DEVB TC(W) No. 3/2023, Annex A 5(12)(e)
Tower crane monitoring: lifting zone alert for people under the hook
Clause 5(12)(e) of DEVB TC(W) No. 3/2023, Annex A, requires an automated warning system on all tower cranes. It protects people in the loading and unloading zone, generally at least 7 m radius from the hook, from the moving load. A person entering triggers a cab warning, a siren of at least 100 dB on the hook and an alert. Kodifly fits and runs it.
What the circular requires, and where it is mandatory
The circular asks for an automated warning system on all tower cranes operating on site. It alerts the crane operator, and anyone who steps into the loading and unloading danger zone, of the risk of being hit by the moving load under the hook (clause 5(12)(e)). The Safety Officer sets the zone by risk assessment. The Buildings Department and CIC name it the unsafe acts and dangerous situation alert for the tower crane lifting zone.
On a Hong Kong high-rise, the zone moves up the building with the works, so sensors must cover loading and unloading areas at every floor level involved. The Buildings Department also requires the 4S Tower Crane Alert System on private building works above HK$30 million that use tower cranes, as a condition imposed since July 2024 (LCQ13, 24 June 2026).
Requirements in Annex A, clause 5(12)(e), tower crane
| Topic | Requirement |
|---|---|
| Scope | All tower cranes operating on site. |
| Sensor cover | Enough sensors on or around the crane for full cover of the loading and unloading danger zone at all floor levels involved. |
| Danger zone | Set by the Safety Officer from the risk assessment. In general not less than 7 m radius from the crane hook. |
| Clearance trigger | The system activates when the clearance between cargo and the loading or unloading area is below a minimum set by the Safety Officer, in general not less than 3 m, and a sensor detects a person in the zone. |
| In the cab | A warning light on the dashboard and a spoken message telling the operator to stop all crane motion. |
| At the hook | A siren speaker on the hook with flashing red light and continuous warning of at least 100 dB. It switches off when the person leaves the zone. |
| Alert message | SMS or in-app pop-up to site supervisors and the Safety Officer, recorded at the platform with the date and time of the encroachment. |
| Video clip | Where specified, a clip from 15 seconds before the encroachment to 10 seconds after the person leaves. |
When someone is under the load
Lift
The load comes within the set clearance of the loading or unloading area.
Detect
A sensor sees a person inside the danger zone.
Stop the crane
A dashboard light flashes and a spoken message tells the operator to stop all motion.
Warn
The siren on the hook sounds at 100 dB or more with a flashing red light.
Alert and clear
Supervisors and the Safety Officer are alerted. Signals switch off when the person leaves.
How Kodifly supplies, installs and runs it
Sensors, cab unit, hook siren and platform link are fitted to each crane as one project.
Devices, software and installation together
Sensors on and around each tower crane
Cab light and spoken warning for the operator
Hook siren and flashing red light
Danger zone and clearance set with the Safety Officer
Cover moved as floors are added
Alerts to supervisors and the Safety Officer
Event record on the platform
Tower crane monitoring, answered
What does the circular require for tower cranes?
An automated warning system on all tower cranes that protects people in the loading and unloading zone from the moving load, with a cab warning, a hook siren of at least 100 dB and an alert to supervisors (Annex A, clause 5(12)(e)).
How large is the lifting danger zone?
The Safety Officer decides it from the risk assessment. In general it is not less than 7 m radius from the crane hook (clause 5(12)(e)).
What is the 3 m clearance?
It is the minimum clearance between the cargo and the loading or unloading area at which the system activates when a person is in the zone. The Safety Officer sets it, and in general it is not less than 3 m (clause 5(12)(e)).
Where does the siren sit?
On the crane hook, with a flashing red light and a continuous warning of at least 100 dB. It switches off automatically when the person leaves the danger zone (clause 5(12)(e)).
Is it mandatory on private building works?
Yes for building works above HK$30 million that use tower cranes. The Buildings Department has imposed the 4S Tower Crane Alert System as a condition since July 2024 (LCQ13, 24 June 2026).
Is a lifting permit also needed?
The sample permit-to-work covers lifting operations by tower cranes, with a narrow exclusion for light loads near the crane edge (clause 5(12)(c)(i)). The two systems work side by side.
Related guides
Cover your tower cranes
Tell us the cranes and the floors involved. We will plan the sensors and the hook siren.