What is the best practice for amount of UTs that SHOULD be performed on vessels, heat exchangers, ect... when performing API-510 inspections? I see a lot of plants that institute programs. Some are better than others. Same goes for inspection companies. What should be the minimum? Is there a Maximum?
Also. How easy is it to miss potential corrosion defects performing B-scan UT. Is there a normal grid size? What's a good practice?
01:35 Jun-02-2005 John O'Brien Consultant, - Chevron ETC , USA, Joined Jan 2000 278
Re: How much UT to perform There is no maximum or minimum API 510 is written in order that you consider the expected damage mechanisms and then select an inspection coverage considered effective to detect that damage. This is all part of inspection effectiveness. At general corrosion areas with slow corrosion rates you may make few measurements at long periods. On high corrosion rates with localised damage lots of coverage frequently.
This is all about thinking about damage before you inspect and tailoring what you do to that mechanism then amending as and when you have a firm grasp of what may be happening.
If you are working to API 510 you should have an API 510 Certified Inspector and he should understand the need to do this in consultation with a Pressure Vessel Engineer and Corrosion Specialist.
Re: How much UT to perform I guess that also wanted to get some input on how much UT to perform if you go to a site that has no history on a piece of equipment. Example; Inspector goes to a site that has had a vessel in service for 30 years. For what ever reason, site wants to perform a API-510 inspection on the piece of equipment. The site does not have a engineering department or corrosion expert. (Small company.) And also does not open equipment for an internal inspection. If questions are asked about vessel history, answer is no problems.
I understand that it might be to the advantage of the API inspector to perform more UT to be able to get a better insite as to internal condition of the equipment. Is there a reasonable amount that would conform to good inspection practices, or would it be out of line for the inspector to recommend or request a 100% B-scan of the entire vessel? Depending on the amount, will the inspector be able to conclude any condition that might be taking place internaly?
05:12 Jun-07-2005 John O'Brien Consultant, - Chevron ETC , USA, Joined Jan 2000 278
Re: How much UT to perform There will never be a formal answer to this due to the fact that the degree of coverage is related to the anticipated damage mechanism. If for example you expected Microbiological Induced Corrosion (MIC) it occurs as very samll diameter localised pits. Therefore you may require 100% scanning. Maybe you scan with low resolution MFL to identify area fast then profile specific areas with UT.
Is this reasonable or cost effective. Deopends upon the consequemces, high flammable, high toxic product in the middle of a $1 Billion Plant the answer may be yes. Water vessel, in a remote tank farm possibly not.
Ultimately the 510 Inspector is responsible to the owner to bring these issues to the owners attention. if the owner wants to accept the risk thats his call.