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1、Introduction to Safety Engineering,安全工程概论(双语),6.Hazard Reduction Precedence,减小危害的优先次序,课文讲解,NASA has developed an extremely useful hierarchy of hazard reduction. This method is applicable to all industries. 美国国家航空航天管理局发展了一种非常有用的分层次降低危害的方法。这种方法可应用于所有行业。 The first step is to “design out ” the hazard. I
2、f this is not possible, then the next best is to use safety devices. 第一步就是”设计掉”危害（在设计时去除危害）。如果这一步不可能实现，那么下一个最好的选择是应用安全装置。 hierarchyhair:ki 层次, 层级 be applicable to (适)用于 design out 在设计时去除,If safety devices are not sufficient control, then cautions and warnings can be applied. 如果安全装置不能有效控制，那么就要应用警告。 A
3、nd finally, special procedures and training can be used to control the hazard or mitigate the consequences. 最后，应用专门的程序和训练来控制危害和减轻其后果。 safety device 安全装置 cautions and warnings 提示与警告,6.1 “Design out” the Hazard 6.1 “设计掉”危害,The first step, and always the best (from a safety-only viewpoint ), is to “des
4、ign out ” the hazard - take the hazard out of the system completely. 第一步，常常是最优的（从安全第一的观点出发），就是“设计掉”危害也就是把危害从系统中完全排除。 from a safety-only viewpoint 以纯安全的观点来看,For example, four things are required for a fire: combustible material, oxygen, chemical reaction, and an ignition source. If one leg is taken o
5、ut of the fire tetrahedron, then it is physically impossible to have a fire. 例如，火灾由四个因素构成：易燃物，氧气，化学反应和引火源。如果在火灾四面体中去掉任何一个因素，那么，火灾就完全不可能发生了。 tetrahedron tetrhedrn 四面体 physically 自然地,“火三角”与“火四面体”,“火三角”虽为有用的教学工具，但火灾中持续性的化学反应，“火三角”未能辨认得到，因此便出现了“火四面体”，加入了持续化学反应，作为第四种火灾元素。因有不少火灾均在有齐“火三角”元素的情况下未能点燃，或是熄灭。在一
6、些情况下，“火三角”仍不足应用在一些化学火灾处理上。一场火灾通过燃烧过程，其化学反应使之温度更高并能持续下去，传统的“火三角”能应用在不少火灾上，但如果火灾涉及到锂、镁等活跃金属的燃烧，清除“火四面体”中的化学反应元素便能用得著，因单向此等火源射水，会使化学反应加剧，不但不能降温，反使火源温度更高，甚至会发生爆炸，因水会使之引起放热反应，释出易燃的氢气。因此，此等火灾需以切断燃烧的连锁反应来扑灭。,Fire tetrahedron,fire triangle,Engineering talent really comes into play in trying to decide which
7、of the four legs should be designed out. 工程技术人员（精英）真正发挥作用的方面就是决定在设计时去除这四个因素中的哪一个。 The system can be hermetically sealed and back-filled with dry nitrogen gas (taking away the oxygen ). 可以对系统进行密封并充填干燥的氮气(可以排除氧气)。 come into play v.开始活动 hermetically adv.密封地 backfill 充填,Or the system can be fabricated o
8、ut of material that has a very high flash point (assuring that the electrical cable can never reach the burning temperature of its insulation, under all electrical load conditions). 或者采用闪点非常高的材料来建造系统（保证在各种电力负载条件下，电缆永远不会达到其绝缘外套的燃烧温度）。 fabricate vt.制作, 构成 flash point 闪点 electrical load 电力负荷, 电力负载 insu
9、lationinsjulein 绝缘；绝缘体，绝缘材料,Another solution is to disable the power so that electricity does not create an ignition source. 另一种解决办法是不使用电源，这样就不会有电流产生引火源。 disable 使不适用，禁止使用，使无用,Figure 6.1 illustrates how easy designing out the hazard can sometimes be. 图6.1阐明了设计掉危害有时是多么简单。 The first part is a typical
10、engineering design. Gaseous nitrogen is needed to support the operators activities. 第一幅图是一个典型的工程设计，在操作活动中需要应用到氮气。,However, as can be seen in the second block, the nitrogen feed bottles do not need to be located in the same area as the operator. 然而，就像我们在第二幅图中看到的，氮气瓶没有必要放置在操作者所处的同一区域内。 The bottles hav
11、e been moved outside the work area, thus alleviating the asphyxiation hazard. 把氮气瓶移到工作区域之外，就可以减轻窒息的危害。 alleviateli:vieit vt. 减轻 asphyxiationsfiksiein n.窒息,Even though it may seem so, designing out the hazard is not always difficult. 尽管设计掉危害看起来似乎很难，但它不总是这样。 One common example is the hazard of mismati
12、ng power cables. 一个常见的例子就是电力电缆错误匹配的危害。 Many types of electrical instrumentation use various cable sizes both for power and for signal input and out-put. 许多型号的电力仪器采用不同大小的电缆作为电力线或者信号输入输出线。 even though adv.即使 mismate vt.使配合不当 mismating n. 错误接合, 错配合,One hazard is mating a 208-V source to a 110-V system.
13、 有一种危害就是将208V的电源和110V的系统匹配。 If there is concern that cables could be mismated through human error, then the engineer needs to design out that hazard. 如果注意到由于人员失误可能导致错误匹配的情况，那么工程师就需要设计掉这种危险。 Using cable connectors that are keyed differently and scoop-proof would assure that it is physically impossibl
14、e to mismate the cables. 利用不同的键接和卡口式电缆连接器可以保证电缆根本不可能错误匹配。 mate vt.使配对, 使一致, 结伴 cable connector 电缆连接器 keyed v.键入; vbl. 键入 scoop-proof 卡口式连接 scoop-proof connector 卡口式连接器,scoop-proof connectors,scoop-proof connectors,In the late 1980s NASA experienced such a problem. 在20世纪80年代末期，美国国家航空航天管理局遇到过这样的问题。 Af
15、ter arrival at Kennedy Space Center for Space Shuttle launch preparations, the Magellan spacecraft power control unit was reconnected. 在麦哲伦号航天飞机抵达肯尼迪航空中心后，为航天飞机发射作准备，对麦哲伦号航天飞机的能源控制单元进行重新连接。 experience v.经历 Kennedy n.肯尼迪 Magellan n.麦哲伦,An extensive electrical power system check was necessary to ensur
16、e proper performance prior to applying power to other spacecraft subsystems. 为确保正常运作，在把电能应用到航天飞机其他子系统之前，有必要对电力系统进行大规模的检查。 extensive adj.广大的, 广阔的, 广泛的 prior to adv.在前, 居先,A technician was making a blind mate (mating cables without visual verification during the operation) of an electrical harness pow
17、er cable to the Magellan. 一名技术员把铠装电力输送电缆盲接到麦哲伦号航天飞机上。（在操作过程中在没有视觉验证的情况下连接电缆）。 harness 甲胄, 铠装,Because the connection was buried deep in the spacecraft, out of view of the technician, it was impossible to verify visually that the connection was correct. 由于连接处在飞船上埋藏较深，在技术员的视线之外，不可能用视觉来验证连接是否正确。 Sparks, flames, and smoke resulted from the cable connection operation. 结果，因电缆线错误连接操作产生了火花、火焰和烟雾。 Sparks, flames, and smoke 火花、火焰和烟雾 result from v.由.产生,
