Threaded Branch connection

[James01]

I have a 12" dia 10.0mm WT gas line operating at 10barg, there is a Thread-o-let branch connection to a bleed valve, the branch is 1" SCH 80 and has been found to have severe external corrosion damage, Radiography has calculated the remaining WT to be approximately 1.5 to 2.0mm from the thread root. The valve attached to the branch is a 1" gate valve.

The WT is fine for pressure retention but I am concerned that the thinnest location is at the thread root at the top of the union and the stress raiser that is the thread root. The line is subject to low frequency vibration.

Is there any guidance out there for assessing this situation quickly without resorting to a level 3 analysis?

Thanks in advance
Jim

 

[0707]

Is your external corrosion due to CUI? If I understood, you have a 1" pipe 4.55mm thick, threaded in a Thread-o-let socket, and on the thread of the Thread-o-let where the 1" pipe connects you have 1.5 to 2mm thickness, is that clear? If so, in that case, I will replace the assembly or I will weld the external socket thread to rebuild a conservative thickness.

Cheers

Luis

 

[James01]

Luis

Your review is correct, the damage was not caused by CUI just atmospheric corrosion, the line is in the roof area of a process module.

in order to carry out repair welding I am just as quick to replace the spool piece as the system would still require shuting down purging building scaffold & a pressurised habitat as the remainder of the plant would still be operational.

I am planning on replacing the line in the shutdown in August of this year. But I need to know if it will last that long, my management dont want to shutdown now and I need some more evidence other than gut feel to say if I need to force an outage.

Cheers
Jim

 

[BigInch]

If you have lost more than the corrosion allowance for the particular spool piece, you are most certainly running below code and should replace the line immediately or reduce pressure to whatever value the remaining wall thickness permits.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[0707]

James01

If your piping arrangement shape configuration permits, there a possibility to encapsulate or clamp the line system and keep the unit runing till August.

There are several type shapes of high-pressure clamps, which can be installed without the need of welding which could solve your problem.

Cheers

Luis