I want to select a suitable flow meter for measuring water and process solvents with remote indication. I can not go with orifice plates as the density of the process solvent will vary from 750-1500Kg/m3. The line size is also small 1 to 2 inch.

Please suggest suitable cost effective options. I think turbine type and vortex. Will they work? Which will be more accurate and cost effective?

Apart from them any other suggestions also please.

 

Varying liquid density does not affect the accuracy of an orifice flowmeter. Orifice flowmeters measure velocity through the orifice such that velocity times area = volumetric flow rate. If you must know mass flow rate, then you should use a coriolis flowmeter that inherently compensates for and measures density. They are relatively expensive.

Vortex shedding and turbine flowmeters also measure volumetric flow rate and are independent of density. Both are more expensive than orifice flow measurements. If you can use a commercial sharp-edged orifice in an orifice flange (available in 1 and 2 inch sizes) and a quality dP transmitter, then this will be both least expensive and sufficiently accurate flow solution.

Dick Caro
===========================================
Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270
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I believe that the accuracy of flow measurement using DP transmitter and orifice plate can be improved by using pressure and temperature compensation.

 

I can't let this one get away!

The differential pressure developed by an orifice (or other differential pressure element) at a given flow rate IS dependent on the density of the fluid. The density or SG term appears inside the square root - so Qv is proportional to SQRT(DP/SG) and Qm is proportional to SQRT(DP*SG).

Regardless of whether you need volumetric or mass flow rate, the density needs to be considered. Otherwise, why are boiler steam flow measurements (for one) corrected for density?

Cheers,

Bruce.

 

I agree with Bruce, change in density will definately affect the accuracy of flow measurement irrespective of flow mete used (Volumetric). The change in density is quote wide hence metering the fluid in terms of Mass would be recommended. I would look at Coriolis as a better technology on such a small line size due to the fact that it will give you mass metering by calculating operating density.

 

Caro,
I totally agree with Bruce, density is the major part of Orifice.
So which instrument(Vortex, Turbine, coriolis) will suitable in respect of cost and installation?
I am waiting for your reply.

 

It seems that density is important in gas flow measurement. You specified water flow. For water, the density effects can usually be ignored. Perhaps there is some effect of density for measurement of flow of other liquids. As far as I know, vortex shedding is independent of liquid density. Turbine flow measurement is not used very much due to higher cost and maintenance reasons. The best flow
measurement is coriolis, but it is very expensive.

For me, I would use dP measurement with a well-designed orifice. It is by an order of magnitude more popular than all other flow measurement technologies combined. It's not perfect, but it is adequate unless you need the accuracy for custody transfer. Vortex flowmeters are second in popularity because they are easier to install and maintain than the orifice meter with its impulse lines.

Dick Caro
===========================================
Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270
E-mail: [email protected]
Subscribe to the CMC Wireless Report at http://www.CMC.us
Web: http://www.CMC.us

 

Can some body point out whether vortex flow meter is dependent on density of solvents.
I believe mass flow meter is the best but costly solution. As the accuracy required is not very high 2-3% what should be the best solution.

 

Vortex has the capability of giving you a psuedo mass flow using a user defined density. If and when your density changes from your configured parameter, you will have an error. Vortex meters are a velocity type of meter. Vortex may have a higher initial cost, however install and maintenance is typically less than a DP flowmeter. Basically all types of "volumetric" meters are affected by density changes. Some more than others, it depends on the fluid characteristics. Water maybe not so much, but a light solvent may have a big density swing if there is a big temperature swing associated with your process.

Coriolis meters measure Mass and Density directly(temperature too for that matter).... "calculations" for density using a Coriolis meter is not required. Coriolis will easily cover your accuracy requirements. They are more expensive, but as long as the meter is selected with the correct materials and sized correctly, you should get many years of service in this application.

Cheers!

 

What about Turbine type meter. I hope it is not density dependent and definately cheaper than Mass flowmeter where very high accuracy is not required. Can some body comment on Turbine type flowmeters for use for solvents where density is varying from 750 to 1500 kg/m3.

Regards

 

Turbine meters can be an excellent choice for solvents. If there is any lubricity in the fluid they can operate for many years with very high accuracy. Their down fall is principally debris that can get into the bearings. Most vendors will suggest a strainer in front of the meter. They are not density sensitive on liquids but are viscosity sensitive. However, as long as the viscosity stays below 3-5 cP (depending on manufacture and meter size) the accuracy is well maintained. Vendors such as FTI or Hoffer are our first choices.

John Catch
www.inflowinc.com

 

Hello,

Due to my work/hobby, I have been recovering and storing for a few years technical documentation and guides from different vendors on industrial flow measurement.

If you want to know more about flowmeters basics you can visit this site with a lot of guides/docs from several vendors about this issue.

http://instrumentation.eseberri.com/category/measurement/flow/

Thank you.

 

Turbine flowmeters and mag flowmeters will work great unless there is sludge or something like that in the fluid which will eventually form scaling. Ultrasonic flowmeters by Endress and hauser are great for applications like this. But it all depends on the costing.