Monday, November 23, 2009

Possible Case of Electrocution - WSH Bulletin

23 Nov 09

In a recent incident, a worker was deployed to rectify a fault reported during the operation of a tower crane boom. The crane operator was in his cabin waiting for the repair work to be completed. When the cabin fan stopped unexpectedly, the operator looked out and saw the worker lying motionless on the platform in front of the control panel box.

Investigations showed that the worker was probably trying to measure or check the electrical installation inside the control panel box using multi-meter probes (an electrical measurement tool). The burnt marks and strands of hair found stuck on two of the connectors inside the control panel box suggest that he could have been electrocuted and died on the spot.

Fig. 1 Tower crane under repair


1. Conduct risk assessment: Prior to the start of any work, risk assessment must be carried out by employers and workers to identify potential hazards. Appropriate actions should then be taken to eliminate the hazards or reduce the risks involved. Control measures and safe work procedures must be established, communicated and implemented to ensure the safety and health of the workers involved. Some of the hazards relevant to this incident include:

a. Exposed wires/connectors/terminals that are still energized and “live”
b. Working at height while troubleshooting the fault

2. Live testing precautions: Before performing any electrical work, one should ensure that the work can be done without the system being energised. Work on or near live conductors should be avoided. Should live testing be necessary to trace a malfunction of the equipment, suitable safety precautions should be taken, including putting temporary insulating neoprene or polythene sheets over live components and/or applying insulation to parts that are at earth potential. These temporary insulating sheets can also help to prevent the risk of accidental short circuit from tools, components and conductors.

3. Use of dry rubber insulating mat: Where there is the possibility of electrocution, workers should be asked to use dry rubber insulating mats. The rubber mat insulates the floor on which the person stands, reducing the risk of the flow of electrical current through the person. Other electrical insulation methods such as rubber blankets, gloves, sleeves, properly designed and rubber-soled boots may also be used.

4. Provision of adequate training: All workers should be adequately trained in the identification and control of hazards in their workplace. Specialized electrical safety training must be provided to those who may need to work with or around exposed components of electric circuits. The training should include, but not be limited to, basic electrical theory, proper safe work procedures, hazard awareness and identification, proper use of personal protective equipment, proper lockout/ tagout procedures, first aid including CPR, and proper rescue procedures. Provisions should also be made for periodic re-training.

5. Buddy system: For certain electrical works, it is recommended to implement a buddy system. In an emergency, the buddy (i.e. a co-worker) could switch off the electrical supply immediately and render assistance on site.

6. Lock-out procedures: Lock out procedures must be established and implemented for the inspection, repair and maintenance of any machinery or equipment. All energy sources to the relevant machinery or equipment should be isolated, disconnected or discharged to prevent any part of the machinery or equipment from being inadvertently activated or energised.

7. Personal protective equipment: Those who are potentially exposed to live components should be provided with appropriate protective clothing and equipment, such as electrical protective resistance glove for measurement and testing work. Such equipment should be inspected regularly by a competent person. Those working at height (e.g. on platform) must also be provided with a proper fall protection system, incorporating safety harness and secured anchor points to reduce the risk of falling.

Further Information

1. Workplace Safety and Health Act
2. Electricity Act (Cap. 89A)
3. Electricity (Electrical Workers) Regulations
4. Electricity (Electrical Installations) Regulations

* Please note that the information provided is intended to enhance workplace safety and health so that a similar recurrence may be prevented, and is not exhaustive. The information provided should not to be construed as implying any liability to any party nor should it be taken to encapsulate all the responsibilities and obligations of the reader of WSH Alert under the law.


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