Tools, Equipment, Materials and Piping Components
This domain tests selection, care and correct use of the tools and materials that make a gas system reliable: pipe and tubing, fittings, valves, connectors, gauges, detectors, threading and joining equipment.
Materials and components
- Steel: Schedule 40 black steel pipe with malleable iron fittings is the default above-ground gas carrier. Cut square, ream and thread; protect cut threads and exposed pipe with a listed coating.
- Copper tubing: must be listed for fuel gas, joined by flare or brazing as permitted; protect from abrasion and from contact with materials that promote corrosion.
- CSST: listed only, cut with the manufacturer's tool, supported at the manufacturer's spacing, protected by striker plates at penetrations, and bonded to the electrical grounding system - commonly 6 AWG copper, sized per manufacturer and the electrical code.
- Appliance connectors: listed, not concealed in walls or floors, not kinked or reused, and within the maximum length stated by code and manufacturer.
- Polyethylene: outdoors underground only, joined by qualified fusion, with tracer wire, anodeless riser and a listed transition fitting.
- Valves: listed gas shutoff valves, accessible and marked, installed at each appliance; quarter-turn ball valves are typical. Never use a valve to regulate pressure.
- Sediment trap: downstream of the shutoff valve, as close to the appliance as practical, with a capped nipple.
Measuring and test tools
Use a water-column manometer or calibrated digital gauge for inch-of-water readings, and a pressure gauge whose range puts the test pressure near mid-scale. Combustible-gas detectors must be calibrated and bump-tested; combustion analyzers need a water trap and fresh calibration. Never use an oxygen or acetylene regulator on a nitrogen or air test.
Worked example
You must air-test a 1 in. steel system at 15 psig for one hour. A 0–15 in. w.c. manometer would be destroyed and cannot resolve the test; a 0–200 psi gauge cannot show a 1 psi drop. Select a 0–30 psig gauge with 0.5 psig graduations, calibrated within the past year, plus a small needle valve and tee so the gauge can be isolated and watched. Reasoning: instrument accuracy must match the acceptance criterion, not merely survive the pressure.
Traps that cost marks
Using a hose, fitting or valve not rated for the test pressure; putting dope or tape on a flare seat; using an out-of-calibration detector; concealing a connector or union; installing a non-listed valve from a plumbing supplier.