Steve,
The financial controller returns next week (my wife) so as to add much needed frozen pizza to the freezer.
I thought that I should contribute, rather than being eternally slack and just sitting in the grand stand watching our blokes play cricket against your blokes. Sorry.....I carn't (whoops) help it, snigger, snort. When your on top, make the most of it, it's a long way tho the bottom.
This magflow metre that you are installing, I am assuming this is an electronic instrument that has no moving parts that are in contact with your medium? If so I would think that if you are not that fussed as to being dead accurate that your installation would be acceptable.
I have read Bruce's (or was it Al's, I can't recall) response and he is
likely more experienced than I and
the numbers that he is quoting do not seem unreasonable. However, I cannot
quantify what the expected accuracy will be and perhaps, due to some of you
previous indiscretions to the list, that this could well be you project for
the group by actually providing a paper, (one page would be sufficient don't
you think). Err, lets say that this is your pennants. Ha,Ha, (sorry there I
go again).
Seriously, if you are measuring your flow with a Doppler effect type instrument I feel you will be impressed with the actual accuracy you will attain.
A number of years ago we had a situation arise where a mechanical meter was installed in what could only be described as a torturous flow path. In a pump discharge, close to valves and bends and immediately upstream of an in-line screen filter. The unit used to vibrate that bad you could hardly read the dials. For a number of reasons we wanted to control this pump stn. on flow and the only obvious place to install our new electronic, opposing probe meter insert was, you guessed it, right where the old mechanical unit was. To cut a very long story short, the unit performed above expectation and would "appear" to be accurate as far as repeatability was concerned. Once adjusted it worked nicely and to the best of my knowledge is still doing so. The pipeline velocity was in the order of 3m/s(through the instrument) and it was a 100mm wafer body insert increased up to fit the 150mm steel conduit which was the original pipe size. The transition from 100mm to 150mm was done in two steps. Our meter was remotely mounted, as in the display and controls were not subject to any vibration associated with the pipeline operation.
It should be remembered, we generally are working with cold clean water and will not be subject to some of the problems that you may experience with entrained solids, air, or even elevated temperatures.
Just have a go, you've probably got a few second-handy's out in the stores cupboard. Does this help?
Cheers for now.
Robin
>
> 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 Fri Feb 18 05:08:00 2005
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