Dear Rakesh,
The flow elements are placed in the pipe where we get a streamline flow. That is all the particals of the fluid are travelling in the same line, with uniform velocity. The flow element should not be placed near anyfitting, as it is the area where flow tubulance takes place, due to pressure difference, change in velocity and change in direction. Generally the upstream of the flow element is smaller in length that the downstream. For the venturi effect, the upstream is generally 5D and the down stream is 10D. But these guidelines are onlt applicable for single phase fluids. Also, generally no flow element is placed after atleast 5D distance from the bend.
I hope I have clarifie your doubt to some extent. Regards,
K. V. JOSHI
PRDH-A306,
L&T POWAI WORKS,
MUMBAI-400072
INDIA
TEL: 8581401 Ext. 2880
E-mail : <a href="/group/PipingDesign/post?postID=-54dgaHgBHZVtorPNFeTsNaYv3gDlmK6pLUapgGYbtHzL_upU21nmjCIdLnV9mrmiMVoRR8iBcdQulkpcw">kvj@epc.ltindia.com</a>
>>> macharla777@yahoo.com 11/26/01 10:21AM >>>
Rakesh,
I suppose you are looking for the philosophy behind
deciding the straight lenths before and after flow
element.
It links to theory of Boundary Layer and Secondary
Flows in fluid path. After any bend, there will be
secondary flows induced near the pipe wall...it
proportionately effects local velocity/pressure of the
fluid. Considering the length of pipe required to
reach to full velocity of liquid, standard straight
lengths ahead of Flow Element are established.
For after FE, also staright length is required to
reach to full velocity after the Vena Contracta
condition at FE.
Hope it clarifies upto some extent.
Macharla
--- saud <saud@bushnak.com> wrote:
> Dear Rakesh
>
> The standard recommended dimensions upstream and
> downstream of a flow
> measuring instrument sensor (paddle wheel type etc.)
> is 10 times the
> diameter of the pipe (D) for upstream and 5 D for
> down stream.
>
> With latest magnetic flow meters, this dimension is
> reduced to 5 D and 2 D
> respectively.
>
> Regards
>
> Saud
> ----- Original Message -----
> From: "RAKESH PATIL" <rpa@epc.ltindia.com>
> To: <PipingDesign@yahoogroups.com>
> Sent: Friday, November 23, 2001 6:15 PM
> Subject: [PipingDesign] Flow Elements
>
>
> > ** High Priority **
> >
> > Can anybody give me the basic criteria behind
> deciding the upstream and
> downstream dimensions between Flow Element and
> connecting Fitting /
> accessories in piping?
> >
> > regards,
> > rakesh
> >
> >
> >
> >
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Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Mon Nov 26 00:09:00 2001
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