---
title: "Francis versus Kaplan applicability"
subject: "Power Plant Design"
chapter: 3
key: "semester_8/power_plant_design:francis-vs-kaplan"
source: https://www.bctengineer.com/q/semester_8/power_plant_design/francis-vs-kaplan
site: BCT Engineering
---

# Francis versus Kaplan applicability

Power Plant Design · Chapter 3: Hydro Power Plant Design

- Asked in: 2078 Chaitra, 4 marks
- Video: [Kaplan, Francis and Pelton Hydroelectric Turbines](https://www.youtube.com/watch?v=AT7B7IWmOtU) — 3D-knowledge
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/power_plant_design/francis-vs-kaplan
- Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-3

## Question

Differentiate applicability of Francis and Kaplan Turbine in reference to hydropower project.

## Short answer

Francis is a mixed-flow reaction turbine for medium heads, 10–350 m, medium discharge, Ns 60–300, fixed blades and guide-vane regulation. Kaplan is axial-flow for low heads, 2–40 m, large discharge, Ns 300–1000, adjustable runner blades with double regulation, better part-load efficiency but needs deeper setting.

## Answer

Both Francis and Kaplan are **reaction turbines**, but the Francis is a mixed-flow turbine for **medium heads**, while the Kaplan is an axial-flow turbine with adjustable blades for **low heads and large discharge**.

| Point | Francis | Kaplan |
|---|---|---|
| Flow | Radial in, axial out (mixed) | Axial |
| Head range | About 10–350 m (typically 30–300 m) | About 2–40 m |
| Discharge | Medium | Large |
| Specific speed (kW) | 60–300 | 300–1000 |
| Runner blades | Fixed, 9–19 vanes | Adjustable, 3–8 blades |
| Regulation | Guide vanes only | Guide vanes and runner blades (double) |
| Part-load efficiency | Falls below ~40–50% load | High over wide range |
| Cavitation | Moderate | Higher; needs deep setting |
| Typical project | Medium-head ROR/PROR in hills | Barrage or canal-drop plant on large rivers |

**In hydropower projects:** Francis suits most medium-head schemes in Nepal's hills (e.g. Kaligandaki "A", Middle Marsyangdi). Kaplan suits low-head, high-flow sites such as barrages on large rivers in the plains, canal falls and run-of-river schemes with large and varying flow.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which head range suits Kaplan?
   A. About 30-300 m
   B. About 2-40 m
   C. About 300-1300 m
   D. About 100-600 m
   Answer: B. Kaplan is for low heads and large discharge; Francis for medium heads. (Key point: Head range)

2. How is Kaplan regulated?
   A. Guide vanes only
   B. A spear and nozzle
   C. Guide vanes and runner blades (double)
   D. Runner blades only
   Answer: C. Francis has guide vanes only; Kaplan has double regulation. (Key point: Regulation)

3. Where is Kaplan typically used?
   A. High-head Himalayan schemes
   B. Micro-hydro only
   C. Above 300 m head
   D. Barrage or canal-drop plants on large rivers
   Answer: D. It suits low head, high flow sites. (Key point: Typical project)

## Related in Power Plant Design

- [Kaplan turbine suitability in Nepal](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Akaplan-suitability-nepal) — Power Plant Design, chapter 3
- [High dam hydropower project components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahigh-dam-components) — Power Plant Design, chapter 3
- [Combined cycle gas turbine versus hydro](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Accgt-vs-hydro) — Power Plant Design, chapter 1
- [Hydropower versus solar PV in Nepal](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahydro-vs-solar-pv-nepal) — Power Plant Design, chapter 1
- [Grid-tied solar PV versus hydropower](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Agrid-tied-pv-vs-hydro) — Power Plant Design, chapter 1
- [ROR versus PROR hydropower plants](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aror-vs-pror) — Power Plant Design, chapter 3

## Related in other subjects

- [Number of Francis/Kaplan units (300 m³/s, 30 m)](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aturbine-units-number-francis-kaplan-300cumec) — Hydropower Engineering, chapter 7
- [Powerhouse layout with vertical axis Francis turbine](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Apowerhouse-layout-vertical-axis-francis) — Hydropower Engineering, chapter 8, asked 3×
- [Kaplan turbine construction and working](https://www.bctengineer.com/question.md?key=semester_5%2Ffluid_machines%3Akaplan-turbine-working) — Fluid Machines, chapter 3
- [Kaplan turbine discharge and blade angles](https://www.bctengineer.com/question.md?key=semester_5%2Ffluid_machines%3Akaplan-turbine-numerical) — Fluid Machines, chapter 3