Physical Degradation
A mechanical degradation mechanism alters the inner wall geometry and stiffness of vibrating measuring tubes in flow measurement devices. Particle impingement in slurry applications causes coriolis mass flowmeter erosion, which thins tube walls and alters the natural resonant frequency of the meter. This loss of structural mass reduces tube stiffness and skews the phase shift measurement used to calculate mass flow rate.
The boundary of this phenomenon sits where clean gas or non-abrasive liquid flows through the system, leaving the internal wetted surfaces intact.
Tube Thinning
Velocity profiles across curved sensor tubes concentrate abrasive force along outer bend radii. Fluid velocity accelerates local material loss, creating localized pitting or uniform wall loss depending on particle size distribution. Structural integrity drops prior to burst pressure limits, altering tube stiffness parameters stored during factory calibration.
Calibration Drift
Frequency response changes force the meter drive circuit to adjust drive gain values to maintain vibration amplitude. As coriolis mass flowmeter erosion progresses, the zero point shifts and baseline sensitivity strays outside specified error bounds. Field zeroing hides the underlying wall loss without restoring original stiffness, causing span errors across the entire operating range.
A recalibration against a reference gravimetric rig isolates mass loss from electronic gain shifts.
Qualification Standard
Verification procedures set by ISO 10790 require periodic baseline comparisons against recorded reference tube frequencies. Wall thickness checks using ultrasonic thickness gauges or high-frequency acoustic monitoring establish remaining service life before mechanical failure occurs.
