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UW-16 (f)(2) weld size exemption and Compress

UW-16 (f)(2) weld size exemption and Compress

UW-16 (f)(2) weld size exemption and Compress

Hi All

The below query in reference to UW-16 (Minimum Requirements for Attachment Welds at Openings) and options available in Compress.

Background Info:

  1. Design Standard = ANSI N14.1.
  2. Code of Construction (as specified by ANSI N14.1) = ASME Section VIII, Div. 1 (U-stamp).
  3. Vessel Material = SA-516 Grade 70, Wall Thickness = 12.7 mm.
  4. Nozzle Material = SA-105, Size = ASME B16.11 NPS 1" Class 6000 Half Coupling.
  5. Nozzle Weld Details (required by ANSI N14.1 - see attachment) = Full penetration groove weld plus fillet weld, fillet weld leg length = 4.7 mm (welded only from outside, similar to Figure UW-16.1(c)) .
  6. Design Software = Codeware Compress.
  7. The nozzles are exempt from area calculations as per UG-36(c)(3)(a)(2).


  1. I can use the rules of UW-16(f)(1) since the nozzles are standard ASME fittings.
  2. The weld size exemption of UW-16(f)(2) is applicable since the fittings are smaller than NPS 3" (given that the stated requirements of UW-16(f)(2) are met).
  3. UW-16(f)(1) states that full penetration groove welds are allowed, therefore a weld configuration as shown in Figure UW-16.1(c) is allowed.

Problem Statement:

  1. Compress does not give me an option of adding a set-in coupling (only set-on as shown typically in Figure UW-16.2), therefore I chose a uniform thickness style nozzle and specified the NPS 1" class 6000 threaded coupling using the standard lookup function.
  2. This means Compress sees the nozzle as a UW-16(c) type nozzle and it imposes the size limits of UW-16(b) for tc, this conflicts with weld size as specified in ANSI N14.1. Compress therefore lists a deficiency in the design report (I need to address this deficiency).

  1. Am I reading the Code correctly, in that UW-16(f)(1) and (2) are applicable in this case?
  2. Given that there are countless U-stamped vessels that meets the requirements of ANSI N14.1 already in the market, is this just an oversight in the way Compress handles standard ASME fittings?
Thank you.

RE: UW-16 (f)(2) weld size exemption and Compress

lr005, I think I have read your post fairly carefully and am following pretty well. BTW, a well explained situation and presentation of the problem, thanks for that.

First, Assumptions: I'd agree

Second, Problem Statement: I have no knowledge of Compress, can't comment exactly but I'd tend to agree with your #2

Third, Questions, your #1, in my opinion, yes, #2, again no knowledge of Compress, but I'd tend to agree. Its just software, after all :)

I don't know the best way to address your design report, but in other software I sometimes have to manually edit the output document, which I hate doing, but it sometimes can't be avoided.



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

RE: UW-16 (f)(2) weld size exemption and Compress

Hi Mike,

Thank you for the reply and for addressing each subsection of my question.

I agree with your conclusion that it is "just software overall", but since I am still fairly new in the pressure vessel world it is good have someone else checking that I am not missing something.

When I get a chance I will follow up with Compress (the company) as well.

At this stage I am going to leave the "deficiency" in the Compress Report and only attach the Compress Report as an appendix to my main report. Will address the deficiencies in the main report. In that way the design process will remain transparent.


RE: UW-16 (f)(2) weld size exemption and Compress

lr005, I'd be interested to know what you hear from Compress, please post as a reply here if possible.

I like your approach to address the reports. Good luck.

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

RE: UW-16 (f)(2) weld size exemption and Compress

lr005, you might want to update your version of COMPRESS as one of the recent builds includes the option for Set In Couplings.

RE: UW-16 (f)(2) weld size exemption and Compress

DandB, thanks for the info. I recently got the new update (Build 7900) which has the "Set In" option as you indicated.

SnTMan, I got feedback from Compress regarding the weld size exemptions of UW-16(f)(2). They state that currently (Build 7900) Compress does not consider the rules and weld size exemptions of UW-16(f)(2), the weld sizes are checked using UW-16(c). Therefore our conclusion above is correct. They also added they will include the rules UW-16(f)(2) in a future update.

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