Turbine Meters vs. Thermal-Dispersion Mass Flow Meters

Greetings,

The turbine type flow measurement devices use a signal generator attached to a turbine fan mounted directly in the flow stream. The magnitude of the generated signal is proportional to the rotating speed of the turbine fan which is dependent upon the quantity and viscosity of the fluid flowing through the tube/container. The major concern for this type of device is component failure due to the temperature rating of the shaft bearings and the bearing lubricant. These devices are not normally used for high-heat applications.

The thermal-dispersion type flow measurement devices use a temperature-sensitive junction of dissimiliar metals/oxides immersed in the flow stream of the fluid being measured. The flow of the fluid past the junction heats or cools the junction thereby changing the impedance of the device which proportionately alters the magnitude of current flowing through the measuring loop circuit. These devices can be used for higher temperature applications.

An in-depth search on the internet will yield several different manufactures that produce many different devices used for flow measurement of many different fluids at a very broad range of temperature applications which will meet your needs. I recommend that you contact at least three (3) different vendors and solicit their input as to application specific details on their respective equipment/devices.

I hope this has helped you in some way.

The first respondant is correct. I ended up with an "Annubar" device. They built it to fit what I needed and gave me the temperature and density sensitive calculator to allow accurate use. We have no reason to doubt its' accuracy and heve been using it for more than a year. There are a few systems that are likely to be as good, so shop around a little and use what best fits your use and capability.

h2om@hotmail.com

Thanks for the info..it do gives me some ideas.

BTW, currently we are using the annubar by Rosemount but after a few years of usage we've done some calibration for the flowmeter we found out the reading is not accurate & out of range & also was said the annubar not so applicable due to low dp inside the ducting will effect the inaccurate reading.

We also try to look for some upgrading & modification, after do some research on few other manufacturers but end up they unable to support us because of high running temp.

Is there any other type/brand which is applicable for this condition?

Thanks.

Thermal dispersion type flowmeter can be used. if cost is not a factor, use Ultrasonic flowmeter with more accuracy. To start with you can use non intrusive type (clamp on type) Ultrasonic flowmeter.

Dear Sir,

Could you recommend some good branch for Thermal-Dispersion Mass Flow Meters?

Thanks

derek

The first and important thing to look at is your measurement units ? Are you measuring in mass or volume ?

Mass means Kg/hr, tons/hr, lb/hr or it can be in corrected volume SCFH, NCMH, etc.

Thermal Mass is Mass flow device, it is robust, accurate and they offer an insertion model. It will save you a lot of money.

Turbine meter is volumetric device, it is has a moving parts, and they are not design for big pipes.

Annubar is differential pressure device, it is called an average pitot tube. Basically it is a pitot tube with many measurement points and they take the average of the points. I personally tried it, and it tends to drifts !

Ultrasonic is a volumetric device. Ultrasonic gas meter is expensive, and the clamp on ultrasonic gas is hard to use. I think is the most overated meter.

Thanks,

Raymond (ASQ CCT)