angle of inspection

Date 10-02-2008 11:19

It's greater than = 30 degrees off the plane of the item to be inspected, and 24" or less. It's found in ASME Section V article 9.

By kipman

Date 10-02-2008 12:56

Gerald as always is right on the money. However, ASME Sec V is the only place that is found - have a real good look through AWS D1.1 and you will find that there is no requirement or information on the VT technique that must or should be used to examine a weld or other component. It only gives acceptance criteria.
I personally think that it is very good practice to adhere to the 30 degree / 24" rule of ASME V, no matter what code you are working to. I have done alot of experimentation looking at welds at, for example, an angle of less than 30 degrees. You might be surprised by how much you can miss if you don't use a mirror to correct the angle.
Mankenberg

By jrw159

Date 10-02-2008 14:24

I know it is not in D1.1, but I seem to remember AWS addressing angle, distance, and lighting requirements. I am unable to find it at this time, and will keep searching.

Maybe I am way off base?

jrw159

By ctacker (****)

Date 10-02-2008 13:52

Thanks, I remember seeing it, just couldn't remember if it was in the books I studied or an actual standard or even a job spec. I try to stay within 12 inches when looking at welds also but sometimes its impossible!

By 3.2 Inspector (***)

Date 10-02-2008 13:58

It very impossible indeed, and so is the lux requirement.
IMHO its one of thoose things we have to live with.

3.2

By CWI555

Date 10-02-2008 15:08

There are times when you can be to close. As people age the lenses of the eye tend to harden and the muscle control of the same gets a bit weaker. This makes it hard for some people to focus on the nearer by object. You will note in the illustration that 6" is mentioned. For an 18 year old, thats about where they can focus, and that will extend up to 12-14" with age even with corrected vision. On the other side of that, if you get past 24" your ability to resolve to a proper sensitivity level is impaired. While AWS does not specifically mention it, it is inferred. As for angle, the ASME portion is 30 degrees as judged from the surface to be examined. The ASME requirements are based on the 20/20 acuity standard developed in the late 1800's. The 20/20 value is the baseline for 100 percent visual acuity. That does not necessarily mean that is required physically to note the smallest rejectable discontinuity. For instance: simple line detection. (18 percent nuetral grey card) has a 1/32 black line (750 micro meters). a legally blind person (20/200) can reliably detect that line.
AWS has taken all that into consideration in their physical requirements for CWI's.

There are a host of factors that play into this (parallax, training, physiological, luminance/chromatic etc contrast, sharpness to name a few) but at the end of the day, the inspector will have been expected to detect the rejectable indications as found in the relevant code. If you are looking at something less than 30 degrees and more than 24" away without having qualified your ability to detect the required minimal elements, then you will find yourself trying to explain why you did that when there are industry standards out there that as a minimum, give relevant information in that regards. If for instance the crack opening dimention is < 25 micrometers/1mil and this is the probable flaw type, and your looking at it from 4 feet away and at an angle nearly parallel with the examination surface, your going to find it really hard to justify why you didn't see it should something go south on that component.

My opinion for what it's worth,
Gerald

By ctacker (****)

Date 10-02-2008 15:13

>My opinion for what it's worth,
>Gerald

Worth much, thanks for taking the time to explain!