Pipe Fabrication, Joining, Hanging and Support
What the exam tests
This domain covers cutting, threading, grooving, welding, brazing, hanging and bracing sprinkler pipe. Questions test joint integrity, hanger spacing and rod sizing, seismic and sway bracing, expansion and clearances.
Core rules and concepts
- Preparation. Cut pipe square, ream burrs and keep the inside clean. Debris left in pipe can plug heads and alarm devices.
- Threaded joints. Use the correct die and taper, apply a listed sealant to male threads, and avoid over-tightening. Do not use excessive dope inside the pipe.
- Grooved joints. Match the coupling to the pipe material and wall thickness, lubricate the gasket, and torque to the manufacturer's specification. Do not mix components from different listings.
- Welded and brazed joints. Use qualified procedures and personnel, and protect combustibles.
- Hangers. NFPA 13 sets maximum hanger spacing by pipe size and requires hangers near changes in direction and at concentrated loads. Rod diameter also comes from the NFPA 13 table.
- Seismic and sway bracing. Lateral and longitudinal bracing is required where the building code or NFPA 13 seismic provisions apply. Brace at the specified intervals and to structural members capable of carrying the load.
- Clearances and expansion. Allow for thermal expansion, building movement and clearance from other trades.
Worked example
A 6 in schedule 40 main requires hanger rods. NFPA 13's rod table gives 3/4 in rod for 6 in pipe. At 12 ft hanger spacing, the hanger and rod must carry the pipe, water and any insulation. Check that the clevis is sized for 6 in pipe, that the concrete anchor is listed and has the required embedment and edge distance, and that a hanger is placed near the change in direction. If the area is seismic, add lateral and longitudinal sway bracing at the required spacing and do not use the hanger rod as a brace.
Traps that cost marks
- Skipping reaming, which leaves burrs that affect flow and grooving.
- Using the wrong coupling gasket for the pipe material.
- Spacing hangers beyond the NFPA 13 table because the pipe looks stiff enough.
- Using hanger rods as seismic bracing.