Terminologies in asme 9

[duongwe]

i have read some standards as ASME 9, i see "essential" & supplementary essential" & "nonessential" on some table QW ...
So i didn't understand those terminologies which was effected to CVN test how...
Somebody can explain to help me about terminologies.

 

[DVWE]

Which parts of Section IX did you read?

 

[duongwe]

i didn't. so you can be brief not it for me. thanks a lot

 

[DVWE]

It is explained in QW-251.

 

[trottiey]

I'll take pity on you. I remember having to re-read that paragraph many times before I finally got it.

Basically, your qualification coupons have to be similar to your production welds, but they don't have to be identical. The "essential variables" are the important things that have to be the same (within prescribed limits) in the production welds as they were in the qualification welds. The "non-essential variables" are things that are important enough that they should be documented in your weld procedure, but the code doesn't require you to qualify them.

If your vessel will never get cold, you don't need to worry about the "supplementary essential variables." But if it will operate below certain limits, you will have to do CVN tests on some weld coupons. For those weld coupons that will be CVN tested, and only those coupons, the supplementary variables are essential variables.

This is just a rough outline to orient you in the right direction. There is no substitute for reading the code.