Description

1. Part-number breakdown AT120 = Otis door-machine frame size 120
   Material: GG-25 cast iron, phosphate primer + top-coat RAL 7035
   Grooves: 5 × 10 mm pitch, 9 mm belt width, 45° tooth profile
   Bore: Ø 30 mm with 8 mm keyway, 2 set-screws M6 × 10 mm
   Moment of inertia: 0.042 kg·m², balance grade G2.5 @ 1 800 rpm
   Rated torque: 45 N·m, max 1 500 rpm
2. Safety first—lock-out & verify The pulley sits inside the door-machine header; belts and terminals remain live during inspection. Lock the main disconnect, hang a lock-out tag and wait 60 s for the 24 VDC rail to fall below 5 V. Confirm zero energy with a CAT-III meter before removing guards.
3. Mechanical installation—keep it centred a) Remove door-machine cover (4 × M4 screws).
   b) Slide old pulley off keyed shaft; clean shaft with Scotch-Brite.
   c) Apply Loctite 638 to bore, insert new NYE AT120 pulley until shoulder seats.
   d) Torque set-screws 10 N·m in turn, then rotate 180° and re-torque—this eliminates run-out.
   e) Align belt teeth with grooves; misalignment >0.5 mm causes edge wear and noise.
4. Belt tension & tracking Frequency method: pluck belt; target 110 Hz ±5 Hz for 9 mm AT belt, 1 200 mm centre distance.
   Deflection method: 10 N force at midpoint; deflection = 2 mm.
   Every 0.5 mm under-tension reduces belt life 20 %. NYE supplies a free tension gauge (NY-TEN-AT120) and Kevlar-reinforced belt (NY-BELT-AT120-9).
5. Lubrication & corrosion protection Bearings are sealed-for-life (SKF 6204-2RS1), grease life 40 000 h @ 70 °C.
   Wipe pulley grooves with lithium spray every 6 months; prevent rust that accelerates belt wear.
   If surface rust >0.05 mm, polish with 400-grit paper and re-paint.
6. Vibration & balance check Run door at 0.7 m/s; vibration <1.5 mm/s RMS on bearing housing (ISO 10816).
   If >3 mm/s, balance has shifted—replace pulley immediately.
7. Wear limits & replacement triggers Groove depth: new 3.0 mm, replace at 2.7 mm (0.3 mm wear).
   Belt side clearance: new 0.1 mm, replace at 0.4 mm.
   Bearing noise: >65 dB(A) @ 1 m indicates dry balls—replace assembly.
   Cracks in web or hub: any visible crack schedules immediate change.
8. Replacement cycle model Belt life: 20 000 h @ 1 200 rpm, 110 Hz tension, 25 °C.
   Translate to door cycles: Light traffic (residence, 300 cycles/day) – 109 k cycles/year → pulley ≈ 18 years; inspect every 3 years. Medium traffic (office, 1 000 cycles/day) – 365 k cycles/year → pulley ≈ 7 years; inspect every 2 years. Heavy traffic (mall/metro, 2 500 cycles/day) – 913 k cycles/year → pulley ≈ 3 years; inspect every 6 months.
9. Rapid swap (downtime < 10 min) a) Lock-out main supply, engage inspection.
   b) Remove belt guard (2 × M4 screws).
   c) Release belt tensioner, slide belt off.
   d) Remove pulley set-screws, slide old pulley out.
   e) Install new NYE AT120 pulley, torque 10 N·m, re-tension belt.
   f) Run door 5 cycles, check vibration and tracking.
   g) Log serial number and groove depth; return old unit for recycling.
10. Recycling & sustainability Nanjing Zhuye offers prepaid UPS labels inside every carton.
    Returned pulleys are stripped: steel shaft re-ground, iron body re-smelted, bearing grease incinerated for energy.
    One recycled AT120 saves 3.2 kg CO₂—enough to power the same door machine for a month.