I have a rather expensive problem, and would like to ask for a sanity check.
There is a DN250 oxygen line feeding our plant (it's a Steel plant with Electric arc furnaces), and the existing metering system is Orifice based, with pressure and temperature compensation. The supplier has declared the measurement system to be accurate enough over a 10:1 turndown starting from the peak flow rate of 23,000Nm3/hr. Below the minimum, the flow shall be deemed to be at the minimum. That is, once the supply valve is open, we are charged at 2,300Nm3/hr, whether we use it or not. The trouble is, we often run at 500Nm3 to 1000Nm3/hr when the plant is on standby.
The oxygen pressure is around 20 bar.

I have suggested to the supplier that our company pay for the installation of a better metering system, so that we are more likely to pay for what we use (obviously he is not keen to do this, since now he is making a fine profit...), and to that end, I put forward several coriolis mass flow catalogues. Fortunately for us, the contract has one little line that says we can do this. Their answer was that 'head office' doesn't approve those type of meters for custody transfer, which I thought was 'curious'.globle vlave

The questions that I would like to put to you are as follows:

What is so wrong with Coriolis measurement, that a major oxygen supplier would refrain from using it? I assume for the time being that the head office is being quoted correctly.

What other metering options/ piping systems are possible?

Of course, we have them checking what options there are, but all the same, I would like to get some parallel.comments.

NPS 10 is as big as available for any Coriois meter and much larger than most.  If dealing with pure oxygen, the piping reductions create impingments that require monel etc.  The meter tube might need to be monel.  It sounds like a much bigger deal than multiple dp transmitters to accommodate wide turndown on the existing orifice plate.

Orifice meters are very accurate and 16 to 1 turndown is very acceptable with "smart" tranmitters.  Make sure your supplier has the latest version of API chapter 14 and that they comply with it.  I assume you witness calibrations and inspect the test equipment to see if it has been NIST traceable certified correct.

The next best option would be to install a ultra sonic meter, they have a 100 to 1 turndown.  Again SAPI 14 will give all the specifications.

The next is a turbine meter, 50 to 1 turndown is resonable. I think API 8 covers these meters.

The Coriolis meter has not been widely accepted in vapor phase, the industry has performance standards, but you'll still need to calibrate it to one of the meters above.

There are ISO standards that correspond to the API.  I would have my own meter installed as a check and back up if the suppliers meter fails.  I hope the meters are all EFM too.

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