Finishing, Cladding, and Jacketing
Finishing, Cladding, and Jacketing
This domain tests protective finishes and weatherproofing: metal jacketing, mastic, fabric, cement, bands, fasteners, and removable covers. The exam asks how to keep insulation dry, secure, and durable.
Core rules
- Choose the finish for the environment: aluminum for general weather, stainless steel for corrosive or hygienic areas, PVC for indoor and chemical resistance, and mastic or fabric for irregular shapes.
- Lap metal jacketing to shed water. On horizontal runs, upper sections overlap lower sections; place longitudinal laps at the sides, not on top. On vertical runs, upper sections overlap lower sections.
- Provide a 50 mm minimum lap and stagger joints. Band spacing is typically 300 mm outdoors and 450 mm indoors, with bands near ends and at laps.
- Fasten with the specified screws or bands. Do not drive fasteners through the insulation or puncture a vapour retarder on cold service.
- Allow for thermal expansion. Use expansion joints or slip joints on long hot lines; do not rigidly lock jacketing that must move.
- Seal penetrations, terminations, and overlaps with the specified sealant. Keep sealant compatible with the jacket and service temperature.
- Isolate dissimilar metals to prevent galvanic corrosion, especially stainless steel under aluminum in wet environments.
Worked example
You are jacketing a 15 m outdoor horizontal steam line with 1.2 m aluminum sections. The effective coverage per section is 1.2 m minus a 50 mm lap, or 1.15 m. Number of sections: 15 divided by 1.15 equals 13.04, so order 14 sections. Install with the upper lap over the lower lap so water runs off, place the longitudinal seam at the side, and band at 300 mm centres. Add an expansion allowance at the end. Reasoning: the lap direction and band spacing control water entry and wind uplift; the extra section covers the lap and cutting allowance.
Traps
Marks are lost by lapping backward, putting the seam on top, spacing bands too far apart, using self-tapping screws through the insulation, omitting expansion joints, and sealing with an incompatible caulk. Another trap is failing to isolate aluminum from stainless steel.