Gas Flow Measurement

Hello,

In the factory i work, we have many flow-meters which are used to measure gas flows like nitrogen,steam,hydrogen,natural gas etc.

Measureing methods used are generally vortex and orifice. different brand of meters are used like krohne, dresser..

My problem is that i come across many problems with those meters. They are not %100 reliable, they have malfunctions very often.

My question is , which measuring method and which brands are sucessful at gas flow measurement?

Regards,

EK

You should not be having failures to a great degree using the metering you have mentioned. The steam application might have a few failures if the steam is not clean, meaning it has a high moisture content. Water will wear away your measuring elements inserted in the line. The other gases should not be a problem. I have used the Yokogawa vortex meter on steam applications and had great success. I am not familiar with the two brands you mentioned, so you might have better luck with the Yokogawa. Good luck!

At what pressures and what temperatures are you measuring the gas flows?

Are the gases manufactured as part of you process or purchased, clean commercial gases?

What are all the kinds of failures you are experienceing?

Some common examples of flow failures can be
- sensing problems (clogged impulse lines to a DP),
- installation problems (impulse lines coming out the low side and filling with condensate; insufficient meter run lengths)
- inaccuracies: changes in process conditions that fall outside design criteria (what are you proving flow with?)
- electrical or electronic failures (lightning strikes, bad power, bad grounding)
- mechanical failures - impulse lines leak, Orifice plate installed backwards, beveled edge worn, cover left off transmitter head and head filled with water

to name only a few

Without knowing
- what kinds of failures you have
- what the operating conditions are
- what you're instrumentation you are using

recommendations for improvement are merely speculation.

For instance, I speculate that you're orifice measurements are failing because you have varying levels of condensate in the impulse line causing zero shift.

There, you have an answer.

Is my answer valid? No, because it is merely speculation on my part.

Dan

emokar said:

My question is , which measuring method and which brands are sucessful at gas flow measurement?

EK

Click to expand...

The best on the market is Endress&Hauser.

-For your Vortex instruments, becarefull about the vibration it can affect it. Usually if your parameters are set properly (density,type of product like gaz or liquid, etc..)you should not have any problem with this vortex technology.

-With the Orifice technology you have to be sure that both pressure cells are well calibrated. Very sensitive technology.

You might also look at a Coriolis type flowmeter, if cost isn't a big problem. You can do the measurement in density if needed. Endress +Hauser would be a good place to start. They have units that are used for custody transfer that need to be accurate and reliable.
John

Emokar
I would also vouch for Endress and Hauser but you will not find a single type of instrument which is suitable for all types of gas.
Steam metering is nearly always done with orifice plates and DP cells and this should be very reliable. If you have problems I would look at your process connections and consider a different transmitter supplier.
Flammable gases will require properly certified instruments.
Non hazardous gases such as air or nitrogen can be measured with a variety of different technologies such as E&H's T-Mass thermal mass flowmeters.
Any of the major instrument manufacturers such as E&H, Foxboro or Rosemount will be able to offer a number of alternatives but you might find them expensive. Unfortunately this is an area where you get what you pay for.
Andybr

Consider using thermal mass for some application. FCI or Sierra Instruments are two that I have used successfully for gas flow rate of nitrogen and CO2.
http://www.fluidcomponents.com/
http://www.sierrainstruments.com/


For natural gas, Dresser is one of the better products.

The McCrometer V-Cone primary element coupled with a Foxboro IMV30 multivariable flow transmitter is excellent for measuring mass flow of gasses, especially steam. The V-Cone does not require long upstream straight pipe runs as do most other differential pressure elements.