Vessel Age

[cabigdon]

All things being equal, such as service conditions, materials of construction and inspection data, would a pressure vessel that is 60 years old require more frequent inspections than a vessel that is 15 years old? Why?

 

[metengr]

No, not necessarily. In some applications of pressure retaining items you have no time dependent damage mechanism(s), assuming all things being equal. So age really has no bearing on more frequent inspections or retirement of the vessel.

 

[deanc]

BE CAREFUL! Please see RB-9010 of the NBIC.

Then again 60 years isn't that far back for some of us.

 

[MJCronin]

bigdon,

Does "all things being equal" include corrosion ?

I guess what you are really saying, (with a sixty year old vessel) is that there was no corrosion....

-MJC

 

[James01]

Are you running a Risk Based Inspection strategy? Your frequency of inspection will be dependant more on the number and extent of any repairs, the service conditions, degradation mechanisms, liklihood and consequence of failure etc rather than just the age of the vessel.

 

[cabigdon]

It is an RBI question. All the programs I've seen do not take into account the age of a vessel. In fact, it is intentionally omitted. An argument has been made saying that as I age, I go to the doctor more often. So why shouldn't the same be true of a pressure vessel?

 

[TomBarsh]

Aren't some materials subject to deterioration of their properties with exposure to their process conditions? I am not a metallurgist but in my experience with vessel design I have heard about embrittlement from a number of sources, which would occur over time and exposure.

Even in my personal life, I know that as my possessions age they tend to deteriorate without any seeming cause in many cases (ie: not through mechanical wear and tear). I guess that is 'entropy' in everyday life.

Anyway, I would consult with someone who was experienced with metallurgy, materials sciences, and related issues.

 

[metengr]

Vessel age is one of many factors that determines the useful service IF you have time dependent damage mechanism(s). Being a hypothetical question, establishing remaining service life requires a rigorous condition and risk-based inspection program.

As a side note, there are few Jurisdictions that mandate specific hydro testing after a boiler or pressure vessel reaches a certain age. This requirement is not practical and should be revised.

 

[unclesyd]

Here is a set of vessels that have had to undergo alterations and repairs from essentially day one.

We have numerous 304/304L SS vessels in cyclic, high rate, service inside an occupied building that are still in 24/7/365 service after 48-54 years continuous service. Every vessel has had at least 5 major alterations, while still maintaining the original design parameters. Even though we are not a code state all vessels were built to code and stamped and all still maintain the stamp. At the present all vessels undergo at least a yearly inspection by our people (only) consist of both internal and external PT. All repairs, at every inspection, are under the auspices of the AI and carried out by our welders (owner user) or a contract welders with all the paper trail.
I just checked and the 4 largest vessels have undergone a least 200 individual repairs each.

Our heating D tube vaporizers (5 and ea. is 10,000,000 BTU) are 52 years old on the average and are on a 3 yr inspection schedule. These vessels underwent major modifications within one year of going on stream. The modification was the essentially changing of all nozzles to RTJ flanges from RF and shorting some nozzle necks, where people like me could get inside. These are inspected by our inspector and AI concurrently. This inspection schedule was changed to yearly due to major fire in 1998. After 5 years on the yearly schedule it was changed back to a 3 year interval, no problems since 1993.

The paper work on all these vessels is maintained and is current with the exception of a 3 year period that was loss due to a document management program.

The life of a well designed and constructed vessels is contingent on operating within the design parameters and having a instituted workable inspection program coupled with a enforceable maintenance plan.

PS:
The SS vessels mentioned have scared the hell out of every risked based inspection guru that has been appraised of the operation and the maintenance and repair history. It was and probably still is fun to watch when you bring out the records and pictures of the repairs on each vessel. The last meeting I attended the two visiting experts closed the cover on the laptops and just started listening.

 

[adrianviorel]

it's not only a matter of material's aging. We've been part of a revamping project, recently, and we discovered that, even pressure vessels were in service for 20 years, and engineering required 10% X-ray only, after performing this task, we were forced to require 100% X-ray, due to the huge number of weld's defects.
Just for info...