steve
it is possible to look at the outcome of this in
a CFD program and we have had good success eliminating bend flow
perturbation
(upsetting pneumatically driven control valves) with the tools. With far
less than 5D after a complex bend Geometry alterations were still able to
get stable control at the control valve and still was predicted by the
analysis.
There was considerable resistance in both instances to any change , but this
was unreasonable and they were desperate.
in the one case they switched from pneumatic to electronic control, although
this alone was insuficient as the shaking and cavitation was extreme.
in the other case with similar tight and out of planeY geomtery almost immediately followed by a 90 and then 3D to the valve the control valve settled right down after flow smoothing by geometry alteration
i dont think you will find any data as each case is far too custom. What you are looking for is the flow behaviour and that is geometry dependent.
>
> Hi Robin
>
> from your burst of excellent and detailed responses to queries, it
> appears you have some time on your hands.
>
> My question#1 is when does your boss get back from his vacation?
>
> Question #2, I have to bang a magflow into an existing line and intend
> using the 2/3 upstream, 1/3 downstream that I normally use. Trouble is
> that I wont have my normal minimum 10D up and 5D down probably more like
> 5D up and 2.5D down, closer to your numbers. The disturbances at each
> end are 1.5D bends, same plane. Line size is probably 150NB and flow
> rate around 170m^3/h, water. The metering is for process control, not
> accounting, so accuracy isnt hellish important but it would be
> comforting to know the expected accuracy. Have you or anyone else seen
> any data on the effect on accuracy when departing from "the rule"? I
> expect a slightly higher reading than actual at higher flow rates (due
> to spin), but someone has surely done a bit of research on this. Am up
> to my ears in rules of thumb and would prefer a bit of supporting
> research data. Have perused ISO5167, but it doesn't really apply to an
> induction driven meter.
>
> Personally, I feel this question may take a couple of hours of digging
> to find the answer, which I am sure would be of use to a number of list
> members. I suggest that any member who makes a "crime" against this
> group be "fined" by being required to provide a well-researched and
> referenced (1 page minimum) response to a nominated question, such as
> this (question #2, or course), within one week.
> It would improve the knowledge base of this group, and reset the clock.
> Paul could judge if such a crime has occurred. He would like it as he
> likes throwing his weight around.
> Whaddayathink?
>
> Cheers
>
> Steve
>
>
>
>
>
>
>
> -----Original Message-----
> From: Robin Badcock [mailto:rbadcock@vision.net.au]
> Sent: Thursday, February 17, 2005 1:57 PM
> To: PipingDesign@yahoogroups.com
> Subject: Re: [PipingDesign] querry....
>
>
>
> Vaibhav,
>
> There exists numerous distances for devices that are inserted within the
> pipeline and these vary somewhat to the duty they are to perform, i.e.
> paddle switches may have a requirement of 5 times pipe diameter of
> straight pipe up-stream and down-stream from the point of installation.
> Sensitive propeller type instruments may call for 10 times pipe
> diameter. Generally speaking the manufacturer will provide you with
> guidelines on the correct installation. These guidelines are in the
> interest of having the device operate, and achieve the base line
> accuracy that the maker claims on their literature.
>
> This does not answer your question fully. The reason for the straight
> pipe sections is for the reduction of possible turbulent flow that may
> affect the devices operation.
>
> In answer to you query on the straight pipe sections associated with
> check valves, we have witnessed first hand non return valve mechanical
> failure due to excessive turbulence when installed too close to the down
> stream side of a pressure sustaining valve. The end result was total
> internal valve failure within two years. This less than ideal
> installation was due to space constraints. One solution was to install a
> more robust valve and be prepared to live with the extra maintenance.
> The correct solution would have been to observe a greater distance of
> straight pipe work, down stream of the sustaining valve, if space would
> have permitted.
>
> If you goggle pipeline turbulence you may turn up some useful info.
> Perhaps Paul has a link or some information on the Piping Design web
> page.
>
> The orifice plate that you may be manufacturing yourself for head
> loss/flow regulation will also be subject to straight piping
> requirements for the same reason of attaining reliable and repeatable
> regulation. If installed into a turbulent pipeline area variations may
> well exist. Software is available from the likes of Dorot, Bermad and
> quite likely other control valve manufactures and although I have not
> checked, software and information is likely to be freely available on
> this subject. This was certainly the case some years ago.
>
> I hope that this helps.
>
> Cheers for now.
>
> Robin Badcock
>
> ----- Original Message -----
> From: <VAIBHAV_DEVDHAR@ril.com>
> To: <PipingDesign@yahoogroups.com>
> Sent: Wednesday, February 16, 2005 11:22 PM
> Subject: [PipingDesign] querry....
>
>
> >
> >
> >
> >
> >
> >
> >
> >
> > Can any one please tell the required straight upstream and downstream
> > requirement for Restriction Orifice? Please note that this orifice is
> > only for pressure drop purpose and not for flow measurement. What
> > could be the reason for this requirement?
> >
> > Has anyone come across the straight length requirement for check
> > valves, especially swing check valves? Why is this needed?
> >
> > Request members to throw some light on this.
> >
> > Regards
> >
> > Vaibhav Devdhar
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> >
> >
> >
> >
> > =========================================
> > PipingOffice - Excel Spreadsheets for Piping Calculations
> > http://www.pipingoffice.us/ =========================================
> > Main site: http://www.pipingdesign.com
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/ =========================================
> Main site: http://www.pipingdesign.com
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
> =========================================
> PipingOffice - Excel Spreadsheets for Piping Calculations
> http://www.pipingoffice.us/
> =========================================
> Main site: http://www.pipingdesign.com
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
Received on Thu Feb 17 04:50:00 2005
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