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Ask almost any electrician or maintenance tech how to check if a connection is tight, and you probably won’t get the correct answer. In fact, it’s a trick question.
The only time you can check the tightness of a connection is when you make the connection. The reason is the mechanical physics involved.
A bolt obtains maximum clamping power when it’s stretched to the upper limit of its “elastic limit.” Stretching it more just reduces its clamping power. When you “retighten” a bolt, you actually make the connection weaker.
What if you loosen a bolt, then tighten it? Unfortunately, that initial tightening resulted in “strain,” which means the elastic limit of the bolt will significantly decrease (typically, by 50%) as soon as the bolt is relaxed. That’s why you don’t re-use fasteners on critical connections.
What if you just check the bolt with a torque wrench? Two problems:
To see which connections need replacing, you have two methods:
Final tip: To tighten new busbar fasteners, use the torque values for that particular hardware kit.
Source: Mark Lamendola | Mindconnection