Looking for a reasonably priced flowmeter for gas measurement

[IanGodfrey]

We are measuring using a thermal mass flow meter right now and it works great, but I am looking for something under $5K. The application is 20,000 SFPM in a 3" sched 40 pipe

 

[TiCl4]

How much pressure drop can you take, what turndown do you require, and how much accuracy do you require?

Orifice meters are cheap, but have some drawbacks.

 

[IanGodfrey]

5 PSI pressure drop, 100:1 turndown and just need repeatability with +/- 3%

 

[georgeverghese]

At 100:1 turndown, you may be limited to an ultrasonic meter selection - doubt it will suit your budget though. Pressure drop is negligible.

 

[TiCl4]

The turndown is going to be a problem - an orifice meter, even with a good dP sensor, isn’t going to cut it.

I’m not actually sure what other gas flow meters have a 100:1 turndown other than coriolis meters.

Vortex meters might be okay - the one I’ve seen states good accuracy down to a Re of 10,000. Does that give you enough turndown?

In any case, you aren’t getting 100:1 turndown on the cheap.

Is this a clean, non-condensing gas?

 

[1503-44]

Branch to several meters, each one sized for various turndown flow ranges, but that gets expensive quickly as well. Covering all bases always has its costs.

 

[LittleInch]

Ian,

I assume this is 20,000 SCFM? Is this your max flow?

So you also want to measure down to 200 SCFM??

What is the pressure / velocity range?

DO you have space for long (10-20D) straight lengths upstream and d/S of your meter location.

If your current meter works great, why are you looking for something else?

What sort of output do you need? - ready calculated SCFM to what metering spec?

All data that a vendor will need to know.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IanGodfrey]

Hi Little,

20,000 SPM or 1050 SCFM equivalent for our pipe size, I worked out the specs with the company I bought from before that information is listed here-

https://www.foxthermal.com/configure/?AppID=25497

What we have works well, but this is a research facility and I'm looking for a more cost effective solution. we have 10 more measuring points so $50K might be a little pricey.


TiCl4,
It is a composition of non-condensing gases. I will look into Vortex, that might be a good alternative.

 

[georgeverghese]

From memory, you wont get more than approx 8:1 turndown with vortex meters, so you'll need at least 2 vortex meters piped up in parallel to get 70:1 or so ( a low range and a high range meter). Plus you'll need an inline densitometer for mol wt correction to give you a corrected standard volumetric flow readout.

 

[danw2]

To elaborate on vortex, at low flow, there aren't enough vortices generated within the 'reporting' or update time period, so vortex meters report zero flow, a self induced low flow cutoff. Rule of thumb is about 10% of max flow is the low flow cut-off, but it depends on the pipe size and flow, but it's a physics thing that all vortex have to deal with.

Beware. Note that the origin point of a typical sizing chart for the design conditions is not (0,0); the flow cuts off in the example at 15.2 GPM, any lower flow rate is reported as zero.

 

[IanGodfrey]

georgeverghese,

I think you are correct from what I have read up on the vortex meters.

danw2,

Thank you for elaborating on why the vortex meter is probably not suitable. I found a less expensive model of the one we originally purchased from the same company so I think I'm good for my gas flow measurement needs.

 

[LittleInch]

I found a less expensive model of the one we originally purchased

Which one?

And does it do 100:1 turndown??

Still don't know what 20,000 SPM is though... "Something Per Minute"??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[IanGodfrey]

Fox Thermal's model FT1, apparently it can go higher than 100:1. I was looking at 20,000 SFPM standard feet per minute in a 3 inch schedule 40 pipe. It can also switch between gases like the FT4A we have.