The Electrical and Mechanical Services Department (EMSD) today (October 25) released a technical investigation report on the lift incident which occurred at lift no. 11, Block 4, Tsui Lai Garden, Sheung Shui, on September 11.
According to the report, the incident, which trapped a passenger inside the lift car, was caused by detachment of the lift counterweight components.
The EMSD's investigation revealed that shortly before the incident the lift car was descending from the 24th floor to the 15th floor under normal speed and conditions. When the lift car reached the 15th floor, the counterweight components were detached from their frame.
Without the balance of the counterweight, the lift car started descending at increased speed. The safety gear was activated immediately and the lift car stopped at the 14th floor. On-site measurements revealed that the lift car stopped within a distance of 20 centimetres following the activation of the safety gear. The lift car's four suspension ropes were found intact.
The EMSD engaged the City University of Hong Kong to examine and test the failed counterweight frame. The material specifications and mechanical properties of the counterweight frame were found to be in compliance with the manufacturer's technical specifications. However, localised embedded particles, which had formed during manufacturing, were found in the fracture surface of the frame. This latent defect led to material strength reduction in some local spots which caused the failure of the counterweight frame.
After the incident, the EMSD arranged on-site tests on the counterweight frames of other 23 lifts in Hong Kong, which were manufactured from the same batch of materials as those in the counterweight frame of lift No. 11 in Tsui Lai Garden. No similar defect was found in all these counterweight frames.
The registered lift contractor of Tsui Lai Garden, Sigma Elevator (HK) Limited, agreed to replace the counterweight frames of the 23 lifts by the end of December this year to enhance users' confidence in their lifts. The EMSD will closely monitor the replacement work.
No similar failure in a counterweight steel frame has been reported before in Hong Kong or overseas. The incident in Tsui Lai Garden was an extremely rare one. The EMSD has reviewed and agreed with the trade to enhance regular inspection of the counterweight frame with a view to enhancing safe operation of the counterweight.
The full report is available for browsing at the EMSD's website, www.emsd.gov.hk/emsd/eng/pps/le_pub.shtml.
Ends/Monday, October 25, 2010
Issued at HKT 14:01