Re: thoughts- Flange Bolt Array Positioning

That's what I seem to remember as well (I.E., alignment being the major concern in the field) although the two-bolt hanging theory also seems logical.

I'm on a lame, unreliable wi-fi connection so maybe someone else could CC the original asker with the cumulative replies.

Paul

Quoting Al <alwynk@shaw.ca>:

> i hear this a lot of times , the best answer from discussing with grey hairs
> was largely CONSTRUCTION
> you can get a true centreline TDC better and easier when marking and
> straddling
> a line down the face of the flange body circle. much more time consuming and
> never
> as good trying to find and mark centre of line.
>
> I think going Along a line doing this each time gets near perfect matchup
> with no worries.
> eg wont get axial misalignment loading and the same would apply at pump and
> hardware series
> bolt up, thats what i think
>
> I entirely agree chris comments ""Lower stress argument is correct, but I
> still can't imagine that it would make a lot of difference."", but avoids
> risk of introducing
> "twisted stresses" ...theres a good term.
>
>
> ** Altecheng@shaw.ca
>
> ' 001(780)465-9762
> 6 Fax/Msg(780)465-9762

> -----Original Message-----
> From: PipingDesign@yahoogroups.com
> [mailto:PipingDesign@yahoogroups.com]On Behalf Of Christopher Wright
> Sent: Saturday, May 20, 2006 1:32 PM
> To: PipingDesign@yahoogroups.com
> Subject: Re: [PipingDesign] Flange Bolt Array Positioning
>
>
>
> On May 20, 2006, at 4:02 AM, Paul Bowers wrote:
>
> > The question is based on flanged connections and is about the holes for
> > the bolts. Why are holes on a flange never positioned on the vertical
> > centerline?
> The story I was told is that such positioning forces the topmost bolt
> to carry more stress when the attached pipe is subject to bending about
> a horizontal axis. This is true but I can't imagine it's significant
> for flanges with more than 4 bolts. With 4 bolts the difference in
> bending stress is about 30%; with 8 bolts the difference is less than
> 10%
>
> Since the number of bolts on standard flanges is always a multiple of 4
> straddling the vertical centerline also makes the bolt pattern straddle
> the horizontal centerline, so bolt stresses from horizontal loading
> would also be lower. Maybe the lower stress argument is correct, but I
> still can't imagine that it would make a lot of difference.
>
> I think I overheard someone say that it was for accessibility from
> underneath, but again, for more than six bolts it isn't going to make
> much difference.
>
>
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw@skypoint.com | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania
> 1864)
> http://www.skypoint.com/~chrisw/
Received on Sat May 20 19:58:00 2006