German (DIN) stud bolt callouts

[KLee777]

I have some old high pressure reactors, built in Germany during the 1930s. All of the drawings are written in German, with English scattered here and there.

Need some help deciphering the stud bolt callouts. We are replacing the stud bolts since they have never been replaced (yes, you read that right) and they've been quite abused over the years. We've had flange leaks and replacing these is only one step in a new bolting procedure I am putting together for these connections.

Typical callout looks something like this: W99 x 1/4" x 438 lg.

Here's what I *can* understand:

W99 = nominal diameter of stud (99mm)
438 lg. = length of stud (438mm)

...But what is the 1/4" for?

Further info: The studs are not nutted on both sides, they are actually countersunk into the top head of the reactor. So, one end terminates in a taper (the countersunk end), the other is nutted. The center of the shaft is not threaded, but smooth, and has a smaller diameter of 90mm. The diameter of the hole is 105mm.

I'd also like your thoughts as to why studs are made/used with threads on either end but not in the center. Thanks in advance.

 

[KLee777]

Sorry, I didn't mean "countersunk" into the flange. Perhaps "screwed into tapped holes in the flange" is a more appropriate description....

And the shaft of the studs looks like this: Link

 

[OSIRIS7]

I do not have the DIN here at my disposal, but if I am not mistaken, you should take a look at DIN 2510 part.... now I have to guess..... 10? In German it is called DIN 2510 T10 or Teil 10. This describes bolts with wasted shank. They are called Dehnschrauben in German.

W99 does not ring a bell.

Maybe you can scan a part of the drawing?

 

[micalbrch]

I think here are the information you are searching for:

http://www.gewinde-normen.de/en/whitworth-fine-thread-din-239.html

 

[OSIRIS7]

And DIN 2510-3 describes the Dehnschaft:

I am at my desk now, and I see that DIN 2510-4 has also reduced shank, but they are called "Stiftschrauben". I do not realy understand the difference, then I should read the Standards.

Is this what you need?

 

[KLee777]

Yes, thank you all for your replies. I was able to find that same link, micalbrch, which confirmed my suspicion that the 1/4" dimension was a thread pitch.

I had the idea to go find the original project job books. After much digging in dark, musty places, I turned up a dimensional drawing which showed me that confirmed my theories on the dimensions.

Ours are "Form K," as shown in your post, OSIRIS7. Thank you for that picture, it is very interesting.