AS PER UCS-56 DOES PWHT ASSESSED BASED ON WELD THICKNESS OR VESSEL THICKNESS

[staticmh]

Hi Folks!

This has been an quite significant misconception in regard of ASME Sec VIII Div. 1 UCS-56 PWHT criteria.

Please any body correct me that PWHT is always being assessed based on the maximum weld thickness or it can also be done based on vessel metal thickness.

I'm designing a vessel and it contain a top body blind flange of having thickness of 150mm (With Raised face) & 148mm (Without 2mm Raised face)

There is a one NPS-4" nozzle welding with RF Pad as set on, instead of set in. The reason that Why i'm using set on is that, as per my understanding i am exempting the PWHT not to calculate the higher weld thickness (Above 38mm) which can conclude the PWHT as per UCS-56 and saving the cost of PWHT.

Below is my case all the welds shown as per exact situation.

148mm is the Blind flange thickness.


Please advice whether PWHT shall be yes for this case or NO ?

 

[goutam_freelance]

It is based on weld thickness for groove welds in general. For fillet welds it is based on throat thickness. So your weld may not require PWHT.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[staticmh]

thank you very much for your feedback.

If its based on the weld thickness then why PV Elite is calculating it as PWHT "Yes"

My top body blind flange is coming as impact test and i have checked as impacted test in software but now my question is that on what basis PV elite is showing as "YES" in MDMT summary.

See below...

 

[weldstan]

For P No. 1 materials weld thickness governs the requirement for PWHT. For low alloy steels like P4, P5, P15E the base metal thickness governs. For your case, why would you not PWHT the entire vessel including the 4" set on nozzle?

 

[DVWE]

For low alloy steels like P4, P5, P15E the base metal thickness governs.

I've never heard that one before, weldstan. I've always understood these materials to be governed by the weld thickness also. Care to elaborate?

The devil is in the details; she also wears prada.

 

[mk3223]

It may be helpful if:
First, try to fix the input data, i.e Curve, MDMT, etc.
And then, to verify if the Gov Thk of 37mm is correct.

 

[SnTMan]

staticmh, based on the definitions of "nominal thickness" per UW-40(f)(3) and (5)(d), I am getting nominal thickness per the sketch of 17.1 mm. This may or may not need PWHT, as the material is unknown. Could the software be invoking UCS-68(b)? Can't say, as the MDMT is unknown as well.

It appears to me the Blind Flange "Governing Thickness" per the report is determined per UCS-66(a)(1)(a). That is, 148 / 4. This is not the same as the "nominal thickness" for determining PWHT per UW-40.

Who knows what the software is doing? In end, you are the designer. To PWHT or not is your decision.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[weldstan]

DVWE, I no longer have access to ASME I, VIII, B31.1 and B31.3 so I am unable to quote "exemptions from PWHT" but from my experience the base metal thicknes governed commonly used low alloy steels and it is quite clear that the weld thickness governed for low carbon steels.

 

[r6155]

staticmh
1)PWHT is nor required for P1 number in your example
2)Check calculation of UG-37, it may be that reinforcement is not necessary.

Regards

 

[staticmh]

SnTMan, as per my interpretation PWHT is only require if the weld thickness increase from 38mm, although in my case there is not any full penetration of the top blind flange nozzles. which can conclude the weld thickness above the 38mm. However, as per my judgement, PWHT is exempted.

But why i am discussing here that might be possible, is there any clause in ASME SEC VIII Div. 1, which i'm not considering during the assessment of the PWHT.

As per UCS-56 see below where it say about weld thickness instead of metal thickness.

About governing thickness terminology describe in UCS-66(a)(1)(a) is totally about impact test. It is not for the consideration of the PWHT criteria assessment.

This PV elite software is having alot glitches, even we cant blindly trust and use it. Meanwhile, already under discussion with the software developer team to rectify and validate it. If its correct then tell us the basis of this YES shown in report.

Being a designer, as per my judgement PWHT is Exempted but our client point out at very last stage of the project that why it is being coming YES in report. This is worry point for us now. If you can advice on it please share your opinion.

 

[staticmh]

weldstan,

On what basis you can claim simply that P-1 material shall be PWHT, untill unless the weld nominal thickness may not concluded higher than 38mm ? do you have any basis please share with me..

I'll be appreciated to have your positive feedback.

Furthermore, at this certain thickness of 150mm Impact test is required Which we are performing but as per my judgement PWHT shall be exempted but issue is that the software is declaring as YES. which is the contradiction in between my manual assessment and software programmed.

 

[r6155]

@ staticmh
"in my case there is not any full penetration of the top blind flange nozzles"
Oh NO!- Full penetration is required !!!!.
It is not possible to speak of impact test when a complete penetration is not carried out.
You are wrong.

Regards

 

[SnTMan]

staticmh, r6155, can we agree that full penetration is thru the nozzle neck rather than the blind?

It is not possible to speak of impact test when a complete penetration is not carried out.

Well I can't agree with this. It is possible to speak of impact test when no welding is performed at all.

...is there any clause in ASME SEC VIII Div. 1, which i'm not considering during the assessment of the PWHT.

As I said before the only added PWHT requirement that may apply is per UCS-68(b). If that does not apply then I do not believe PWHT is required in your case.

I am sorry your are facing this difficulty with the software. The job is hard enough as it is

Best of luck with both the vendor and your client.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[weldstan]

staticmh, I possibly made an inaccurate assumption that your vessel required PWHT. If the nozzle is only welded to the bolted on blind flange and the vessel does not require PWHT, no PWHT is required for the weld in question.

 

[DVWE]

DVWE, I no longer have access to ASME I, VIII, B31.1 and B31.3 so I am unable to quote "exemptions from PWHT" but from my experience the base metal thicknes governed commonly used low alloy steels and it is quite clear that the weld thickness governed for low carbon steels.

Not to dwell on the subject too much, or hijack this thread, but ASME Div 1 and B31.3 are clear that PWHT is based on weld thickness for CS and low alloy steels, all the way up to P15E.

The devil is in the details; she also wears prada.

 

[DVWE]

Here is a small snippet from Div. 1

The devil is in the details; she also wears prada.

 

[DekDee]

DVWE,
Maybe for ASME VIII but not for B31.3.
B31.3 nominates control thickness which is the lesser of weld metal thickness and base metal thickness.

331.1.3 Definition of Thicknesses Governing PWHT
(a) The term control thickness as used in Table 331.1.1
and Table 331.1.3 is the lesser of
(1) the thickness of the weld
(2) the thickness of the materials being joined at the
weld or the thickness of the pressure-containing material
if the weld is attaching a nonpressure-containing material
to a pressure-containing material.

staticmh,
Your "nominal thickness" can be calculated from UW40(f)(5)(d)
I will also ask - why is it shown as a partial penetration weld ?

 

[DVWE]

Agree, DekDee.

However, more often than not, the weld metal thickness is the driving factor. Seldom is the base metal the lesser of the two. The exception to that is certain branch welds, where the weld metal thickness can be greater than base metal thickness. Again, I didn't want to get too far into the weeds.

That rule applies to CS and low-alloy steels the same.

The devil is in the details; she also wears prada.

 

[staticmh]

can we agree that full penetration is thru the nozzle neck rather than the blind?

Yes, its through the nozzle neck (Set On) instead of Set in.


Impact is not exempting at this higher thickness, However impact test is considered in design.


I'm seeing that Pvelite developer team are not fully engageing in the settlements of the glitches and even they are updating the things silently.

Recently, i have been came accoss one big blunder in this software. it was regarding UG-44(b) PD value consideration.

As per UG-44(b) the PD value shall be MAWP, but they programmed the PD value as Design P in software. UG-44(b) included since the first day of release of ASME SEC VIII Div. 1 2019 edition.

But its developer responsibility that they suppose to first ensure whether software is updated and comply as per latest code or not, then validate it. But unfortunately they are not doing it efficiently.

See below reference UG-44(b) image & Pv Elite V22 to V23 updated comparison, but it is ridiculous that they have not shown in any revision history and nor stated in "whats new in PV elite circular"

 

[staticmh]

DVWE,


everybody is well aware about the PWHT requirement, we are here to share our different region experience with positive constructive feedback. However PWHT shall be always evaluate based on weld thickness.

Was just trying to get the opinion of different industry experts like you

But the main focus is now on the software consideration, which it is being used and showing as YES. that is obvious wrong. If you have any feedback on PV elite experience of glitches, please do not hesitate to share. Thank you.