Understand Meter Factors

A Meter Correction Factor (MCF) is a compensation factor which accounts for non-ideal mechanical effects such as bearing friction, fluid drag, and mechanical or electrical readout drag. The MCF value is gathered through a process known as meter proving. The meter proving process tests the accuracy of the meter readings. Small inaccuracies that are found through these tests are accounted for, and through this, a meter correction factor that compensates for the meter's deficits can be obtained.

Using the MCF allows the system to process indicated (observed) volume and flow rate values, turning them into Gross Standard Volumes (GSV) and rate values, according to the prescribed API algorithm.

In order to properly apply the MCF, AVEVA Pipeline Operations for Liquids follows the procedures (including the rules for rounding and for the order of calculations) laid out in the American Petroleum Institute’s Manual of Petroleum Measurement Standards (API MPMS), Chapter 12, "Calculation of Petroleum Quantities," Section 2, Part 2.). Using the rules supplied by the API's MPMS, it selects the correct MCF from a grid of factors associated with the specific meter and the type of product currently flowing through the meter. Within the grid, the appropriate MCF is chosen, given the current flowing conditions of the pipeline. Two things are accounted for: the flow rate and the density/gravity of the fluid being metered.

Below, the following diagram depicts what an MCF grid might look like for a particular meter and product type. You and the Administrator have the opportunity to configure the increments used within the grid.

Initially, all of the entries in the grid will default to a value of 1.0. If a meter prove produces a new MCF for a particular entry in the grid (based on the flowing conditions of the prove), that grid entry is updated accordingly. The selection of the correct MCF is based on the flowing conditions. Accordingly, the appropriate MCF is selected on each calculation cycle based on the current flow rate and density / gravity.

If it is found that no meter prove has been performed for that cell, or if the MCF in the cell has expired (as per the configured timeout or throughput values), you will be notified. At this point, you will be able to manually adjust the MCF or issue a request for a prove to be performed, which will result in an update to that MCF.

The entry in the grid is populated either manually by you or automatically by another application responsible for meter proving. When you populate the grid, you will enter the following information: the density / gravity information, the flow rate, the temperature and pressure, and MCF. From the information that you have supplied, the prove date and time will automatically be added.

The expiry time limit defines how long any given MCF can be used before another meter prove should be completed. The MCF is usually considered valid for a time period of 30 days, and the throughput threshold defines how much volume can flow through the meter before another prove should be completed.