ASME API 579 FUTURE CORROSION ALLOWANCE

[falco]

Hi Everyone,
I will appreciate a lot if someone can provide an idea about how shoul I proceed in this case.
I have a customer that request to perform the evaluation of some pressure vessel for vapor service.
Neither his organization nor me were able to find documentation about the vessel such as drawings or any other protocol that can provide useful information. Also they have no data available on previuos thickness measurement. Some of the vessels have a stamped plate which fairly read its manufacture date: 1955. The other doesnt ant its origin is unknow.
We did perform thickness measuremet and know the pint if to perform a fitness for service analysis as required by API 579 practice. We look forward to stablish a future corrosion allowance
We know, average thickness, minimum thickness and per its dimensions it can be possible to estimate a minimun required thickness assuming it is manufactured from a material such as A516 or A576 (remember that we does not know the material)
In such case, could it be possible to assume that FCA can be considered as the minimum measured thickness - the minimum required thickness basing our judgement in the fact that this will be the thickeness to considere it must be removed to reach its supposed minimum thickness?
Can also FCA be considered as the Maximum - Average? taking the fact that Maximum thickness are fairly affected, or Maximum-Minimum? or minus minimum required thickness?
Is there a table or docuemnt that I should look, where there are some common FCA?
I will really appreciate your comments in order to get an accurate point of view
Best regards

 

[blacksmith37]

If the material is ASTM carbon steel from 1955, it is likely A 212 or A 36; which doesen't help you without grade, flange, firebox,etc.
Is it permitted to "reverse" engineer? Remove a sample large enough for a couple tensile test bars, pull them. Then calculate what thickness you need for max operating pressure + design safety factor.

 

[SJones]

You have no corrosion rate data. Assuming that you can successfully sort out the tmin, would it not suggest that you should use the most conservative value? Essentially, one has to ask what is the ultimate purpose of setting a future corrosion allowance.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[metengr]

If you have a nameplate for this vessel you can possibly call the National Board of Boiler and Pressure Vessel Inspectors in the US and see if they have a data report for materials of construction. Talk to your insurer of this vessel (if there is one) and also check with local regulatory bodies or Jurisdictions where this vessel is installed. Most likely you can build a new vessel cheaper than all of the sorting required because of lack of traceability regarding this vessel.