Joining API X65 material to A350 LF2

[Spoonful]

Dear Friends,

I have a situation here at the joint of (pipe) DN850 API X65 PLS2 pipe to (closure) A350 LF 2 Class 1. The design pressure if 10.2 Mpa 65C, Pipe thickness used is 23mm. which is adequate for the pressure for the strength of X65 pipe. At the joint, the closure hub would be machined to suit the pipe at 23mm thick, at that thickness, it is not adequate for the pressure for the strength of LF2, at least 34mm is required (including 3mm CA).

Any suggestion here?

 

[Dhurjati Sen]

Dear Spoonful,

Explore the option of replacing ASTM A 350 LF2 Class 1 with suitable ASTM A 182 grade.

Regards.

DHURJATI SEN
Kolkata, India

 

[LittleInch]

Drawing?

But you need to maintain your 34mm.

If the A350 is a casting/forging you can increase OD and take the difference across the weld with high strength weld material.

Or buy a section of X65 at 34mm and machine an internal taper.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Spoonful]

Hi LittleInch,
That's what I was thinking, increase the OD of the A350, so there is step from say 34 to 23 at the weld joint, looking from the outside. Should stress discontinuity/concetration a issue here?

 

[SJones]

Use the stipulated joint designs for unequal material thicknesses shown in the applicable ASME code. Whether that still leaves you with a degradation issue will be down to a detailed mechanical analysis specific to the design and operating conditions.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[r6155]

Spoonful
API 5LX65 is YS: 65.300 psi and TS: 77.600 psi
ASTM A 350 LF2 is YS: 36.000 psi and TS 70.000 psi

Are you sure about this option for welding?

Regards

 

[LittleInch]

You're just inside the 1.5 t thickness as shown in e.g. fig 434.8.6-2 e) in ASME B 31.4

What is your design code? That will tell you what can and can't be done.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Spoonful]

Hi 6155, could you please shear a bit more on the issue on the welding?

Hi Little inch, the design code AS2885 (piping code)

 

[SJones]

AS 2885.2, Figure 10.3 had virtually identical information to that of ASME. Well, at least it did in the 2007 version that I have.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[r6155]

Spoonful:Good engineering practice is to choose materials with similar yield and tensile stress.

Regards

 

[LittleInch]

Soonful - what is this? A pig trap?
Why is it in the Boiler and PV forum when you're using a pipeline code?

AS2885 is a pipeline code, not piping. Small but significant difference.

I've never needed a copy, but there will be similar guidance as S Jones says, on the ability to weld different thicknesses of pipe.

It's not uncommon to have to weld high strength pipe to cast or forged fittings which are mode from lower strength materials. So long as the ID stays the same so you can take the difference in wt up in the weld then just make the weld metal suitable for high strength and away you go.

Having the same material strength is great if you can do it, but if not it's not a deal breaker. IMHO.




Remember - More details = better answers
Also: If you get a response it's polite to respond to it.