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汽车密封计划和溢流阀英文文献和翻译

更新时间:2011-10-13:  来源:毕业论文

We do not see these types of failures very often, but when we do it can almost always be traced back to human error.  Back in 2008, a tube and shell heat exchanger catastrophically failed when workers accidentally closed two different valves at two different times between the vessel and its relief valve. On June 10, 2008, Goodyear operators closed an isolation valve between the heat exchanger shell (ammonia cooling side) and a relief valve to replace a burst rupture disk under the relief valve that provided over-pressure protection. Maintenance workers replaced the rupture disk on that day; however, the closed isolation valve was not reopened.  On the morning of June 11, an operator closed a block valve isolating the ammonia pressure control valve from the heat exchanger. The operator then connected a steam line to the process line to clean the piping. The steam flowed through the heat exchanger tubes, heated the liquid ammonia in the exchanger shell, and increased the pressure in the shell. The closed isolation and block valves prevented the increasing ammonia pressure from safely venting through either the ammonia pressure control valve or the rupture disk and relief valve. The pressure in the heat exchanger shell continued climbing until it violently ruptured at about 7:30 a.m.原文请+QQ32491.14六.维'论,文~网 毕业论文http://www.lwfree.cn
A Car Seal program could have gone a long way in preventing this incident.  A car seal program is simply a valve management program that contains: a list of safety critical valves, their SAFE positions (could be either open or closed), a description of their location, and some type of seal that will prevent the valve from being deviated from its SAFE position.  This seal can be a plastic tie wrap, chain, or some type of metal banding.  Some facilities even using color coding for their seals (e.g. green is for OPEN and red is for CLOSED valves).  The program should also include your P&IDs; they should be updated to reflect which valves are in this program.  Most P&IDs will use the designation CSO for Car Sealed Open and CSC for Car Seal Closed to show the valves in the program.  Now comes the tricky part...WORKERS!  The program is only as good as the workers who use it and rely on it.  some facilities build the Car Seal deviation procedure into their Management of Change procedure, which means anytime a valve in the program wants to be deviated from it's safe position, a MOC will be completed and this MOC will ALWAYS require a Pre-Start Up Safety Review.  Some facilities will have a very basic board and tagging program where each sealed valve will be tagged with a weather resistant tag that is in two parts. The tab on the end of the tag is the permission tab.  This is the one that is removed and is signed by the appropriate personnel granting permission to deviate the valve.  On the back of the tab there is a matching number that also appears on the part of the tag that is attached to the valve.  The removed tab is hung on a Valve Deviation Board in PLAIN SIGHT in the control room.  Workers then go back to the valve and with the signatures and the tag hung on the board AND communicated to all workers on shift (can be via radio announcement, but then all workers must acknowledge they received the transmission) they will now deviate the valve.  The program will also require an entry into either a paper log book that is used to communicate shift change data or an electronic method, but it is CRITICAL that any and ALL valve deviations be communicated to all workers, including contractors whose work will involve any deviated valve.  A lot of plants will work in valve deviations into their safe work permitting process to provide another layer of communication.2077

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汽车密封计划和溢流阀英文文献和翻译下载如图片无法显示或论文不完整,请联系qq752018766
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