Bridge Crane Reducer Spec: GB/T 23201-2008 Models & Ratios
GB/T 23201-2008 "Gear Reducers for General Purpose Bridge Cranes" is the product standard for special reducers used in overhead cranes. The standard specifies the model designations, load-bearing capacity, transmission ratio series, and technical requirements for reducers applied in hoisting mechanisms and crane/trolley travel mechanisms. This article provides a detailed breakdown of the reducer types covered, key selection parameters, and inspection requirements.
GB/T 23201-2008, published in 2008, applies to spur gear reducers used in the hoisting mechanism, bridge travel mechanism, and trolley travel mechanism of general purpose bridge cranes. It serves as the technical basis for reducer selection and procurement in overhead crane applications. Kelude's QD and LH type bridge cranes are equipped with reducers selected in accordance with this standard.
Reducer Types and Model Designations
The standard covers three main reducer series: QJ type (dedicated to hoisting mechanisms), QJR type (for bridge travel mechanisms), and QJS type (for trolley travel mechanisms). A model designation consists of the reducer type, center distance, transmission ratio, and assembly configuration. For example, QJ-315-20-Ⅰ denotes a hoist gearbox with a 315 mm center distance and a 20:1 transmission ratio.
Center distance series: 150, 180, 200, 224, 250, 280, 315, 355, 400, 450, 500, 560, 630, 710, and 800 mm. In practice, hoisting mechanisms typically use the 315–560 mm range, bridge travel mechanisms use 200–400 mm, and trolley travel mechanisms use 150–280 mm.
Load-Bearing Capacity and Transmission Ratios
The standard specifies the rated output torque and thermal power for each reducer model. Selection must satisfy two conditions simultaneously: mechanical strength (fatigue strength plus short-term overload capacity) and thermal balance. The transmission ratio series includes 10, 12.5, 16, 20, 25, 31.5, 40, 50, and 63.
Allowable torque: For the QJ series, the QJ-315 delivers a rated output torque of approximately 4.5 kN·m, the QJ-400 about 9.0 kN·m, and the QJ-500 roughly 17.5 kN·m.
Reducer Selection Reference Chart
| Model | center distancemm | transmission ratio | rated torquek N·m | applicable mechanism | applicable tonnage |
|---|---|---|---|---|---|
| QJ-280 | 280 | 20~50 | 3.2 | Hoisting / Lifting | ≤5t |
| QJ-315 | 315 | 20~50 | 4.5 | Hoisting / Lifting | ≤10t |
| QJ-400 | 400 | 20~50 | 9.0 | Hoisting / Lifting | ≤20t |
| QJ-500 | 500 | 20~50 | 17.5 | Hoisting / Lifting | ≤50t |
| QJR-315 | 315 | 12.5~40 | 4.0 | Long Travel / Bridge Travel | ≤20t |
| QJS-280 | 280 | 12.5~40 | 2.8 | Cross Travel / Trolley Travel | ≤20t |
| Kruud Recommended | hoist gearbox Press1.3Times Safety factorselection, Ensureservice life≥10Year | ||||
Frequently Asked Questions
Q: Can a QJ hoisting gearbox and a QJR travel gearbox be used interchangeably?
A: Not directly. The QJ hoisting gearbox is designed for heavy-load, low-speed duty with frequent start/stop cycles, and is engineered to handle impact loads and braking torque. The QJR travel gearbox, by contrast, handles light-load, high-speed intermittent operation. The two differ in gear strength, bearing selection, and housing rigidity. That said, QJ and QJR units of the same center distance share identical mounting dimensions, so they can be swapped when necessary.
Q: Why is it necessary to verify both strength and thermal power when selecting a reducer?
A: The mechanical strength check ensures the gearbox will not suffer gear or bearing damage under maximum load, while the thermal power check ensures the lubricating oil temperature stays within its allowable limit (typically ≤ 85 °C) during continuous operation. For low-speed, heavy-load hoisting mechanisms, strength is usually the governing factor; for high-speed, continuously running crane travel mechanisms, thermal power tends to be the limiting condition. Both criteria must be satisfied.
Q: What are the common causes of abnormal noise in a gearbox?
A: Abnormal gearbox noise generally falls into three categories: ① rhythmic meshing impact — poor gear engagement or pitting on tooth flanks; ② a steady hum — excessive bearing clearance or insufficient lubrication; ③ irregular metallic clatter — gear tooth breakage or a damaged bearing cage. If abnormal noise is detected, shut down immediately and inspect the tooth surfaces and oil condition through the inspection window.
Q: How often should the gearbox oil be changed?
A: A new gearbox should have its first oil change after 200–300 hours of operation (break-in period). Under normal service, L-CKD320 medium-duty industrial gear oil is recommended every 6–12 months, depending on the duty classification. For duty levels below A5, change annually; for A6 and above, change every six months. When draining, be sure to clean any sediment from the bottom of the housing.
