Which Pipe Fittings Are Suitable for Fire Protection Projects?
Fire protection engineering pipe fittings must meet four core requirements: high pressure, reliability, ease of maintenance, and corrosion resistance. Priority should be given to four categories: grooved (clamps), hot-dip galvanized steel, flanges, and malleable cast iron (malleable iron). Ordinary plumbing fittings are strictly prohibited as substitutes.
I. Classification by Material (Compliant Commonly Used)
1. Hot-dip galvanized carbon steel pipe fittings (most mainstream, indoor fire hydrants/sprinklers)
Material: Q235 hot-dip galvanized (cold galvanizing is prohibited)
Types: 90°/45° elbows, equal/reducing tees, concentric/eccentric reducers, pipe clamps, unions, flanges, grooved fittings
Standards: GB/T 3091, GB 50974, GB 50261
Pressure: ≤1.6MPa (standard)
2. Grooved fittings (clamps, DN≥100 mandatory, quick assembly/disassembly)
Material: Ductile iron/galvanized cast steel, with EPDM sealing rings
Types: Grooved elbows, tees, crosses, mechanical tees, reducers, flanges, rigid/flexible clamps
Standards: GB 5135.11, FM/UL certified
Pressure: DN≤250 ≤2.5MPa; DN≥300 ≤1.6MPa
3. Malleable cast iron (malleable iron) threaded pipe fittings (DN≤80, branch pipe / end)
Material: KTH350-10, galvanized, 55°BSPT (R/Rp/Rc) thread
Types: elbows, tees, crosses, pipe clamps, fittings, unions, plugs, caps
Standards: GB/T 3287, GB/T 7306
4. Stainless steel pipe fittings (304/316, corrosion resistant / high-end applications)
Material: 06Cr19Ni10 (304) / 022Cr17Ni12Mo2 (316)
Types: grooved / press-fit / flanged elbows, tees, reducers, sanitary pipe fittings
Standards: GB/T 19228, GB/T 12771
5. Ductile Iron Pipe Fittings (Buried Main Pipes, Corrosion Resistant)
Material: QT450-10, inner cement mortar lining, outer asphalt/epoxy coating
Types: Socket elbows, tees, crosses, reducers, flanged short pipes
Standards: GB/T 13295, GB 50974
6. Plastic-Coated/Lined Pipe Fittings (Water Supply Fire Fighting Dual Use, Anti-Scale)
Material: Carbon steel inner and outer epoxy/PE coating
Types: Grooved/Threaded/Flanged elbows, tees, reducers, pipe clamps
Standards: GB 5135.20, CJ/T 120
Scenarios: Combined domestic and fire fighting pipelines, locations with high water quality requirements
II. By Function (Fire Fighting Dedicated, Essential)
1. Turning Types:
90° Elbow: Right-angle pipe turn (most common)
45° Elbow: Low resistance, sprinkler branch pipes/drainage
180° 1. **Bend Type:** Pipe reversal, in equipment rooms/ceilings
2. Branching Type:
Equal diameter tee: T-type branch (fire hydrant/sprinkler branch)
Reducing tee: Main line remains the same, branch pipe becomes smaller (main pipe connects to branch)
Mechanical tee: No-drill welding, direct clamp branch (DN≥100 main pipe connects to DN≤50 branch)
Four-way: Four-way equal diameter, cross branch (pipeline intersection)
3. Reducing Type:
Concentric reducer: Coaxial reducer (vertical/horizontal pipe universal)
Eccentric reducer: Horizontal pipe, top flat (prevents airlock), bottom flat (prevents dirt accumulation)
Matcher (internal/external thread): Small diameter reducer (DN≤50)
4. Connection/Maintenance Type:
Pipe clamp (straight-through): Same diameter butt joint
Union: Removable for maintenance (essential for valves/equipment ends)
Flange: High pressure/large diameter/requires frequent disassembly
Rigid/ Flexible clamps: Grooved connections, flexible for settlement joints/expansion joints
5. Sealing/End-type pipes
Pipe caps: Permanently seal pipe ends (close spare ports after pressure testing)
Plugs (threaded plugs): Temporarily seal internal threaded ends (pressure testing/maintenance)
Blind flanges: High-pressure sealing (equipment maintenance isolation)
