Welding procedure for welding API 6A (4130 to A106 B)

[engr2GW]

Good afternoon all,
As I understand, many API 5ksi flanges are made of SA105 materials. I plan to have welders weld this to A106 grade B line pipe to transition from from API wellhead to B31.3 flow line.

the WPS has the following essentials, and other variables are:
Root is MIG
fill/cap is 7018 (low hydrogen)
Pre-heat minimum is 175 F
PWHT is 1125 +/- 25F
P1 to P1
thickness range for base metal from 0.1875" to 0.944"
etc.

Can this variables be used to join an API 5ksi (SA 105) material to an A 106 grade B in the shop? as long as the two pipes meet the variables like thickness range, strenght of material, etc. This is a qualified WPS.

Thank you.

 

[metengr]

mysarah;
Your subject line references 4130 to SA 106. In the text of your post you reference SA 106 to SA 105. Confused.

 

[engr2GW]

I'm sorry, I blame the 2:30 feeling at work, it's not 4130 at all, it's SA 105.
Thanks for pointing out.

 

[metengr]

No problem. The above welding variables are acceptable for joining SA 105 to SA 106, provided no impact testing/qualification is required.

 

[Duwe6]

Spec the Mig - GMAW wire as ER-70Sx [my personal favorite is ER-70S6] and you are perfect.

 

[engr2GW]

@metengr:
Thanks metengr!
The reason why I was asking is to find out if the pre-heat temperature of 175F is not too small for a wellhead flange as I transition from wellhead to flow line (2"xxh, 3"xxh, or sch. 160).
Also, since the WPS covers P1 to P1, that means I can also use it for line pipe to line pipe as long as I specify the 175 pre-heat requirement is only for the SA105 wellhead flange to A 106 grade B piping right? because the pre-heat shouldn't be a requirement for the A106 to A106 in the flow line right?

@Duwe6:
The MIG wire is ER70S-6

 

[stanweld]

The 175 F min preheat is more than adequate for the intended welds. Why are you using PWHT for the thinner weldments (< or = to 3/4")? Is H2S present in the fluid?

 

[engr2GW]

yes, it will be used for both areas with h2s and without, I didn't want to qualify two procedures. This weld in only one butt weld per well. and it's done in the shop only, so it's not a wps that will be used for an entire facility to make pwht expensive.

 

[Duwe6]

For P-1 materials like SA-105, A-53,SA-103, etc. the preheat requirements are only driven by thickness. The 175°F is to compensate for the heat-sink that the thick flange causes.

If a weld cools too fast, it will rip itself apart due to the shrinkage from the decrease in size of the weld bead. The bead is a LOT smaller at room-temp. than it was when the puddle 'froze' at 2000°-plus. If it cools slow enough, something 'gives' [bead stretches, basemetal is pulled in], allowing the bead to not tear. That is the purpose of preheat, to control the rate of cooling of the weld bead.

 

[engr2GW]

Thanks Duwe6,

so the pre-heat is just enough, but the other point is, for a sour service, the PWHT is not required for thickness below 3/4" but it is a good practice right?

 

[Duwe6]

Correct on the pre-heat for thickness. If it was me, I would PWHT [for process] to greatly reduce the chance of Stress-Corrosion Cracking. Failures due to cracking tend to be catastrophic, so I always PWHT. It's a Risk vs. Cost vs. Consequences thing.

With the good preheat and interpass temperature you intend to maintain, the Risk is low [but not nil]. The PWHT cost is moderate, especially spread out over the useful life of the pipe. The Consequences are $1MM and up, since they include the posibility maiming and/or death of an Operator.

Too much 'exposure' when all the factors are weighed togather, IMHO.