9 replies to this topic

[shahidulislam48]

Hi,

 

I have a Flow Transmitter that is installed upstream of a Control Valve but smaller in size than the Control Valve, could I use this arrangement for accurate flow measurement and controlling action or Flow meter and Control Valve must be in same size?

 

It has been found that vendors sometimes recommend smaller FT than line size. Is it acceptable?

 

Thanks in advance.

 

Shahidul Islam

[Mahdi1980]

In general, you should find the type of flow transmitter and its specification from vendor/manufacturer catalogue to know how much maximum fluid can be handle from it respect to the maximum accuracy.

Flow meters have an accuracy curves which has a range. If the flow rate is more than the defined rate, the accuracy will be dramatically fell down and may cause a problem in measuring and control purposes.

 

Anyhow, please let us know the detail of your matter such as the fluid name and phase, and its operating temperature and pressure,normal and maximum flow rate, line size, and size of flow meter and control valve as well as the type and brand of your flow transmitter.

Then we may conclude if it works for you or not.

 

Good luck

Edited by Mahdi1980, 12 June 2017 - 06:31 AM.

[fallah]

 

I have a Flow Transmitter that is installed upstream of a Control Valve but smaller in size than the Control Valve, could I use this arrangement for accurate flow measurement and controlling action or Flow meter and Control Valve must be in same size?

 

It has been found that vendors sometimes recommend smaller FT than line size. Is it acceptable?

 

Hi,

 

It's actually an orifice plate as a flow element not a flow transmitter itself; mostly has the same size of the line along which has been installed and no need having different size than that of the line or downstream control valve because the required delta P could be generated across it by adjusting Beta ratio i.e. orifice area over relevant line's cross section area.

[shahidulislam48]

Thanks Sir Fallah and Mahdi for your reply.

 

I have attached a doc containing process and vendors data as per requirement of Mahdi.

Please have a look.

 

 Coriolis FM.docx   12.32KB   11 downloads

 

Many Thanks

Shahidul Islam

[chocobang]

With demin water as your service, maybe coriolis is too much.

[shahidulislam48]

Hi,

 

Here is another attached doc. Please have a look.

 Coriolis FM 2.docx   12.29KB   5 downloads

 

It contains Corriolis Mass Flow Meter for N2 gas.

 

Vendor is recommending me to use ½” flow meter. If I still take 1” flow meter it is quite enough to have good measurement.

 

But is it possible to have smaller size flow meter (Corriolis) than control valve/line size? Would there be any effect for controlling during control valve operation?

 

Many Thanks.

 

[chocobang]

Again, coriolis flowmeter is too much for N2 service.

If you will still push through with coriolis, i think there is no problem on having a lower size for flowmeter; it will work fine.

[shahidulislam48]

Again, coriolis flowmeter is too much for N2 service.

If you will still push through with coriolis, i think there is no problem on having a lower size for flowmeter; it will work fine.

As we need mass flow directly then there is no better option than Coriolis.

Furthermore, it's accuracy is high, good rangeability low pressure drop provided a better choice for measuring flow.

It also provide density, temperature and volumetric flow rate simultaneously.

 

Considering these features shouldn't we select Coriolis?

[Mahdi1980]

Hi,

 

Here is another attached doc. Please have a look.

Coriolis FM 2.docx

 

It contains Corriolis Mass Flow Meter for N2 gas.

 

Vendor is recommending me to use ½” flow meter. If I still take 1” flow meter it is quite enough to have good measurement.

 

But is it possible to have smaller size flow meter (Corriolis) than control valve/line size? Would there be any effect for controlling during control valve operation?

 

Many Thanks.

According to your process data and if the pressure drop across the 2" corriolis is no matter, there might be no problem to use the existing flow meter for the measuring and control purposes since, your operational flow is in range and the accuracy is well high.

Anyhow, in most cases the designer prefer to use a control valve which is one or two size smaller than the line size, for your information and clients allow the vendors to determine the size of valve.

 

In summary, I believe that you can control your flow with the existing instruments.

[shahidulislam48]

Thanks Mahdi for your valuable feedback.