Hi all,

I've a situation where the FLow Computer is calculating Gross and Std Volume Flowrate by using metric units (i.e. base T = 15 degree C and P = atm.)

If the customer need the measurement to be based on imperial unit. Can we just use the same Flow Computer setting by setting the base T to 15.556 which is eq. to 60 F.

Plus what if the densitometer is using metric but feeding a imperial flow computer.

Thanks in advance,

 

Depends on your flow computer. Forget the density meter.

The density meter measures the density at the flowing temperature and pressure and you are also measuring the temperature and pressure at the density meter and probably also at the flow meter (these may be different).

It is the flow computer software that will be doing the calculations from this raw data.

The usual reference is the Manual Of Petroleum Measurement Standards.
In this it declares that it is the calculation that is the standard (it used to be the tables, but not any more).

It defines:
Observed Density as the density measured at the operating temperature and pressure, the Base Density as the density at the reference conditions, and alternative density as the density at any other set of temperature and pressure conditions. It also defines the correct calculation sequence which is that the base density is calculated first and then, if the density is required at some other set conditions, that is then calculated from the base density. In other words, the base density at any other set of reference conditions is simple a particular case of an alternative density.

Now it is down to your flow computer.

Some flow computers work in such a manner that if you enter an alternative reference temperature they will automatically follow the MPMS required calculation sequence. If they don't, then technically you are no longer compliant with the MPMS.

Fiscal metering is a touchy subject because there is no such thing as a small error. Any error, accumulated over the sort of volumes involved may represent very substantial amounts of money. The real answer to your question therefore lies with the manufacturer of your flow computer.

 

If alternative base condition means another value (say change from 15 C to 15.556 C), then the Flow Computer can calculate it.

But if alternative base cond. means another unit (15 C to 60 F), then to me the calculation is not correct. The Flow computer is design to refer to either metric or Imperial std. Changing the standard means that all the algorithm and program need to be reset by Vendor it self.

This is because the temp. correction will be based on Table 1 of API 2540. The temp. correction differs between metrics and Imperial.

Thanks for your valuable reply. I guess the Flow Computer better be configured to Imperial Units.

Cheers,