cut down on cracks.
Times change. But get a SA 200 and put it 240/60-70 with a 5/32 and you can clean the wagon tracks without a grinder or a buffing wheel. At that range you are at the top of a 12 inch standard wall welding procedure. And if you slow down or loose your rhythm you have a hole. A big gaping hole.

By Jim Hughes (***)

Date 07-18-2013 02:41

To the poster,
I know you mentioned that you were under API 1104, but, you also asked if other codes address "interruption of welding". The answer is yes. One such code is ASME B31.1. Paragraph 131.6. I know it's not relevent to the code you are under but I wanted to make sure your question was answered.

Thanks
Jim

ASME B31.1
131.6 Interruption of Welding
131.6.1 After welding commences, the minimum
preheat temperature shall be maintained until any
required PWHT is performed on P-Nos. 3, 4, 5A, 5B, 6,
and 15E, except when all of the following conditions
are satisfied:
(A) A minimum of at least 3⁄8 in. (9.5 mm) thickness
of weld is deposited or 25% of the welding groove is
filled, whichever is less (the weldment shall be sufficiently
supported to prevent overstressing the weld if
the weldment is to be moved or otherwise loaded).
(B) For P-Nos. 3, 4, and 5A (with a chromium content
of 3.0% maximum) materials, theweld is allowed to cool
slowly to room temperature.
(C) For P-No. 5B (with a chromium content greater
than 3.0%), P-No. 6, and P-No. 15E materials, the weld
is subjected to an adequate intermediate heat treatment
with a controlled rate of cooling. The preheat temperature
may be reduced to 200°F (93°C) (minimum) for
the purpose of root examination without performing an
intermediate heat treatment.
(D) After cooling and before welding is resumed,
visual examination of the weld shall be performed to
assure that no cracks have formed.
(E) Required preheat shall be applied before welding
is resumed.

By JTMcC

Date 07-18-2013 19:49 Edited 07-18-2013 19:52

Well I disgree with Lincoln about 5% of the time. Like here.
HP is almost universally done with 3/16" or 5mm rods today. At smoking high heat. Maybe not in the lab but in the field for sure.
The heat from the HP burns out wagon tracks probably several hundreds of thousands of times every day in the present economy. That's the only purpose of the HP except to push in/smooth out the bead and lay a clean/concave substructure for the hot filler or heavy fillers. Track melt out is it's main purpose tho.

In the days of the block brush and the file (up till the late 60's early 70's, when SA-200's had a starter as an option and the state of the art rods were the old verson "hippy" and "85" and even the old P5 (not 5P) white rods were still around) the inspection criteria were more lax than they are today with increased govt regulation and much higher grades of line pipe.

It's a whole nuther world in 2013, but one fact remains, the HP does burn out wagon tracks, with or without grinding. I've seen several jobs in the last few years where grinder guards are required to grind the bead but not to wire brush it. That innevitably results in the grinding disc's (and guards) being put away and the heat goes up, up, up on the HP, welders/helpers are a lazy bunch. Several of those jobs have been high profile zero repair mainline work, several in high impact zones. In todays world you really don't have to grind the bead if you don't want to, but the bead hand (or YOU if it's tie in or fab or lowering in work) best not leave soft spots, and the HP hand best be at the upper limits of the procedure and paying attention.

J

By NWPAwelder (**)

Date 07-18-2013 20:52

This has been a great thread. Thanks guys!

By ozniek

Date 07-21-2013 14:04

Hi JTMcC

Thanks for your input. You are correct in assuming that my experience with pipeline welding seems somewhat different to most of you guys. It was good to hear your experiences and add it to my understanding.

As you mentioned, if you make sure that the pre-heats are maintained, or you are welding on thin walled, or low strength grade materials, then HACC is unlikely. It is however still likely under many circumstances. In these circumstances, one of the jobs of the hot pass is to bake out the hydrogen in the root pass, refine the grain structure and give a larger weld cross section to reduce stresses that could lead to HACC. The Australian pipeline welding code (AS 2885 P2) has an appendix dealing with the control of HACC, (Appendix E) and in paragraph E6, entitled "The effect of delay time", has the following:

"In pipeline welding with cellulosic electrodes, when cracking does occur, it usually takes place within minutes of welding because the hydrogen concentration is already saturated, and the accumulation of hydrogen by diffusion (which is the rate-dependent process responsible for delayed cracking) is not required.

The single most important factor that controls whether or not cracking will occur is the time delay between the root and the hot pass. Delays of more than 6 min between the completion of the root pass and the deposition of the hot pass greatly increase the risk of HACC occurring. The hot pass increases the weld throat thickness, reduces the notch effect strain concentration in the wagon track region, refines and tempers the microstructure, and most importantly raises the temperature of the weldment above the critical level for the onset of HACC and reduces the weld cooling rate to enhance hydrogen effusion."

It looks to me like the "hot pass" in cellulosic welding has rather many functions. (Some of which you guys have enlightened me to - Thanks!)

Regards
Niekie

By JTMcC

Date 07-22-2013 00:51

Hey Niekie I'm guessing you're in Australia?

I would appreciate hearing what the standard mainline procedures are in your part of the world.

J

By ozniek

Date 07-22-2013 14:11

Hi J

Most of the stuff I have been involved with on pipelines have been automated welding. (GMAW narrow gap mostly) The labour rates here in Oz are very high, so they will rather spend a lot of money up-front developing automated procedures, and then have less labour to do the welding. The economics here are certainly a lot different that the case in South Africa where I originate from. In South Africa the capital costs were the expensive part, so they would spend as little as possible up-front, and throw a lot of labour at it in the field.

Listening to you guys, it sounds to me like SMAW welding is still economically viable for pipeline welding in the USA, but obviously it needs to be done as fast as possible to stay that way.

Regards
Niekie

By CWI7611 (**)

Date 07-24-2013 02:53

I agree with a lot of the responses I see. It is true that API 1104 does not have a time lapse between passes or how many passes have to be put in before a weld is left to cool. The best place to look is the written welding procedure or the Owner's (or engineering firm's :razz:

) specification. I have found that on higher yield pipe the more passes before the weld is allowed to cool, the better. If I was allowed to contribute to the procedure or the specification I would require that for pipe of API 5L-X60 and higher at least three passes be completed before welding is interrupted. I would include breaks, lunch time, and the end of the day in that requirement as well. Any time welding would be interrupted, three completed passes minimum.

Now, what do we do before we resume welding? Preheat the entire weld thoroughly, not just the skin, let it soak all the way through, and maintain the preheat until the weld is complete. Big pipe, when you are jumping from side to side completing the welds after the third pass, as in later in the day or the next day, preheat to the required temperature and maintain it till the weld is complete. Preheat anytime the welding is interrupted.

As far as delaying the completion and the preheating of the weld I also have an opinion. Most of these pipeline welds are made with cellulosic electrodes that do contain some moisture if they are SMAW (stick) welded. The moisture disassociates in the welding arc and leaves some hydrogen in the weld. Delaying the completion of the weld allows some of the hydrogen to escape over a prolonged period. This is also why preheating and maintaining preheating is so important. It allows the weld to stay hot to warm longer to allow some of the hydrogen to escape.

I have heard of some Owners requiring "delayed" procedures, procedures where root beads and hot passes are left for several days, of up to seven days before the weld is completed then destructive testing the welds to qualify the procedure. This is fine and if I was working for that Owner as an inspector I would comply with that requirement from the Owner although I might not agree with it. Just keep my mouth shut and my eyes open.