RE: Cast iron pump nozzle with RF flange

From: <Conner>
Date: Wed Jan 23 2008 - 14:55:00 EST

Sajit, lest there be any misunderstanding, I am providing some more information. While a quite formidable and versatile piping material for pumps and for that matter all manner of other accessories for piping materials for many centuries, gray cast iron (while arguably stronger than many say "modern" plastics) is however a notably less strong and less tough structural material than ductile cast iron and steel. With regard to your last question, "How does the use of a low strength bolt ensure that the bolt load does not exceed so much as to cause it to break (if the RF were used)"?, I have not seen anyone responding to this thread make that claim. Nevertheless, while I have run neither calculations nor tests myself over-bolting gray cast iron flanges, I am aware that standards such as ANSI B16.1 and others I mentioned have specifically required ASTM A307 Grade B (steel, and with a specific upper limit on tensile strength) bolts required for bolting up some such cast iron flanges. While I know enough of such venerable standards that I would not claim that this is a vacuous requirement, I DO NOT believe that specifying lower strength bolts in and of itself will guarantee more that no gray cast iron flanges will be broken!

Irrespective of the gray cast iron raised face pump flange issue (or for that matter bolting gray cast iron flanges of any description up with ring gaskets or to raised face steel or ductile iron flanges with any gasketing), I think gray cast iron flanges in general can in fact be broken in various loadings that would not break stronger/tougher flanges. I would suggest that any interested readers e.g. to increase understanding can see/hear a brief, graphic visual illustration of this at the web page http://www.acipco.com/afc/videos.cfm , specifically in the video Ductile versus Gray Presentation
<javascript:popUp('videos/DuctilevsGrey.html')> (and specifically in
that part of the video headed, "Comparing Ductile and Gray Iron Valves", that involved actual beam loading flanged valve/pipe joints). [Simply cut and past the URL in your browser if the link doesn't work)

It is for similar reasons that more than 30 years ago the company I work for ceased production of all gray cast iron pipes, long before that would only put ductile iron companion flanges on flanged pipe, and a few years later also stopped producing even virtually all gray cast iron valve and fitting items. We currently produce instead ductile iron and steel piping items for various applications.

Randy Conner, ACIPCO

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From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com] On Behalf Of sviswan@technip.com
Sent: Wednesday, January 23, 2008 1:40 AM To: PipingDesign@yahoogroups.com
Subject: Re: [PipingDesign] Cast iron pump nozzle with RF flange

Thank you all for your responses,

I have decided to ask the vendor to provide a FF flange for the nozzle.

There are some links of interest on this subject,

http://www.eng-tips.com/viewthread.cfm?qid=142521&page=1
<http://www.eng-tips.com/viewthread.cfm?qid=142521&page=1>

http://www.gouldspumps.com/pom_0007.html
<http://www.gouldspumps.com/pom_0007.html>

http://www.eng-tips.com/viewthread.cfm?qid=146060&page=1
<http://www.eng-tips.com/viewthread.cfm?qid=146060&page=1>

How does the use of a low strength bolt ensure that the bolt load does not
exceed so much as to cause it to break (if the RF were used). I suppose this has to be limited by the limiting the torque used for the bolt up.

Sajit

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[Non-text portions of this message have been removed] Received on Wed Jan 23 14:55:00 2008