Unknown Corrosion Rate.

[Joss10]

Fact: PV Corrosion Rate unknown
Question : Values stated in Table 2 of NACE SP 0175 might be taken to determine MAWP (API 510)

 

[metengr]

API 510 provides a means for determination of corrosion rate for PV's. Follow it.

 

[Joss10]

Metengr,
CR of my PV is unknown, no data to determine it as per API 510 (7.1), my question is = Values stated in Table 2 of NACE SP 0175 might be taken to determine MAWP (API 510)

 

[metengr]

No, I would not use them because process condition changes can result in poor assumptions. Why can't you measure the thickness and compare with original or trend. It is not that difficult.

 

[r6155]

Joss10
API 510 7.1 is very clear. Try to understand
Regards
r6155

 

[Joss10]

Dear mates,
Of course I can get the actual thickness but I do not have any other reading recorded either nominal or previous to determine CR as it is very clear as per API 510 7.1, which is also well understood by me as API 510 Inspector.

 

[r6155]

Joss10
Again see API 510 7.1.2 d)
If the probable corrosion rate cannot be determined by any of the above items, an on-stream determination shall
be made after approximately three to six months of service by using suitable corrosion monitoring devices or
actual thickness measurements of the vessel. Subsequent determinations shall be made at appropriate intervals
until a credible corrosion rate is established. If it is later determined that an inaccurate corrosion rate was
assumed, the corrosion rate in the remaining life calculations shall be changed to the actual corrosion rate.

Regards
r6155

 

[Joss10]

r6155,
API 510 7.1.2 d is for Newly Installed PVs ...
Thanks anyway.

 

[r6155]

Joss10
Please, you must read slowly an interpret API 510 7.1.2
"7.1.2 Newly Installed Pressure Vessels or Changes in Service".
This is the correct method for your pressure vessel

Regards
r6155

 

[metengr]

Joss10
First, if you can obtain current thickness readings and compare with nominal thickness from data reports from installation. You can establish a baseline corrosion rate until such time you can re-measure wall thickness and determine ipy corrosion rate between inspection intervals.

 

[Joss10]

r6155
Once again, read it slowly and try to understand, my PV is not new and its service conditions are not being changed, therefore 7.1.2 is not applicable, of course I can take that point "d", but it should not be practical for me now.
What I need right now is an acceptable CR calculation method or assumption for this kind of particular situation I have, it means an existing pressure vessel without previous recorded thickness measurements and all data reports and design docs. lost.

Thanks anyway.

 

[r6155]

This pressure vessel must be out of service until all the required documents will be in order.

Regards
r6155

 

[metengr]

What I need right now is an acceptable CR calculation method or assumption for this kind of particular situation I have, it means an existing pressure vessel without previous recorded thickness measurements and all data reports and design docs. lost.

LOL. Why do you need to establish a corrosion rate on an existing pressure vessel when you no nothing of the vessel design, or materials of construction? Based on your reply you have no original documentation so why bother now for a corrosion rate?

 

[wsu1975]

I fully agree with r6155 that this vessel needs to be taken out of service. Based on what information has been provided, nothing is known as to the design or materials being used.
If the corrosion rate is still important, an estimated corrosion rate could be determined by identifying the materials of construction by testing and perform a literature search of corrosion rates for that material or materials, for the process fluid.
WSU1975