Thanks John
have tracked down Dr Bickford but $150 for an introductory text probably
includes more detail than I have time to read.
I'll check the local libraries, but suspect I will have to wait for the
movie.
I prefer slim volumes.
Oddly enough, I was told by a retired WW2 test pilot that Rolls Royce
conducted blind torque tests with fat and skinny guys. They concluded
the difference was within their assembly tolerances, and banned torque
wrenches to remove the idiot dial watching effect. I belonged to the
latter (idiot) class, and have the trigger pin indents on my torque
wrench adjusting wedge to prove it. The chief advantage of the
overcentre clicker type wrench over the wedge and trigger type wrench is
that the former leaves no witness marks to attest to operator
incompetence. I now use 24" Stillsons.
Cheers
Steve
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=PoZgTQ5kA18ulTQFZFePP45SL0XAsO2lcfvi-_emb2IgF8J9AOTUv-0Y4ERnW51LdVFYRYDkwxYiWNq9A2HMlod0Cbs1oWI">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=PoZgTQ5kA18ulTQFZFePP45SL0XAsO2lcfvi-_emb2IgF8J9AOTUv-0Y4ERnW51LdVFYRYDkwxYiWNq9A2HMlod0Cbs1oWI">PipingDesign@yahoogroups.com</a>]
On Behalf Of John Luf
Sent: Thursday, May 05, 2005 2:03 AM
To: <a href="/group/PipingDesign/post?postID=PoZgTQ5kA18ulTQFZFePP45SL0XAsO2lcfvi-_emb2IgF8J9AOTUv-0Y4ERnW51LdVFYRYDkwxYiWNq9A2HMlod0Cbs1oWI">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] flange stud bolt replacement criteria.
If one has a chance to read Dr. Bickfords "An Introductionto the Bolted Joint" one would probably be inclined to replace the studs more often rather than later. Even if torque is used when assembling the joint the "stress" or "stretch" of the bolts is not neccesarily a consistent number... torque really kind of stinks when it comes to this.
I suppose you could do a little experiment by record keeping and extending the re-use until you have problems with the joint. But at the very least in order to be consistent in assembly a bare minimum would be a torque wrench and a consistent bolt-up procedure.
If you get a fat guy like me on the wrench, I will stretch the studs out more than a skinny guy if we assemble the joint soley be "feel".
Read the book its great stuff....
Steve McKenzie <Mechproj@xtra.co.nz> wrote: O Learned Ones
I do some work at a plant which has many flange stud bolt connections;
some of which are dismantled quarterly. Short cycle fatigue is not an
issue during operation, but perhaps there is a need to replace stud
bolts after a certain number of retensionings. At present studs are
replaced only if they show visual signs of distress, but this approach
seems somewhat arbitrary. Flange classes are 150# thru 600# studs are
typically low alloy steel with a few exotics thrown in and temperatures
are moderate; up to 250C.
I could revert to first principles, calculate bolt stresses and work
out fatigue life, but feel countless people will have done this before.
Does anyone have any references to standard testing/rejection criteria for stud bolts? If so a reference would be appreciated.
Cheers
Steve
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John C. Luf
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