A supply-side isolation valve and gauge, a first spring-loaded check, an intermediate test zone, a second independent check and a downstream pressure source make up this assembly. Set upstream and final downstream pressure, jam check 1 or check 2 open, and observe signed flow, intermediate pressure and the reverse-flow indicator.
• A real-time 3D view with numbered, clickable parts: supply-side isolation and gauge; first spring-loaded check; intermediate test zone; second independent check; downstream pressure source. Scene tools include home view, focus-selected-part, auto-rotate, expand and show/hide labels, and drag-to-orbit with pinch-to-zoom. • Experiment controls: upstream pressure (0–600 kPa gauge); final downstream pressure (0–600 kPa gauge); check 1 stuck open; check 2 stuck open; assumed trapped intermediate pressure (0–600 kPa), plus a show flow/process markers toggle, pause/resume, single-step buttons (0.1 s and 1 s), a playback-speed selector and a restart experiment action. • Live readouts: signed forward flow; applied downstream pressure; intermediate zone pressure; upstream minus downstream; check 1 open state; reverse-flow indicator. A model response curve is drawn beside the 3D view and updates as you change controls. • A Curves & measurements tab with two live charts, the model equations as written in the simulator and snapshot readouts; an Experiments tab with 3 guided presets (one failed check; both checks failed; normal forward delivery) plus a model-verification bench, timestamped event log and copyable trial report. • A Learn & assess tab with 3 lessons (follow the system; connect the measurements; interpret the model), a 2-question knowledge check with reset, and a written model-scope statement.
In normal forward delivery both checks open once the upstream-downstream difference overcomes their spring cracking pressures, modeled at 5 kPa each: forward Q = 0.8 √max(ΔP − ΣPcrack, 0) L/min. When downstream pressure exceeds upstream pressure, a healthy sealed check blocks reverse flow.
Jamming only one check open leaves the other as a barrier, so modeled reverse flow stays zero. That is the point of providing two checks in series.
If both are stuck open, reverse flow is Q = −0.8 √(Pdown − Pup) and the signed flow goes negative with the reverse-flow indicator on. Closed checks are perfectly tight in this model, and downstream pressure ramps to its setting over two animation seconds.
Intermediate-zone pressure is an assumed value constrained between limits because two boundary pressures do not uniquely set it. The lab models an ideal double-check assembly, not a reduced-pressure-zone device, does not assess any hazard class, and does not simulate field tests or certification.
It is reversal of flow in a piping system so that water from downstream, possibly contaminated, moves back toward the potable supply.
Two independent check valves in series mean that if one fails open, the other can still stop reverse flow.
The signed flow becomes negative when downstream pressure exceeds upstream pressure, showing an unprotected reverse path.
No. It models one ideal device type and makes no recommendation about hazard classification or required assembly.