API 579 Part 12 - Dent Radius

[Michael Oey]

I am a pipeline integrity engineer working a fitness for service assessment on dents found by an inline inspection tool. The formulas in API 579 Part 12 are fairly straightforward, but I am a bit unsure what to use for the dent radius. It is stated that if the dent radius is greater than or equal to 5 times the future corroded wall thickness, the dent is determined to be a smooth dent. If it is less than 5 times the corroded wall thickness, the dent is determined to be a sharp dent. API 579 states that the radius measurement to be used is the radius at the base of the dent... I don't exactly know what that means. At this point, I only have dent length (along pipe axis) and width (along pipe circumference). What I've done so far was take whatever is smaller between the dent width and length, divide it by two, and call that the radius. However, I'm not sure if that's correct. Could somebody clarify what is exactly the radius at the base of a dent? Thank you all in advance.

 

[pdiculous963]

Take a look at Figure 12.2. It is a measurement of the local curvature of the pipe at the base of the dent.