minibenny
Mechanical
- Oct 28, 2013
- 21
I've can't seem to find a good answer to a few questions I've been trying to solve. I'm hoping someone can lead me in the right direction. Perhaps an ASME interpretation is out there that someone can direct me to...
My first question is whether a WPS developed per ASME Sec. IX, QW-193 needs to be supplemented with impact testing, if the tubesheet is not exempt from impact testing per UCS-66(a) or UHA-51(d)(3)?
If an I.T. WPS is required, as far as I know, CVN's can't be done on the tube-to-tubesheet mock-up due to geometry, so a butt-joint weld coupon would probably need to welded in order for CVN's to be done. Whether that is an acceptable way to do this, I'm not sure. But, I don't see why not.
Now, if I.T. is required, I assume the minimum qualified base metal thickness would need to be at least the thickness of the tube. Per QW-403.6, the minimum qualified base metal thickness is half the thickness of the PQR coupon, if the PQR coupon is less than 1/4" (6mm). So, in order to qualify for a 12 BWG (0.109" nom. t) tube, the PQR coupon would need to be 0.218" (5.5mm) or thinner. This is fine, but from my understanding, there is an issue for qualifying for 16 BWG or thinner tubes.
The thinnest subsize specimen shown in SA-370 is 0.098" (2.5mm). Per SA-370, at least 0.020" (0.5mm) must be removed from the surfaces of the specimens. So, the thinnest weld coupon allowed, prior to removing 0.020" (0.5mm) from each side, is 0.138". If a 0.138" thick butt-joint coupon was welded (and straightness maintained with no hi/low), the minimum base metal thickness qualified could be 0.069".
How do you qualify for a 0.065" thick or 0.049" thick tube?
Is it exempt because the thickness of the tube is below 0.099" (2.5mm) (see UHA-51 and UG-84(c)(3)? If so, how should the minimum qualified thickness be written in a WPS?
Example: We have an impact tested WPS (not a QW-193 procedure) with a minimum qualified base metal thickness of 0.100" (the thickness of the PQR coupon was 0.200"). If we were to apply this WPS to a tube-to-tubesheet joint with 14 BWG tubes (0.083" nom.), as far as I know, the WPS would not be qualified because of the thickness of the tube. However, since the tube is below 0.099" thick, is it exempt from impact testing? But, the tubesheet it gets welded to is not exempt from impact testing, so an impact testing WPS is required I presume. Had impact testing not been required, the 0.200" PQR coupon could qualify the WPS to 0.0625" minimum base metal thickness. It is possible the WPS could be written with both impact testing applicable to material thickness ranges form 0.100" to _______", and non-impact tested thickness ranges of 0.0625" to ________"? Could the non-IT part apply to the tube, and the IT part apply to the tubesheet?
I'm needing to develop a couple tube-to-tubesheet WPS in a very timely manner, so any help is greatly appreciated! Thanks.
My first question is whether a WPS developed per ASME Sec. IX, QW-193 needs to be supplemented with impact testing, if the tubesheet is not exempt from impact testing per UCS-66(a) or UHA-51(d)(3)?
If an I.T. WPS is required, as far as I know, CVN's can't be done on the tube-to-tubesheet mock-up due to geometry, so a butt-joint weld coupon would probably need to welded in order for CVN's to be done. Whether that is an acceptable way to do this, I'm not sure. But, I don't see why not.
Now, if I.T. is required, I assume the minimum qualified base metal thickness would need to be at least the thickness of the tube. Per QW-403.6, the minimum qualified base metal thickness is half the thickness of the PQR coupon, if the PQR coupon is less than 1/4" (6mm). So, in order to qualify for a 12 BWG (0.109" nom. t) tube, the PQR coupon would need to be 0.218" (5.5mm) or thinner. This is fine, but from my understanding, there is an issue for qualifying for 16 BWG or thinner tubes.
The thinnest subsize specimen shown in SA-370 is 0.098" (2.5mm). Per SA-370, at least 0.020" (0.5mm) must be removed from the surfaces of the specimens. So, the thinnest weld coupon allowed, prior to removing 0.020" (0.5mm) from each side, is 0.138". If a 0.138" thick butt-joint coupon was welded (and straightness maintained with no hi/low), the minimum base metal thickness qualified could be 0.069".
How do you qualify for a 0.065" thick or 0.049" thick tube?
Is it exempt because the thickness of the tube is below 0.099" (2.5mm) (see UHA-51 and UG-84(c)(3)? If so, how should the minimum qualified thickness be written in a WPS?
Example: We have an impact tested WPS (not a QW-193 procedure) with a minimum qualified base metal thickness of 0.100" (the thickness of the PQR coupon was 0.200"). If we were to apply this WPS to a tube-to-tubesheet joint with 14 BWG tubes (0.083" nom.), as far as I know, the WPS would not be qualified because of the thickness of the tube. However, since the tube is below 0.099" thick, is it exempt from impact testing? But, the tubesheet it gets welded to is not exempt from impact testing, so an impact testing WPS is required I presume. Had impact testing not been required, the 0.200" PQR coupon could qualify the WPS to 0.0625" minimum base metal thickness. It is possible the WPS could be written with both impact testing applicable to material thickness ranges form 0.100" to _______", and non-impact tested thickness ranges of 0.0625" to ________"? Could the non-IT part apply to the tube, and the IT part apply to the tubesheet?
I'm needing to develop a couple tube-to-tubesheet WPS in a very timely manner, so any help is greatly appreciated! Thanks.
