Bi-directional flow measurement

  • Thread starter Amitabha Thakur
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Thread Starter

Amitabha Thakur

Hi friends,

Could you please help me giving idea on bi-directional mass flow measurement? In one of my project, we have linked two process units. In the event of deficiency of STEAM in one unit, the other unit will supply the required steam and vice-versa. I need to put a mass flow meter to measure steam flow in either direction.

Please intimate me some applications, share your experiences and name of some vendors with their e-mail addresses.

Amitabha Thakur
 
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Sumeet Chimalkar

Some questions. What is the steam temperature and is it saturated? What is the line size?

I would suggest a bidirectional orifice plate with temperature compensation and two dp transmitters as this will give the lowest installed cost with generally well accepted accuracy. The other option is to use two vortex meters each measuring flow in one direction. To choose between these two options consider the installation and maintenances costs of each. For smaller line and meter sizes and pressure ratings, vortex meters are more economical upto say a 100mm pipe size. Beyond this size, orifice plates are more economical. You may also consider averaging pitot type sensor instead of orifice plates for larger lines.

For orifice plates, there is no maintenance required but DP transmitters may require checking once in a while. Even if the DP transmitters are out of service, the flow is unaffected. With vortex meters, also there is no need for routine maintenance but if there is a meter fault, the flow may have to be shut off unless a bypass arrangement is provided. The bypass may add to the installation cost.

Also think about what is the purpose of the measurement. Vortex may give a better accuracy but will still require temperature compensation unless a multivariable instrument is used. The multivariable instrument may again have a higher cost.

For measurement between process units, my preference would be dp flow measurement but it is always good to study all options from different vendors.

Regards
Sumeet
[email protected]
 
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Amitabha Thakur

Thank you sumeet. For this application, press=61Kg/sq.cm, Temp=485 deg C, Line size= 10 inch. I am trying to consult with flow meter vendors also.

Amitabha thakur
 
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Sumeet Chimalkar

For your application, averaging pitot tubes may be better. You will have to use two as they are not individually bidirectional. Also to achieve the turndown, you may need multiple DP transmitters for each pitot tube.
The best option would be to approach the vendors such as Emerson, Yokogawa and Endress & Hauser to quote for a complete solution. You have a very high temperature and so you need to bring this to the attention of the vendors. Make sure that they quote with a drawing of installtion requirements with the bid. Otherwise there could be additional costs later. Several vendors manufatcure averaging pitot tubes but the ones listed can provide complete packages.

Hope this helps
Regards
 
S

Standard Plan

Since we are in the specialty flow measurement business we come across these bi-directional situations in a variety of systems. For these applications we generally use a symmetrical venturi (same inlet and exit cone angles). This then gives a very reliable, high accuracy flow measurement system. Either two DP transmitters are used or a one transmitter with a little creative valving.

John Catch
www.inflowinc.com
 
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Sumet Chimalkar

Apologies for not leaving my name on the last post.

A rethink on the use of the pitot. You might get away with using a single bi-directional orifice plate instead of two averaging pitots. Orifice plates are perfectly fine for a ten inch line. That will pull your installation costs down.
Let us know how it goes.

Regards
Sumeet
 
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Amitabha Thakur

Hi John, It appears that either bi directional orifice or double cone type venturi will meet the requirement. I feel that for venturi, accuracy will be better compared to orifice but orifice is cost effective. I shall take up the matter with my client for final decision. By the way, Jhon could you give your e-mail id so that in future I can cmmunicate. I have Sumeets mail ID.

Regards
Amitabha Thakur
[email protected]
 
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