# Neqsim Compressor Antisurge Recycle > Set up anti-surge recycle control for a centrifugal compressor in NeqSim, including compressor-chart generation, steady-state AntiSurgeRecycleCalculator use, dynamic AntiSurgeController PI control, and CompressorAntiSurgeApplication topology binding for hot/cold recycle valves and speed runback. USE WHEN: a task needs to protect a NeqSim compressor from surge with a recycle (spill-back) loop and a compressor performance chart is either supplied or must be generated. - Skill: `equinor/neqsim-compressor-antisurge-recycle-2` (Agent Skill, multi-file: 7 files) - Install (CLI): `npx skillmds@latest add equinor/neqsim-compressor-antisurge-recycle-2` - Raw SKILL.md: https://api.skillmd.com/api/skills/equinor/neqsim-compressor-antisurge-recycle-2/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Productivity - Author: equinor (https://skillmd.com/u/equinor) - Updated: 2026-09-22 - Page: https://skillmd.com/skills/equinor/neqsim-compressor-antisurge-recycle-2 --- # Compressor Anti-Surge Recycle Setup This skill explains how to protect a centrifugal compressor against surge in a NeqSim `ProcessSystem` by adding a recycle (spill-back) loop. It covers the preferred steady-state helper (`AntiSurgeRecycleCalculator`), the dynamic reverse-acting PI controller (`AntiSurgeController`), and the application-level supervisor (`CompressorAntiSurgeApplication`) that can bind directly to real NeqSim topology objects such as a compressor, hot recycle valve, cold recycle valve, cooler, mixer, recycle blocks, and `ProcessSystem`. It also explains how to **auto-generate a compressor chart with surge and stonewall curves** when no vendor chart is available, because every anti-surge option needs a surge limit to act against. The pure-Python helper (`AntiSurgeRecycleModel`) is an educational planning aid that mirrors NeqSim's proportional anti-surge step so an agent can pre-estimate the recycle flow and decide whether a chart must be generated first. Real control design must use the validated NeqSim equipment classes below and a qualified rotating-equipment review (API 617 / API 692). ## When to Use Use this skill when: - A NeqSim compressor operating point can fall to the left of its surge line at low throughput (turndown, start-up, trips) and needs recycle protection. - You must build the anti-surge recycle topology (surge curve, recycle stream, discharge splitter or recycle branch, anti-surge valve, `Recycle`, and optional cooler/mixer). - You need an executable dynamic application model where `CompressorAntiSurgeApplication` writes hot/cold recycle valve openings and optional compressor speed runback to real NeqSim units. - **No vendor compressor chart is provided** and a chart with surge and stonewall curves must be generated from the compressor's design point. - You want a screening estimate of the recycle flow required to keep the compressor off surge before running the full simulation. Do not use this skill as a substitute for vendor performance maps, anti-surge controller tuning, dynamic surge/transient analysis, or rotating-equipment design review. ## Inputs - Compressor inlet (suction) volumetric flow at the operating point (m3/h). - Surge-limit flow at the operating head and speed (m3/h). When no vendor chart is available, this comes from the generated surge curve. - Whether a vendor compressor chart is provided (`chart_provided`). - Existing recycle flow, if any (m3/h). - For chart generation: a design speed, the number of speed lines, and optionally impeller diameter / number of stages for advanced corrections. ## Outputs - `needs_chart_generation` — whether a chart must be generated before control. - `in_surge` — whether the operating point is at or below the surge flow. - `surge_margin_fraction` — `(inlet_flow - surge_flow) / surge_flow`. - `recommended_recycle_flow` — screening recycle flow to add at suction (m3/h). - `total_suction_flow` — inlet flow plus recommended recycle (m3/h). - `recycle_warning` — `ok`, `recycle`, or `surge`. - Assumptions and limitations. ## Engineering Method A centrifugal compressor surges when the inlet volumetric flow drops below the surge flow at the current head/speed. Anti-surge control opens a recycle line from discharge back to suction to keep the **total** suction flow above the surge limit plus a margin. For steady-state recycle sizing and initialization, prefer `AntiSurgeRecycleCalculator` for a charted compressor. It runs the compressor, checks natural inlet flow against the surge-control line, and iterates a cooled recycle stream until the target distance-to-surge margin is met. Use the older splitter-based `Calculator` / `AntiSurgeCalculator` pattern only when you need to reproduce an existing flowsheet that already uses a discharge splitter. The legacy splitter-based topology is: 1. A **surge curve** on the compressor chart provides the surge flow versus head. 2. A low-flow **recycle stream** is added into the compressor suction. 3. A **splitter** on the compressor discharge creates a forward branch (`getSplitStream(0)`) and a recycle branch (`getSplitStream(1)`). 4. An **anti-surge `Calculator`** (legacy name-prefix API) or typed `AntiSurgeCalculator` reads the compressor and writes the splitter recycle flow each iteration. Internally it compares the inlet flow to the surge flow: far from surge (`inlet_flow > 1.2 * surge_flow`) it drives recycle to a minimum; otherwise it adds a proportional, capped step `0.5 * (surge_flow - inlet_flow)` to the recycle branch. 5. An **anti-surge valve** on the recycle branch drops the discharge pressure back to suction pressure. 6. A **`Recycle`** unit closes the loop, feeding the valve outlet back into the placeholder suction recycle stream. ### Generating a Compressor Chart When None Is Given The anti-surge loop needs a surge limit, so if no vendor chart exists a chart must be generated first. NeqSim builds a chart from the compressor's design operating point and **automatically populates both the surge curve and the stonewall curve**: - `Compressor.generateCompressorChart("normal curves", numberOfSpeeds)` builds a multi-speed chart whose lowest-flow points form the surge curve and whose highest-flow points form the stonewall curve. - `CompressorChartGenerator` gives finer control (chart type, Reynolds/Mach corrections, multistage surge correction, impeller diameter) and also returns a chart with surge and stonewall curves attached. After generation, the surge flow at the operating head is available through `Compressor.getSurgeFlowRate()` and the distance to surge through `Compressor.getDistanceToSurge()`. The `AntiSurgeRecycleModel` mirrors step 4 so you can estimate the recycle flow and flag whether chart generation (`needs_chart_generation`) is required before wiring the loop. ## Python Usage Pattern Screening estimate of the recycle flow (no NeqSim required): ```python from compressor_antisurge_recycle import AntiSurgeRecycleModel model = AntiSurgeRecycleModel() plan = model.plan( inlet_flow=4200.0, # m3/h at suction surge_flow=5000.0, # m3/h surge limit at operating head chart_provided=True, current_recycle=0.0, ) print(plan.recommended_recycle_flow, plan.recycle_warning) ``` Generate a compressor chart (with surge and stonewall curves) when none is given, using NeqSim through the `neqsim` package: ```python from neqsim import jneqsim # `compressor` is an existing neqsim.process.equipment.compressor.Compressor compressor.setSpeed(8000.0) # design speed (rpm) compressor.run() # solve the design point first compressor.generateCompressorChart("normal curves", 5) # 5 speed lines # Surge and stonewall curves are now populated automatically. chart = compressor.getCompressorChart() surge_flow = compressor.getSurgeFlowRate() distance_to_surge = compressor.getDistanceToSurge() ``` Finer control with the generator (optional corrections): ```python from neqsim import jneqsim generator = jneqsim.process.equipment.compressor.CompressorChartGenerator(compressor) generator.setChartType("interpolate and extrapolate") generator.enableAdvancedCorrections(numberOfStages) # Reynolds + Mach + multistage chart = generator.generateCompressorChart("normal curves", 5) compressor.setCompressorChart(chart) ``` Wire the anti-surge recycle loop (generic data, after a chart exists): ```python from neqsim import jneqsim splitter_pkg = jneqsim.process.equipment.splitter valve_pkg = jneqsim.process.equipment.valve util_pkg = jneqsim.process.equipment.util suction_pressure = compressor.getInletStream().getPressure("bara") # 2. Low-flow placeholder recycle stream into the compressor suction. recycle_gas = compressor.getInletStream().clone() recycle_gas.setName("anti surge recycle gas") recycle_gas.setFlowRate(1.0, "kg/hr") recycle_gas.run() process.add(recycle_gas) # 3. Splitter on the compressor discharge: branch 0 forward, branch 1 recycle. gas_splitter = splitter_pkg.Splitter("anti surge splitter", compressor.getOutletStream(), 2) gas_splitter.run() process.add(gas_splitter) # 4. Anti-surge Calculator (name MUST start with "anti surge calculator"). anti_surge_calc = util_pkg.Calculator("anti surge calculator 1") anti_surge_calc.addInputVariable(compressor) anti_surge_calc.setOutputVariable(gas_splitter) process.add(anti_surge_calc) # 5. Anti-surge valve on the recycle branch back to suction pressure. anti_surge_valve = valve_pkg.ThrottlingValve("anti surge valve", gas_splitter.getSplitStream(1)) anti_surge_valve.setOutletPressure(suction_pressure, "bara") anti_surge_valve.run() process.add(anti_surge_valve) # 6. Recycle unit closes the loop into the placeholder suction stream. recycle = util_pkg.Recycle("recycle anti surge") recycle.addStream(anti_surge_valve.getOutletStream()) recycle.setOutletStream(recycle_gas) recycle.setTolerance(1e-2) process.add(recycle) process.run() ``` The forward process continues on `gas_splitter.getSplitStream(0)`. Preferred steady-state helper for a charted compressor: ```java AntiSurgeRecycleCalculator calc = new AntiSurgeRecycleCalculator(compressor, suctionStream); calc.setSurgeControlMargin(0.10); calc.setRecycleCoolerTemperature(35.0, "C"); AntiSurgeRecycleCalculator.Result result = calc.solve(); ``` ## Dynamic Anti-Surge Control (AntiSurgeController) The `Calculator`-driven loop above is a **steady-state** recycle solver. For a **dynamic (transient)** anti-surge response, NeqSim provides a dedicated reverse-acting PI controller, `AntiSurgeController` (`neqsim.process.controllerdevice.AntiSurgeController`), that reads `Compressor.getDistanceToSurge()` and drives a recycle `ThrottlingValve` open as the margin falls below the set point, then closes it again on recovery. ```python from neqsim import jneqsim controllerdevice = jneqsim.process.controllerdevice # `recycle_valve` is the anti-surge ThrottlingValve on the recycle branch. asc = controllerdevice.AntiSurgeController("anti-surge", compressor, recycle_valve) asc.setSurgeMarginSetPoint(0.10) # protect a 10% distance-to-surge margin asc.setProportionalGain(400.0) # percent opening per unit margin error asc.setIntegralTime(20.0) # s asc.setOpeningRange(0.0, 100.0) # valve opening clamp (%) with anti-windup asc.setActive(True) recycle_valve.addController("anti-surge", asc) ``` Control law each transient step: `error = setPoint - distanceToSurge`, `integral += Kp/Ti * error * dt`, `opening = clamp(Kp*error + integral)` with anti-windup. A reproducible benchmark, `neqsim.process.util.scenario.AntiSurgeDynamicBenchmark`, drives the real controller against a transparent first-order gas-path surrogate (`m_next = m - disturbance*dt + authority*(opening/100)*dt`) and is the preferred way to verify or tune the control law without solver fragility. **Critical gotchas when building a full dynamic recycle flowsheet:** - A fixed-factor `Splitter` (`setSplitFactors([0.97, 0.03])`) **pins the recycle fraction** in dynamic mode, so the anti-surge valve has no authority over the actual recycle flow — it can reach 100% open with no effect. Let the recycle flow be set by the valve (`Cv`/resistance), or keep the steady-state `Calculator` pattern. - Once the operating point crosses left of the surge line, `getDistanceToSurge()` **clamps at -1.0 and the steady solver cannot recover**; a flowsheet driven into deep surge will not self-heal even after the inlet is reopened. Apply gradual/ramped disturbances and keep the machine off deep surge. - Aggressive proportional gain can slam the recycle valve to minimum opening, starve a stream, and trigger an SRK flash `NaN` (`PhaseSrkEos:molarVolume ... NaN`). Keep gains moderate. Dynamic controller tuning and transient surge analysis still require qualified rotating-equipment review (API 617 / API 692). ## Application-Level Dynamic Topology Binding For realistic dynamic studies with coordinated pressure, speed, hot recycle, and cold recycle behavior, use `CompressorAntiSurgeApplication`. It is a deterministic supervisory scan layer that can write directly to real NeqSim objects and then advance the bound process one transient step. ```java CompressorAntiSurgeApplication application = new CompressorAntiSurgeApplication("export compression"); CompressorAntiSurgeApplication.StageApplication stage = application.addStage("K-101"); CompressorAntiSurgeApplication.TopologyBinding binding = stage.bindTopology( process, compressor, hotRecycleValve, coldRecycleValve, recycleCooler, suctionMixer, hotRecycle, coldRecycle); binding.enableSpeedControl(95.0, 25.0, 8500.0, 12500.0, 150.0); application.setRunningMode(); application.runDynamicStep(null, 0.25); ``` When the scan input is `null`, the stage reads the bound compressor margin and inlet flow where available, falls back to the stage design basis where needed, writes the hot and cold recycle valve openings, applies the optional compressor speed command/runback, and advances the bound `ProcessSystem` with `runTransient()`. Keep `Recycle` blocks algebraic unless the specific class has transient inventory support; the valve, compressor, cooler, mixer, and any volume-capable equipment carry the dynamic response. `CompressorAntiSurgeApplication` is still a simulation and advisory layer. Its certification status remains `NOT_CERTIFIED_FOR_PROTECTION`; use it for engineering studies, training, digital twins, and commissioning evidence, not as a certified machinery-protection package. ## MCP `runProcess` Physical Topology Contract Use two distinct JSON surfaces deliberately: - Compressor property `antiSurge` configures the compressor's embedded screening control. It does not create or certify a physical recycle path. - Root-level `antiSurgeSystems` binds `CompressorAntiSurgeApplication` to named units that already exist in the submitted `process` topology. It never synthesizes hidden valves, coolers, mixers, or recycle blocks. A single-area cold-recycle declaration has this shape: ```json { "autoSizing": {"enabled": true}, "antiSurgeSystems": [ { "name": "Export anti-surge", "stages": [ { "name": "Stage 1", "compressor": "Comp", "suctionMixer": "Suction Mixer", "aftercooler": "Aftercooler", "coldRecycleValve": "Cold ASV", "coldRecycle": "Cold Recycle", "recycleDesign": { "controlMargin": 0.10, "valvePressureDrop": 10.0, "pipingVolume": 1.0, "requiredResponseTime": 5.0 }, "speedControl": { "dischargePressureSetPoint": 40.0, "minimumSpeed": 5000.0, "maximumSpeed": 15000.0, "speedGain": 40.0, "recycleRunbackRate": 80.0 } } ] } ] } ``` The referenced names must resolve to the expected concrete types: `Compressor`, `Mixer`, optional `Cooler`, `ThrottlingValve`, and `Recycle`. At least one complete hot or cold recycle path is required. For a multi-area `ProcessModel`, every system also requires an `area` matching a submitted area; unqualified and unknown-area definitions return bounded per-system failures. Every stage needs an active surge curve. Supply `properties.compressorChart`, enable `autoSizing`, or set `generateScreeningMap: true` on the stage. The response reports truthful map provenance: - `submitted`: chart was present in the submitted canonical process JSON. - `auto_sized_screening`: `autoSizing` generated the chart earlier in the run. - `stage_generated_screening`: the anti-surge stage generated the chart. The latter two set `screeningGradeMap: true`. They are estimates, not vendor maps. `generatedScreeningMapCount` counts all configured stages using a screening-grade map, regardless of which generation path created it. The response `antiSurgeSystems` object contains configured/failed counts, per-stage physical binding and map provenance, optional speed-control status, and `runCommissioningChecks()` evidence. Its certification status is always `NOT_CERTIFIED_FOR_PROTECTION`. The canonical `processDefinition` preserves the declaration, and the generated Python replays that canonical post-design JSON. When a canonical response is replayed, its exported compressor chart is now an explicitly submitted chart for that new request. Therefore its provenance is `submitted`; replay does not generate another map. This makes JSON round trips stable while preserving the original run's generation evidence in that run's response. ## Validation Checklist - The compressor has a chart with an active surge curve before the loop runs; if not, generate one and confirm `getSurgeCurve().isActive()` is true. - For steady-state recycle initialization, use `AntiSurgeRecycleCalculator` when practical; if using the legacy splitter path, the anti-surge `Calculator` name starts with `"anti surge calculator"` or the typed `AntiSurgeCalculator` is used. - For the legacy splitter path, the `Calculator` input is the `Compressor` and the output is the discharge `Splitter`. - The anti-surge valve sits on `getSplitStream(1)` and drops to suction pressure. - The `Recycle` outlet stream is the placeholder suction recycle stream. - After `process.run()`, the total suction flow exceeds the surge flow plus the intended margin (`getDistanceToSurge()` is positive). - Recycle convergence tolerance is set (for example `setTolerance(1e-2)`). - For `CompressorAntiSurgeApplication` topology binding, hot/cold recycle valves are real `ThrottlingValve` units, speed-control limits are bounded, and `runDynamicStep(...)` is used only after the process has a converged initial state. - For MCP `runProcess`, use root-level `antiSurgeSystems` only after all named physical units are present in `process`; require `area` for every multi-area system and inspect `configuredCount`, `failedCount`, `mapProvenance`, `screeningGradeMap`, commissioning checks, and certification status. ## Common Mistakes - Naming the legacy calculator anything that does not start with `"anti surge calculator"` — the legacy anti-surge logic then never triggers. - Wiring the anti-surge valve to the forward branch `getSplitStream(0)` instead of the recycle branch `getSplitStream(1)`. - Running the loop without a surge curve, so there is no surge flow to compare against (generate a chart first when no vendor chart is given). - Using a zero or negative placeholder recycle flow that the `Recycle` cannot converge from; start from a small positive flow (for example 1 kg/hr). - Reading the surge flow at the wrong head or speed — the surge flow must match the operating head and speed. - Treating the generated chart as a vendor-validated map; generated charts are estimates for modelling, not design certification. - For dynamic studies, leaving a fixed-factor `Splitter` on the recycle branch so the `AntiSurgeController` valve has no authority over the recycle flow. - Driving a dynamic recycle flowsheet straight into deep surge, where `getDistanceToSurge()` clamps at -1.0 and the steady solver cannot recover. ## Limitations - Screening logic only; it does not tune an anti-surge controller or set recycle valve `Cv`, response time, or surge control line offset. - The Python helper does not perform dynamic surge, ESD, or transient recycle analysis; for dynamic response use NeqSim's `AntiSurgeController` / `AntiSurgeDynamicBenchmark` under qualified review. - Generated compressor charts are model estimates, not vendor performance maps. - It does not replace API 617 / API 692 rotating-equipment design and review. - Results require qualified human review before any design or operating use. ## Multi-Body Compressor Trains on One Shaft (common speed) When several compressor bodies sit on **one driver shaft** (a single gas turbine or motor, often through a gearbox) they must all turn at the **same speed**. A 2- or 3-body recompression string is the classic case. Model it with `neqsim.process.equipment.compressor.CompressorShaft`, NOT by letting each body solve its own speed. **Degrees of freedom.** A shared shaft has exactly **one** mechanical degree of freedom — the common speed — and exactly **one** controlled target: the string's **final discharge pressure**. Every intermediate inter-body pressure is a *result*, not a spec, and must be allowed to **float** off the charts. | Approach | DOF accounting | Verdict | |---|---|---| | Fix every stage outlet pressure **and** set a common speed | over-constrained | ❌ non-physical | | Adjust ONE common speed → hit the final discharge; intermediates float | 1 variable, 1 target | ✅ correct | **Pattern.** Put each body in fixed-speed, chart-forward mode and iterate the one common speed until the reference (last) body hits the target discharge: ```python CompressorShaft = jneqsim.process.equipment.compressor.CompressorShaft shaft = CompressorShaft("recompression shaft (single GT)") shaft.addCompressor(body1) # LP body (lowest suction) shaft.addCompressor(body2) shaft.addCompressor(body3) # HP body = reference shaft.setSpeedBounds(8000.0, 16000.0) # re-run the whole flowsheet between speed guesses so inter-body streams, # scrubbers and mixers update: run_proxy = jpype.JProxy("java.lang.Runnable", dict(run=lambda: process.run())) shaft.solveSpeed(body3, 49.0, "bara", run_proxy) # one speed -> 49 bara at HP discharge rpm = shaft.getSpeed() mw = shaft.getTotalPower() / 1e6 ``` **Shared pressure nodes.** Where another unit ties into an interstage (e.g. a 2nd-stage separator gas that joins the recompressor between bodies), model it as a **pressure equality**, not a second spec: slave that unit's pressure to the floating interstage discharge (a setter each iteration) or drop a small adapting valve there. This removes a DOF rather than adding one. A `Mixer` at the join already resolves to the lowest inlet pressure, so a small let-down is automatic. **Fixed-/single-speed drivers.** If the driver is a constant-speed motor (no variable-speed drive) speed is **not** a DOF — do **not** iterate it. Use `shaft.runAtFixedSpeed(rpm, run_proxy)`: the discharge floats off the chart at the locked speed and any pressure spec is met by anti-surge recycle, suction throttling, or inlet guide vanes — never by moving speed. Inlet guide vanes are a **first-class** fixed-speed control on `Compressor`: `comp.setInletGuideVaneOpening(f)` (`f=1` fully open) or `comp.setGuideVaneAngle(deg)` closes the vanes to reduce head and efficiency **and** lower the surge flow (via a configurable `InletGuideVaneModel`), so `getDistanceToSurge()` reflects the shifted surge line — distinct from moving speed. If you have vendor **IGV-position** maps (a full chart per vane position), attach a `CompressorChartIGV` family with `comp.setInletGuideVaneChart(family)`; it interpolates the positions into the active chart at each opening (and bypasses the parametric model). Use the parametric `InletGuideVaneModel` for screening / fixed-speed discharge control, and `CompressorChartIGV` to supply real per-position vendor maps. **Single body.** A `CompressorShaft` with one compressor also works: `solveSpeed` just finds that one machine's speed for its discharge target. So export / re-injection / gas-lift machines (one body each on their own shaft) use the same API — separate shafts keep separate speeds. **Anti-surge coexists.** The per-body anti-surge loops (recycle splitter, valve, `Recycle`, `AntiSurgeCalculator`) stay attached and keep protecting each body; they adjust *recycle flow*, while the shaft sets *speed*. Apply the shaft solve **after** the charts and anti-surge are active. `solveSpeed` uses a bracketed false-position (Illinois) secant — the speed↔discharge map is smooth and monotonic (higher speed → higher discharge), so it converges superlinearly. Each iteration re-solves the whole flowsheet, so on a large multi-train plant make the shaft solve **opt-in** and solve each train's shaft in turn. **Parallel machines and multi-stage strings.** Real duties often use two parallel bodies (A/B) rather than one machine: split the feed 50/50, give each body its own anti-surge loop, and commingle with a `Mixer`. Splitting one large machine into two halves the per-machine gas load (a suction scrubber that reads ~168 % of design on one body drops to ~80 % on two). For a multi-stage duty (e.g. re-injection), commingle the parallel 1st-stage discharges then feed a common 2nd stage at an interstage pressure. Route a recompression train's HP discharge back to the gas header, not straight into the export suction. **Process-integrated control (`CompressorShaftCalculator`).** Instead of the external `solveSpeed` callback, add a `CompressorShaftCalculator` to the `ProcessSystem`; it converges the one common speed **inside** `process.run()` (one damped secant step per pass, like `AntiSurgeCalculator`) so the shaft speed converges together with the recycles in a single run — no separate full-field solves. Add it **after** the compressor bodies / anti-surge. ```python CompressorShaftCalculator = jneqsim.process.equipment.util.CompressorShaftCalculator shaft = CompressorShaft("recompression shaft (single GT)") shaft.addCompressor(body1); shaft.addCompressor(body2); shaft.addCompressor(body3) shaftCalc = CompressorShaftCalculator("shaft speed", shaft, body3, 49.0, "bara") shaftCalc.setSpeedBounds(8000.0, 16000.0) process.add(shaftCalc) process.run() # shaft speed converges with the recycles rpm = shaftCalc.getSpeed() ``` **Feasibility result + pressure control (eCalc-style).** A single-speed string cannot make an arbitrary pressure — the max-speed curve is a ceiling and the min-speed curve is a floor. Both solvers **saturate and flag** instead of crashing, and expose a `CompressorShaft.SolveResult` (read with `getLastSolveResult()`, or the shortcut `isFeasible()`). The two speed-bound bracket evaluations give the **min-/max-achievable** discharge pressures for free. ```python shaft.solveSpeed(body3, 49.0, "bara", run_proxy) r = shaft.getLastSolveResult() if not r.isFeasible(): # r.getStatus(): PRESSURE_ABOVE_MAX_SPEED / PRESSURE_BELOW_MIN_SPEED / OVER_POWER / STONEWALL / SURGE ceiling = r.getMaxAchievablePressure() # most the string can make # too-low target -> shed the surplus head instead of flagging infeasible: PressureControl = jneqsim.process.equipment.compressor.CompressorShaft.PressureControl shaft.setPressureControl(PressureControl.DOWNSTREAM_CHOKE) # or UPSTREAM_CHOKE / ASV_RECYCLE ``` `CompressorShaftCalculator` carries the same `getLastSolveResult()` / `isFeasible()` / `setPressureControl(...)`, so an optimizer or `evaluate()` loop can gate on `shaftCalc.isFeasible()` directly. Downstream, `Mixer.isPressureMismatch()` flags where an unmet pressure collapses a commingling node to the lowest inlet — the signal that an upstream machine missed spec. A worked end-to-end example (three-stage separation + shared-shaft recompression + control) is in the NeqSim repo notebook `examples/notebooks/CompressorShaft_ThreeStageSeparation.ipynb`. ## Related NeqSim Functionality - `neqsim.process.equipment.compressor.CompressorShaft` — groups several compressor bodies on one shaft at a single common speed; `addCompressor(...)`, `solveSpeed(reference, targetP, unit, runnable)` (iterate one speed to the final discharge, intermediates float), `runAtFixedSpeed(rpm, runnable)` (constant-speed drivers), `setSpeed(...)`, `setSpeedBounds(...)`, `getSpeed()`, `getTotalPower()`. - `neqsim.process.equipment.compressor.Compressor` — `generateCompressorChart(...)`, `getCompressorChart()`, `getSurgeFlowRate()`, `getDistanceToSurge()`, `setSpeed(...)`. - `neqsim.process.equipment.compressor.CompressorChart` — `getSurgeCurve()`, `getStoneWallCurve()`, `generateSurgeCurve()`, `generateStoneWallCurve()`, `checkStoneWall(...)`. - `neqsim.process.equipment.compressor.CompressorChartGenerator` — `setChartType(...)`, `enableAdvancedCorrections(...)`, `generateCompressorChart(...)`. - `neqsim.process.equipment.compressor.AntiSurgeRecycleCalculator` — preferred steady-state recycle helper for charted compressors (`setSurgeControlMargin`, `setRecycleCoolerTemperature`, `solve`). - `neqsim.process.equipment.compressor.CompressorAntiSurgeApplication` — application-level supervisor with `StageApplication.bindTopology(...)`, `TopologyBinding.enableSpeedControl(...)`, `scan(...)`, and `runDynamicStep(...)` for direct writeback to real hot/cold recycle valves and compressor speed. - `neqsim.process.equipment.splitter.Splitter` — discharge split into forward and recycle branches. - `neqsim.process.equipment.util.Calculator` — steady-state anti-surge engine (`runAntiSurgeCalc`) triggered by the `"anti surge calculator"` name prefix. - `neqsim.process.controllerdevice.AntiSurgeController` — dynamic reverse-acting PI controller on `getDistanceToSurge()` driving a recycle valve (`setSurgeMarginSetPoint`, `setProportionalGain`, `setIntegralTime`, `setOpeningRange`, `setActive`). - `neqsim.process.util.scenario.AntiSurgeDynamicBenchmark` — reproducible surrogate benchmark for verifying/tuning the dynamic control law. - `neqsim.process.equipment.valve.ThrottlingValve` — anti-surge recycle valve. - `neqsim.process.equipment.util.Recycle` — closes the recycle loop. The `total_suction_flow` (net forward flow + recycle) computed here is the **actual compressor throughput**. When you go on to compute polytropic head/efficiency or shaft power from measured conditions, use this actual throughput — not the metered net/export flow. Using net flow while the recycle is open understates suction volume and power and mis-locates the operating point on the surge map (a common error when diagnosing compressor degradation at turndown). In Python these classes are reachable through the `neqsim` package (for example `from neqsim import jneqsim`). ## References - NeqSim: https://github.com/equinor/neqsim - NeqSim Community Skills: https://github.com/equinor/neqsim-community-skills - API Standard 617 — Axial and Centrifugal Compressors. - API Standard 692 — Surge Control for Centrifugal Compressors.