Can anybody suggest the best way / flow meter to measure accurate flow & quantity in a 14" pipeline carrying Acetylene gas at 0.3 Kg/m2 & 3200 m3 / hr. rate?

Please post if more details are desired.

Thanks & regards.

 

i think for this application could be usefull a non intrusive ultrasonic flowmeter. Recently, most brands (E&H, Emerson, Panametrics (G&E metering)..... developed this technology, even for custody-transfer applications. The main restriction, in your case, could be the relative low presure, due this technology is very conditioned by that parameter.

good luck

 

The "best way" is always a compromise that involves cost, maintainability, accuracy, and longevity. We've used Rosemount 3095 multivariable flow meters on our 7FA combustion turbines and have not experienced failure or significant drift over the past seven years.

They measure line pressure, DP across an orifice plate, and line temperature. They have a sophisticated algorithm that uses a configurable table of individual gas characteristics into account. We have them configured to output in lbs./hr, but they'll output other varibles as well. Or you can extract the three variables via a Tri-loop Hart to 4-20mA converter and do the math in your controller like we do on a steam flow applicationS. I prefer the simplicity of having the 3095 output the flow directly and avoid the Tri-loops altogether.

The 3095's are accurate at moderate to full flow rates, but like all DP flow measurement, they're not very accurate at low flow rates. That doesn't matter much to us because we spend so little time at low flows.

One of the main advantages to the 3095's is that they're relatively easy to shop calibrate, or calibrate in place if they're not 30 feet above the ground like ours are, in ways that satisfy the EPA. We once made the mistake of installing a very accurate(and expensive) Daniel turbine meter on one of our CT's, only to find out that the EPA required full disclosure of Daniels' proprietary design so they could validate the calibration requirements, which was something Daniel refused to provide. So we ended up scrapping the Daniel and putting in a 3095. Less was more in this case. Turbine meters have a good accuracy but they have the disadvantage of relying on moving parts, which I'm not a big fan of.

On our duct burners, we use an orifice plate, an ABB DP transmitter with another ABB for static pressure measurement, and a thermocouple for temperature. Again, they're easy to calibrate. The flow calculation is done in the DCS.

Our gas suppliers' billing meters are actually a set of three ultrasonics in parallel. (I don't know the manufacturer off the top of my head). The gas flows through the smallest line at low flows, the mid size line at the mid range flows, and so on. I was surprised to see ultrasonics being used for natural gas billing purposes as I've always thought of them as being marginally accurate but there they are. The valving for the parallel headers added a lot of extra cost as well, but I suppose the annual bill of $250,000,000 made the extra cost seem trivial.

If the your flow element is subjected to fouling and gas line shut down isn't a viable option, you might want to consider a flow element that's extractible under pressure, such as the Annubar elements that Rosemount provides. They're a lot easier to pull than an orifice plate.

I hope this helps.

 

You have a number of options depending on your budget and accuracy requirements. Least expensive are insertion turbine meters from sources such as InFLOW, INC., Flow Technology, Hoffer, etc. These meters are very reliable on gas service and are very econmical compared to other types. Insertion pitot tubes generally don't work too well at very low pressures and flow rates although you should review actual performance with the respective manufacturer such as Veris or Annubar. Increasing in cost but still very good for low pressure applications are venturi sections. Venturi meters can be very accurate when properly applied, have no moving parts, and will last until the next ice age. With the today's smart DP transmitters they also offer a fair flow rate turndown.

Some of the new technology designs such as multipath ultrasonics can perhaps be used at very low densities, but are far more expensive than the other choices, and may or may not be more accurate than a venturi.

John Catch
www.inflowinc.com

 

You may try a properly designed orifice or annubar alog with sensitive DPT and a density computing unit. This will give you overall accuracy of 2%. I have used this technique several times for flow measurement of biogas where even still lower pressures are to be handled. As long as the density of gas does not change this method gives good repeat accuracy.

From:Shrikant S.
shrikant. manas at yahoo. com
http://www.manasmicro.com

 

For low flow rate applications and constant gas compositions you should also take a look at thermal instruments. There are several manufacturers to look at, both in the USA and internationally. Based on the known heat transfer rate to a specific gas, the instrument quantifies mass flow.

Thermal technology excels at providing solid performance at low flow rates even in low pressure to vacuum conditions.

Obviously I am partial to Kurz Products, but in all honesty this is a pretty simply "run-of-the-mill" application for a thermal instrument and Sierra, Eldridge, Fox and Sage would likely perform as well.

Marty Vandermolen
Kurz Instruments Inc.
800-424-7356

 

There are few technologies that can handle this application with perfection. VERABAR Flow Element, Thermal Mass Flow Meter, Venturi (With some pressure drop), Optical Flow Meter (better than Ultrasonic since it is a low pressure gas application where Ultrasonic Gas Meter fails), etc.

I would advice you to consult the manufacturer to see what rangeability you will achieve & based on your requirement you can select an appropriate technology.

rohit at chandakinstruments. com

 

For low pressure gas, don't forget insertion style Turbine Flow Meters, which are likely the most inexpensive technology. Meters are available
from vendors such as Hoffer, InFLOW, Inc., Engineering Measurements, Flow Technology, etc.

John Catch
www.inflowinc.com