One common method of measuring fuel gas is to use a positive displacement meter. Measurement standards set by organizations such as the American Gas Association (AGA) do not allow this measurement type for fuel gas, but the ease-‐of-‐use, a perceived lack of difference in the ownership, and the low-‐value of the fuel being measured are often used to justify the use of PD meters for gas volumes.
While positive displacement meters are quite inexpensive and easy to use, their meter readings must manually be pressure and temperature compensated for gas services, generally using monthly average pressure and temperature readings.
Potential issues of using positive displacement meters in gas service:
- If pressure and temperature compensation is not calculated, the recorded volume will generally only be 10% to 20% accurate, as the combined pressure and temperature compensation factor is typically between five and ten.
- If both the field and production accountant apply corrections, the recorded fuel volumes will be too high.
- If a record is not kept of how the correction factor was generated, problems can occur when the property is audited.
This is a problem that is unique to positive displacement meters in gas service because PD meters are designed for liquid services only.
How FacilityStudio provides value
Your company should spot-‐check all of your positive displacement meters’ pressure and temperature compensations where they are installed on a gas stream to ensure the right adjustments are being made. If issues emerge, we recommend reviewing all of your gas service positive displacement meter calculations.
The image below represents two PD meters in a FacilityStudio generated measurement schematic, one installed on a gas stream and one installed on a liquid stream. The liquid service PD meter does not require any additional adjustments for pressure and temperature. Any gas service PD meter will require the pressure and temperature of the gas service to be manually calculated because PD meters do not automatically calculate these values
The raw meter reading and standard condition readings are stored in your metering system. This is not currently stored in FacilityStudio.