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管子本体
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连接件（UNION）
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衬套（SLEEVE）
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B螺帽（B-NUT）
如上图所示，连接件（UNION）和衬套（SLEEVE）通过专用工具压接在管子本体两端，B螺帽（B-NUT）能够在管子本体上滑动。
估计很多人和我一样好奇，管子组件里的“B-NUT”这个词里的B是怎么来的？为什么是B，而从来没有见到A或C呢？
其他我们能理解的术语，比如O型封圈截面是O形状的，D型封圈截面是D形状的。
A nut used in aircraft tubing to connect a piece of flared tubing to a threaded fitting. B-nuts are used with a sleeve that is slipped over the flared tubing.
B螺母：一种用于航空管路的螺母，用来将一段喇叭形管路连接到螺纹连接件上。B螺母与压接在喇叭形的管路上的衬套一起使用。
昨天也有人问到这个问题，分享一个之前在google上搜到的答案：B-nut出现后，A-nut从此消失了。
Why the B in B-nuts? Most technicians are familiar with the AN standards nut which is commonly referred to as the B-nut. But do you know where the B' came from?
About two generations ago when our forefathers were flying around in open cockpit planes, a sleeveless coupling nut was used in connecting the airplane's copper tubing. However, this nut would often gall or twist the flared end of the tubing when it was tightened.
大约在两代人以前，当时我们的先辈还在用开放式驾驶舱的飞行，一个不带衬套连接螺母被用来连接飞机的铜管路。然而，这种螺母在拧紧时，经常会使管路的扩口端磨损或变形。
In order to reduce the wear and tear on the tubing, a protective sleeve was added. To distinguish between the two coupling nuts, the mechanics began referring to the sleeved nut as the B-nut. Thus the B designation came into existence where there had never been an A-nut.
为了减少管路的损坏，后来增加了保护衬套。为了区分这两种连接螺母，机械师开始将增加衬套的连接螺母称为B螺母。从此，B-nut这个名称出现了，却再也没有A-nut。
曾发生过发动机燃油管路上的B-nut松脱导致的事故，为此，FAA还发了一个安全维护提示，关于B-nut：
https://www.faasafety.gov/SPANS/noticeView.aspx?nid=4301
The “B” Nut Can Be Deadly
All aircraft maintainers have heard or used the term “B” nut. It is the common description of the nut that is used to connect fluid lines and hoses. It is a very simple component; but does a critical job. It provides a reliable seal in plumbing systems and usually results in ease of maintenance for AMTs. It is designed to provide years of reliable service. However, “B” nut reliability is only as good as how you treat it.
所有飞机维修人员都听说过或使用过“B”螺母。这是用于连接油管和软管的螺母的常见名称。它是一个非常简单的组件，但却起着关键的作用。它在管道系统中提供了可靠的密封，并且通常使维修人员易于维护。在设计上它能提供多年的可靠服务。然而，“B”螺母的可靠性取决于你如何对待它。
We disconnect and connect them many times during our careers - right? However, do you “tighten” or “torque” this simple critical component? No matter how simple this component is, it requires a specific “torque” to keep it reliable in maintaining plumbing system integrity. You may have seen a maintenance record entry where the sign-off stated, “Tightened B nut.” Does this mean it was tightened enough to stop a leak, or was it tightened to a specific torque? If you are just tightening the “B” nut, you could be setting the stage for future failure or fracture.
在我们的职业生涯中，我们经常脱开和连接它们-对吧？然而，你对这个简单的关键部件是“拧紧”还是“上紧力矩”？不管这个部件有多简单，它都需要一个特定的“力矩”来保持它在维持管道系统完整性方面的可靠性。你可能已经看到一个维护记录，上面写着“拧紧B型螺母”。这是否意味着它被拧紧到足以阻止渗漏，或者是被拧紧到特定的力矩？如果你只是拧紧“B”型螺母，将来可能会出现失效或断裂。
Just get the tools you need to get it done right!
Another “gotcha” is finger tightening then “forgetting” to torque the “B” nut. A high risk of this occurring can be distractions (like telephone calls) and interruptions (like multi-tasking) while on the job.
另一个“问题”是手指拧紧，然后“忘记”给“B”螺母上紧力矩。出现这种高风险的情况，可能是工作时的分心（如电话）和干扰（如多任务处理）。
A good technique to follow is if you connect a “B” nut, finish the job with the proper torque. Otherwise, tag it or write it up so it is not overlooked, especially if you leave the job site or another AMT finishes the job!
一个好的技巧是，如果你连接一个“B”螺母，就一步到位拧紧到正确的扭矩。否则，标记它或写下来，使它不被忽视，尤其是如果你离开工作现场或由其他维修人员完成该工作！
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