Understand the methods and calculations used in meter proving

The system Administrator can configure the meter factor to use the American Petroleum Institute (API) calculations.

The new meter factor for each meter is calculated based on the values read back from the PLC/RTU. Standard API correction factors for volume, compressibility, and temperature are calculated and applied along with correction factors for temperature and pressure effects on the prover pipe.The meter factor is calculated using the recommended API calculation. The calculation is as follows using double precision arithmetic and rounded to 4 decimal points:

where:

prover diameter is the prover pipe diameter in millimeters (mm)

prover pipe thickness is the pipe wall thickness in mm

MF is the meter factor

MCF is the meter correction factor, it is an average of all meter factors from good runs.

CCF is the composite correction factor. It can come from the prover or the meter. It is calculated by multiplying two or more correction factors together to obtain one correction factor that may be applied. The individual correction factors must be multiplied in the following set sequence: MCF, CTS, CPS, CTL, CPL, CSW

K is the number of pulses per 0.1 m3

CPSp is the correction factor for pressure on steel for the prover. The correction factor allows for the effect of pressure on the prover pipe volume. The prover pipe will stretch elastically and the volume will change accordingly when under pressure.

CTSp is the correction factor for temperature on steel for the prover. The correction factor allows for the change in volume of the prover pipe due to changes in temperature based on the coefficent of cubical expansion.

CPLp is the correction factor for pressure on liquid for the prover.

CPLm is the correction factor for pressure on liquid for the meter.

CTLp is the correction factor for temperature on liquid for the prover. The correction factor allows for the change in the volume of the liquid with the change in temperature, expanding as the temperature increases, contracting as the temperature decreases. The volume change is proportional to the thermal coefficient of the expansion of the liquid.

CTLm is the correction factor for temperature on liquid for the meter.

CTLp and CPLp are calculated using one of the following methods:

1. API standard formula

2. A routine that is automatically selected based on the product density

E is the modulus of elasticity for container material, typically 3.0 x 107 and used for mild steel. This is configured in the Modulus of Elasticity field.

¡ is the coefficient of cubical expansion. It is typically 1.86 * 10-5 and used for mild steel. This is configured in the Coeff. of cubical expansion field.

PBV is the Prover Base Volume in m3. This is configured via the Base Volume field.

PCavg is the average pulse count of all runs.

Pmavg is the average meter pressure of all runs in kPa.

Ppavg is average prover pressure of all runs in kPa.

Tmavg is the average meter temperature of all runs in ºC.

Tpavg is the average prover temperature of all runs in ºC.

Vmcorr is the volume measured by the meter corrected for temperature and pressure.

Vpcorr is the volume of the prover pipe corrected for temperature and pressure.