This simulator models a globe control valve — plug, seat, stem and bonnet packing driven by a diaphragm actuator and positioner — and compares its linear or equal-percentage inherent flow characteristic against the installed characteristic that results once available system differential pressure is shared with upstream and downstream piping resistance.
• A real-time 3D cutaway of the globe body and flanges, the plug/stem/seat trim, the bonnet and packing gland, the diaphragm actuator and spring, the positioner and feedback linkage, the upstream/downstream piping, and a flow and pressure recorder, with home view, focus-selected-part, toggleable full enclosure, exploded view, auto-rotate, expand and label controls plus tappable numbered components. • Ten live controls: opening demand, an inherent-characteristic selector (linear / equal percentage), rated Kv, equal-percentage rangeability (R), available system differential pressure, equivalent pipe conductance, liquid specific gravity, position response time constant, a travel-error hold band (stiction), and a jam-the-valve-stem toggle. • Play/pause, single-step (0.1 s) and larger-step (1 s) time controls, plus a playback-speed selector from 10× slow motion to 1-minute-per-second. • A dedicated "step opening demand" action alongside start/stop trial controls. • Eight live metrics: requested travel, actual travel, effective Kv, valve pressure drop, piping pressure drop, installed flow, the hypothetical flow if all differential pressure were across the valve, and travel error. • A Curves & measurements tab with two charts (command vs. actual travel, and installed flow vs. the constant-differential-pressure estimate), the full Kv/flow equations, and snapshot measurements. • An Experiments tab with four guided scenarios (linear trim, equal-percentage trim, restrictive piping, jammed stem), a model-verification bench of independent automated checks, and a timestamped event log with a copyable trial report. • A Learn & assess tab with guided lessons (setting travel, exposing flow area, sharing differential pressure, diagnosing a mismatch), a knowledge-check quiz and a written scope/reference statement.
Linear trim maps travel to effective Kv directly: Kv equals rated Kv times travel fraction. Equal-percentage trim instead multiplies rated Kv by the rangeability raised to the power of (travel fraction minus one), so equal increments of travel near full open produce much larger conductance changes than the same increments near the seat — though in this model that characteristic is interrupted by an ideal shutoff very close to zero travel.
Inherent characteristic describes how the valve alone would behave with constant pressure drop across it, but the installed characteristic accounts for how available system differential pressure is actually divided between the valve and the piping: valve pressure drop equals available differential divided by (1 plus (Kv/pipe-Kv) squared), so restrictive piping — a lower pipe conductance — steals a larger share of the available pressure drop, leaving the valve less differential to work with and installed flow measurably below the constant-differential-pressure estimate, exactly as the restrictive-piping experiment demonstrates.
The positioner compares requested travel (command) against actual travel and reports the travel error. The stiction control sets a hold band inside which small travel-error changes do not produce movement, a simplified representative of positioner deadband rather than a full stick-slip friction law. A true mechanical jam is different and more severe: the jammed-stem experiment shows actual travel staying fixed at its prior value even as commanded travel changes substantially, which is the clearest evidence of a jam rather than ordinary stiction.
This is an incompressible, non-choked liquid model with lumped piping resistance: it excludes cavitation, valve leakage class, fluid-induced actuator forces and manufacturer-specific trim curves, and equal-percentage behavior transitions to an idealized hard shutoff near zero travel rather than a continuous exponential down to true zero flow.
No. Installed flow depends on both the inherent trim characteristic (linear or equal-percentage) and how available differential pressure is shared between the valve and the piping. The restrictive-piping experiment shows installed flow measurably below the naive constant-differential-pressure estimate once pipe conductance is reduced.
Linear trim sets effective Kv as rated Kv times travel fraction directly. Equal-percentage trim instead multiplies rated Kv by rangeability raised to the power of (travel fraction minus one), giving much larger conductance changes near full open than near the seat, though an idealized shutoff interrupts that curve very close to zero travel.
Stiction is a configurable travel-error hold band representing positioner deadband — small errors do not produce movement. A jam is more severe: the jammed-stem experiment shows actual travel staying fixed at its earlier value even as commanded travel rises substantially, a persistent command/travel mismatch that stiction alone would not produce.
It models incompressible, non-choked liquid flow with lumped piping resistance only. It excludes cavitation, valve leakage class, fluid-induced actuator force sizing and manufacturer-specific trim curves, and equal-percentage trim is interrupted by an idealized hard shutoff rather than a continuous curve to true zero flow.