Pipe Supports, Hangers and Expansion Control
What this domain tests
This domain tests support selection, spacing, and thermal expansion control. The exam expects you to calculate expansion, recognize when a loop or expansion joint is needed, and distinguish anchors, guides, and spring hangers.
Core rules
- Support spacing depends on pipe size, material, wall thickness, fluid weight, and the project specification; do not use one spacing for every line.
- Thermal expansion is estimated by ΔL = L × α × ΔT, where α is the coefficient of linear expansion.
- Anchors restrain movement; guides allow axial movement but prevent lateral displacement; spring hangers carry load while permitting vertical movement.
- Expansion loops, offsets, and bellows joints absorb movement. Bellows require correct anchoring and guiding, or they will fail.
- Supports must not be installed on unsupported spans that allow sag or vibration.
Worked example
A 30 m carbon-steel line operates 80 °C above installation temperature. Take α = 12 × 10⁻⁶ per °C. ΔL = 30 × 12 × 10⁻⁶ × 80 = 0.0288 m, or about 29 mm. If both ends are anchored rigidly, that movement must go somewhere; provide a loop or approved expansion joint and guide the line so it moves axially. Reasoning: the calculation shows the magnitude, and the support arrangement determines whether the movement is controlled or destructive.
Traps
- Anchoring both ends of a straight hot line with no expansion provision.
- Omitting guides near a bellows expansion joint.
- Using the wrong hanger type for a line that moves vertically.
- Setting support spacing from habit rather than specification.