surge reply to GS DD&D. Unsustained Loading -Flange Pressure Rating

Geoff DD&D
Your paper is great for raising the issues and airing what is frequently described as
"that can of worms we dont want to open". Unfortunately the denial / vanishing acts pulled by contractors is allowed by the courts.
Case in point British Columbia high rises & condo scandals,& Tim Manning Taradal Developments (Ponsonby et al NZ) but there are many many more.

However regarding "valid response in another forum. The answer was basically that all standard components are included in the allowance for surge that allows excursions due to unsustained occassional loading." i couldnt agree with this .

(1). allowance for surge .... excursions due to unsus - occ loading....Not any designs I have seen. What allowance would be used, what is occasional, how would you know it was unsustained. There is no way this could be easily quantified in advance other than by guesswork, or by "using up" or "built into" the safety factor allowance in the design.(leaving the undesirable situation of little or no FOS). Stress concentrations (often unidentified) may already be consuming that safety factor without any other loading considered.

Quickfea (widely used these days in black box mentality) allows design factors to be added or FOS built in, but it is not non linear based and no dynamic analysis is done or compared to a static FOS. Impact factors may be used but done so in a broad brush approach only.

(2)if you do a flange analysis of a standard ANSI flange it does not meet code rules as is, statically with pressure loading,, let alone piping or bending or any other applied load. Determining loads is often the hard part. So how could such a standard flange that doesnt meet existing code rules include an allowance for xxx??? They are accepted as is because they were grandfathered in on the basis that they met (by service in practice and trial and error from original manufacturer research as specified to Ansi B16.5 conditions (P&T) only."decades previously as stated in Geoffs paper, and current resources not understanding the design."

Geoff was interested to know how many people actually do surge analysis on process plants?
> .my.recent response (repeated below) to same question previously didnt
elicit any comment.
> ............

  is there really a need to do dynamic analysis. it is a good idea to do it , but as you discovered, collecting the data to do it properly is a big
> exercise. Mostly people dont want to pay to do this until a problem is
already identified, because of the effort required.
> Usually it is left in a wait and see scenario. The blame falls after this
> "wait and see option is chosen" , but later a dynamic problem rears its
ugly
> head.
>
> An experienced engineer will be able to design a system that is inherently
> "protected" or at least minimises such risk. (hence all my comments). By
> knowing where to look and what to do that will minimise such risk.
>
> the trend these days is too pass everything off to the vendor/supplier.
This
> is ridiculous as they do not have the tools or knowledge to do this. They
> then scrounge around looking for the cheapest solution with no clue as to
> the information required ....as you discovered to be the case.
>
> As has been said many times on this site, cheapman pays more than twice,
get
> someone who knows what they are doing. It saves time and money.
> There are good software packages out there now to do this, and experience
> with them, even caesar , helps in knowing what to do right.
> The most sensible and practical things can be done in advance to avoid the
> need to do the full blown surge and dynamic analysis. It is my exp that
this
> is usually the course taken.
>
> -----Original Message-----
> From: <a href="/group/PipingDesign/post?postID=tod2XmVkjR1ND91nZbnEUxbgeENtLYkxRUaz1fDhHHEtR8_5rG50ysYdZZ4ryRo6DfwCt2bLq64xMtUvh2L6oGwmZw">PipingDesign@yahoogroups.com</a>
> [mailto:PipingDesign@yahoogroups.com]On Behalf Of Geoff Stone DD&D
> Australia
> Sent: Tuesday, August 16, 2005 4:13 PM
> To: <a href="/group/PipingDesign/post?postID=tod2XmVkjR1ND91nZbnEUxbgeENtLYkxRUaz1fDhHHEtR8_5rG50ysYdZZ4ryRo6DfwCt2bLq64xMtUvh2L6oGwmZw">PipingDesign@yahoogroups.com</a>
> Subject: Re: [PipingDesign] Unsustained Loading -Flange Pressure Rating
>
>
> Hi Chris,
>
> I actually received a valid response in another forum. The answer was
> basically that all standard components are included in the allowance for
> surge that allows excursions due to unsustained occassional loading. If on
> the other hand you have design a special flange to ASME or AS1210 then you
> will need to use the surge pressure in the design of that special
component.
>
> I would be interested to know how many people actually do surge analysis
on
> process plants?
>
> regards
>
> Geoff Stone
>
> Christopher Wright <chrisw@skypoint.com> wrote:
>
> On Aug 16, 2005, at 7:41 AM, Saha, Tanmoy wrote:
>
> > Usually surge loads are quite high and flanges cannot be designed for
> > that due to economic reason.
> So what do you tell your customer when you're standing over the ruins
> and he asks you why the hell his system came apart?
>
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw@skypoint.com | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania
> 1864)
> <a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
>
>
>
> ---------------------------------
> YAHOO! GROUPS LINKS
>
>
> Visit your group "PipingDesign" on the web.
>
> To unsubscribe from this group, send an email to:
> <a href="/group/PipingDesign/post?postID=MD3Z1f7864zASqc1hV-YSwQ9naIswgxdWIHZxPAxGRgxlnMH8o79ssJXdktjiigyKrGP-PqWGgElLk_IxZhrd1FrUvum0O-2FzwdKfphblrdtBw">PipingDesign-unsubscribe@yahoogroups.com</a>
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
>
>
> ---------------------------------
>
>
>
>
>
> Design Detail and Development (a division of Blenray Pty Ltd)
>
> Mail Address PO Box 1351 Castle Hill NSW 1765 Australia Tel Mob 0402 35
2313
> Office 02 8850 2313 AH 02 8850 2324
> We specialise in pipe network and waterhammer analysis, pipe stress
> analysis, the design of buried pipelines and thermoplastic pipe systems.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> <a href="http://www.pipingoffice.us/">http://www.pipingoffice.us/</a>
> =========================================
> Main site: <a href="http://www.pipingdesign.com">http://www.pipingdesign.com</a>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
Received on Wed Aug 17 13:35:00 2005