FieldEngineersKitEngineering Reference & ASME Code Basis
1. Core Formula & Variable Definitions
Hydraulic Institute ANSI/HI 14.3 — Rotodynamic Pumps for Hydraulic Performance Acceptance Tests · Affinity / classical BHP sizing practice (US customary & SI) · IEC 60034 motor kW ratings · common NEMA HP frames (recommendation only)
TDH = Hs + Hf + Hp
BHP = Q·TDH·SG / (3960·ηp) · P = ρ·g·Q·TDH / ηp
Hydraulic Institute ANSI/HI 14.3 · affinity / duty sizing (screening)
TDH is the total head the pump must develop: static elevation Hs (may be negative downhill), friction Hf (from Darcy ΔP → head), and pressure head Hp = (Pd−Ps)/(ρg). Brake power divides hydraulic power by pump efficiency η_p. Motor input divides brake power by motor efficiency η_m; the app multiplies by motor service factor SF (default 1.15) then recommends the next IEC kW or NEMA HP rating. HI 14.3 is the hydraulic performance acceptance context — not a guaranteed datasheet.
- Hs (Static head) — Discharge elevation − suction elevation (negative if downhill / gravity-assisted).
- Hf (Friction head) — Pipe + fittings + strainer losses (convert ΔP/(ρg) from Pressure Drop tool).
- Hp (Pressure head) — (Pd − Ps)/(ρ g). Often ≈ 0 for open tanks at atmosphere.
- TDH (Total dynamic head) — Hs + Hf + Hp — head the pump must develop at the duty flow.
- η_p (Pump efficiency) — Hydraulic efficiency at the operating capacity from the OEM curve.
- BHP (Brake horsepower) — Shaft power = Q·TDH·SG/(3960·η_p) (gpm·ft) or ρ·g·Q·H/η_p (SI).
- SF (Motor service factor) — Multiplier on estimated motor input before IEC/NEMA pick (typical field default 1.15).
2. Allowances, Tolerances & Standards
Use OEM η_p at the actual duty point. Motor recommendation = next standard rating ≥ (brake/η_m)×SF.
Estimate piping ΔP with the Pressure Drop calculator, convert to head, include fittings.
Do not use BEP efficiency if the duty is far off BEP — power rises when η drops.
IEC kW or NEMA HP ≥ estimated motor input × service factor (default SF 1.15).
Viscous services need HI / OEM viscosity correction charts — not applied in this app.
Quick Reference Lookup Table
| Case | TDH | Focus |
|---|---|---|
| Water 50 m³/h · Hs 20 m · Hf 5 m | 25 m | Default metric · ~7.5 kW IEC @ SF 1.15 |
| Water 100 m³/h · Hs 40 m · Hf 10 m | 50 m | Higher head |
| Water 100 GPM · Hs 60 ft · Hf 15 ft | 75 ft | Default imperial case |
| Seawater 50 m³/h · Hs 15 m · Hf 5 m | 20 m | Higher SG → more BHP |
| Light HC 40 m³/h · Hs 30 m · Hf 6 m | 36 m | Lower SG → less BHP |
3. Material & Code Limitations
Clean liquid centrifugal / rotodynamic screening. Not for positive-displacement volumetric power models or multiphase flow.
| Material Group | Temperature Range | Allowable Stress / Limit | Engineering Notes |
|---|---|---|---|
| Water / seawater / condensate | Ambient screening densities | N/A — hydraulic power | Use project fluid properties when temperature shifts density significantly. |
| Light hydrocarbon | Screening SG | Lower BHP vs water | Confirm vapor pressure / NPSH separately — TDH does not check cavitation. |
| Viscous liquids | μ ≫ 1 cP | HI derate required | This tool does not apply HI viscosity correction charts. |
Code Applicability & Safety Boundaries
- Field screening only — not HI 14.3 acceptance test documentation.
- Motor recommendation applies the entered service factor (default 1.15); set SF = 1.0 to size on raw motor input.
- Velocity head differences and complex control-valve losses must be folded into Hf/Hp by the user.
- Export / PDF is a duty sizing sheet — not a stamped pump datasheet.
4. Step-by-Step Worked Example
Field VerificationShowHide
Step-by-Step Worked Example: Water 50 m³/h · Hs 20 m · Hf 5 m
Screen TDH and brake power for a fresh-water centrifugal pump at 50 m³/h, static elevation 20 m, friction 5 m, open tanks (Hp = 0), η_p = 70%, η_m = 92%, motor SF = 1.15 (HI 14.3 / affinity screening).
Form TDH
Hydraulic & brake power
Motor input × SF & standard rating
Open /water-50m3h-hs-20m-hf-5m for the live default case. Pair with Pressure Drop for Hf and NPSH for suction margin.
5. Frequently Asked Questions & Technical References
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Total Dynamic Head is the head the pump must develop at the duty flow: TDH = Hs + Hf + Hp (static + friction + pressure head).
Run the Pressure Drop & Friction calculator for suction + discharge ΔP, then convert Hf = ΔP / (ρ g). Include fittings and strainers.
ANSI/HI 14.3 is the Hydraulic Institute standard for rotodynamic pump hydraulic performance acceptance. This app uses the same power/η language for field screening, not a formal witness test.
Motor input ≈ brake power / η_m. The app multiplies by service factor SF (default 1.15), then picks the next IEC kW (metric) or NEMA HP (imperial) ≥ that sizing basis.