Pump Affinity Laws Calculator mechanism

Model scope

The speed-only equations are standard under their stated similarity assumptions, but the diameter-change claim and the undefined “speed/diameter ratio” require specification before release. The panel should explicitly distinguish speed ratio from diameter ratio and identify the type of power being predicted.

• The stated formulas are standard for changing rotational speed at corresponding, geometrically similar operating points, assuming the same pump geometry, fluid, and approximately constant efficiency.
• The instrument claims to handle impeller diameter changes, but no diameter variable or diameter formula is provided. For full geometric similarity, the combined scaling is Q2/Q1=(N2/N1)(D2/D1)^3, H2/H1=(N2/N1)^2(D2/D1)^2, and P2/P1=(N2/N1)^3(D2/D1)^5. Common impeller-trimming approximations use different diameter exponents and are not equivalent to the stated speed formulas.
• The phrase “new speed/diameter ratio” is ambiguous: it does not specify whether the ratio is N2/N1 or D2/D1, nor which diameter-scaling model should be used.
• The formulas do not apply to arbitrary points on a pump curve or arbitrary system operating points; the operating points must be corresponding dynamically similar points.

Units and conventions

• Q1 and Q2 must use the same volumetric-flow unit.
• H1 and H2 must use the same head unit, such as metres of the pumped fluid.
• P1 and P2 must use the same power unit and should be explicitly identified as shaft, brake, or input power.
• N1 and N2 must use the same rotational-speed unit; the ratio is dimensionless, so rpm may be used if both values are rpm.
• The fluid density, viscosity effects, pump geometry, and efficiency are assumed unchanged unless additional correction formulas are supplied.
• The formulas assume positive baseline speed N1 and corresponding operating points.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "Q1": 100,
    "Q_unit": "m3/h",
    "H1": 40,
    "H_unit": "m",
    "P1": 10,
    "P_unit": "kW",
    "N1": 1750,
    "N2": 2100,
    "speed_unit": "rpm",
    "ratio_type": "speed"
  },
  "expected_outputs": {
    "Q2": 120,
    "H2": 57.6,
    "P2": 17.28
  },
  "working": "N2/N1 = 2100/1750 = 1.2. Q2 = 100 x 1.2 = 120 m3/h. H2 = 40 x (1.2)^2 = 40 x 1.44 = 57.6 m. P2 = 10 x (1.2)^3 = 10 x 1.728 = 17.28 kW."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

A zero baseline speed makes the required speed ratio undefined and must be rejected. The specification also leaves the speed-versus-diameter and ratio-direction conventions implicit, allowing materially different outputs if the ratio is interpreted reciprocally.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json