ut

Date 01-10-2006 22:05

John
The acceptance chart has several factors to take into account to get to the ratings..Class A, Class B, Class C, Class D.
If you have gotten that far then it is a matter of evaluating the length of your discontinuity by using the 6 dB drop method to determine if it is acceptable per those Classes.

Now if you need to figure which Class something you find with UT is in, then peak up on your indication and then take out dBs until you get the signal to the reference line, now note how many dBs your gain is at.
This is your Indication level(a), take that and subtract your reference level(b) from that figure, then subtract that answer from your attenuation figure(c)[attenuation = Sound Path minus 1, times 2] and that will give you your Indication rating(d). Now look at your table 6.2 (for statically loaded structures) and find your material thickness and transducer angle to see which class your Indication rating(d) falls into.

ie. 70* transducer with 1/2" material
Class A = +5 or lower
Class B = +6
Class C = +7
Class D = +8 and up

If I mis understood your question post the question again.
John Wright

By - Date 01-10-2006 23:06

John,
Looks like John65 has a TYK problem (Class X welds).

John 65,
The Class X acceptance criteria of Figure 6.8 require that the UT tech size for both length and width of the reflector. Easier said than done, especially on a TKY. When L and H are determined as per the sketch at the top of the Figure (i.e. the size of a rectangle that totally encloses the reflector) those values are compared to the appropriate table of Figure 6.8 based on where in the weld the reflector is located (i.e. either "root" or not root) to determine acceptance. If you have an indication that is determined to be 1/8" in width, for instance, the maximum allowable length would be 2". Over 2" would be a reject.

I've been on a number of projects for which Class R was used instead of Class X (or Level A instead of Level C per API-RP-2X), even though a comparison of the two acceptance criteria would seem to indicate that Class R is more stringent. This was done simply because Class R is much faster and easier to apply. Essentially, instead of having the UT techs spend hours and hours of evaluation time in using Class X, it was determined that for the project as a whole it was more desirable to use an amplitude/length criteria (Class R) because it is much faster, even though in theory there could be more rejects.

Hope this helps.
Mankenberg

By jwright650 (*****)

Date 01-11-2006 11:10

Good catch Kip! :)
I read the question too quickly and took Class "X" as an algebraic expression("X" could stand for anything). As you can tell, I don't get to see many T,Y,K connections in my type of work.(thank goodness)
John Wright

By - Date 01-11-2006 14:36

Come on John, TKYs are alot of fun.
Kip

By JOHN_65 Date 01-13-2006 18:05

Thanks Kip for the information. I still have some more doubts on the same subject. Please help me over this.
1. For TYK root discontinueties the graph (fig.6.8) shows that below defect width of 1/16th inch as accept without a limit[is there no limit?] and also on the x-axis what does 6" or D/2 convey.Also since porosities in the root normally do not have enough amplitude and could be below disregard level. So does it mean that it is acceptable throughout the length of the weld.
2. For internal reflectors and other welds the graph (fig.6.7) has any* written there at the bottom and says reflectors below standard sensitivity are to be disregarded. Does it mean that below disregard level defects are accepted throughout the weld length. On the x-axis what does 6" or D/2 convey for length.
3. For class R graph (fig.6.7) what does the statement ''evaluate over this length ( not to exceed D/2 where D is diameter) '' convey.

Regards,
John.

By - Date 01-13-2006 19:20

John,
1. For Figure 6.8, you are correct in that if a reflector is determined to be 1/16" or less H, then unlimited length is acceptable (this is root area only).
For the definition of D/2, you have to go to the sketch at the top of Figure 6.8. D is the tube diameter, and according to the second general note at the top, D/2 will come into play only when the brace diameter is less than 12".
For porosity, you have to look at the text at paragraph 6.13.3.2(1), where it says that for spherical reflectors to use Class R.
2. (I think you meant fig 6.8 here) if you note, the bottom horizontal line representing H does not correspond to a dimension on the left axis. What this effectively means is that the standard sensitivity level is what is used to control the minimum H, and below standard sensitivity is acceptable regardless of length.
D/2 is defined in the parentheses ("WHERE D IS DIAMETER")
3. What "evaluate over this length (not to exceed D/2...)" means is that, for instance, if the thickness is 1" you evaluate the length of accumulated (i.e. intermittent) reflectors over a length of 6". So you pick your worst 6" and evaluate. If the thickness is 1" and the diameter is only 10", for instance, then you would evaluate over a length of 5" (D/2) - so you would pick the worst 5" and evaluate.

Hope this helps,
Mankenberg

By JOHN_65 Date 01-14-2006 14:18

Thanks a lot for the information kip.
Regards,
John.

By - Date 01-14-2006 14:41

Anytime.
Mankenberg

By jwright650 (*****)

Date 01-14-2006 15:03

Kip,
We need your help over here....

http://www.aws.org/cgi-bin/mwf/topic_show.pl?id=8385

John 65, sorry for the hijack of your thread.

John Wright

By - Date 01-14-2006 15:25

You don't need my help there. You got it. There is no restriction on diameter for fillet weld qualification. Should there be? I suppose everyone would have an opinion on that.

I think (my opinion) this is generally viewed as not being that big of an issue, because due to the nature of most structural steel jobs there just usually are not a lot of critical small diameter fillet welds. On a lot of the jobs I've been on the task of small diameter fillet welding is generally (but not always) given to guys that can handle it (6GR or 6GR+box tubing guys), otherwise there tends to be a big mess made with alot of cleanup time.
Mankenberg

By vonash

Date 01-16-2006 21:00

Well golly,
We don't need kip's input in order to survive.

By jwright650 (*****)

Date 01-16-2006 21:25

Ok....Play nice

By JOHN_65 Date 01-13-2006 17:42

Thanks john for the information.

By reyrons Date 06-03-2007 01:39

Hi 2 all. I'm doin UT using class x acceptance criteria. Just want 2 check if my interpretation is correct. If weld thk is 12mm, discontinuity height of 3mm located at root region. What is d max allowable individual length? Which height will I use on Fig 6.8? Is it (a) 1/4 (6mm) OR Tw/4 which has a limit up to 12mm length, or d other (b) 1/8 (3mm) which has a limit of 50mm? I'm confuse coz Tw/4 is also equal to 3mm on this case.

Thanks 4 d help

Reyrons.