Im currently working flare line. The problem is expansion overstress on the branch which is unreinforced tee. I cannot change routing because we're now in the latter part of the project. I made an honest human mistake in the input of the sif before. I input welding in sif instead of unreinforced tee. Im a new stress engineer, but I know this not an excuse. Im really stressed right now and don't know what to do. Please please help me.

PS: We are not allowed to use reinforcing pads in branches.

Some considerations, not necessarily recommendations-
-Can you control the expansion through use of guides and stops
-Does material and number of cycles permit the use of stress range factor greater than 1 as per latest B31.3, if this is indeed your code.
-Are the design conditions realistic
-Are you using the liberal stress range
-If so, does sustained stress play much of a role, eg what happens when you vary the 'sustained stress SIF multiplier'
-Have you treated the branch as an anchor with applied displacements? If so, modelling more of the header may reduce calculated stresses.
-Make sure you consider the full temperature range from Max to Min temperatures, and multiple operating scenarios if significant
-Is there a corrosion allowance and if so have you considered 'all cases corroded'
-Have you considered the WRC 329 SIF
-Can you use a thicker wall, or a welding tee or a weldolet
-Discuss all this with your lead
-I find you can almost always get a line rerouted if need be

regards
Martin

McLovin

I will assume that your modeling is correct and all your loading cases are correct.

You must face the reality of your situation. Your options are limited and your explanation has eliminated all the possible remedies. Your problem is in many ways like trying to reduce the loadings on a vessel nozzle (except that this "nozzle" likely moves a lot more)

The flare header exists and cannot be readily modified.

Your new flare piping branch must be connected and you have ONLY these options:

1. Reroute your new flare piping branch for more flexibility and provide restraints and guide the expansion such that you decrease the moment(s) that is (are) causing the high stress.

2. Use a ASME B16.9 welding Tee at the connection to the flare header (lowest stress).

3. Use a "weld-on" (i.e., weld-o-let) or (preferably) a "weld-in" (sweep-o-let) integral reinforcing fitting at the connection to the flare header (a little more stress).

4. Provide an adequate reinforcing pad at the connection to the flare header (even more stress)

5. Introduce some cold spring in your new flare piping branch to lower the moment(s) that cause the bending stress at the connection to the flare header. Not recommended as it is difficult to get the cold springing done correctly. This is a "wishful thinking" fix.

6. Go to your supervisor "with your hat in your hands" and admit the error and tell him what options you now have.

Regards, John

Everybody makes mistakes. Do what John says item 6. Present the problem and possible solutions. Looking John's list and costs item 2 or 3 would be my recommendation depending on the pipe sizes.

I would not accept a person who:
- hides his/her mistake
- is of the opinion then he/she will not make a mistake
- makes the same mistake all the time

I will allways accept a person who makes a mistake, admitts it , proposes a solution and learns.

First what D/T ratio piping????? FEA via FEPIPE for instance may say that everything is OK.....


Also John Breen number 5 is not necessarily correct when you look at the stress RANGE

Our project is now on construction phase so drastic change to the line is not acceptable. I already used Liberal stress allowable but still not ok. The only possible solution I can think right now is to change stopper locations and additional guides to control expansion. But this afternoon, I'll discuss this matter to my boss.
Thank you so much to everyone. I really appreciate it. This is a lesson for me.