Analysis Model for Orifice Flow Meter Correction Factor in Measuring in-Pipe Natural Gas Flow based on Numerical Simulation

Abstract

Orifice Flow meter (OFM) is widely used for measuring the flow in industry. However, in many cases, the measurement value of OFM some times will differ from the other meter, for instance Ultrasonic Meter (USM), that also measure the flow of the same pipe. The inaccuracy of the flow measurement using OFM can be caused by: i). the geometry of the OFM hole that experiences the shape changes due to abrasion or deformation as the result of the gas flow pressure on the inner surface of OFM metal holes; ii). the presence of a liquid fraction in the measurement of gas flow. To match the value measurement between the OFM and USM, a numerical simulation process of natural gas flow through OFM is needed. In this research, an analysis model for Orifice Flow Meter Correction Factor in Measuring in-Pipe Natural Gas Flow based on Numerical Simulation, is proposed. This model can be used to correct the error measurement of the OFM. The analysis process is conducted by analysing the Pearson correlation and testing the Kolmogorov-Smirnov data normalization on 9 populations of flow measurement data using OFM and USM. However, only 4 of the data that matches to the Pearson correlation criteria and the Kolmogorov-Smirnov normalization. Based on the 4 populations of data, a correction factor model was developed using a regression analysis consisting of two factors, namely OFM and USM correction factors that refer to the actual data from the measurement of gas flow rate. Based on variations in gauge pressure of 393.65 psig, 404.67 psig and 413.37 psig at a temperature of 80.710F and numerical simulation results in the form of different pressure and flow discharges, the resulting correction factors are in the form of 3rd degree polynomial equations.