thickness to be used for modelling a corroded pipe
thickness to be used for modelling a corroded pipe
(OP)
I have a subsea inspection report where readings where taken at 0deg, 90deg, 180deg and 270deg (contained in one diameter of the pipe), at three different locations along a pipe, having a total of 12 readings.
I would like to model this pipe, using a unique representative thickness for the whole length of the pipe.
Is there any approach to find this thickness? mean value? mean value minus one standard deviation?
Any help will be appreciated.
I would like to model this pipe, using a unique representative thickness for the whole length of the pipe.
Is there any approach to find this thickness? mean value? mean value minus one standard deviation?
Any help will be appreciated.
RE: thickness to be used for modelling a corroded pipe
Mike Halloran
Pembroke Pines, FL, USA
RE: thickness to be used for modelling a corroded pipe
As usual it depends on the details - if your variances are very small you could use the mean, but the number of your data points is too low for any serious analysis.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: thickness to be used for modelling a corroded pipe
This is a structural member 18"OD and 60ft long that is part of a 4-legged jacket platform. I should have said that my intent just was to model the member (not designing it) so that the variation of thickness will be represented in the stiffness of an equivalent element with uniform thickness. I think that using the minimum value will be overconservative to represent the stiffness of the member.
I agree with you that the minimum thickness should be used to check the structural capacity of the element.
RE: thickness to be used for modelling a corroded pipe
I hate Windowz 8!!!!
RE: thickness to be used for modelling a corroded pipe
1. The radial external pressure capability?
2. The structural capability?
3. What?
If you use the minimum thickness then fine for (1) but will be totally wrong for anything else as you will be under-estimating the stiffness of the system.
RE: thickness to be used for modelling a corroded pipe
You need an ultrasound "B-Scan", a continious line of data [actually several hundred measurements per inch] electronically stored. At 18" diameter, I would be comfortable with 4ea. 'lines' along the pipe. Now you can determine the 'real' internal profile of the pipe, and make some stiffness calculations based on nominal as-corroded thickness [rigidity] in various areas of interest. Don't forget to project the Corrosion Rate out at least 5-years [ask client]. Nobody really wants to know about their structure 'today'. They want to know how far into the future that it will be acceptable, and when repairs may be required.