we are going to purchase orifice based custody metering package to measure flow of hydrocarbon gas produced in gas plant for selling purpose.
Questions are:

-What is recommended accuracy of metering package required for custody transfer of mentioned fluid?

- Is there any standard in this regard?

thanks in advance.

 

Better is the best, generally based on API guidelines linearity of +/-0.15% of reading with repeatability of +/-0.02% of reading is defined as custody transfer accuracy on liquids. AGA3 which is related to gas flow measurement using Orifice Plate calls for +/-0.5% of reading as accuracy required. If you plan to use orifice than follow AGA3 guidelines and expect accuracy of +/-0.5% of reading as an most reliable and defined for custody transfer. The other choice of meter could be Turbine (AGA7)or Ultrasonic (AGA8 please this)

 

If you are measuring a type of refinery fuel gas, the AGA8 method can be used (same as API 14.3). The API MPMS (American Petroleum Institute Manual of Petroleum Measurement Standards) is a great resource for requirements of Custody Transfer; you should look at chapter 14 for sure if you are measuring gas phase fluids.

For any FCCU tailgas (thermal cracked gas) flows, the standard that should be out soon this year will be API 14.11, which better models this type of fluid.

In addition to a copy of the API MPMS, I recommend getting a GPA set of books.

J. Miles