Engineering context

Cavitation and flashing risk are screened as a diagnostic objective inside a steady-state model, not judged by hand one component at a time. They are driven by how local static pressure, temperature, and vapour pressure interact with pump suction conditions, valve and restriction pressure drops, and elevation changes.

The practical method is to build a model configured to reproduce the suspected condition, solve it, and then identify where risk arises from the solver’s enunciated warnings, the pressure and NPSH results, and the relevant charts. This workflow identifies risk within a steady-state model and does not replace detailed equipment review or safety-critical assessment. For liquid-gas two-phase and slug-flow modelling, see the liquid-gas two-phase piping systems workflow.

Engineering workflow

1. Define the diagnostic objective and acceptance criteria — state whether you are screening for pump cavitation or flashing/vapour formation, and the criteria you will judge against (for example, a minimum NPSHa margin above NPSHR, and static pressure staying above the fluid’s vapour pressure).
2. Set the calculation basis — select the fluid’s vapour pressure data and the NPSH margin philosophy.
3. Build and connect the network — place and define the boundary conditions (the fluid is selected from the database, which carries its properties including vapour pressure, and applied at the boundary), then add pumps, valves, restrictions, fittings, and pipework. Pay particular attention to suction-side elevations and lengths.
4. Set up the operating cases that expose risk — model worst-case conditions: maximum flow toward end of curve, minimum suction level or pressure, hot versus cold, turndown, and similar.
5. Solve and run a visual sweep — confirm solution health on the status bar, check flow-direction arrows on all open paths, and look for red component highlights.
6. Work through the Messages tab — review cavitation, low static-pressure/vapour-pressure, and high-velocity messages to understand where and why risk arises.
7. Compare results against vapour pressure and NPSH — read static pressure across the network against the fluid’s vapour pressure, and for pumps compare NPSH available against NPSH required at the duty point.
8. Use charts to locate and characterise the risk — the pump’s Flow vs NPSHR chart, pump-versus-system curve, and EGL/HGL composite plots. Document the basis, margins, and assumptions.

Why the full system matters

Cavitation and flashing risk arise from the interaction of multiple system factors — suction arrangement, valve pressure drops, elevation, and fluid vapour pressure. Reviewing one component in isolation misses how the connected system raises or lowers the local pressure at a given point. A solved network model shows where and why static pressure falls below vapour pressure, and provides the NPSHa result that includes all upstream pipe and fitting losses on the suction side.

How FluidFlow helps

FluidFlow screens cavitation and flashing risk within steady-state pipe network analysis — combining vapour pressure data, NPSH results, and its message and charting tools (NPSH charts and EGL/HGL plots) to show where risk arises in the connected system. For liquid-gas two-phase and slug-flow modelling, see the liquid-gas two-phase piping systems workflow.

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