Browse Prior Art Database

Publication Date: 2017-Jun-09
Document File: 4 page(s) / 123K

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The Prior Art Database



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[0001]          In industries such as at the oilfield, bolts are used on a variety of different equipment types such as manifolds.  Of course, there is a desire to have the bolts tight enough to maintain structural security, avoid leaks and so forth but without over-tightening so as to damage the bolt or equipment.  Further, depending on the type of operations, the tension of a given bolt may be prone to change over time.  For example, a bolt appropriately torqued on a manifold may loosen over time such that a leak develops.  However, it is not always immediately apparent that just because a leak has developed that this is due to a given loosened bolt.  Therefore, some manner of checking tension at each bolt may be required.  This may be no small feat in circumstances where access to the bolts presents a challenge in and of itself, such as in a subsea environment.

[0002]          Efforts have been undertaken to provide visual indicators at bolts.  Thus, even if difficult to access, each bolt may not require physical intervention in order to make a determination of bolt tension.  However, these efforts largely fail to reveal the precise level of tension and stress on the bolts.  There are alternative efforts, such as ultrasonic tension measuring which may provide greater accuracy but such techniques are often cost prohibitive.  Therefore, the present cost effective technique of providing an automatic visual indicator at a head of the bolt is proposed.


[0003]           The invention is a bolt or stud with a built in tension indicator.  See the illustrations below.  Specifically, as a bolt is tightened, a “strain rod”, secured to the leading end of the bolt is “stretched” or pulled in such a way that induces a visible rotation at the opposite end thereof.  This rotation may be visibly and directly correlated to the amount of tension on the bolt.  Thus, tension may be visibly perceived at any given time without the requirement of any direct manual or physical intervention.

[0004]          As noted above, the strain rod is rigidly fixed via an unlubricated threaded connection at the bottom or leading end of the stud.  On the opposite end of the stud is a counter-bored hole that the pointer nut and retainer cap will sit in.  The pointer nut is connected to the strain rod via highly lubricated threads.  The retainer cap is rigidly attached to the stud body via an epoxy or similar adhesive.  As the stud is put into use and torqued up it will stretch.  This will cause a p...