I believe that with gamma you can have 2.0, with x-ray 1.8, and composite 1.3
I have also seen some labs try to add in there densitometer tolerance to allow an even lower density, that never worked.
Hogan's right. 1.8 min for x-ray (single film), 2.0 min for gamma ray (single film), and 1.3 min for each radiograph for composite technique (for either x- or gamma ray). It's a requirement (the word "shall" is used). See Section V T-282.1. Of course, there are all sorts of other requirements as regards density (e.g. density variation between IQI and area of interest, etc).
Mankenberg
Hogan and Kipman have the right of it in regards to the requirements. However, I seem to recall you asking some questions from the oil and gas world.
I've ran across your source of confusion, both in that, and the section VIII world, which btw, got it's start back in the day during the early issuances of ASME III.
ASME V itself was an unmitigated cluster F$$$ when it was first issued, as were the no density limitations or odd ball limitations as found in winter 71 section VIII D1, Summer 73 Section III, 74 Section V, etc.
Most of these were clarified by 77 and forward but one thing that lived on was the statement in Section VIII UW-51 Which stated "The requirements of T (that years place of residence for that paragraph, which more recently is T-285) of Article 2 of Section V are to be used only as a guide. Final acceptance of radiographs shall be based on the ability to see the prescribed penetrameter image and the specified hole or (in later years) the designated wire of a wire penetrameter"
Anyone who has worked to Section VIII in the late 60's and early 70's can tell you what a mess it was. It makes very interesting reading to see what they were thinking at the time. Especially when you get a hold of additions that pre-dated the use of Section V.
API has a hand in this confusion as well as exemplified by this dated (02) paragraph out of API 620:
7.15.1.1
Except as modified in this section, the radiographic
examination method employed shall be in accordance
with Section V, Article 2 of the ASME Code. The
requirements of T-285 in Section V, Article 2, are to be used
only as a guide. Final acceptance of radiographs shall be
based on the ability to see the prescribed image quality indicator
(IQI) (penetrameter) and the specified hole or wire.
As you can see, they pretty well just copied Section VIII. Why re-invent the wheel? right?
The kicker is if you didn't research the code and go back several years, the intent of "are to be used only as a guide" is lost.
Lately, to ASME's credit, they have been catching up with modern business practices in which dime store lawyers/code interpreters and sometimes real lawyers are taking vagaries like that to the bank. The wording changes are subtle, but very very important.
The 04 Section VIII read nearly word for word like the 02 API 620.
New to the 08 addenda of section VIII is the following:
"(a) All welded joints to be radiographed shall be examined
in accordance with Article 2 of Section V except as
specified below."
followed by three conditions that are subparagraphs of that one. One of which is the old language, but with the new caveat at in the lead paragraph (UW-51a)
"(3) The requirements of T-285 of Article 2 of Section
V are to be used only as a guide. Final acceptance of
radiographs shall be based on the ability to see the prescribed
penetrameter image and the specified hole or the
designated wire of a wire penetrameter."
The subtle but absolutely most important difference to me is rather than specifically exclude the remainder of the Sect V art 2 requirements, UW-51a 08 add. specifically clarifies the intent with this "examined in accordance with Article 2 of Section V except".
Going to section V article 2 you'll find this paragraph:
"T-221.2 Procedure Demonstration. Demonstration of
the density and image quality indicator (IQI) image requirements
of the written procedure on production or technique
radiographs shall be considered satisfactory evidence of
compliance with that procedure."
Demonstration of the ""Density and"" being key.
So with that it's been clarified that the intent is to keep densities within the range of para T-285.
It also clarifies this paragraph in the 08 addenda of Section VIII
"(2) A written radiographic examination procedure is
not required. Demonstration of density and penetrameter
image requirements on production or technique radiographs
shall be considered satisfactory evidence of compliance
with Article 2 of Section V."
If one doesn't get you the other will.
With that, every code that reference Section VIII is turned on its ear. (API 620, API 650 etc and other ASME codes)
The intent never was to allow low densities.
Now to get more specific about your statement/question (which I've heard more times than I care to recollect) "as long as I can see the required wire".
That goes back to the intent, and what an image quality indicator is.
An IQI is a spatial resolution gage, not a contrast sensitivity gage.
There is a world of difference between those two. This is why you can see a wire at much lower than allowed densities. The IQI measures this in terms of Geometric unsharpness or blur. Obviously if the image is blurred excessively, it's not going to do you a lot of good.
When you start getting into contrast sensitivity, you're getting into the RT systems ability to pick up the contrast of a small area against the back drop of a larger area. I.E. A crack against the larger volume of the weld. If that crack is blurred I.E. no spacial resolution, you're not going to see it and you're not going to see it if you don't have sufficient change in optical density either (contrast sensitivity)
To sum it up, to see and qualify a flaw, spacial resolution alone will not cut it (IQI). It's nothing more than a blur/blow check. That is where the density requirements come into play. If your meeting the density requirements and the IQI requirements, and the film class requirements, then it can be safely assumed that the contrast sensitivity is obtained. I've put that to test personally utilizing both hole and wire type IQI's and SE 1647 contrast sensitivity gages. You cannot have one without the other.
/edited for spelling
Thank you, you have pinpointed my issue, i have not read your post in detail yet but i see that you have adressed some things that im wondering about.
CWI555 i will be picking your brain a bit more on this after i read you reply in detail, again thank you.
MDK
SO ......
In UW-51 Radiographic examination of welded joints
(a) ALL welded joints to be RT SHAL be examined in accordance with Article 2 section V except as specified below......
In short Am I correct in thinking that all 3 exceptions need to be considered?
(1)Radiographs and Records..............................................
(2) A written procedure .............................................
And now the one that I just cant seem to make any sense out of
(3) the requirments of T-285 are only to be used as a guide............final acceptance is based on the ability to see prescribes PENE or wire.................
I would think that fist we satisfy number 1 records.
Then number 2 proceedure
And finaly 3 requirments of 285
No matter what I would need to show my density to prove that im in compliance with art2 sec v.
As for t-285 and the statement to be used as a reference only....only appies only to T-285 correct.
And T-285 seems to be about documentation not density.
By CWI555 
Date 05-04-2009 15:48
Edited 05-04-2009 15:52
"(2) A written radiographic examination procedure is
not required. Demonstration of density and penetrameter
image requirements on production or technique radiographs
shall be considered satisfactory evidence of compliance
with Article 2 of Section V."
Key wording "demonstration of density and penetrameter".
It's not an and or situation, it's inclusive and mandatory. Paragraph (3) is assuming the requirements of Paragraph (2) have already been addressed.
Now have a look at Section V T-285
"T-285 Evaluation by Manufacturer
The Manufacturer shall be responsible for the review,
interpretation, evaluation, and acceptance of the completed
radiographs to assure compliance with the requirements of
Article 2 and the referencing Code Section. As an aid
to the review and evaluation, the radiographic technique
documentation required by T-291 shall be completed prior
to the evaluation. The radiograph review form required
by T-292 shall be completed during the evaluation."
No mention of density requirements changing in the paragraph. What you can do is eleminate the tech sheet per T-291 if you desired (not a good idea)
All in all, the latest revision of Section VIII D1 has in my eyes clarified the density requirements and intent thereof for all. Before it wasn't so clear, and if someone wanted to pass off some bad film ( to light) they could under the wording given. Especially after 96 when wire penetrameters effectively became legal to use across the ASME board and others (allowed earlier, but not by all sections)
Still, even given the blantant clarification I hear people argue "well if I can see the wire why isn't it good"?
Where a hole type penetrameter is judged by the absence of material, I.E. the hole,
The wire type is judged by the ability to see the presence of material, I.E. the extra thickness.
In both cases that brings you back to boundary and edge detection.
Anyone who's ever shot with the hole type has probably run across the times when you can see the plaque with no problem, but not the hole.
This is due to the additive value of the plaque in contrast to the thinner sections around it.
The same logic is applied to the wire, the wire is visible due to the contrast of the added material of the wire over the thinner areas around it.
Where a hole and a wire type differ is, the hole has an added step in that you have to be able to see the 2T hole I.E. the absence of the material within the plaque itself. Some would argue the spacing between the wires serves the same purpose, but the regular geometric pattern of the wire makes it easier on the eyes, and therefore easier to pick out at lower densities.
Typically, you can see a hole type down to 1.5 and a wire down to .9 HD assuming your GU is good (which is all the image quality indicator is to begin with, that being a blur/sharpness gage as a measure of technique rather than a measure of what potential flaws can be seen)
have a look at this, and tell me whats easier to pick out:
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQOQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQOQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
The field of Q's above is a representation of a common viewing field with common qualities with the exception of two "O"s planted in the body of them.
It's not so easy to pick those "O"s out. This represents looking for the lack material.
Now lets look at added material.
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ
It's a lot easier to see that added value vs the lack of a value. (bold Q)
That does not mean Wires are crap. What it does mean is that it has to be remembered what an IQI is there for, and not turn into an FLAW Quantification indicator. There is no FQI.
That is my understanding of the matter.
Regards,
Gerald
