Remaining life assessment of ammonia plant waste heat recovery boiler 1

[Muhaka22]

Dear All,

An ammonia plant waste heat recovery boiler (consisting of 3 exchangers) has been in service since 30 years. The first leakage incident happened recently with a tube pinhole leakage that was plugged successfully.

Recent inspection reports show
•first exchanger: 20 Tubes with wall thickness loss greater than 40%
•second exchanger: 01 tube sheet wall thickness loss greater than 22% in the second exchanger.
•tube material is 13CrMo44, range of Pressures 30-120 kgcm2, and temperatures 350-900 °C

I'll be grateful for any help on the following:
•what code/standard, eg API 579 or 581, can help determine remaining life of the tubes and tubesheet? the boiler is ASME Sec VIII div 1/2
•are there any relevant fatigue/creep life and failure studies available for 13CrMo44 waste heat boiler tubes and?
•A source mentioned that a WHB ran for 50 years before failure, is there any more evidence for running a WHB past 30 years before onset of mechanical/creep failure?


Looking forward to your response (sorry for the long post),
Best regards


attached
drawings, 13crmo44 paper, sample calculation API 579, literature review

 

[GD2]

Muhaka22,
The best way to go with it is perform API 579. It can calculate the remaining life as well re-rate the exchangers.
From your perspective, just make sure that the service fluid and the design conditions haven't changed.
As a guidance, most plants are deigned for 20 years of life with powerplants deigned @30 years life. As you have run the plant for 30 years, you got the life. Now, it's time to invest some fund and get some bonus life.

GDD
Canada

 

[Muhaka22]

GDD,

Thanks for confirming!