GB/T 9462-1999 Tower Crane Specifications
Tower Crane Types and Technical Parameters
GB/T 9462-1999 applies to top-slewing tower cranes used in construction, including fixed-base, anchored, and rail-mounted configurations. Classified by load moment, the range spans from QTZ63 (630 kN·m) to QTZ125 (1250 kN·m). Maximum working radius reaches 50–60 m, maximum lifting capacity is 5–10 t, and free-standing height is 40–45 m.
Structural steel is Q235B or Q345B, with primary load-bearing welds subject to ultrasonic testing (UT) sampling of ≥20%. Mast section connection bolts are Grade 10.9, with M24 bolts torqued to approximately 800 N·m. Guide rail mast perpendicularity deviation is limited to ≤4/1000.
Safety Devices and Structural Requirements
Safety device requirements — the load moment limiter (LML) automatically cuts off hoisting and luffing-up operations when the load exceeds 110% of the rated moment, while preserving lowering and luffing-down functions for safe descent. Additional devices include a load limiter, luffing limit switch (deceleration begins 2 m before the end limit), slewing limit switch (restricts rotation to ≥1.5 turns to prevent hydraulic pipeline entanglement), height limit switch, and an anemometer (early warning at ≥20 m/s, automatic shutdown at ≥25 m/s). Safety devices must be verified weekly, and the load moment limiter calibrated monthly to ensure accuracy. These devices are fundamental to safe crane operation — any failure requires immediate shutdown and maintenance.
When the crane height exceeds the free-standing height, an anchorage device must be installed and fixed to the building structure, with anchorage point spacing ≤20 m. Connection bolts are Grade 10.9. After anchoring, tower mast perpendicularity must be maintained within ≤4/1000.
The standard specifies the following safety devices for tower cranes: a load moment limiter (automatic shutdown of hoisting and luffing-up at >110% of rated moment, retaining lowering and luffing-down as safe directions), a load limiter, a luffing limit switch (travel limit and radius limit for trolley luffing, with deceleration initiated 2 m before the end position), a slewing limit switch (limiting rotation to ≥1.5 turns to prevent hydraulic hose winding), a height limit switch, and an anemometer (warning at ≥20 m/s, automatic stop at ≥25 m/s).
Safety devices should be checked once a week, and the load moment limiter calibrated monthly to maintain accuracy. The safety devices of a tower crane are the fundamental guarantee of safe operation — if any safety device fails, work must stop immediately for maintenance. Regarding structural requirements — the main steel structure uses Q235B or Q345B steel, while primary load-bearing components (tower main chords, boom top and bottom chords, and the slewing turret) are fabricated from Q345B steel and above.
Mast sections are joined using socket-type or flanged connections, with high-strength bolt pretightening torque executed per design requirements — approximately 800 N·m for M24 bolts and 1,200 N·m for M30 bolts. Primary load-bearing welds must undergo non-destructive testing (ultrasonic testing with sampling of ≥20%), and weld quality must meet Grade II or higher.
Anchorage device — when the crane height exceeds the free-standing height (typically >40 m), an anchorage device must be installed and secured to the building, with anchorage point spacing ≤20 m.
| Parameter/Model | QTZ63 | QTZ80 | QTZ100 | QTZ125 |
|---|---|---|---|---|
| Torque(k N·m) | 630 | 800 | 1000 | 1250 |
| Working radius(m) | 50 | 55 | 55 | 60 |
| Lifting Capacity(t) | 5 | 6 | 8 | 10 |
| Height(m) | 40 | 45 | 44 | 43 |
Test and Inspection Requirements
Structural testing includes stress testing (resistance strain gauges placed on critical load-bearing sections, with stress at 100% rated load not exceeding allowable stress), static load testing (1.25 × rated load held for 10 minutes), and dynamic load testing (1.1 × rated load for 3 cycles). Complete machine testing covers no-load, rated load, stability, and traveling tests. Each installation requires a full installation inspection, including tower mast perpendicularity, safety device functionality, and load testing.
In-service equipment requires a comprehensive safety inspection every six months and an annual load test.
Structural testing per the standard includes stress testing (resistance strain gauges placed on critical load-bearing sections, with stress at each measuring point under 100% rated load not exceeding allowable stress), static load testing (1.25 × rated load lifted in the most unfavorable direction and held for 10 minutes to check for permanent deformation), and dynamic load testing (1.1 × rated load with combined operation for 3 cycles to verify brake and safety device reliability).
Complete machine testing includes no-load testing, rated load testing, stability testing, and traveling testing (for rail-mounted tower cranes, the travel mechanism is inspected). During testing, stress and deformation data at each measuring point should be recorded, and load-deformation curves plotted.
The standard requires that every installation of a tower crane (including re-erection after relocation) undergo a full installation inspection—covering tower mast perpendicularity measurement (≤4/1000), safety device functional testing, crane rail inspection (for rail-mounted units), and load testing. In-service cranes require a comprehensive safety inspection every six months and an annual load test. After attachment, tower mast perpendicularity must be re-measured to ensure ≤4/1000.
Foundation settlement should be monitored monthly, with prompt corrective action taken if uneven settlement is detected. Kelude can provide supporting services for tower cranes according to the standard.
| safety device | Alarm Value | Trip Value | verification Cycle |
|---|---|---|---|
| torque limiting | 90%early warning | 110%Trip | Monthly |
| Capacity limitation | 100%Display | 110%Trip | Monthly |
| luffing limit switch | Limit-2m | Polelimit switch Set | Weekly |
| slewing limit | ≥1.5Revolution | 2Revolution | Weekly |
| Anemometer | 20m/searly warning | 25m/s Trip | Daily |
Tower Crane Safety Devices: FAQ
Q: Which safety device on a tower crane is the most critical?
A: The load moment limiter (LML) and the lifting capacity limiter are equally vital—both trigger an automatic shutdown of hoisting and luffing-in operations at 110% of the rated moment. The slewing limit switch restricts the number of slewing revolutions to prevent hydraulic hose entanglement. The anemometer issues an early warning at wind speeds of ≥20 m/s and halts operations at ≥30 m/s, at which point anchoring measures must be taken. All safety devices should be verified on a monthly basis.
Q: What are the requirements for the anchorage device on a tower crane?
A: An anchorage device is required once the crane height exceeds the free-standing height (typically >40 m). The spacing between anchorage points must not exceed 20 m, and the tie rods should be fabricated from seamless steel pipe or structural steel sections. Connection bolts must be high-strength bolts of property class 10.9. After anchoring, the perpendicularity deviation of the tower mast must be kept within 4/1000. The building structure at the anchorage points must be verified for adequate load-bearing capacity.
Q: What are the key points for the climbing and mast section insertion procedure?
A: This operation must only be carried out at wind speeds of ≤13 m/s, and the slewing mechanism must be locked. Before climbing, confirm that the tower mast perpendicularity deviation is ≤4/1000 and that the hydraulic cylinder pressure is normal. After inserting a new mast section, check the pre-tightening torque of the connection bolts on the mast section. Slewing or luffing operations are strictly prohibited during the climbing process.
Q: How should a tower crane be secured against wind in a non-working condition?
A: Operations must cease at wind speeds of ≥20 m/s. Raise the hook to its highest position and release the slewing brake to allow the boom to weathervane freely, thereby reducing wind-induced bending moments on the structure. At wind speeds of ≥30 m/s, additional reinforcement is required. For extended shutdowns, lower the boom to its lowest position or implement other wind-anchoring measures.
