Power Failure and Brake Drift at 14/F
At 15:40, a dual-point platform is at 14/F on a 22-storey residential tower. The control pendant suddenly goes dead; the platform stops. The operator notices that after each attempt to release the joystick, the platform drifts downward about 150 mm before stopping. The hoist brake area is oily and the brake smells hot. Both workers are harnessed to the independent safety rope. The platform is 1.2 m from the facade, with no openings nearby. Wind is 20 km/h and rain is starting; the typhoon signal is still No. 1, but the forecast says No. 3 may be issued within two hours. The supervisor radios that the electrician can “reset the RCD and bypass the emergency stop” from the roof. The platform’s manual lowering device is available but has not been used on this site. The logbook shows the last brake inspection was eight months ago.
1. What is the likely nature of the fault, and what immediate action should be taken? Consider the supervisor’s proposal.
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The dead control pendant points to a loss of electrical supply or a control-circuit fault, but the downward drift and hot, oily brake are more serious. A brake that allows 150 mm of drift after each stop may be contaminated, worn or overheated, and it may not hold the rated load reliably. The oily area suggests lubricant or hydraulic fluid has reached the brake lining. The supervisor’s proposal to reset the RCD and bypass the emergency stop is unacceptable: bypassing a safety device defeats the emergency stop and may allow movement with a faulty brake. The operator should stop all attempts to move the platform, keep the workers attached to the independent safety rope, isolate the power if it is safe to do so, and tag the controls. The area below should be cordoned off. The platform should be treated as defective until a competent person has inspected the brake, hoist and electrical system. The workers should not attempt to climb out or jump to the facade.
2. How should the platform be brought to a safe condition, and what rescue considerations apply?
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The platform should be brought to a safe condition under a planned procedure, not by repeated jogging. If the manual lowering device is to be used, it must be operated by a trained person following the manufacturer’s instructions, with the brake condition understood and a secondary means of control available. Because the brake is suspected of slipping, lowering should be controlled and monitored; if control cannot be maintained, the platform should be secured and the emergency services or specialist rescue team called. The workers should remain connected to the independent safety rope and should not unclip until they are on a safe landing. Communication should be maintained between the platform, roof and ground. If the platform cannot be lowered safely, rescue from a safe access point should be arranged. The workers should be monitored for cold, stress and fatigue, and the platform should not be left suspended overnight if it can be lowered safely. The incident should be recorded, and the platform should not be re-energized until the fault is repaired and tested.
3. What reporting, record-keeping and weather actions are required?
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The defect should be reported immediately to site management and the contractor’s competent person, and the platform should be tagged out of service. The logbook should record the time, platform location, symptoms, control-pendant failure, brake drift, oily brake area, the eight-month gap since the last brake inspection, and the isolation action. A defect report and maintenance request should be raised, and the platform should be inspected and repaired before any further use. If the event meets the statutory definition of an accident or dangerous occurrence, the required notification should be made. Because the typhoon signal may rise to No. 3, the site should follow its tropical-cyclone procedure: stop work, lower the platform to a safe level or ground, isolate power, secure loose items and ensure the platform is not left in a vulnerable suspended position. The rain and wind should be monitored, and work should not resume until the weather and the platform’s condition are both acceptable.