Welding space requirements

Date 07-19-2012 19:15

Luis,

WELCOME TO THE AWS WELDING FORUM!!

Could you be more specific??

1) Which code are you working to?
2) Are we talking about distance between girth welds on pipe? Distance between fillet welds? Distance beween...??
3) Or is this question totally in general? You say "any standard, best practice, code," etc.

Have a Great Day, Brent

By Superflux (****)

Date 07-20-2012 03:04

Ah yes, the infamous "minimum pup length" debate. Sometimes, the project specs will dictate this for girth welds.
Best practice??? "Rule of Thumb".... Usually I hear from 1.5 to 3 pipe diameters "minimum pup length". My first response, just to have fun with them is; "Is that nominal or actual pipe diameter?" Or, "What about that 6"X4" reducer? It is less than 1.5 pipe diameters in O.A.L.?"
From my experience, it is cosmetic. The main thing is to not let the smaller (less than "X" pipe diameters in length) get over heated and violate maximum interpass temperature.
I have yet to find any such mandate in any of the codes I've been working under.

By 803056

Date 07-20-2012 15:23

How do you make a weld without "violating" the maximum interpass temperature?

Every weld I have made in my life "violated" the minimum interpass temperature if you measure the temperature during or just after the weld bead is completed.

There is a story behind my smart ass question. While welding on a high rise I had an inspector run up and stab his tempil stick into my weld crated just as I extinguished the arc. As you can imagine, the tempil stick melted immediately and the inspector proclaimed the weld rejected because the interpass was exceeded.

I pulled the entire welding crew aside and told them were no longer permitted to weld on the project because the inspector said we couldn't exceed the interpass temperature. It was at that time the inspector figured out that he pulled a boner, but still didn't exactly understand what he had done wrong or why my entire crew were laughing.

Best regards - Al

By Superflux (****)

Date 07-20-2012 15:47

Now I feel violated.....

One of the hardest things is to explain preheat to welders. They always want to heat the joint and not the base metal.
D1.1 (2004), 5.6 says minimum interpass is measured 3" from the weld or at least the thickness of the thickest member. Curiously though, maximum interpass temp is not addressed.

By 803056

Date 07-20-2012 17:23 Edited 07-20-2012 17:26

The minimum interpass temperature is addressed by D1.1. It must be at least equal to the minimum preheat temperature.

The maximum interpass temperature is typically not an issue when welding carbon and high strength low alloy steel unless notch toughness is a concern.

Think about how typical carbon steel and high strength low alloy steels are made. They are rolled while they are hot, allowed to air cool with no further heat treatment. Essentially, they are normalized, i.e., the are austenized and air cooled to ambient temperature. In some cases (most of the time) the steel surface is flooded with cold water to minimize the thickness of the mill scale. While it isn't considered to be a "full quench" because it isn't cooled with water below the austenizing temperature range, it is still closer to normalizing than it is quenching.

In general, if acceptable mechanical properties are developed by allowing the steel to cool from austenizing temperatures to ambient temperature in air; interpass temperatures in the same temperature range are probably no worse.

D1.1 lists those (few) base metals where the maximum preheat and interpass temperature must be observed in the notes/footnotes of Table 3.2.

Best regards - Al

By welderbrent (*****)

Date 07-20-2012 19:57

While the maximum may not "typically" be an issue there are definitely times when it is a consideration. Even with HSLA steels. Example:

Recently I was performing TPI on a job in AZ headed for CA with Seismic limitations. We had several good sized columns: over 2" flanges and webs with 2-2 1/2" continuity plates. Most of the time no issues. The welders were being really good about their pre-heats and doing it so that they had soaked the parts and had proper pre-heat 3" from the joint on both sides of the parts. Normal welding left the heat in the 300 - 350* range during most of the welding.

One day I'm watching as they stand a piece on end and strap it into a support frame so they can weld the 3 welds of the continuity plates (that is 3 welds on each side, but on end they get three at a time), all six of them per side the length of the beam, without rolling the beam. They pre-heat and put two welders on the same beam, welding opposite each other. These guys take off and hardly stop longer that a quick chip of the slag. Finally I know I have trouble brewing. They are using FCAW dual shield with 3/32 wire. Two of them in the same area on this column with no breaks. I check the heat= 350*. A couple more passes= 425*. Then over 500*. Finally they run a pass and I hit 530* and I call a halt. Seismic says it is not to exceed 550* inter-pass temps. I tried to get them to work on different levels but to no avail. I think they wanted to take more breaks at that point. They could do it and blame it on me.

Have a Great Day, Brent

By Superflux (****)

Date 07-21-2012 04:52

Meanwhile back on track.
The op was a bit vague in the question and broad spectrum in the requested referencing.

I too am curious on this. Especially concerning weld-o let spacing.
Is it acceptable per ASME B31.3 or B31.1 to have an O-let weld adjoining to a girth weld?

By 803056

Date 07-21-2012 15:52

Post under ASME

Al