ACCURACY DEGRADATION OF MEASUREMENT CHANNELS IN GAS TRANSPORT SYSTEMS AND EARLY DETECTION OF METROLOGICAL FAULTS.

Abstract

The paper systematically analyses the in-service degradation of the accuracy characteristics of measurement
channels (pressure, temperature, and flow rate) in gas trunk pipelines and the causal link between this process, metrological
failures, and the safety of the gas transport system. A structural error model, a Wiener process with drift describing
instrument drift, and an apparatus for estimating metrological reliability are presented. Failure precursors (growth in signal
variance and Allan variance, speed-of-sound residual, divergence trends of redundant channels, and inter-parameter
residuals) and the statistical tools for their detection (CUSUM, EWMA), together with their limitations, are assessed.
Following the GUM methodology, an uncertainty budget for an orifice metering run is developed, and the economic and
safety dimensions of uncertainty are demonstrated. The need to move from calendar-based to condition-based management
of calibration intervals and towards multivariate, regime-aware, data-driven diagnostics is substantiated.