Pump Affinity Laws Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Thermodynamics, Fluids & Aero

Tranche

tranche-4

Evidence ID

t4-262

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "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."
}

Related workflows

Sources and evidence

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

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