Piping, Valves, and Fittings
Core concepts
Know pipe schedules, nominal sizes, materials (carbon steel, stainless, copper), and expansion/contraction. Understand valve types: gate (isolation), globe (throttling), ball and butterfly (quick shutoff), check (one-way), safety/relief (overpressure), and control valves. Know the meaning of pressure ratings, ANSI classes, and temperature derating. Understand steam traps (thermodynamic, thermostatic, float-and-thermostatic) and their role. Familiarize yourself with expansion loops, anchors, and pipe supports.
Traps to watch
- Using a gate valve for throttling (it should be fully open or closed).
- Confusing check valve function with isolation.
- Forgetting that safety valves must be set at or below MAWP and tested regularly.
- Overlooking thermal expansion when sizing supports and loops.
- Mixing schedule number (wall thickness) with nominal pipe size.
Worked example / rule of thumb
A 100 m carbon-steel steam line heats from 20 °C to 300 °C; α ≈ 12 × 10⁻⁶ /°C. Expansion = 100 × 12 × 10⁻⁶ × 280 ≈ 0.336 m. Rule of thumb: ~3.4 mm per metre for that temperature swing - plan loops accordingly.