HP SUPERHEATED STEAM LINE WELDING JOINT

[GAL02]

Dear all, Good afternoon !
We are working over outlet of Super heater Gate valve (12" X 10" X 12" X 2500# BW)on superheated steam line
(12", Des.Pressure 130 Kg/ Cm2, Temp.: 540°C ) this valve having equalizing line (1")with 1" Globe valve.
(Line is from Valve body to Valve body), My question is as follows:
1) What should be the type of welding joint for equalizing line 1" to Globe valve 1"x 2500 # - SW or BW?
2) Should we follow 12" main line specification for above weld joint? if not then..
3) Does any separate spec. for such Equalizing/ balancing line? if yes which one.

With Regards

 

[davefitz]

For pipes under 2", SWE is normal , but there are distinct performance advantages to use a BWE on high temperature piping welded to a thick walled casting. The stress concentration factor that acts on the unwelded pre-existing crack of a SWE can eventually cause a fatigue failure if there is imposed either high line loads or very high thermal stresses , as would occur if the SW fitting was directly attached to the thick walled valve. If the attached SW is at least 1 diameter away from the valve body and the line is flexible with neglible piping loads, then a SW would be a good choice. If there are high loads imposed on the joint , then a BW shuld be considered, and if the manual welder cannot accomplish it on small bore pipe then an orbital welder would work.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

 

[GAL02]

Dear Mr. Davefitz, Good morning!
Thanks for your reply,
My further question is,
1) In my case HP steam line PIPE CLASS says BW joint does it applies to valve equalizing line too?
2) If not then do we have any specific coding for such lines (Equalizing/Balancing, etc.)in valve construction codes?
i.e do we have any Guideline which state line (Equalizing/Balancing, etc.)should be of SW or BW etc.? (connecting to valve body)

With regards

 

[europipe]

You have a pipeclass, so what does it say, bw or sw?
Mostly the components with sizes are in that pipeclass.

 

[GAL02]

Pipe class insist for BW
With regards

 

[weldstan]

I have seen both socket weld and butt weld specified for your application. If the 2"and under pipe in the pipe class calls for BW joints, you must comply unless you receive acceptance by the owner/engineer for a deviation request therefrom.

 

[GAL02]

Dear Mr. Weldstan, Good morning!
We are the owner and want to validate SW but couldn't get the code where it is clearly mentioned that SW is allowed?
This valve is supplied & installed in early 60's so which code they refer for construction (here specifically equalizing line)?

With regards

 

[europipe]

I think the code is asme b31.3, but that is not the issue here, your pipeclass proscribes BW,
why should You change that, SW is not that good because of the corrosionspace between pipe and socket.

 

[GAL02]

Dear all, Good afternoon !
Pl. check the attached Dwg. for the Valve (Highlighted) portion which is the concern here
and if still no change in your opinion then it's done.

With regards

 

[europipe]

What is the concern? Would it be different when it was an SW valve?

 

[GAL02]

Actually as it is a HP superheated line pipe spec. call for BW & here in valve construction it is SW.
As SW is weak enough to crack development under 130 Kg/ Cm2 & 540° C as it is just a fillet welding.
Valve Equalizing line also under line cond'n it is suppose that it is wrong construction.

With regards

 

[weldstan]

The Code of construction was most likely B31.1, if the valve is in Power service. It could be B31.3, if in a Process plant. A socket weld is indicated by the drawing and could be used in either case. Fitness for service is a matter for you to decide. I assume that the valve and equalizing line has been in service for over 50 years based on your 1960's comment; if so why would you think it was under designed?

 

[GAL02]

Dear Mr. Weldstan, this is right from experience point of view
but by reliability & RCA point of view it is substandard design.
Thanks for all of you guys for your valuable comments & expect in future too !

With regards