Averaging thickness readings in a pitted exchanger shell
Averaging thickness readings in a pitted exchanger shell
(OP)
I have a coded hair pin exchanger with general pitting. If certain pits are below tmin, what guidance should I follow for taking an average of the area? API 510 7.4.3? Can someone give me a quick understanding of general corrosion and pitting guidance that is a good practice to follow for understanding at what point further measures must be taken?
Also, if the hairpin exchanger is a 5" diameter and 30' long is this required to be a coded vessel (plant is in a non-coded state). All I have been able to locate is ASME Sect VIII regarding equipment greater than 6" must be coded and stamped.
Thank you
Also, if the hairpin exchanger is a 5" diameter and 30' long is this required to be a coded vessel (plant is in a non-coded state). All I have been able to locate is ASME Sect VIII regarding equipment greater than 6" must be coded and stamped.
Thank you





RE: Averaging thickness readings in a pitted exchanger shell
Your first failure point will be across the line of least thickness ... the sum of the biggest pit in a line across a point... near where the maximum stress in the whole surface is. On that line, the thinnest material will fail first. Then the rest very quickly will follow.
RE: Averaging thickness readings in a pitted exchanger shell
RE: Averaging thickness readings in a pitted exchanger shell
If leaking is your concern then the very deepest ones are all that matter.
An average is meaningless.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Averaging thickness readings in a pitted exchanger shell
National Board Inspection Code, NBIC Part 2, 4.4.8.7. All of the information is there for evaluating corrosion pits.