Lock the duty condition first, then talk to suppliers
Hidden requirements differ sharply by industry. Write down your parameter sheet before contacting anyone:
Wind power: yaw/main-shaft brake, salt mist, low temp (‑30 °C response), OEM approval (Goldwind/Envision/Siemens Gamesa class)
Port & offshore: salt corrosion, IP66+, high cycling (>1M cycles), anti thermal-fade
Metallurgy & mining: dust/water/explosion proof, heavy-load holding, wet multi-disc or forced cooling
Crane & hydro: safety factor ≥1.5, fail-safe, manual emergency release
Servo / AGV / machine tool: response ≤50 ms, thin hollow-shaft, hold + e-stop dual function
Hard gates (single veto per item)
Real factory, not trading reseller: own plant + CNC machining + heat treatment + brake comprehensive test bench / fatigue rig. Video audit or third-party audit acceptable.
System & certs: ISO 9001 is baseline; wind power → GJB/MW-class OEM qualified supplier; export → CE; explosive atmosphere → ATEX/IECEx; marine → CCS; rail → IRIS. For safety chains, ask for third-party type-test report (torque, temperature rise, fatigue life, IP grade).
R&D trace: provincial tech center, participation in GB/T 12973 or industry standards, patents on friction formulation. Pure casting-assembly shops are skipped.
Same-duty references: not "we made brakes," but "we made brakes for your equipment class + your environment." Ask for 3 reference end-users you can call.
Pitfall list
Pure low-price award: recycled friction mix, high-temp smoke, torque decay >30 %
Trading company pretending to be source: contract stamped by trader, finger-pointing on failure
"General purpose" substituted for "fail-safe": crane/wind safety brake must be spring-applied closed-on-power-loss
Fake IP rating: claims IP66 but junction box unsealed, rusts in salt mist in 6 months
No SIL/PL rating but calls itself "safety brake": ISO 13849 safety chain needs PL d or above
