1. Equipment Foundation Design and Construction Requirements
Equipment foundation construction shall be based on GB 50204-2015 and GB 50461-2008. Foundation design requirements: equipment foundations shall be cast with concrete of grade C25 or above; the thickness shall be determined according to equipment weight and vibration characteristics, generally not less than 200 mm, and not less than 300 mm for large equipment; the foundation dimensions shall be 200 mm wider than the equipment base, i.e., 100 mm on each side; the specification of embedded anchor bolts shall follow the equipment manufacturer's requirements, generally not less than M16, and the exposed bolt length shall be the nut height plus washer thickness plus 30 mm; the upper surface of the foundation shall be flat, with a gap of not more than 5 mm when checked with a 2 m straightedge.
2. Vibration Isolator Selection and Installation Requirements
Vibration isolator selection shall be based on GB 50463-2008 and the equipment manufacturer's technical requirements. Vibration isolator type selection: spring vibration isolators are suitable for medium- and low-frequency vibration equipment such as chillers, water pumps, and fans, with frequencies of 2-10 Hz and vibration isolation efficiency not less than 90%; rubber vibration isolation pads are suitable for small and medium-sized equipment, with frequencies not less than 10 Hz and applicable temperatures of -10°C to 60°C; air springs are suitable for precision equipment or occasions with ultra-low vibration requirements, with frequencies of 1-5 Hz. Selection parameters: rated load = equipment static load plus dynamic load coefficient 1.2-1.5; natural frequency = 1/3 to 1/5 of motor speed; damping ratio: 0.02-0.05 for springs, 0.05-0.15 for rubber.
3. Inertia Foundation and Floating Floor Technology
The inertia foundation (inertia block) is used to reduce the transmission of equipment vibration to the structure. Design points: mass equal to 2-4 times the equipment mass, 2 times for large equipment and 4 times for small equipment; material shall be reinforced concrete with density not less than 2400 kg/m3, or steel structure filled with concrete; spring vibration isolators below the foundation shall be arranged uniformly according to mass distribution. Floating floor technology (floating floor slab): a vibration isolation pad with thickness of 10-50 mm, made of rubber granules plus polyurethane or glass wool, shall be laid on the structural layer; a concrete layer with thickness of 80-150 mm and reinforcement Φ6@200 single-layer bidirectional shall be cast on the vibration isolation pad.
4. Acceptance Standards and Vibration Testing
Acceptance of equipment foundations and vibration isolation installation shall be based on GB 50204-2015 and GB 50463-2008. Foundation acceptance standards: concrete strength not less than the design value, tested by rebound method or core drilling method; foundation dimension deviation not more than ±20 mm, elevation deviation not more than ±10 mm; embedded part position deviation not more than ±5 mm; foundation surface flatness not more than 5 mm (2 m straightedge). Vibration isolation installation acceptance: compression deviation of each vibration isolator not more than 2 mm; equipment levelness not more than 0.5 mm/m for precision equipment or not more than 1 mm/m for general equipment; vibration isolation efficiency not less than 90%.