How to calculate weld thickness for joining WN flange to Pipe

That almost sounds like a full-pen weld to me.

Anyways - I can do some rough and dirty calculations for you :

Note that they will be 'rough and dirty' and only based on internal pressure - because there are other external forces on the pipe that would need to be factored into a more realistic stress value.

So how about a little more information - such as: diameter/thickness/schedule of the pipe that you are using, material of the pipe, temperature, welding with what process/filler material, any type of NDT done to the weld?.

Lastly - what exactly is your product? What does it do?

Dear friends,

This is a rough estimate:

Weld height x length x strength per mm2 or inch2 (specified on welding rod)

Your comments are welcome.

Regards,

Ram

You are correct, it is almost a full pen weld, but the bead on the inside of the weldneck does not tie into the outside weld, nor do we back gouge.

Basing your rough calculation on internal pressure only is great. This product is an atmospheric vent on an aboveground storage tank that simply allows the tank to "breath" during filling/discharge/thermal expansion.

There is a 4" 150# RF WN 316LSS welded to a 316LSS fabricated reducer 4.125" ID X 4.625" OD x .25" thick. It would be close to the same as the WN welded to a 4" SCH40 pipe. The weld is visually examined (E=0.6 I think). FCAW is used to weld.

Thanks,

jc

Alright. Are you ready for this?

Just for arguements sake I went with the ASME B31.3 pressure design equation.

It could be done a couple ways, but this seems the most 'appropriate'.

So:

t=PD/[2(SEW+PY)]

P = 15 psig - internal design gage pressure

D = 4.625" - outside diameter of pipe

S = 16,700 psi - B31.3 allowed stress for A312 SS at ambient

W = 1 - weld joint strength reduction factor (ambient temp)

E = 0.8 [up for debate] - B31.3 quality factor (electric fusion welded tube, single butt)

Y = 0.4 - B31.3 random coefficient

SO: t = 15(4.6250)/[2(16,700x0.8x1 + 15X0.4)]

For a grand total of 0.0026"

So based on internal design pressure only you need a weld that is 0.0026" thick - that is, "deep" in penetration.

I am sure that you have a weld thicker than this.

If there are any questions/comments/criticisms/laughter, just reply.

Thank you for your help. I was sure that the weld was thick enough based on practical experience, but this will be a quick way to prove it mathematically.

Please review your calculations on line "SO: t = 15(4.6250)/[2(16,700x0.8x1 + 15x0.4)]". You have not given effect of multiply by 2 to all figures kept in braket). Hence results is different.

Hi, Guest (the one with the original question)!

Just curious about one thing. Given that this was a vent stack --where only backup pressure might have occurred at maybe 1 atm.-- and the weld was completed and checked for accuracy, then why was the client concerned about the weld depth?

"I was asked by a customer to prove that on our product, that the weld of a weld neck flange to a pipe was thick enough."

Since the client had nothing real to be concerned about in the first place unless a power back flush was going on, and then almost a spot weld would've sufficed...but been a little messier (you could just as well have glued the thing together!), what else could be going on there?

Be careful around clients like this! I smell potential misuse of the final result (although I am not creative enough to know what that misuse could possibly be), and you being held 'responsible' in some regard if the misuse causes problems.

Even if the customer is just nutsy, watch out for problems.

Finish the order and think twice about this little episode --maybe investigate gently about the treatment of the received tank by the client-- before doing a repeat business with them.

Sorry to sound a little pessimistic. Maybe everything is OK. But that request raised a red flag in the back of my mind for you.

Mark

That is a good point. We were scratching our heads over here wondering why they are concerned about our weld since it is operating under atmospheric conditions.

1. Standard welded edges V-like preparation (gap, root face - about 1-3 mm) & RT can guaranty full penetration joint

2. Weld metal stresses are always less than stresses in base metal

4. Maximum stresses are appear in weld metal-to-base metal transition (stress concentration factor is about 1.35)

5. Stresses calculation can be made with FEA software (e.g., AxiPro, Paulin Research Group program)

Best regards

Yuri

Hi Guest,

If you contact the company that sold you your welding equipment they will supply you with an "A hight measuring tool",

This tool measures the hight of the weld from the center top to the bottom of the weld at the thickest point ie, the A hight. This is only used for non-penertrating welds like pipe flanges, the A hight should be as thick as the pipe wall welded to the flange!

Spencer.

Hi Guys.

My point of view , is you can go and see the AWS to dig or ASME VIII or API codes and see or calculate the qty and type of welding that applies on your situation.

Israel Barron

ibarron@sfmex.com