Thread Design On High Pressure Cylinders

[state03]

Good afternoon everyone. I am looking for information regarding thread designs for high pressure applications. I have a large cylinder that is threaded into a fixed cube, the cylinder is then loaded with a large amount of axial force (6000 psi). I need to know how to analyze the stress on the threads, and I am looking for information on different thread designs to prevent crack propogation and catastrophic failures. Thanks!!!

 

[0theblacksmith0]

Hi state 03
Whilst working on hp vessels for Charles Maddans at Broadheath,Manchester UK the vessel in question was 18" od
36" in length it had a 6" dia bore,and an internal length of 30", the vessel had to withstand 10,000 psi.
The vessel had a screwed cap which was 18" diameter with a 8.5" thread diameter.
The thread diameter on the vesel was internal 8.5" diameter by 7.5" in length.
The thread was a whitworth form 55 degree included angle.
When I asked the Question why had they used a whitworth form thread?
I was told that in the past they had used a butress thread, which had failed.
There were no casualties, but the insident promted an inquiry, resulting in tests, at the NPL.
There findings were, in this vesel, 8.5"diameter by .5" pitch, single start thread was the most suitable.
This thread proved to withstand the pressure, and was more suitable than the 60 degree angle as used on metric and american threads.
I believe that, square,and acme thraeds were also tried, and were found not to be not satisfactory in this application.
It was in the early 1970's, but I have not come across any thread developments since then.
Allthough I have not answered your initial question about calculations, I hope this information is of some use to you.
Kind regards
Gerry Clarke, visitor.

 

[CoryPad]

Do the threads only need to provide mechanical force resistance or do they also have to be leak proof? Does this joint have to provide preload? These questions help determine the thread form - ACME, buttress, or 60 degree. When you have decided upon a thread form, you can do joint analysis by a few methods - simple hand calculations, more detailed calculation methods using standards/guidelines, or even Finite Element Method analysis.

Some good resources for fastened joint information are:

VDI 2230, Systematic Calculation of High Duty Bolted Joints, available at:

http://www.beuth.de

Handbook of Bolts and Bolted Joints, available at:

http://www.dekker.com/servlet/product/productid/9977-1

ASTM Special Technical Publications 1236 and 1391, Structural Integrity of Fasteners, available at:

http://www.astm.org

 

[nickelkid]

You may want to contact Autoclave in the USA, PA. They may high pressure joints.

 

[metalonis]

Check with High Pressure Equipment Company, Erie, PA USA.

http://www.highpressure.com

 

[sancat]

I dont know if this is what are you looking for, but, there is a new piping thread that could be useful:

http://www.tenaris.com/Blue/

sancat