Small Hole in ASME B16.5 Blind Flange 5

[bayardwv]

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.

 

[TGS4]

It is indeed no longer a B16.5 flange, because that standard does not allow for off-center holes in a blind flange. If you are using this in ASME Section VIII, Division 1 construction, you would still be permitted to calculate the thickness of the flange on the basis that you described.

 

[Cuemaster64]

Bayardwv

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,

 

[bayardwv]

Thanks everyone. this leads me to another question. I did run calc's per UG-34 but my problem is that I'm using a Spiral Wound Gasket & Intermediate Bolts, SA193B8M Cl.2. The Actual bolt load is less than the Required Bolt Load. I would not have picked up on that had I not run the UG-34 Calc.
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?

 

[bayardwv]

I forgot to ask in my last reply, WHERE in ASME B16.5 or Sect. VIII Div.1 does it state that once an off center hole is added to a blind flange its no longer an ASME flange?

 

[XL83NL]

bayardwv, TGS4 hit it to the nail (as usual ).
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.

 

[bayardwv]

I guess one could say I'm playing games with the wording but Table 6, Note 1, doesn't specifically state "on center", therefore it is assumed and assumptions are not fact. In addition Table 6 is Specific to Reducing Flanges, and this is not the purpose of this offset hole. So my question is.....Where does the latest editions of ASME B16.5 or ASME Section VIII, Div.1, clearly state that a blind flange is no longer an ASME B16.5 flange after a hole has been placed off center?

 

[TGS4]

B16.5, paragraph 6.3.2.

 

[XL83NL]

6.3.2 of the 2013 edt is about raised to flat face conversion - you sure TGS4?

 

[Cuemaster64]

Two questions.

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.

 

[TGS4]

6.2.3 - my mistype.

6.2.3 Reducing Fittings. Center-to-contact surface or center-to-flange edge dimensions for all openings shall be the same as those of straight size fittings of the largest opening. The contact surface-to-contact surface or flange edge-to-flange edge dimensions for all combinations of reducers and eccentric reducers shall be as listed for the larger opening.

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.

 

[bayardwv]

Is there anyway I can prove that a vent connection located of center, exempt from reinforcement per UG-39 can use the B16.5 ratings?

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?

 

[bayardwv]

...and here I go again with yet another question.....6.2.3 is to address the required dimensions for Reducing Fittings. It does not apply the the hole location in a Reducing Blind flange, so now I'm back to my question where does B16.5 state that a nozzle hole has to be located on center?

....would anyone agree with that?

 

[moltenmetal]

This is obviously an angels dancing on the head of a pin argument. Clearly the small single vent hole is OK regardless WHERE in the flange it is placed. The question isn't whether or not the resulting part is adequately strong, or safe, but whether or not it is compliant with the text of B16.5.

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?

 

[bayardwv]

Then I would follow the rules for openings in Flat Heads, the same as I would if the head were designed as a flat cover per UG-34.
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.

 

[TGS4]

Unfortunately, for compliance with B16.5, any hole in a blind flange makes it a reducing flange. This standard simply doesn't have a provision for what you are trying to do. Doesn't make it wrong or unsafe, just not compliant with this particular standard. moltenmetal's comment is bang-on.

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.

 

[Duwe6]

"Then I would follow the rules for openings in Flat Heads. . . "
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.

 

[jtseng123]

bayardwv,
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.

 

[Bmechz]

Kindly go through the below link in which HSB interpretation regarding opening on blind flange is available..

I hope this will help you...

http://www.hsbglobalstandards.com/uploadedFiles/CTWeb/AllImages/PP-1999-06.pdf

Bmechz

 

[bayardwv]

I'm completely perplexed that many code fabricators are building code vessels using UG-34 & UG-39 as their design basis for adding small offset connections on blind flanges without providing calc's, and I can not find a code case or interpretation addrssing OFFSET nozzles.