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Flow to Full Treatment Control (Engineered Unit)
The inlet works control that holds the flow to full treatment and spills the rest. Its subject is a legal number — the consent — rather than a sized machine, and everything the unit does is measured against it.
Which simulation? Running this unit uses the client-side, PLC-style scan simulation in your browser, not the server-side biokinetic process simulation. See Which "simulation" this section is about.
| Slug | fft-flow-control |
| Name in the library | FFT Flow Control (Engineered Unit) |
| Category | Process Units/engineered |
| Seeded | version 0.1.0, maturity published |
| Interface points | 6 — inlet, to_treatment, to_storm, fft_spare, power, signals |
| Asked on drop | 15, the same list for a new and an existing installation |
| Editable setpoints | 16 |
| Fault catalogue | 25 cases, filtered to what is fitted |
| Control loops | 8 generated graphs |
What it models
An inlet chamber with a storm overflow weir and a modulating control device on the forward main, so that the flow passed to full treatment is held at the consented rate and everything above it goes over the weir.
The drawing it generates carries the inlet chamber with its level transmitter LT-x01 and high-high level switch LSHH-x01, the storm overflow weir with its own head transmitter LT-x02, the modulating device with its actuator and position transmitter ZT-x01, the metered forward main with FT-x01 and the hardwired forward-flow-high switch FSH-x01, the isolating valve, the control panel and the off-page connections.
The plant model integrated during a run is the chamber level, the flow the device passes at the head across it, the weir's head–discharge behaviour above the crest, the actuator's travel, and the instruments reading all of it — together with a compliance account: the volume passed above the consent, and the worst excess in any averaging window. "Did it hold the consent" is a question about an average, not an instant.
No new/existing axis. Unlike the first three units, this one deliberately has no new / existing parameter. The reference case states that new-versus-existing is not a configuration axis for this unit, and adding it would double the asserted configuration matrix. The drop panel therefore shows the same fifteen fields either way.
Key parameters
Asked on drop
| Parameter | Unit | Type |
|---|---|---|
| Population equivalent | — | number |
| Impermeable contributing area | m² | number |
| FFT derivation | — | consent formula / declared |
| FFT setting | l/s | number |
| Aerobic volume of the works downstream | m³ | number |
| Declared accepted flow downstream | l/s | number |
| Inlet chamber plan area | m² | number |
| Storm weir crest above the floor | m | number |
| Chamber wall crest above the floor | m | number |
| Control method | — | modulating penstock and others |
| Flow meter | — | electromagnetic / flume |
| Forward flow meter fitted | — | yes / no |
| Storm destination | — | storm tank / watercourse |
| Storm weir crest length | m | number |
| Trunk DN | mm | integer |
The fifteen are the whole budget: the catchment the consent is derived from, the consent itself and where it comes from, the works downstream that bound it, the chamber and its two critical levels, the device and the measurement, the storm split, and the forward main's governing bore. The template carries 55 parameters in total.
Editable setpoints
| Setpoint | Unit |
|---|---|
| Flow to full treatment · Control deadband · Hardwired forward-flow-high trip · Cross-check absolute tolerance | l/s |
| Flow loop gain | % per l/s |
| Flow loop integral time · derivative time · Cross-check delay · Position deviation delay · Spill reporting delay · Compliance averaging window | s |
| Minimum travel · Maximum travel · Permitted measurement uncertainty · Cross-check proportional tolerance | % |
| Setpoint-hold band below the crest | m |
Eight of these (minimum and maximum travel, the permitted measurement uncertainty, the compliance averaging window, the two cross-check tolerances, the cross-check delay and the spill reporting delay) start from the rule set. An edit you make to any of them is kept: it stays in force when you close and reopen the installation, and the rule set fills only a value you have not set.
Control loops
Eight generated graphs:
Measurement health · FT versus position-implied flow · Chamber level · FFT flow control · Actuator and positioner · Storm detect and spare capacity · Hardwired protection · the outstation
Two of those deserve a word:
- FT versus position-implied flow is a cross-check: the measured forward flow against what the device's travel implies it should be. Disagreement beyond the tolerance for longer than the delay is itself a finding — the point of a consent is that you can show you held it, and a meter you cannot corroborate does not show that.
- Hardwired protection runs even when the PLC is not energised, and includes a forward-flow-high open-inhibit: it commands nothing, it only prevents the device opening further.
What the outputs mean
Published port values
| Port | What it publishes |
|---|---|
inlet | Dry weather flow and design peak on the diurnal profile |
to_treatment | The flow passed forward, with the loss through the forward main |
to_storm | The spill at the design peak and at the extreme peak |
fft_spare | The spare capacity under the consent, plus a storm flag — this is a published value, and it is what a storm tank downstream consumes to decide how fast it may return |
power | kW, kVA, amps, essential load and largest start |
signals | The size of its signal set |
For the reference configuration inlet reads 23.4375 l/s dry weather flow and 103.4375 l/s design peak; to_treatment 60.9375 l/s at 0.394167 m of main loss; to_storm 42.5000 l/s at the design peak and 122.5000 l/s at the extreme; fft_spare 37.5000 l/s at dry weather flow; power 0.370000 kW / 0.435294 kVA / 0.628293 A; and the signal set 11 DI / 2 DO / 4 AI / 1 AO plus 2 communications registers.
Two of those are run-derived. The forward flow actually achieved and the hours spent spilling come from a completed run. A freshly placed instance has not run anything, so those two fall back to the design-time figure and to absence respectively.
Overview figures
Control device, flow to full treatment, what downstream accepts, inflow (dry weather and design peak), spill (design and extreme peak), the breach flow and the compliance window, the chamber (area, weir crest, wall crest), maximum demand, design findings, control loops.
Live facts during a run
Titled Inlet works: the clock, the unit's mode, the chamber level with the transmitter's reading, inflow, forward flow (measured and actual), the setpoint against the breach flow, the device's travel, the spill, the consent excess, the published spare, and the state of the hardwired circuits.
Trend panels
Four: chamber level (with the LT reading dashed, and reference lines at the wall crest, the high-high switch, the weir crest and the hold band), forward flow (with the FT reading dashed, and reference lines at the consent and at the breach flow), spill rate, and device position.
The calculation charts
Two:
- the device law — flow against travel, drawn at both ends of the operating band (the bottom of the band and the weir crest), with the consent marked across it and the duty travel where the crest curve meets it. The two curves are what make "the plant gain is not constant" a picture rather than a claim.
- the storm weir curve — head against spill flow from the crest upwards.
Faults you can inject
| Group | Cases |
|---|---|
Forward flow meter FT-x01 | signal lost · frozen · four drifts (−8 %, ±10 %, ±20 %) |
Chamber level LT-x01 | signal lost · +0.50 m drift · a −0.50 m drift under a lost FT |
Position feedback ZT-x01 | lost |
| The device | stuck mid-travel · failed open · failed shut in the storm · failed shut on a dry day |
| Supply | the actuator's own · the whole site's, for 2 h |
| Hardwired | LSHH stuck operated / will not operate · FSH stuck operated / will not operate |
| The spill route | the weir blocked · the weir head transmitter lost |
| Setpoints | the deadband set to 10 % · the deadband set to 0 % |
A configuration without the position transmitter drops its cases, and so on — the catalogue is filtered to what is fitted.
Honest limits
- Seeded at
publishedmaturity: its configuration matrix passed, so it is visible to every user who passes the plan, tenant and allocation gates. - The itemised fittings of the forward main are not parameterisable yet.
- Tag builders carry an area placeholder (
LT-x01), so two installations on one drawing will not take distinct tag numbers. - The run verdict and the design findings are shown on the workspace's Validation view.
- Nobody has recorded watching this unit run in a browser.