UT Acceptance Criteria for Structural Aluminum

Date 02-13-2008 14:26

The application is an 6061-T6 aluminum crane boom. Due to the capacity of the boom we need to fabricate an aluminum box section that will be inspected, heat treated then re-inspected using VT, PT and UT. We will use UT instead of RT because out NDE contractor tell us that RT cannot properly access all of the connections. The acceptance criteria for VT and PT are clearcut. That being said AWS D1.2, clause 5.13.1 states that "When ultrasonic testing is required by the contract documents, the extent of testing, the procedure and the acceptance criteria shall be specified therein." In this case the customer has not specified any welding or inspection requirements. We don't want to take to develop our own UT acceptance criteria and want to ensure that the welds meet an industry standard or industry accepted acceptance criteria. Any suggestions for UT acceptance criteria for a 6061-T6 weldment? We have great confidence in our UT Tech; however, we want to ensure that if someone is challenged (ie NDE Tech or the welds) that we are all on the same page as to what the acceptance criteria is.

Sean

By swnorris (****)

Date 02-13-2008 17:19

Sean,

The only way to get all involved on the same page is to go back to the author of the contract documents and have that person specify the acceptance criteria. State that there is no mention of acceptance criteria, and in accordance with AWS D1.2, paragraph 5.13.1 requires that the acceptance criteria for ultrasonic testing be specified in the contract documents. Get those requirements in writing, signed, and retain a copy in your project folder.

By CWI555

Date 02-13-2008 17:56

Good advice.

By 803056

Date 02-13-2008 18:04

Wow, 6061-T6 for a crane boom! That's one of the last materials I would select for an application like that. The properties even after PWHT don't meet the mechanicals of the as-purchased condition.

Make sure you qualify a procedure with the same post weld heat treatment so you know what the final mechanical are.

Best regards - Al

By Bill M

Date 02-14-2008 14:09

Make sure you get the aluminum ultrasonic cal blocks too!

By ssbn727 (*****)

Date 02-15-2008 13:59

I agree with Al... Sounds like a problem waiting to happen!!! :) :) :)

Respectfully,
Henry

By Sean

Date 02-15-2008 19:08

I'm not involved in material selection for the design, I'm just helping them with some welding details. Everyone I know of that is involved in the design is aware of the effects of welding and the PWHT on the mechanicals. This material wouldn't have been my first choice (or the designers I think); however, there is an issue with material size &/or supplies. The design has accounted for the limitations of the 6061 (wrt to its welding and the effect of the PWHT). All welding procedures are supposed to be qualified and there is a coupon being done during production to verify the PQR results and validate the mechanicals of the components after the PWHT.

As for the UT acceptance criteria, we are trying to go back to the customer to obtain UT acceptance criteria. We have also in our internet search for acceptance criteria found the following Norwegian standard (M-102) that we feel will be useful (http://www.side2.webkonsepter.no/dok/tekniskestandarder/M-102.pdf).

Sean

By 803056

Date 02-15-2008 19:37

Its better than a sharp stick in the eye!

As you indicated, you will be contacting the client to obtain their approval before implementing the Norwegian standard.

You might consider making several calibration standards with different diameter side drilled holes and perhaps a couple of saw cut notches of varying depths to compare their reflected signals.

I did something similar for 1/4 inch thick carbon steel. The minimum base metal thickness under AWS D1.1 is 5/16ths. I made the calibration standard using 1/4 inch thick bar with a 1/16 and 1/32 inch diameter holes as a means of establishing the basis of acceptance or rejection. The client agreed with the method and we agreed that anything with a gain of 6 db or less was rejected, anything more than 6, but less than 12 db and over 1 inch in length was rejected, and anything over 12 db was accepted. The sensitivity was based on the signal from the 1/16 inch hole set at 60% of the screen height. In this case the client didn't realize D1.1 had the thickness limitation.

Good luck. It sounds like you have a rational approach to present to your client.

Best regards - Al