1. The copyright to this material belongs to the Korea Occupational Safety and Health Agency. Unauthorized use and distribution are prohibited. If an individual uses this for non-commercial purposes, the Korea Occupational Safety and Health Agency must be cited as the source. A corporation using this material must obtain permission from the Korea Occupational Safety and Health Agency first. Using thi material without prior permission will be considered copyright infringement, and legal action may be taken. Manufacture Hit by flying lid owing to bolt fracture during vessel leakage test ( Flying Object ) 2009.05 -Serious Accidents in Manufacturing - 안전분야 - 교육자료 미디어개발 2009-75-451

2. Table of Contents I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions

3. I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions I.Fatality Overview Date & Time: 14:00, November O, OOOO Place: electric equipment manufacturing workplace in Kyeongsangnam-do Victim: a production worker While the victim was removing bolts on the round and flat flange plate (blind plate) during leakage test of a tank for gas- insulated switchgear (GIS) that was not depressurized. The flat plate flew by bolt fracture and hit the victim in the face to kill him on the spot. Fatality reconstruction not fasthened bolts round and flat plate

4. II.Process Overview Process Overview (gas-insulated switchgear) Fatality Process –To manufacture external shape of a gas-insulated switchgear, they work on canning, welding and finishing. After that, they seal tank Freon gas and compressed air in the tank to perform leakage test using a gas detector. –gas-insulated switchgear A combined transformer with built-in switches such as circuit breaker and disconnector, and earthing switch and accessory devices such as current transformer, voltage transformer, lightening arrester in metal outer tank that is filled with SF6 gas with high insulating performance and grounded. Welding FinishingInspectionShipping Material Receipt Canning I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions Fatality Process

5. III. Fatality Object Fatality Object: pressure vessel –Product: gas tank for gas-insulated switchgear –Body thickness: 12 ㎜ –Dimensions: ID795 ㎜ ×L1975 ㎜ –Material: rolled steel material for general structure SS400 –Cubic content: 1.18 ㎥ –Weight: 797 ㎏ I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions

6. IV. Fatality Process At 08:00, November O, OOOO the victim went to the site and started trimming of gas-insulated switchgear tank. The victim usually did trimming and leakage test in a canning team. At about 11:30, he fixed a round and flat flange plate (blind plate) with bolts and clamps for a leakage test for a rimmed tank and sealed Freon gas of 1 ㎏ f/ ㎠. G and compressed air of 6 ㎏ f/ ㎠. G. –The leakage test: Seal Freon gas and compressed air and keep the pressure for more than 3 hours. After that, the first test is conducted using a leakage detector and bubble test is conducted using soap bubble. At about 14:30, the victim opened a gas-sealing valve after finishing leakage test. He was supposed to check for removal of internal pressure of the tank. He did not, however, check for internal pressure of the tank and started to dismantle bolts (M12, 16 ea) on round and flat flange plate (OD: 675 ㎜, thickness: 22 ㎜ ) using an impact wrench. At about 14:40, while he was dismantling the 11 th bolt among 16 bolts (clockwise rotation) A bolt popped by the internal pressure of the tank and the round and flat plate flew to hit victim in the face to death. I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions

7. IV. Fatality Process (Pictures) I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions Fatality Overview tank for a gas-insulated switchgear round and flat flange plate victim Freon + air

8. IV. Fatality Process (Pictures) I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions Standard of the fractured bolts and bolts of the same standard

9. V. Fatality Cause No operation stop during maintenance –When there is any danger of emission of compressed gas in the tank during air pressure test to workers, you must conduct protections against hazards such as emission of compressed gas. However, dismantlement of bolts on round and flat flange plate of the tank was conducted when compressed gas was not emitted. No special safety & health education - When protections against hazards of installation and handling of pressure vessel with gauge pressure of 1 ㎏ f/ ㎠ are required, you must conduct special safety education of safety facilities and safety standards, dangerousness of pressure vessel, safety inspection and methods. Nevertheless, the air pressure test was conducted not observing these rules. I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions

10. Thorough operation stop for maintenance –When there is any danger to workers due to emission of compressed gas in the tank during air pressure test, you must prepare protections against hazards like previous emission of compressed gas. Special safety & health education –When protections against hazards of installation and handling of pressure vessel with gauge pressure of 1 ㎏ f/ ㎠ are required, you must conduct special safety education of safety facilities and safety standards, dangerousness of pressure vessel, work safety inspection and methods. I. Fatality Overview II. Process Overview III. Fatality Object IV. Fatality Process V. Fatality Cause VI. Precautions

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