Deaerator Inspection Frequency

[Whin]

We have deaerator operational for a decade, during which we have conducted annual internal inspections focusing on weld magnetic particle testing and ultrasonic thickness measurements of the shell and heads. To date, no deterioration has been noted in these areas. However, we have identified significant issues with the water/steam box, which has multiple cracks and has undergone local repairs. No operational upset also recorded on boiler feedwater quality. My concern is whether we can extend the inspection interval to a maximum of five years, given that there are no major integrity concerns with the primary pressure component. Could someone provide relevant codes (i.e., NBIC) to support the appropriate inspection frequency for the deaerator?

 

[r6155]

I suggest continuing the annual inspection until there are no defects in any component.

 

[Trestala]

Could someone provide relevant codes (i.e., NBIC) to support the appropriate inspection frequency for the deaerator?

See API RP 581 and 580

 

[Whin]

I suggest continuing the annual inspection until there are no defects in any component.

The root cause of defects in the water box has been identified as thermal fatigue and has been addressed; furthermore, it does not affect the pressure component of the vessel nor the quality of BFW output.

 

[r6155]

However, we have identified significant issues with the water/steam box

Why do you mention it if it doesn't affect?.

 

[jt1234]

Lost million $ at every shut down. So you don't necessary shut down every year for inspection or repair if it can be continued operating as long as it does not impact pressure part. Also there are many monitoring devises in the equipment that can tell whether it shall be shut down for repair, like your deaerator system.
We built so many plants that owners have their own schedules, may be 2 or more years for routine maintenance. Even they saw problems, such as hot spots, they will keep continue operating and spray with steam to cool it down without shutting down until next scheduled maintenance. Experience tell you what to do. Don't listen to people who has no plant experience.

 

[Minatious]

NBIC doesn't prescribe a set interval. Taking what you've provided as fact, I would tell one of our customers they can use a longer cycle so long as operating conditions are held near constant. If you've run the DA with the same water quality/treatment, same pressure/temperature, same throughput etc. for 5 years and seen negligible corrosion and no mag particle indications, then there's really no reason to worry for the next 3-5 years unless something notable happens. Save the money, and buy a cheap thickness tester and do an external reading around some of the bottom nozzles each chance you get if it puts your mind at ease.

API and other documents may say differently, but they aren't any kind of authority in this instance, just simply good references. The only authority you should worry about are your state regulations and any insurance company requirements. So check with them as a last step before making a decision.

 

[r6155]

I inspected several international plants and found operators working on pressure vessels without the Final Data Book: irresponsible operators.

 

[EdStainless]

Don't go from 1yr to 5yrs in one step.
If there is a slight change in conditions or if long term effects start kicking in you could be in a lot of hurt.
Why do you want to extend this?
You are shutting down for other reasons aren't you?
How frequent are your major shutdowns?