Thread Engagement Requirements

[CodeRef]

Background - the bonnet of a check valve is assembled by threading studs into the valve body and nuts on the exterior surface of the cover. Each nut has complete thread engagement. In this particular valve design, the hole for each stud projects through a edge of the valve body. Thus, it is possible to see the bottom or end of each stud that is installed in the valve body by looking up from under the valve. The thickness of the valve body in the region of the hole is approximately 2 inches. The studs are 1 -1/4 inches in diameter. The studs are assembled in a manner that each nut has full thread engagement (from the top) but the studs do not project completely through the hole of the valve and some variation on the order of approximately 1/8 inch exists in engagement length in the valve.

Q1 - Is this minor variation in engagement length on the valve side acceptable?
Q2 - What criteria should govern for magnitude and variation of thread engagement on the valve body?

There are three kinds of people in this world. Those who can count and those who can't.

 

[itsmoked]

And you have posted this in:

Nuclear engineering other topics?!?!?!

You should copy your question, then paste it into forum404.

Then red flag this one.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[vpl]

You would get more replies if you posted in another forum, simply because the more specialized the forum, the fewer the people who visit it on a regular basis. So a mechanical forum will get far more visits than a nuclear one.

But, before you run off and post elsewhere, please look at thread292-116613, which may answer your question. Also do a search on "thread engagement" and see if any of the other replies to previously asked questions on thread engagement answer your question.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[CodeRef]

vpl,
If I were to say this was a nuclear valve would it make a difference where I posted this?
I am posting here because of the specialized forum. I want the opinion of Nuclear Engineering professionals regarding a nuclear valve where valve body thread engagement is not clearly specified by the valve designer/manufacturer.

ASME Section III paragraphs NX-4711 states that "the threads of all bolts or studs shall be engaged by design".

If the valve design rules specify thread engagement for nuts but are silent regarding the valve body(tapped thru hole), can I base the thread engagement in the body of the valve upon "good engineering practice"? or at least the nut engagement?

Also, if I based the valve body thread engagement acceptance criteria on the nut engagement rules and less than full engagement existed in the valve body (a single thread short) is it considered to be a failure of Section XI visual examination requirements if lack of a single thread engagement in the valve body is not flagged as a recordable indication?

There are three kinds of people in this world. Those who can count and those who can't.

 

[vpl]

Code Jackal

No. I'm saying more people would see the post if it were in a different forum. But the fact that the thread has been posted for five days without an answer says that just as well.

I also went on to say to check previous threads before you cross posted.



Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[CodeRef]

Thanks for the reply, I'll just let this issue rest. I find this thread to be the most comprehensive thread404-162674 and answers my question.

There are three kinds of people in this world. Those who can count and those who can't.

 

[CodeRef]

Perhaps I should start a group identifying as Nuclear Inservice Inspection ASME Section XI since I can't get any responses here.

There are three kinds of people in this world. Those who can count and those who can't. OR
The next statement is False.
The previous statement is True.

 

[hydrae]

Just so you are not snagged by the next XI inspector during the next refueling I would 'if possible' move or replace the studs 'so the plane of the stud breaks the plane of the nut' in both cases above in the nut and below in the valve body.
Hydrae