Tham khảo tài liệu 'what went wrong part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Preparation for Maintenance 3 TYPE A. FOR LOW-RISK FLUIDS SPADE POSITION FOR FLEXIBLE LINES SPECTACLE SPADE FOR LINES IN FREQUENT TYPE B FOR HAZARDOUS FLUIDS WITH VẸNTT0 CHECK ISOLATION ALTERNATIVE DESTINATIONS ACCORDING TO HAZARD USE TYPE c FOR HIGH PRESSURES I 600 PSI AND OR HIGH TEMPERATURES OR FOR FLUID KNOWN TO HAVE ISOLATION PROBLEMS DOUBLE BLOCK AND BLEED DOWNSTREAM VENT ALSO FOR VERY HIGH-RISK FLUIDS VENT DRAIN TYPE D FOR STEAM ABOVE 6Q0 PSI ALLWELOED E EQUIPMENT UNDER MAINTENANCE p PLANT UP TO PRESSURE - OR SPADE OR RING AS REQUIRED Figure 1-1. Summary of isolation methods. people injuring more than 130 and causing extensive damage. Debris was thrown six miles and the subsequent fire caused two liquefied petroleum gas tanks to burst. The valve was operated by compressed air and the two aử hoses one to open the valve and one to close it were connected Lip the wrong way around. The two connectors should have been different in size or design so that this could not occur. In addition they were not disconnected and a lockout device on the valve a mechanical stop had been removed. It is also bad practice to carry out work on equipment isolated from hot flammable gas under pressure by a single isolation valve. The take-off branch should have been slip-plated and double block and bleed valves should have been provided so the slip-plate could be inserted safely Figure 1-1 16 17 . 4 What Went Wrong There was another similarity to the first incident. In this case the equipment also had been prepared for repair and then had to wait for a couple of days until the maintenance team was able to work on it. During this period the air lines were reconnected the lockout removed and the isolation valve opened. Figure 1-2. The take-off branch was dismantled with the Demco valve open. illustration courtesy of the . Department of Labor. Preparation for Maintenance 5 In both incidents the procedures were poor and were not followed. Il is unlikely that the accidents occurred .
