How many weld passes to weld a pipe.

Portable Welder · Jun 24, 2016

I was down at the local round table this morning having coffee and the big shot retired plumber that knows everything asked me ( How many passes are required to weld a pipe ) He knows that commonly 3 passes are required for what his welders did when welding pipe in the range of 3" - 8".

I asked him what size pipe was he referring to, he said it doesnt matter, they all take 3 passes, I said no, it depends on the size and schedule of the pipe.

hobbyman · Jun 24, 2016

You are right that thickness determines the number of passes. Waste of time to argue. These blanket statements made over coffee is just there to invite a pissing contest.
I made the mistake trying to explain to a guy burning plate that the water on the plate was not because the plate had been left out in the rain.

johnoder · Jun 24, 2016

Probably different for Schedule 10 and Schedule 160

Heavey Metal · Jun 24, 2016

Root

Hotpass

Cap

So 3 passes

Not the number of times around

E.F. Thumann · Jun 24, 2016

As others have said, depends entirely on wall thickness. Some specialty piping is say, 3" wall on an 8" pipe, etc.

adama · Jun 24, 2016

Around here std water pipe what ever that is in your number system but say circa 5-6mm wall on 3" would just get 2 passes with tig. Root then cap - fill all in one, root with 1.6mm filler then 2.4mm filler for the fill - cap. Mind you this is only for a local company doing smaller sub 2 mega watt community heating projects. No real pressure on the systems, may be a bar or 2 at worst generally just a dozen or so feet of head. We are not coded, but have such a low leak rate there happy for us not to pressure - leak test em just visual inspect. get maybe 1 leak a year on say probaly close to 2K joints on everything from 3/4" pipe upto about 6".

Problem for em is they started using someone cheaper who was mig welding them with no prep, straight over the rust, hence they have supposedly been leaking like a lawn sprinkler system, hence its looking like we have got the job back. Were normally about £5-8 a weld, but its worth adding we are not doing it on site, all in the shop. Normally a couple of dozen welds per setup, so its good low qty job shop production type stuff.

DMF_TomB · Jun 24, 2016

it is fairly basic, weld stops and starts could have porosity leakage that is at pressure you would see dampness or a drop of water when done with only one pass. by using at least 2 passes and the starts and stops not on top of one another the chances of any leakage goes down 100x
.
more than 2 passes is a simple reason there is a limit on how big a weld puddle you can control. usually smaller and more passes are easier to control. thus why one welder might use 3/32 rod and another welder might use 1/8 or 5/32 rod size for the same pipe

adama · Jun 24, 2016

We cheat on puddle control and just roll the work around, so much easier - comfy compared to welding upside down. That too changes things massively. Its not uncommon for one of us to weld and one of us to roll the work too, can be incredibly efficient time wise on some jobs. 2 passes and a constant arc on gets things done fast.

PlasmaOnTheBrain · Jun 24, 2016

How thick is your pipe? Thats how many passes you need.

Root, Hot, Fill, Cap. On the smaller, thinner pipes the last 3 can blend together...

Pete Deal · Jun 24, 2016

I bought a bridgeport milling machine from a shop that makes parts for nuke subs. They had a pipe fitting there a guy was welding a side stub onto. I think it was 2+ inches thick. They said one joint took several weeks to comlete. So it depends aparently.

Portable Welder · Jun 24, 2016

Keep in mind, the guy that said this has been banned from our round table for a couple of years, He still likes to listen in and make snide comments.

snowman · Jun 25, 2016

hobbyman said:
You are right that thickness determines the number of passes. Waste of time to argue. These blanket statements made over coffee is just there to invite a pissing contest.
I made the mistake trying to explain to a guy burning plate that the water on the plate was not because the plate had been left out in the rain.

Was it raining at the time?

badfinger22 · Jul 4, 2016

Always remember that it is pointless to argue with stupid people, unless you are the "jackass whisperer"!

Cast Iron · Jul 7, 2016

The number of passes is determined by the WPS (welding procedure specification) which is generated by the WPQR (welding procedure qualification record), this is the laboratory report which is produced as a result of destructive and non destructive tests to qualify that the weld is suitable for the pipe it is intended to join together, it is then given to the welder to reproduce as closely as is possible in the joint in order to give sustained quality when joining the material group, hope this is clear.

Cast Iron · Jul 7, 2016

In the land of the blind the one eyed man is king? What if, lots of details missing here.

JNieman · Jul 7, 2016

I remember a previous structural engineer I worked for was doing a weld design on an offshore rig caisson. Maybe it was just a random tubular cross section structural member. Can't remember. Point was that it took welders running 3 shifts around the clock a week to weld the connection.

It was a few more than 3 passes.

FabChipCNC · Aug 28, 2016

Depends on the thickness of the pipe. I have welded pipe 4' in diameter that was 4" thick.
You are not gonna do that in 3 passes.
Are you sure he was only drinking coffee (-:

johansen · Aug 28, 2016

FabChipCNC said:
Depends on the thickness of the pipe. I have welded pipe 4' in diameter that was 4" thick.
You are not gonna do that in 3 passes.
Are you sure he was only drinking coffee (-:

if you could rotate the pipe and cool it with a water cooled copper plug, you might be able to do it in three passes if you used 3/4" diameter welding rods. I've heard the pool of molten metal is about a square foot in area for such rods. might need 5 passes for such an operation, unless your V groove was 8 inches wide and the pipe 6 inches thick though. :nutter:

if one was damn insane enough to think such a processes was a viable solution. engineer must have been ... :cheers:

How many weld passes to weld a pipe.

Cast Iron

Hot Rolled

Diamond

Banned

Cast Iron

Diamond

Diamond

Diamond

Cast Iron

Titanium

Cast Iron

Diamond

Plastic

Plastic

Plastic

Titanium

Plastic

Stainless

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