Drum Level Process Identifier

Identify a drum level process model from open-loop bump test data using two-phase manual fitting. Phase 1 captures the shrink (inverse response) dip; Phase 2 fits the ramp slope (integrator gain). The result is a transfer function ready for the 3-Element Drum Simulator and IMC PID Designer.

Model: G(s) = K(1-βs)/s · e-Ls — 3 parameters

Phase 1 — Shrink Characterization

Read values off the DCS trend after a feedwater valve bump. The shrink dip is the initial level drop caused by cold feedwater collapsing steam bubbles before mass inflow takes over.

Dead Time L

—

seconds

Shrink Depth

—

% level

Shrink Duration

—

seconds

Phase 2 — Ramp Slope Fitting

Enter (time, level) pairs from the ramp portion of the response — after the shrink dip bottoms out and level starts rising steadily. The tool fits a linear regression to get the integrator gain K.

Only points after the trough time (t = — s) should be included.

Time (s) PV (%)

Ramp Slope

—

%/s

Integrator Gain K

—

%/(s·%valve)

Fit R²

—

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