Yield Strength of 24CrMo5 studs

[iangineer]

Hi all,

I've been tasked with providing torque values on some studs in an old German-made high-pressure vessel. Do any of you have any information on the yield strength of a 24CrMo5 stud at 392°F, or could possibly point me in the right direction to a code that states the information, please?
Design pressure = 4715 psig
Design temperature = 392°F
Bolt Material = 24CrMo5
Hex Nut material = CK35
Gasket type = Lens ring (CK15)
Stud sizes = 5/8", 1-1/4", and 1-3/4"

Are there any tips on working with these kind of studs (like when working with stainless steel studs, add 20% to the nut factor when calculating torque)?

I found this existing thread, but wanted to see if there was any additional information.

Based on the above thread, at my design temperature, it looks like the allowable bolt stress would be about 13,490psi, but I tend to base my calculations off yield strength.

Thank you!

 

[iangineer]

It's washed out a good bit on the drawing I have, but it looks like the yield strength at 68°F is 440 N/mm², at 392°F is 410 N/mm². I'll go with that information.

 

[desertfox]

Hi Iangineer

What is the code that the pressure vessel was originally designed in accordance with?
The bolt preload should be worked out in accordance with the loads the pressure vessel will see in service and including thermal loading and not just based on the bolt yield strength, also the vessel material needs to be considered not only from the point of view of its age but also the strength of the internal thread.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[iangineer]

Good question. It does not appear to be built to any real code outside of company standards. The nameplate shows the year built as "1961/1984". Some other equipment out here is even older and a few are even made from giant WW2 German artillery barrels.

 

[XL83NL]

Can you post a photo copy of the name/ID plate perhaps?

Huub
- You never get what you expect, you only get what you inspect.

 

[desertfox]

Hi Iangineer

Well what do the company standards reveal?
The way I see this is that the initial preload will need to be less than is required at 392F because the expansion of the vessel during heating up to service temp could cause a joint failure which might be the stud failing in tension or the thread stripping and finally but be no means the least the internal thread strips out.
Look at the company standards and see what you can find about bolted joints would be my starting point.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein