neqsim-water-hammer git:20260510.f20567cA

Immutable. This exact content is served forever at /api/v1/blob/c32bdebda2c1135f.

---
name: neqsim-water-hammer
description: "Water hammer and liquid hammer screening workflow for NeqSim. USE WHEN: evaluating fast valve closures, pump trips, check-valve slam, hydraulic surge, STID/P&ID route extraction, tagreader event windows, or MCP runWaterHammer studies. Covers WaterHammerPipe, WaterHammerStudy, STID route geometry, tagreader field-data overrides, pressure envelopes, Joukowsky checks, and screening limitations."
last_verified: "2026-05-10"
---

# Water Hammer and Liquid Hammer Screening

Use this skill when a task involves hydraulic surge from fast valve movement,
pump trip, check-valve slam, ESD closure, or other rapid liquid-flow changes.
The core model is `WaterHammerPipe`; the workflow facade is
`WaterHammerStudy`; MCP clients use `runWaterHammer`.

## When To Use

- Fast ESD or isolation-valve closure in water, condensate, oil, MEG, glycol, or
  other liquid-rich lines.
- Pump trip, pump start, check-valve slam, or sudden flow setpoint changes.
- STID/P&ID/E3D/stress-isometric route screening before a detailed surge study.
- Tagreader event-window replay where measured pressure, flow, temperature, and
  valve position should override design-basis values.
- Ranking which lines need detailed vendor or specialist surge analysis.

Do not use this as final pipe-stress approval. Treat it as a fast screening and
evidence-pack workflow.

## Workflow

1. Extract line geometry from STID/P&ID/E3D/stress isometrics: length, internal
   diameter, wall thickness, roughness/piping class, elevation change, fittings,
   valves, and source references.
2. Extract or infer event data: initiating valve, start time, closure/opening
   duration, start/end opening, pump trip status, and relevant controller action.
3. Pull plant data with tagreader when available: inlet pressure, temperature,
   flow rate, valve opening, pump speed/status, and downstream pressure.
4. Run `WaterHammerStudy` or MCP `runWaterHammer` with the equivalent route,
   field-data overrides, and event schedule.
5. Report wave speed, Courant time step, wave round-trip time, Joukowsky surge,
   max/min pressure envelope, design-pressure margin, assumptions, and evidence.
6. Recommend detailed surge analysis when peak pressure approaches design
   pressure, the route has varying diameters/branches, vapor cavities are likely,
   or support loads/stress checks are required.

## MCP Input Pattern

```json
{
  "studyName": "ESD valve closure screening",
  "model": "SRK",
  "temperature_C": 20.0,
  "pressure_bara": 45.0,
  "components": {"water": 1.0},
  "flowRate": {"value": 120000.0, "unit": "kg/hr"},
  "designPressure_bara": 95.0,
  "pipe": {
    "length_m": 1200.0,
    "diameter_m": 0.2032,
    "wallThickness_m": 0.0127,
    "roughness_m": 4.6e-5,
    "elevation_m": 8.0,
    "numberOfNodes": 80
  },
  "fieldData": {
    "inletPressure_bara": 46.0,
    "inletTemperature_C": 19.0,
    "flowRate_kg_hr": 118000.0,
    "valveOpening": 1.0
  },
  "eventSchedule": [
    {
      "type": "VALVE_CLOSURE",
      "startTime_s": 0.10,
      "duration_s": 0.15,
      "startOpening": 1.0,
      "endOpening": 0.0
    }
  ],
  "simulationTime_s": 4.0,
  "sourceReferences": [
    "generic STID line-list row",
    "generic tagreader event window"
  ]
}
```

For route extraction, use `stidRoute.segments` with segment lengths, diameters,
wall thickness, roughness, elevation change, and `minorLosses` K values. The
study facade aggregates a serial route into an equivalent single line for fast
screening and warns when diameters vary.

## Result Interpretation

- `maxPressure_bara` and `minPressure_bara`: pressure envelope extrema during
  the transient.
- `pressureSurge_bar`: calculated surge above the initial outlet pressure.
- `joukowskySurgeEstimate_bar`: independent screening estimate using rho times
  wave speed times velocity change.
- `waveRoundTripTime_s`: acoustic round-trip time; closure faster than this is
  a fast-closure case.
- `maxStableTimeStep_s`: Courant time-step limit used to control numerical
  stability.
- `designPressureExceeded`: true when the supplied design pressure is exceeded.

## Standards And Review Triggers

Use applicable pipeline and piping standards as context: DNV-ST-F101,
NORSOK L-001, ASME B31.3, ASME B31.4, ASME B31.8, API 14E, and company piping
classes. Escalate to detailed study if any of these apply:

- Peak pressure exceeds design pressure or MAOP.
- Surge margin is small after including instrument uncertainty and model
  uncertainty.
- The route has branches, non-return valves, pump curves, relief devices, or
  vapor-cavity risk.
- Pipe stress, supports, nozzle loads, or valve actuator closure curves matter.
- The line contains multiphase fluid; simplify only with explicit assumptions.

## Related Skills

- `neqsim-pid-process-operations` for valve actions and operational scenarios.
- `neqsim-stid-retriever` and `neqsim-technical-document-reading` for route and
  evidence extraction.
- `neqsim-plant-data` for tagreader snapshots and event windows.
- `neqsim-process-safety` for risk framing and escalation into safety studies.
- `neqsim-flow-assurance` for broader pipeline operating-envelope work.