When Pressure Vessels Blow

[bob330]

Greetings All,

I have a question about actual cases where pressure vessels have catastrophically failed (Deaerators, paper mill digesters, etc). With cracks present in the vessel, final sudden failure could occur via two means. One is by a fast cleavage fracture where K1c or J1c are reached at the edge of pre-existing cracks. The other possible mechanism is ductile tensile overload of the remaining unbroken ligament. When actual failures have been studied, did the cracks initially propagate by fast fracture/cleavage or by tensile overload (leaving micro-dimples characteristic of overload on the fracture surfaces)?

Bob

 

[metengr]

bob330;
It is impossible to answer your question because the cause of pressure vessel failure can be from several damage mechanisms separately or working synergistically; cleavage (low toughness), ductile rupture (over stress condition), creep rupture, mechanical fatigue failure, creep-fatigue, etc.

I would suggest you Google pressure vessel failures. On occasion, there are detailed public reports issued by various organizations that promote public safety.

 

[bob330]

Thanks MetEngr,

I am only talking about the nature of the final catastrophic failure of the remaining ligament (which happens instantaneously) and not what may have caused the pre-crack (typically SCC say for paper mill digesters or corrosion fatigue for deaerators). Thus, the only options are cleavage (fast fracture) or ductile overload.

bob

 

[metengr]

bob330;
Ok, having understood your OP, I would say that for your cited examples of service, the final fracture would be from ductile overload.

The reason is that the operating temperature of the vessel would favor the upper shelf region of the notch toughness curve (assuming no in-service thermal embrittlement or very low toughness steel from steel making practices).

 

[chicopee]

National Board Bulletins have excellent analysis of catastrophic events and failures. For example I have copies of features titled "Creep and Creep Failures", "Short Term, High Temp Failures","Microstructural Degradations" and a few others. Since I have been out of the loop for about 15 years, I don't these analysis anymore. I would suggest that you contact this organization as I am quite certain they have a feature that may answer your inquiry.

 

[MJCronin]

bob,

One of the more experienced engineering consultants who have dealt with many cases of PV failure is:

THIELSCH ENGINEERING, INC.
195 Frances Avenue, Cranston, RI 02910
Telephone: (401)467-6454 Fax: (401)467-2398

http://www.thielsch.com

There is an extensive list of publications on this website that you may or may not be able to access...

Helmut Theilsch literally "wrote the book" on pressure vessel inspection, repair and failure analysis.

-MJC