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I want to measure gaseous hydrogen flowing in a 3" line, maximum flow of 200 cfm, static pressure below 2 PSI. Which flow measurement element provides the lowest permanent pressure loss? Flow tube? V-cone? Other technology?

A transit time Ultrasonic has zero pressure loss. A thermal mass would be very low but any DP type has quite high losses.

Roy

You can have a DP type flow meter with a low pressure loss (compared to 2 PSI). 2 PSI = 54 Inches H2O. There are plenty of DP flow transducers used in the HVAC industry that incur less than 2 inches H2O, which would be only about 4% of the supply pressure.

Robert Scott
Real-Time Specialties
Embedded Systems Consulting

Hi, There are various technology that can help to minimize the pressure loss few of them are VERABAR (Averaging Pitot Tube), Thermal Mass, Ultrasonic Flow Meter (Clamp On or Intrusive), Vortex Meter etc. To measure gas I would recommend VERABAR, Thermal Mass or Vortex. The choice of selection entirely depends on whether flow is measured in mass or volume, accuracy required, maintainance practices, price etc.

What flow measuring technology provides lowest pressure loss? I don't require high accuracy - a rough measurement is fine. Also, any suggestions for a purely mechanical flow measurement device? One that does not require power to function - just a visual flow indication.

Magnetic Flow Meter, or any clamp on ultrasonic type. There is NO pressure loss except for pipe friction.

If you want a mechanical device, any turbine or positive displacement flowmeter will work, or if you can put it in, a variable area meter. But you aren't talking about what you are wanting to put through the flowmeter. If you are putting raw sewage through it, there are NO mechanical designs that will work longer than 10 minutes. If you are putting clean water through, or something with the same viscosity, density and particle sizes, any mechanical meter will work fine. Is there entrained air or gas? Mechanical meters, in fact, all meters, don't like that.

Give us more information, and we can give you better advice.

Walt Boyes
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Walt,

In the original post Hydrogen gas 200 cfm @ 2 psi 3" line. Can you get a turbine meter with mechanical readout?

Roy

Yes, you can get fully mechanical turbine meters. The first turbine flowmeter was built before 1800 AD...

But I would be inclined to not use a turbine meter for H2 at all.

Walt