RE: [PipingDesign] Thread engagement?

From: <Conner>
Date: Fri Jul 15 2005 - 11:45:00 EDT

You have not stated the specific application, any other specifications, whether regular or heavy hex nuts are involved, nor service etc., but I believe some steel flange specifications do have information that might at least relate to this issue. For example, AWWA C207 talking about steel pipe flanges for waterworks service provides tolerances for many components such as flange thicknesses, states on page 5 that the minimum bolt lengths shall basically be the sum of the maximum thicknesses of mating flange thicknesses, plus the gasket, plus the nut plus 1/8 in., and on pg 6, "If threaded rods are used, they shall be the same length as the bolts determined previously, plus the depth of the nuts, plus 1/8 in. (3.2 mm)."

That being said (and perhaps checked per your specs etc.?) I do suspect the engagement as described will develop substantial bolting strength, as I think I've seen many years ago incomplete thread engagement issues discussed in some technical articles on design of threaded fasteners (to the effect that most or all bolting load is normally carried by the first few threads nearest the bearing face, and of course the bolts and threads have apparently successfully taken whatever torque load the installer has put on them so far!) -- I guess whether that is adequate for your long term service might depend on the service requirements, the actual bolting material properties, or other factors etc. I hope this information is of help.

Randy Conner

-----Original Message-----
From: PipingDesign@yahoogroups.com
[mailto:PipingDesign@yahoogroups.com]On Behalf Of Davis McConnico
Sent: Friday, July 15, 2005 9:37 AM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Thread engagement?

sorry, replied to Paul as a posted question, should have had a pertinent "subject".

-Davis

   Does anyone know of any codes pertinent in the USA which address the engagement of bolt/stud with the nut on ASME B16.5 Class 150 and 300 flanges? I have a customer that recently installed some gaskets in a shutdown. The studs were a bit short and the nuts lacked about a half thread on each end before full engagement. I've asked around and read some literature and found only suggestions stressing the importance ranging from full engagement to having at least two threads showing beyond each nut. But I can't find any relevant codes. Re-installing these gaskets with longer studs would require plant shutdown again.

   Thanks all,

   -Davis

     Linked from the current version of the main page, www.pipingdesign.com<http://www.pipingdesign.com/<http://www.pipingdesigncom<htt\ p://www.pipingdesign.com/>>:

     The Art of Checking Pipe Stress Computer Programs [PDF]

     Treatment of Support Friction in Pipe Stress Analysis [PDF]

     The Art of Designing Piping Support Systems [PDF]


     An excerpt from one of the above links is quoted below:

     "Pipe stress analysts are normally too timid in challenging a well
     established computer program. However, if we recognize that to err is
     computer program, we may be able to more objectively ensure the quality
     of our analysis. It is important to realize that everything has its so
     called norm. In other words, if something looks unrealistic then it
     probably is unreal. Therefore, it is important to be able to look at the
     output and point out the irregularities that might exist. That is the
     art. From time to time we have seen some experienced engineers who are
     able to judge whether a system is satisfactory just by looking at the
     model. The computer analysis is just confirming a check. However, they
     are the exceptional rather than the normal.

     The inconsistent results in an analysis comes either from the bug in the
     program or from the misapplication of the program. Nowadays, people like
     to boast that you don't even need to read the manual to use their
     computer program. The so called user friendly is probably what they
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     =========================================
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     Main site:
http://www.pipingdesign.com<http://www.pipingdesign.com/<http://www.pipingdesign\ .com<http://www.pipingdesign.com/>>

     Yahoo! Groups Links

   [Non-text portions of this message have been removed]



   PipingOffice - Excel Spreadsheets for Piping Calculations    http://www.pipingoffice.us/<http://www.pipingoffice.us/>

   Main site: http://www.pipingdesign.com<http://www.pipingdesign.com/>

   Yahoo! Groups Links

[Non-text portions of this message have been removed]



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