Small Hole in ASME B16.5 Blind Flange
Small Hole in ASME B16.5 Blind Flange
(OP)
I am using an 8" 150# ASME B16.5 Blind flange with a 1/2" NPT connection drilled & tapped directly into the flange 3" off center. I am being told the Flange is no longer an ASME Flange and that calculations are required. I disagree for several reasons,
1.) The Flat head formulas in UG-34 don't change when there's a hole added. The addition of the hole is addressed in UG-39, so why would the thickness of an ASME flange change?
2.) ASME B16.5 allows holes less than 3-1/2" to be added to an 8" blind flange to create a reducing flange using the published press/Temp rating. I don't see why this can't still apply to small holes that are located off center and exempt from reinf per UG-39.
3.) The design in questions is exempt from Reinforcement per UG-39 & UG-36(c)(3) which implies the material removed is not enough to affect the integrity of the part with the hole. Why would this be different on a flange?
4.) Where does Sect. VIII Div.1 or B16.5 say that a flange thickness calculations is required when a hole is added to an ASME Blind Flange.
1.) The Flat head formulas in UG-34 don't change when there's a hole added. The addition of the hole is addressed in UG-39, so why would the thickness of an ASME flange change?
2.) ASME B16.5 allows holes less than 3-1/2" to be added to an 8" blind flange to create a reducing flange using the published press/Temp rating. I don't see why this can't still apply to small holes that are located off center and exempt from reinf per UG-39.
3.) The design in questions is exempt from Reinforcement per UG-39 & UG-36(c)(3) which implies the material removed is not enough to affect the integrity of the part with the hole. Why would this be different on a flange?
4.) Where does Sect. VIII Div.1 or B16.5 say that a flange thickness calculations is required when a hole is added to an ASME Blind Flange.





RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
Doing a quick search for offset tapped blind flanges with google came up with this thread here at eng tips.
http://www.eng-tips.com/viewthread.cfm?qid=261110
Might be useful to you. Once you check that thread, use the function at the top for similar threads and you might get clearer insight to your question.
Regards,
RE: Small Hole in ASME B16.5 Blind Flange
B16.5, 5.3.2 allows the use of intermediate bolts provided the user verifies the ability to seat the gasket and maintain a sealed joint under operating conditions. Our previous Lead engineer determined that as long as the vessel was hydrotested with the service bolts and identical gasket and the joint did not fail we have met the intermediate bolt requirements. Should I assume that this no longer applies either?
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
To directly answer your first question, VIII-1 (by means of UG-44) allows the use of fittings to listed standard (B16.5 included); B16.5 flanges only allow holes in the center; refer to B16.5 table 6.
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
1) is a blind flange classified as a fitting as per B16.5?
2) If it is classified as a fitting then would 6.12.2 qualify for tapping a blind flange as in making an Auxiliary Connection (which IMHO it is)
Just trying to figure out if I too have to raise questions for all the Offset tapped blinds that we have been using in our testing program. Not one failed yet.
As they say. Curious.
RE: Small Hole in ASME B16.5 Blind Flange
The center-to-flange edge sentence is my justification.
I suppose that it is possible that you could argue that you are creating an eccentric reducer without a hub...
Cuemaster64 - I don't think that this is an issue of safety, but one of compliance with the Standard.
RE: Small Hole in ASME B16.5 Blind Flange
My justification is the B16.5 addresses holes in blind flanges for use as a reducing flange. This is not the intent of a tapped vent hole.
Sect. VIII UG-34 allows B16.5 blind flanges to be used as flat heads. No where does it say if a hole is added the B16.5 ratings don't apply.
In regards the response from TGS4, how can I argue that we're creating an off center eccentric reducer without a hub when 6.2.3 is saying the center of the opening and/or center to flange edge distance has to be the same as the largest opening?
RE: Small Hole in ASME B16.5 Blind Flange
....would anyone agree with that?
RE: Small Hole in ASME B16.5 Blind Flange
Now when you start adding multiple holes, things get more interesting. And when you use ASME VIII appendix 2 and the basic design of the B16.5 flange without holes fails, where are you now?
RE: Small Hole in ASME B16.5 Blind Flange
Thats part of my logic, UG-34 fomulas calculate flat heads with and wthout holes exactly the same way. The addition of holes has nothing to do with the requirements of designing a head in UG-34, so why would it effect the ASME B16.5 requirements. The addition of and requirements for holes in a flat cover are addressed in UG-39. If the holes added to the Blind Flange require reinforcement per UG-39 then thats when it has to be designed per U-34.
RE: Small Hole in ASME B16.5 Blind Flange
If for whatever reason you were stuck with needing to use a B16.5 flange, then your sole recourse would be to approach the Code Committee with a proposal for an addition of a clause permitting vent holes (small) in an off-centre location. See the Section in B16.5 Titled "Correspondence With The B16 Committee" on pge x of the 2013 Edition. If your need is urgent, you may qualify for a "Case". You could also attend the meetings - B16.5 falls under B16 Subcommittee C. The next meeting is March 23-26 in Vegas - contact the secretary for additional details.
RE: Small Hole in ASME B16.5 Blind Flange
Exactly! There is nothing 'magic' about B16.5 flanges, other than they are pre-engineered, readily available, and cheap. Calc it, add your offset hole [with reinf. if the calc's show it necessary, and grind off the "ANSI/ASME B16.5" stamping on the rim.
RE: Small Hole in ASME B16.5 Blind Flange
Rigidity is what it accounts for a flange design to prevent leak. If you compare how much area can be removed within the "y" dimension of a slip-on flange with a small hole removed in your blind, you can for sure doing nothing in your case and I can guarantee it will be fine. We have so many real cases from numerous projects, even 3 nozzles on a blind, never been a problem or concern.
Keep in mind the flat head reinforcement calculation UG-39 is not really good for blind because it does not take rigidity into consideration. UG-39 as well as UG-37, allows large deformation because that is not a concern. However, for flange and blind, deformation or rigidity is a major concern more than stress analysis. That is why you do not use formula in Appendix 2 to verify standard B16.5/ B16.47 flanges. These standard flanges are rigid enough even though they fail Appendix 2.
To let yourself feel and sleep better, do (1) compare with the area in a slip-on flange with a standard pipe installed within "y' dimension. (2) make sure the hole is inside the standard pipe diameter (3) run the head reinforcement calc per UG-39. You can use weldolet or reducer if you like to gain more area. Pad is fine. In you case, you need nothing.
And wait for years until someone invents better approach.
RE: Small Hole in ASME B16.5 Blind Flange
I hope this will help you...
http://w
Bmechz
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
Just one fabricator speaking...
RE: Small Hole in ASME B16.5 Blind Flange
Let's put aside what the code said, consider a flat head(blind flange), under pressure, most deflection is at the center, and stress, of course not considering bolting load around the edges. If a small opening with/without its reinforcement can be placed at the center, why can can't the same be placed off the center? where there is less stress, hence less compensation required for the removed material. Hence safer?
I do agree once flange dimension is modified, it is no longer a B16.5 flange, hence custom calculation. But I believe we all have seen vent/instrument holes drilled from the side of the flange, in between two hold holes. How would you do you calculation for this case?
RE: Small Hole in ASME B16.5 Blind Flange
If B16.5 allows you to drill & tap through the side of a fitting why would it not allow drilling & tapping through the blind flange ?
Are they not both subject to the same pressures ?
6.12.1 Pipe Thread Tapping. Holes may be
tapped in the wall of a fitting if the metal is thick
enough to allow the effective thread length specified
in Fig. 3. Where thread length is insufficient or the
tapped hole needs reinforcement, a boss shall be added.
Only problem with that is 6.12.4 requires a 3/4" connection for an 8" fitting so the 1/2" connection would not be compliant with B16.5,
Cheers,
DD
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
Well done, bayardwv!
RE: Small Hole in ASME B16.5 Blind Flange
Out for SC Ballot- the interpretation is currently balloted by the Subcommittee.
I was able to address my current problem by changing the spiral wound closure gasket from a CGI style to an LSI style which has a minimum seating stress ("Y") of 5,000 vs the CGI stress of 10,000. This allowed the ASME B16.5 flange to meet the required code calcs.
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
Here's the question I submitted...
Are minimum thickness calculations per UG-34(c)(2) in Section VIII, Division 1 required if an ASME B16.5 or B16.47 circular blind flange, used as an unstayed flat head, otherwise conforming to the requirements of UG-34(c)(1), has a hole added off center that meets the requirements of UG-39(a) and the nozzle opening size is exempt from reinforcement per UG-36(c)(3)?
Here is the reply I received...
Question (1). If a B16.5 or B16.47 blind flange is modified in a manner that is not covered by those standards, may pressure/temperature ratings of these standards be used in accordance with UG-44?
Reply (1). No.
Question (2). In the situation described in Question 1, would calculations using the design provisions of UG-34 and UG-39 be required?
Reply (2). Yes.
RE: Small Hole in ASME B16.5 Blind Flange
This, to me, highlights the need to be attending the Code Committee meetings where these issues are going to be addressed. Frankly, if you had an interest in the answer, then you should be there when the issue is discussed.
What was the BC item number (the tracking number that you would have been provided)?
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
I also don't understand why they reworded my question in a way that no longer addressed my key points. I don't completely disagree with keyen's comments however I still plan on resubmitting with different wording.
RE: Small Hole in ASME B16.5 Blind Flange
See, the ASME Codes are essentially run as a consensus committee of volunteers, who work in industry just like you and me. Each individual has become involved for their own unique reason, but often got started with a single issue, such as this one. The way the system works is that everyone gets involved, makes logical, yet passionate arguments for their issue, their peers listen and respond accordingly. My experience is that the group of engineers are extremely experienced, and very open-minded and fair. They only want what is in the best interests of public safety.
To see when meetings are, go to https://cstools.asme.org/csconnect/CommitteePages..... The future meetings link is on the top left. The next meetings are in Atlanta in a few weeks. You can register to attend (free) via https://www.asme.org/events/boiler-pressure-vessel....
RE: Small Hole in ASME B16.5 Blind Flange
To really answer your question, the committee would have to re-write the standard to define the conditions under which off-centred holes, or multiple smaller holes etc. would be considered safe modifications without requiring additional calculations or a de-rating of the blind flange. That would be a lot of work to do properly, so the easier and quicker answer is "no, read the standard as written".
Clearly it doesn't matter to the blind flange whether a small hole such as the one considered in the OP (a 1/2" NPT tapping in an 8" blind flange) is put in the dead centre of a blind flange or anywhere such that the small hole's OD is entirely within the ID of the flange's raised face. It would be easy enough for the committee to establish whether that is also true at the maximum permitted hole size which the standard permits for an on-centre hole in a standard (flat) rather than a high hub blind flange. But then there's the issue of multiple holes, and it starts to get fairly complex fairly quickly. Is it a simple matter of total hole area? I would imagine that if the total area of the holes is no larger than the area of the largest hole permitted on centre, multiple holes wouldn't matter wherever they were placed. But getting that written into the standard is a lot to ask, I guess. So instead of using engineering judgment, a lot of unnecessary calculations and work-arounds will be done. So it goes- it is the 2nd edge of the double-edged sword of codes and standards.
RE: Small Hole in ASME B16.5 Blind Flange
RE: Small Hole in ASME B16.5 Blind Flange
I am unable to locate any part of B16.5 that specifically includes permission to weld a lug on the side of blind flange, although I have been accused many times of having a "boy look" for things.
RE: Small Hole in ASME B16.5 Blind Flange
Stuff welded to the side of the flange which puts no meaningful load on the flange in service, should not cause any problems as long as the welding process doesn't affect the metallurgy of the flange itself, i.e. welds done per ASME IX and examined properly shouldn't be a problem. Little different than bolting things to the extended threads of a couple of the flange studs.
RE: Small Hole in ASME B16.5 Blind Flange
Orifice flanges are covered in ASME B16.36. Drilling holes in a B16.5 flange between stud holes will make your flange not compliant with B16.5
RE: Small Hole in ASME B16.5 Blind Flange
by doing so make your flange not compliant with B16.5 but to B16.36, but isn't B16.36 flange has the same pressure temperature of B16.5?