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thread engagement
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Posted by: maytag

09/30/2004, 23:09:07

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The steel mill I'm with has recently installed a new,much heavier door for their reheat furnace. What used to be a 1 cylinder door lift has now become a 2 cylinder operation. The thought process being that if 1 cylinder fails then system pressure can be increased and 1 cylinder can raise the door. The question I have is at what point should I be concerned about the load placed on the piston -rod thread engagement and also the clevis end that is threaded on the opposite end. Piston rod size is 2 1/2-the clevis end has about 4 1/2 inches of thread engagement. Thread appears to be 2 1/2 12-I could not find a chart to confirm this is the correct number of threads per inch. The door is raised when the cylinder retracts. Thanks,Maytag






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Re: thread engagement
Re: thread engagement -- maytag Post Reply Top of thread Forum
Posted by: Cragyon
Bart
10/01/2004, 08:06:21

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To calculate the thread stress based on length of thread engagement check out the following /thread_strength/thread_bolt_stress.htm .

Additionally, to determine the thread stress area do a search /search/search.cgi for thread stress area.

 

 







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Re: thread engagement
Re: thread engagement -- maytag Post Reply Top of thread Forum
Posted by: randykimball
Barney
09/30/2004, 23:34:02

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Maytag,
If you have doubts, the situation may should be investigated by a PE. Anytime an engineering strength/load situation is involved in which a load could fail and result in serious human injury a PE should be used and the results should be recorded. If a PE decides the structure is not within a safe range and the advice is not followed, then an accident occurs, serious legal results could occur. On the other hand if a PE is not involved and an accident occurs the same thing can happen. I would think your company has used a PE in this situation. Your insurance company may would insist. It is one of a PE's responsibilites to make sure such are designed within a standard safety margin.

-randy-




The worst suggestion of you lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.


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Re: thread engagement
Re: Re: thread engagement -- randykimball Post Reply Top of thread Forum
Posted by: zekeman

10/02/2004, 22:20:58

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You don't need a PE for such a simple calculation. Any 3rd year engineering student can solve it. Furthermore, insurance companies don't require PE certification for machinery as far as I know. Correct me if you can document otherwise.

 

SSK, PE







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Re: thread engagement
Re: Re: thread engagement -- zekeman Post Reply Top of thread Forum
Posted by: randykimball
Barney
10/03/2004, 23:51:57

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No, I may stand corrected... big smile
I was under the impression that the situation a serious chance for human danger such as under huge swinging doors. In such a situation I would prefer to know the "solve" was reviewed and agreed on by a PE. Not all engineers are automatically able to figure such calulations correctly just because they are an engineer. I've known some that should have not become engineers. It is my opinion such a program as the PE program assures some standard knowledge and the ability to use it is present and tested for. This can be the difference of an added safety factor and a serious mistake. And yes if you are designing a machine to be used and sold with liability insurance it is my understanding it might well be required to be reviewed by a PE and/or UL and/or other certifications to gain underwriting. Besides such is a wise check and balance. Can I document it, ... no, I can not... but I do not know all the constantly changing liability laws in all the states nor countries. ... better safe than sorry... when human life is at stake.
... this is my own opinion and not necessarily the opinion of this web site.
... fair?...

-randy-




The worst suggestion of you lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by randykimball at Mon, Oct 04, 2004, 00:00:39

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Re: thread engagement
Re: Re: thread engagement -- randykimball Post Reply Top of thread Forum
Posted by: zekeman

10/04/2004, 09:37:41

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Randy,

Your point is well taken. I also agree on the capability of some "engineers".

ssk







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Re: thread engagement
Re: Re: thread engagement -- randykimball Post Reply Top of thread Forum
Posted by: maytag

10/01/2004, 01:51:53

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  Randy  ,There's not much chance of any injury ,only equipment failure and the resulting downtime.  I would assume the weak link would be the clevis end and was just curious as how much load the the clevis end would hold before it pulled the threads out.  Thanks ,Maytag






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