In a certain day in 2001 , the Hebei Engineering Foreman class hanger to install a pump inlet line , at the time of installation of the valve, using a 2 -ton chain hanging down on the 4.5 -meter motorized chain hoist pipeline out of the pipe rack , hook directly hook valve flange bolt holes force to enhance valve. When the valve is raised to the interface flange , inverted chain hook rack under splints on both sides of the tension due to lateral bending , and lower down the chain hook hook rack off, resulting in the valve from the flange to 1.85 meters high east side fall motorized chain hoist, scraping Sao welding handle Ryu who hit his legs . The above case studies prove a serious violation rigger foreman rules, a direct violation of the inverted chain hook hook on the valve flange bolt holes , pour down the chain hook hook plywood shelf on the side of the valve flange side , resulting in fall under the direction of the vertical force hook rack with hooks down the chain forms an angle motorized chain hoist, bending it i dark Star , which is connected with the lower hook off the hook from the frame of the pin bending plywood shelf under the hook , resulting in lower down the chain hook rack completely scattered , resulting in the fall ; another sense of responsibility to protect themselves because the welders Ryu poor job does not end before lifting , lifting it into the work area , passive harm.