---
title: "Expansion joint and flanged joint"
subject: "Water Supply Engineering"
chapter: 8
key: "semester_5/water_supply_engineering:expansion-flanged-joint"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/expansion-flanged-joint
site: BCT Engineering
---

# Expansion joint and flanged joint

Water Supply Engineering · Chapter 8: Conveyance of Water

- Asked in: 2074 Asoj, 4 marks; 2070 Asar (asked 2 times)
- Video: [Flexicraft Expansion Joints Overview](https://www.youtube.com/watch?v=PWbAgVjrO4U) — Flexicraft Industries "Flexible Piping Solutions" Expansion Joints
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/expansion-flanged-joint
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-8

## Question

Briefly describe the purpose and use of the expansion joint and the flanged joint with sketch.

## Short answer

Expansion joints absorb thermal movement via a spigot sliding in a stuffing box sealed by packing and a gland; used on long exposed lines, bridges, near pumps. Flanged joints use bolted flanges with a gasket to connect pipes, valves, or fittings, allowing easy dismantling but no angular movement.

## Answer

#### Expansion joint
An expansion joint is a special joint which permits the pipe to expand and contract freely due to temperature changes, without causing leaks or stress.

- **Use:** on long straight lines of exposed CI/steel pipe, on bridges, and near pumps and valves.
- **Construction:** the spigot end slides inside a socket (stuffing box); a rubber or lead packing is compressed by a gland and bolts.

```text
   pipe ====[ socket | packing | gland ]==== pipe
                          ^bolts
        spigot slides in and out (10-20 mm)
```

#### Flanged joint
In a flanged joint, flanges (circular plates with bolt holes) are cast, welded or screwed on the ends of the two pipes. A rubber, rubber-fabric or lead gasket is placed between the faces, and bolts and nuts are tightened evenly.

```text
   pipe ===|F|gasket|F|=== pipe
           | |  ||  | |    F = flange, bolts hold
           bolts through the holes
```
- **Use:** to join valves, pumps, meters and other fittings; for pipes in pump houses, treatment plants and exposed lines; wherever the pipe may have to be taken apart and rejoined.
- It is strong, watertight and easy to dismantle, but costly and it cannot take any bending or movement.

## Check yourself

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

1. The expansion joint permits the pipe to:
   A. Expand and contract freely with temperature without leaks or stress
   B. Bend sharply
   C. Be dismantled easily
   D. Carry less water
   Answer: A. Its purpose is to absorb thermal movement. (Key point: Expansion joint purpose)

2. A flanged joint consists of:
   A. A socket filled with lead
   B. Flanges on pipe ends with a gasket between, held by bolts and nuts
   C. A solvent cement layer
   D. A threaded collar
   Answer: B. Flanges are fixed on the ends, a gasket is placed between the faces, and bolts tighten them evenly. (Key point: Flanged joint construction)

3. Where are flanged joints mainly used?
   A. Joining valves, pumps, meters and fittings where pipes may be taken apart
   B. Long buried lines of PVC
   C. Where movement is expected
   D. Inside the soil only
   Answer: A. They suit fittings, pump houses and treatment plants where dismantling is needed. (Key point: Flanged joint use)

4. A limitation of the flanged joint is:
   A. It leaks easily
   B. It is hard to dismantle
   C. It is weak
   D. It is costly and cannot take bending or movement
   Answer: D. It is strong and watertight but rigid and costly. (Key point: Flanged limitation)

## Related in Water Supply Engineering

- [Flanged joint and reflux valve](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aflanged-joint-reflux-valve) — Water Supply Engineering, chapter 9
- [Good pipe requirements; expansion joint](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apipe-requirements-expansion-joint) — Water Supply Engineering, chapter 8, asked 2×
- [Pipe joints; expansion joint](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apipe-joints-expansion-joint) — Water Supply Engineering, chapter 8, asked 3×

## Related in other subjects

- [Why joints are necessary; expansion joint](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ajoints-why-expansion) — Building Technology, chapter 10, asked 2×
- [Expansion joint in a residential building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aexpansion-joint-350wall) — Building Technology, chapter 10
- [Truss joint D: loading, lack of fit, temperature](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Atruss-defl-d-2074) — Theory of Structures I, chapter 3, asked 3×
- [Truss joint B: temperature and vertical members long](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Atruss-defl-b-temp-lackfit-2073) — Theory of Structures I, chapter 3, asked 2×