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08:00 Aug-18-2006

David Mackintosh

Engineering,
Acuren Group Inc.,
Canada,
Joined Feb 2011
85
ASME cal block sizes for piping

In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.

"The basic calibration block shall be
a section of pipe of the same nominal
nominal size and schedule"
(T-434.3)

This requires a very large inventory of calibration blocks to cover all possible pipe sizes.

The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).

The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.

I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)

Thank you.
David Mackintosh
Acuren



 
06:33 Aug-19-2006

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
Re: ASME cal block sizes for piping Hi David

A thought-provoking and interesting post affecting practical NDT from you, David.

I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.

I think that the ASME requirements are often only paid lip-service. The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remote piping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.

Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.

----------- Start Original Message -----------
: In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: "The basic calibration block shall be
: a section of pipe of the same nominal
: nominal size and schedule"
: (T-434.3)
: This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: Thank you.
: David Mackintosh
: Acuren
------------ End Original Message ------------




 
02:38 Aug-19-2006
UT Guy
Re: ASME cal block sizes for piping ----------- Start Original Message -----------
: Hi David
: A thought-provoking and interesting post affecting practical NDT from you, David.
: I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.
: I think that the ASME requirements are often only paid lip-service. The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remotepiping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.
: Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.
: : In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: : "The basic calibration block shall be
: : a section of pipe of the same nominal
: : nominal size and schedule"
: : (T-434.3)
: : This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: : The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: : The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: : I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: : Thank you.
: : David Mackintosh
: : Acuren
------------ End Original Message ------------

I believe the requirements for piping calibration blocks to be the same nominal size and curvature of the pipes mainly has to do with the circumferential scans that are required by ASME. For small diameter piping the diameter can make a difference inthe circ scans with regards to sound or metalpath.


 
02:44 Aug-19-2006
UT Guy
Re: ASME cal block sizes for piping ----------- Start Original Message -----------
: : Hi David
: : A thought-provoking and interesting post affecting practical NDT from you, David.
: : I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.
: : I think that the ASME requirements are often only paid lip-service. The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remote piping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.
: : Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.
: : : In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: : : "The basic calibration block shall be
: : : a section of pipe of the same nominal
: : : nominal size and schedule"
: : : (T-434.3)
: : : This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: : : The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: : : The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: : : I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: : : Thank you.
: : : David Mackintosh
: : : Acuren
: I believe the requirements for piping calibration blocks to be the same nominal size and curvature of the pipes mainly has to do with the circumferential scans that are required by ASME. For small diameter piping the diameter can make a difference inthe circ scans with regards to sound or metalpath.
------------ End Original Message ------------

BTW I am not the same as Old UT Guy. Anyhow, my previous statement is particularly true as the diameter gets smaller and the thickness gets thicker. In thicker small diameter piping a typical 45 degree angle may not be able to reach the ID. You may need steeper angles to see the ID Notch.



 
09:58 Aug-20-2006

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
Re: ASME cal block sizes for piping I suppose that exemplifies what a Code does - it codifies those actions which an experienced practitioner does anyway, i.e. 45 degree transverse weld scans on thick-wall pipework. So setting sensitivity from the the transverse notches informs whether or not the diameter/thickness ratio lends itself to the 45 degree transvere root scan. Though if it does not reach the ID then Code-adherence will be problematical because I dont think many technicians would have a 38 degree probe to hand and in my experience the weld is often completed and tested before anyone truly examines the technique used. Its not a perfect world!

If the probable hypothesis that the transverse notch is to ensure the defect-detecting capability of the transverse scan, I wonder why T-464-1.3. "Alternate Calibration Reflectors" allows side-drilled holes and yet makes no further provision for such choice, e.g. a sketch showing the dimensions and locations of those SDH's. Or should one take the dimensions from T-434.2.1. Non-Piping Calibration Blocks.

No axe to grind against US standards, be they ASME, API or AWS, but I do think that some of their requirements are complicated, whereas in my experience European Standards, keep it as simple and as cost-effective as possible. Inteested to hear what others think.

Start Original Message -----------
: : : Hi David
: : : A thought-provoking and interesting post affecting practical NDT from you, David.
: : : I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.
: : : I think that the ASME requirements are often only paid lip-service.The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remote piping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.
: : : Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.
: : : : In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: : : : "The basic calibration block shall be
: : : : a section of pipe of the same nominal
: : : : nominal size and schedule"
: : : : (T-434.3)
: : : : This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: : : : The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: : : : The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: : : : I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: : : : Thank you.
: : : : David Mackintosh
: : : : Acuren
: : I believe the requirements for piping calibration blocks to be the same nominal size and curvature of the pipes mainly has to do with the circumferential scans that are required by ASME. For small diameter piping the diameter can make a difference inthe circ scans with regards to sound or metalpath.
: BTW I am not the same as Old UT Guy. Anyhow, my previous statement is particularly true as the diameter gets smaller and the thickness gets thicker. In thicker small diameter piping a typical 45 degree angle may not be able to reach the ID. You may need steeper angles to see the ID Notch.
------------ End Original Message ------------




 
02:18 Aug-21-2006

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: ASME cal block sizes for piping Interesting thread this one!
Perhaps unintentionally, other issues have been raised!

I am rather in favour of the new requirement for "schedule-specific" calibration blocks for pipe girth welds. When directing the beam perpendicular to the girth weld axis the effect of the curvature of the ID is to de-focus the beam and the OD tends to focus the beam. The smaller the radius the more pronounced this effect. By ensuring that at least that variable is fixed, the inspection can be somewhat more reliable.

The ASME pipe calibration block is based on a long notch. Unfortunately ASME does not specify the notch shape (although we seem to assume that a square notch cross section is implied). A square notch will have significant variability in dirctivity of the reflected wave and at 10% of a 25mm wall the 2.5mm high notch will have a fair bit of specular effect compared to a 10% notch in a 6mm wall where the 0.6mm profile will provide a somewhat more spherical backscatter effect.

The other issue raised in this thread was the transverse scan. I have seen very few weld caps removed since my early experiences in nuclear work. But North American AND European codes all seem to expect we are to do a scan parallel to the weld axis (2 directions and from both sides with the beam directed "essentially parallel" to the weld axis).
At least the normative instructions in EN1714 make this a requirement only when required by special agreement.
But trying to make a useful transverse scan on a pipe can be more than just a little challenging! A flat probe on a curved surface has only a small point of contact (EN 1714 also limits the gap for such a condition to 0.5mm). Very little pressure may actually get into the pipe wall and that would be very skewed due to the double curvature. If you curve the wedge to direct the beam parallel to the weld axis the curvature prevents directing the beam into the weld! The weld cap and wedge width also prevent any real access to the weld metal and HAZ. No skewing is possible with such a shaped wedge!
On small diameter pipe (e.g. 50-75mm diameter) milling a curvature for the wedge to fit on the pipe has other effects on the beam. IF the wedge is milled correctly only the nominal centre of the beam still retains the nominal refracted angle intended. All other points result in other angles occurring. Under some conditions there is virtually no pressure entering the pipe from the back of the probe as the incident angle is above the second critical angle.

Unless the pipe diameter is large and the probe dimensions small, the transverse scan is effecively restricted due to geometry. If there is a good probability that there is a failure mechanism in this orientation it may require very specially designed scanning tools...or the fabricator will have to accept the fact that the weld caps will need to be ground flush with the pipe so a propoer examination can be performed.

Ed

----------- Start Original Message -----------
: I suppose that exemplifies what a Code does - it codifies those actions which an experienced practitioner does anyway, i.e. 45 degree transverse weld scans on thick-wall pipework. So setting sensitivity from the the transverse notches informs whether or not the diameter/thickness ratio lends itself to the 45 degree transvere root scan. Though if it does not reach the ID then Code-adherence will be problematical because I dont think many technicians would have a 38 degree probe to hand and in my experience the weld is often completed and tested before anyone truly examines the technique used. Its not a perfect world!
: If the probable hypothesis that the transverse notch is to ensure the defect-detecting capability of the transverse scan, I wonder why T-464-1.3. "Alternate Calibration Reflectors" allows side-drilled holes and yet makes no further provision for such choice, e.g. a sketch showing the dimensions and locations of those SDH's. Or should one take the dimensions from T-434.2.1. Non-Piping Calibration Blocks.
: No axe to grind against US standards, be they ASME, API or AWS, but I do think that some of their requirements are complicated, whereas in my experience European Standards, keep it as simple and as cost-effective as possible. Inteested to hear what others think.
: Start Original Message -----------
: : : : Hi David
: : : : A thought-provoking and interesting post affecting practical NDT from you, David.
: : : : I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.
: : : : I think that the ASME requirements are often only paid lip-service. The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remote piping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.
: : : : Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.
: : : : : In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: : : : : "The basic calibration block shall be
: : : : : a section of pipe of the same nominal
: : : : : nominal size and schedule"
: : : : : (T-434.3)
: : : : : This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: : : : : The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: : : : : The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: : : : : I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: : : : : Thank you.
: : : : : David Mackintosh
: : : : : Acuren
: : : I believe the requirements for piping calibration blocks to be the same nominal size and curvature of the pipes mainly has to do with the circumferential scans that are required by ASME. For small diameter piping the diameter can make a difference inthe circ scans with regards to sound or metalpath.
: : BTW I am not the same as Old UT Guy. Anyhow, my previous statement is particularly true as the diameter gets smaller and the thickness gets thicker. In thicker small diameter piping a typical 45 degree angle may not be able to reach the ID. You may need steeper angles to see the ID Notch.
------------ End Original Message ------------




 
08:05 Aug-23-2006

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
Re: ASME cal block sizes for piping Thanks for your post, Ed. Did you make a slight error though, viz:

"When directing the beam perpendicular to the girth weld axis the effect of the curvature of the ID is to de-focus the beam and the OD tends to focus the beam."?

I believe that should read along the lines of "..directing the beam essentially parallel to the girth weld axis."

I used the formula from your very useful UT2 paper on ndt.net to calculate that for a 12" OD 73mm wall transverse scan, a 30 degree transducer should be used. Luckily we had just taken delivery of such a beast and its is being evaluated against the ASME block notches today. Its a SWSQC 2.25 MHz, 0.38" diameter transducer screwed into a wedge. Should do a reasonable job., especially as the results from gamma (no X-ray here in kazakhstan) even at 25mm partial fill give poor root images.

Our welding engineer will not put himself out on a limb and say that there is no chance of transverse defects in these welds (manual TIG root, SMAW complete) to his credit. In any case the transverse scan is a Code requirement so we shall do the usual of two scans one from each direction and from both sides of the welds, with the caps on.

What happens to transverse scans if ASME Code Case 2235-9 is used to deploy TOFD or (as allowed by the footnote) phased array. Have you come across such scans yet?

Look forward to your reply.

----------- Start Original Message -----------
: Interesting thread this one!
: Perhaps unintentionally, other issues have been raised!
: I am rather in favour of the new requirement for "schedule-specific" calibration blocks for pipe girth welds. When directing the beam perpendicular to the girth weld axis the effect of the curvature of the ID is to de-focus the beam and the OD tends to focus the beam. The smaller the radius the more pronounced this effect. By ensuring that at least that variable is fixed, the inspection can be somewhat more reliable.
: The ASME pipe calibration block is based on a long notch. Unfortunately ASME does not specify the notch shape (although we seem to assume that a square notch cross section is implied). A square notch will have significant variability in dirctivity of the reflected wave and at 10% of a 25mm wall the 2.5mm high notch will have a fair bit of specular effect compared to a 10% notch in a 6mm wall where the 0.6mm profile will provide a somewhat more spherical backscatter effect.
: The other issue raised in this thread was the transverse scan. I have seen very few weld caps removed since my early experiences in nuclear work. But North American AND European codes all seem to expect we are to do a scan parallel to the weld axis (2 directions and from both sides with the beam directed "essentially parallel" to the weld axis).
: At least the normative instructions in EN1714 make this a requirement only when required by special agreement.
: But trying to make a useful transverse scan on a pipe can be more than just a little challenging! A flat probe on a curved surface has only a small point of contact (EN 1714 also limits the gap for such a condition to 0.5mm). Very little pressure may actually get into the pipe wall and that would be very skewed due to the double curvature. If you curve the wedge to direct the beam parallel to the weld axis the curvature prevents directing the beam into the weld! The weld cap and wedge width also prevent any real access to the weld metal and HAZ. No skewing is possible with such a shaped wedge!
: On small diameter pipe (e.g. 50-75mm diameter) milling a curvature for the wedge to fit on the pipe has other effects on the beam. IF the wedge is milled correctly only the nominal centre of the beam still retains the nominal refracted angle intended. All other points result in other angles occurring. Under some conditions there is virtually no pressure entering the pipe from the back of the probe as the incident angle is above the second critical angle.
: Unless the pipe diameter is large and the probe dimensions small, the transverse scan iseffecively restricted due to geometry. If there is a good probability that there is a failure mechanism in this orientation it may require very specially designed scanning tools...or the fabricator will have to accept the fact that the weld caps will need to be ground flush with the pipe so a propoer examination can be performed.
: Ed
:
: : I suppose that exemplifies what a Code does - it codifies those actions which an experienced practitioner does anyway, i.e. 45 degree transverse weld scans on thick-wall pipework. So setting sensitivity from the the transverse notches informs whether or not the diameter/thickness ratio lends itself to the 45 degree transvere root scan. Though if it does not reach the ID then Code-adherence will be problematical because I dont think many technicians would have a 38 degree probe to hand and in my experience the weld is often completed and tested before anyone truly examines the technique used. Its not a perfect world!
: : If the probable hypothesis that thetransverse notch is to ensure the defect-detecting capability of the transverse scan, I wonder why T-464-1.3. "Alternate Calibration Reflectors" allows side-drilled holes and yet makes no further provision for such choice, e.g. a sketch showing the dimensions and locations of those SDH's. Or should one take the dimensions from T-434.2.1. Non-Piping Calibration Blocks.
: : No axe to grind against US standards, be they ASME, API or AWS, but I do think that some of their requirements are complicated, whereas in my experience European Standards, keep it as simple and as cost-effective as possible. Inteested to hear what others think.
: : Start Original Message -----------
: : : : : Hi David
: : : : : A thought-provoking and interesting post affecting practical NDT from you, David.
: : : : : I wonder why the ASME Code is so much more restrictive than European Standards. Europe allows the use of flat blocks when testing girth welds. I suppose this is on the basis that, when parallel scanning, curvature is only an issue on very small OD's when even a miniature angle probe may rock. Blocks may contain either 3mm side-drilled or 1 - 3mm flat-bottomed holes or 1mm notches. I think there is a thickness and material range which I cannot remember off-hand and I do not have the standards in front of me.
: : : : : I think that the ASME requirements are often only paid lip-service. The Code is used worldwide throughout the oil & gas sectors as it is referenced by other US codes apart from BPV such as B31.3. Its not like ASME U-stamped vessels where an AI will be involved and will presumably check the blocks availability and (presumed) use. Where several remote piping fabricators are contracted ensuring conformance is made difficult by the Code, exacerbated by the Article 4 revision.
: : : : : Has anybody run a sensitivity comparison between ASME and EN requirements? Surely they must be comparable. But entrencehed camps on both sides of the pond will ensure that standards globalisation is a long way off.
: : : : : : In ASME PVPC 2004 Sec V Art 4, there are very stringent requirements for piping calibration blocks.
: : : : : : "The basic calibration block shall be
: : : : : : a section of pipe of the same nominal
: : : : : : nominal size and schedule"
: : : : : : (T-434.3)
: : : : : : This requires a very large inventory of calibration blocks to cover all possible pipe sizes.
: : : : : : The requirement is applied only to pipes. The paragraphs for non-piping allow specified ranges for cal block curvature (T-434.1.7) and thickness (T-434.2.3).
: : : : : : The previous edition of the code, PBVC 2001 Sec V Art 5, allowed a range of thicknesses (T-542.2.1) and a range of surface curvatures (T-542.3.4 and T-542.3.5) for piping calibration blocks. During the re-write of Articles 4 and 5, when weld examination became consolidated into Article 4, the “range of value” paragraphs were removed from piping and became applicable only to non-piping.
: : : :: : I'd be glad to hear any comments on this. What was the reason for the change? And does anyone else have a problem with the tight requirements? (Or are they mainly just ignoring them?)
: : : : : : Thank you.
: : : : : : David Mackintosh
: : : : : : Acuren
: : : : I believe the requirements for piping calibration blocks to be the same nominal size and curvature of the pipes mainly has to do with the circumferential scans that are required by ASME. For small diameter piping the diameter can make a difference inthe circ scans with regards to sound or metalpath.
: : : BTW I am not the same as Old UT Guy. Anyhow, my previous statement is particularly true as the diameter gets smaller and the thickness gets thicker. In thicker small diameter piping a typical 45 degree angle may not be able to reach the ID. You may need steeper angles to see the ID Notch.
------------ End Original Message ------------




 
03:44 Aug-26-2006

E. Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: ASME cal block sizes for piping I have attached a small Word file that enhances my explanation to Nigel as
it might be interesting for others on the Forum.

http://www.ndt.net/wshop/attach/nigel_explanation.pdf

Regards
Ed




 
02:38 Aug-29-2006

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
Re: ASME cal block sizes for piping Sorry for my delayed response - I travelled home to my family during the last week and ultrasonics goes slightly (but not competely) on the backburner for a few days!

Thanks for the clarity of your explanation, Ed - and for correcting my (mistaken) view that the circumferential scan was less troubled by beam spread than the transverse scan. Now I am wondering how often pipe-weld defects have been oversized and therefore unnecessarily rejected and repaired. With manual scanning, beam spreads are usually checked on flat blocks in half-skip mode on side-drilled holes where none of the effects you describe occur.

During AUT the effect of beam spread is nullified by measuring the "overlength" of the traditional 3mm flat-bottomed hole, so if the appropriate channel scan gives a signal > 20% from the FBH for 6 mm then the beam spread is considered as 3mm and this is deducted from any relevant indication. This would appear to be reasonable as the calibration reflector is scanned in the same way as the production weld, i.e. if the zone is scanned "bottom-up" skipping in off the ID then the reflector is scanned in the same way and the beam spread deduction will be taken care of. However manual scanning is not executed in the same way and some over-sizing may occur. In critical thick wall welds marginally acceptable slag lengths can be measured as unacceptable.

Has any work been done to quantify these beam spread affects that anyone knows of?


----------- Start Original Message -----------
: I have attached a small Word file that enhances my explanation to Nigel as
: it might be interesting for others on the Forum.
: http://www.ndt.net/wshop/attach/nigel_explanation.pdf
: Regards
: Ed
------------ End Original Message ------------




 


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