---
title: "Classification of steam boilers"
subject: "Applied Thermodynamics"
chapter: 1
key: "semester_3/applied_thermodynamics:boiler-classification-examples"
source: https://www.bctengineer.com/q/semester_3/applied_thermodynamics/boiler-classification-examples
site: BCT Engineering
---

# Classification of steam boilers

Applied Thermodynamics · Chapter 1: Boilers

- Asked in: year not given, 5 marks
- Video: [Classification of Boiler (Boiler Types of based on Different Parameters) Explained](https://www.youtube.com/watch?v=qi80_lXgREM) — Engineering Funda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/applied_thermodynamics/boiler-classification-examples
- Whole chapter: https://www.bctengineer.com/md/semester_3/applied_thermodynamics/chapter-1

## Question

Classify steam boilers on different bases and give one example for each class.

## Short answer

Boilers are classified by: tube content (fire tube e.g. Lancashire, water tube e.g. B&W); axis (horizontal e.g. Lancashire); furnace position (internally fired e.g. Cochran); use (stationary e.g. Lancashire); pressure (low/medium/high); circulation (natural e.g. Lancashire, forced e.g. La Mont); number of tubes; gas passes; and fuel (coal, oil, gas, waste heat).

## Answer

Boilers are classified in the following ways.

| Basis | Types | Example |
|---|---|---|
| Tube content | Fire tube / Water tube | Lancashire / Babcock and Wilcox |
| Axis of shell | Horizontal / Vertical / Inclined | Lancashire / Cochran / rarely used |
| Furnace position | Internally fired / Externally fired | Cochran / Babcock and Wilcox |
| Use | Stationary / Mobile (portable) | Lancashire / Locomotive boiler |
| Pressure | Low (below 10 bar), medium (10 to 80 bar), high (above 80 bar) | Cochran / Babcock and Wilcox / Benson |
| Circulation | Natural / Forced | Lancashire, B&W / La Mont, Velox |
| Number of tubes | Single tube / Multi-tube | Cornish / Lancashire, Cochran |
| Passes of flue gas | Single-pass / Multi-pass | Simple vertical boiler / Lancashire |
| Fuel | Coal / Oil / Gas / Electric / Waste-heat | Lancashire (coal), electrode boiler (electric), waste-heat boiler |

**Note:** a boiler may belong to several classes at once. For instance, the Babcock and Wilcox boiler is a water tube, horizontal-drum, externally fired, stationary, natural-circulation boiler.

## Check yourself

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

1. Classified by tube content, which pair is correct?
   A. Fire tube: Lancashire; water tube: Babcock and Wilcox
   B. Fire tube: Babcock and Wilcox; water tube: Lancashire
   C. Fire tube: Benson; water tube: Cornish
   D. Fire tube: Velox; water tube: Cochran
   Answer: A. Lancashire is a fire tube boiler; Babcock and Wilcox is a water tube boiler. (Key point: Tube content)

2. Which boilers use forced circulation?
   A. Lancashire and Babcock and Wilcox
   B. La Mont and Velox
   C. Cornish and Cochran
   D. Locomotive and Lancashire
   Answer: B. La Mont and Velox are forced-circulation boilers; Lancashire and B&W use natural circulation. (Key point: Forced circulation)

3. Which classification of pressure is given?
   A. Low below 1 bar, medium 1 to 5 bar, high above 5 bar
   B. Low below 25 bar, medium 25 to 40 bar, high above 40 bar
   C. Low below 10 bar, medium 10 to 80 bar, high above 80 bar
   D. Low below 50 bar, medium 50 to 200 bar, high above 200 bar
   Answer: C. The answer classes boilers as low (<10 bar), medium (10-80 bar) and high (>80 bar). (Key point: Pressure classes)

4. A single boiler such as Babcock and Wilcox
   A. can belong to only one class
   B. is a fire tube, internally fired boiler
   C. is a mobile boiler with forced circulation
   D. can belong to several classes at once (water tube, horizontal drum, externally fired, stationary, natural circulation)
   Answer: D. The classes overlap; B&W is water tube, externally fired, stationary and natural circulation at the same time. (Key point: Multiple classes)

## Related in Applied Thermodynamics

- [Classification of air compressors](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_thermodynamics%3Aair-compressor-classification) — Applied Thermodynamics, chapter 2
- [Boiler: definition and applications](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_thermodynamics%3Aboiler-definition-applications) — Applied Thermodynamics, chapter 1
- [Boiler trial heat balance sheet](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_thermodynamics%3Aboiler-heat-balance-sheet) — Applied Thermodynamics, chapter 1

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