Indirect Gas Flow meter

There are a number of ways of doing it.

• Differential pressure across an orifice plate
• Differential pressure with a Pitot-tube
• Vortex-shedding flowmeter
• Thermal dissipation flowmeter

Pelton wheels are probably best avoided in this particular case.

Hi ;

I think I could give you some solutions to try to answer to you, but you know, my knowledge of specifics technical expressions is a little bit limited.

So, please indicate me the followings :

_ What is a "Flare head" ?

- Which are the characteristics of the gas you have to measure the flowrate (density, viscosity, temperature, operative pressure, mini/maxi flowrate) ?

- Which are the characteristics of your pipe (internal diameter, thickness, material) and the maximum straight length without any obstruction is installed ?

- Wich are the maximum uncertainty limits you search for (% of maximum scale or measured value) ?

At first, if I have all understood, you search for a non-intrusive system, and the only way I know to do so is with a clamp-on ultrasonic flowmeter (with transit time principle), but it only works under precised limits. From this reason all my questions.

Finding accurate flows to flare can be difficult, primarily because you don't know what is heading out of the stack most of the time. It is also a low pressure application so some of the traditional methods may not work very well. We have seen success with thermal dispersion meters, they work kind of like a hot-wire anemometer in that you can place several elements across the pipe and determine the velocity profile of the fluid by the temperature lost or current required to keep a temperature. Then you just need to know the fluid properties to get a mass or molar flow. We have also tried optical meters that beam some sort of light across the pipe and determine velocity based on deflection or something. We haven't had a lot of success with this meter though.

I have been interested in this problem since about 1997 when someone told me that the EPA was getting nosy about just how much of these waste gases were being burned. I knew about a MEMS based flow sensor technology that I thought just might do this. While at that point the chip had some catastrophic weaknesses, we are now part of a group that has licensed this technology, improved it and we are now characterizing the chip, finally after 10 years of development. It is 1 mm x 2 mm, robust (we think), very low power, very accurate, DIRECT reading and surprisingly cheap. Depending on the characteristics of the flow, we would be interested in testing the devices for such an application. Can you give us some specs about what is required? I don't think we are going to be able to deal with temperature above about 200C, so if it has to stay that hot we are probably toast (sorry) for that application.