Low Volume Natural Gas Measurement 1

[zdas04]

There has been a recommendation by a quasi-government organization to measure the gas going to pneumatic control devices on wellsites in Oil & Gas operations. They also want to measure fuel gas separately.

The pneumatic control devices would need to measure a flow stream of about 800 SCF/day at less than 30 psig (temperature ranging from 45F to 80F). For sites with multiple devices that number may go as high as 2400 SCF/d. This volume must be electronically available for capture in a SCADA Host System for reporting purposes. Does anyone know of a device that would satisfy these requirements?

The also want to measure the streams that are burned on site (engine fuel, tank heaters, separator heaters, etc.). This stream is probably capped at around 8,000 SCF/d, but it could be as low as 1,000 SCF/d. If there is a device that can handle the first part, does it have the turndown to handle the second?

I've looked at all the devices that I normally use in Field Gas Measurement (i.e., Square Edged Orifice, V-Cone, Vortex, Coriolis, Ultrasonic, etc.) and none of that seems to go down this low. I've looked at Roots Meters and Diaphragm Meters, but I'm having a hard time determining if they have an output that I can take to an RTU (all the diaphragm meters I'm seeing have a local read out).

Thanks for your help.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"

 

[JLSeagull]

If you cannot measure it with a NPS 1/4 Coriolis then the government should not worry so much.

 

[zdas04]

I couldn't agree more, but that is not a direction of latitude that I have.

David

 

[dcasto]

welcome to the goverment world where they want bthe US to produce bio diesel at a rate 3 times higher than we presently produce oils for food ie rapeseed, soy, and corn.


you need lab equipment. go to

http://www.omega.com/green/flow-level.html

to get some ideas.

 

[danw2]

You might want to consider thermal dispersion meters which will provide an inferred mass flow value and which work really well at low flows, and which have considerable turn down, to boot.

Kurz, Sierra Instrument, and FCI are some major brands.

I ran into several brands of thermal flow meters sized just slightly larger than a package of cigarettes, used extensively by the pharmas for measuring low gas flows, as indicated by their small diameter (1/4") tube fitting inlet and outlet ports. But that was 15 years ago and I'm stuck for a brand name at the moment. But for all I know, the Kurz or Sierra now have those smaller units for low flow, too.

Flow Control magazine did a article on thermal dispersion about a year ago, a good overview:

http://www.flowcontrolnetwork.com/issuearticle.asp?ArticleID=327

Dan

 

[mbt22]

800 scf/d is about 1 m3/hr, so say 1.25 kg/hr air. An Emerson CMF010 will give you about +- 0.5% at those conditions. I've used them for similar duties successfully in the past.

Ritter wet gas flow meters might do the job too, though they always have the slightly worrying possibility of contaminating your stream with the packing fluid.

Thermal mass flow meters are great, but you have to know exactly what the composition is to get an accurate reading (calibrated with heat capacity)

Matt

 

[danw2]

Siemens has a compact low flow coriolis.

This spec sheet is the 'tube' in the line part.

http://www.automation.siemens.com/w...en_extract/sitransf_fcmass2100di15_fi01en.pdf

The tube needs an electronics 'converter/transmitter' box.

When I priced one a couple years ago, the tube/transmitter cost was 2x-3x a thermal meter.

But as Matt points out, coriolis gives a mass flow value irrespective of changing heat capacity or density, for that matter.

 

[KiwiMace]

Most Roots meters can be fitted with an optional pulse output head.

Here's another thermal mass flowmeter.

http://www.valleyairsolutions.com/BIOGAS FT2+ Data Sheet (Valley Air Solutions).pdf

 

[zdas04]

Thanks guys. That was what I needed. I finished the report last night and your input was a big help.

David

 

[glowing]

I used to install rotometers right off the top of the scrubber. You would be surprised how much it actually adds up tp when you start adding wells together. You will find yourself looking for more efficient devices.