something on wall thickness

[ihuoma2]

ihave a document with me here it has to do with the wall thickness readings using an ultrasonic device .The readings are like this
loc pipe 12 3 6 9
1 12inche 30.8 31.9 26.7 26.7
2 12in 14.2 13.1 13.3 13.7
please i was trying to find out what the 12, 3, 6, 9 stands for ,is it the time , no of years angle pls i want to know

 

[Zoobie]

How about angle position as referenced to a standard clock. 3 = 90 deg, 6 = 180 deg, etc.

 

[ApC2Kp]

ihuoma2,
The angle position that Zoobie refers to is probably correct and it also serves as reference in other inspection formats like radiography. One reference system has the top of horizontal pipe as the 12 o'clock position, and for vertical pipe the plant north direction as the 12 o'clock position. Be sure to confirm the basis for direction.

 

[ihuoma2]

thank u for the reply zoombie and apc2kp i really have a problem with interpreting the wall thickness readings using the ultrasonic devices in relation to if the pipe will be good to go or replaced

 

[zdas04]

As the others have said, it is clock position, but what they haven't said is "position relative to what?". There is no generally selected convention and good tech's will note direction. The most common orientaiton I've seen is to think of a cross section of the pipe that you would see if you put your back to direction of flow (i.e., looking downstream). Then 3:00 is on the right and 9:00 is on the left. It looks like it might matter on your pipe.

To determine if the pipe is good or bad, re-run your MAWP calculations with the smallest reading and see what the pipe will hold today. I also like to document my expectations of remaining life and expected annual corrosion--then back that much steel off the smallest thickness and recalculate MAWP. It often gives an unpleasant result.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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