Determining maximum pipe wall wear

[Engprofile]

Hello,

We have recently had a pipeline checked for wear and I wan't to determine what the maximum amount of wear (or reduction in wall thickness) before the pipe must be replaced.

We are using ASTM A53B 12" Sch 80 steel pipe with a wall thickness of 12.7mm.

The maximum pipe pressure seen in the line is 45Bar.

Unfortunately I don't have a copy of ASTM B31.3 available therefore don't have access to some of the tables.

I was looking to use the calculator on the link;

http://www.pipingengineer.com/online/pipewallcalc.html

however I don't have some of the information for this type of pipe i.e Stress Value for Mat'l table A-1

If someone could offer some assistance with working on this it would be much appreciated.

 

[BigInch]

Here's the B31.3 allowable pressures based on hoop stress alone,

http://www.engineeringtoolbox.com/astm-steel-pipes-pressure-temperature-d_742.html

 

[BigInch]

Using that would assume that "wear" is uniform smooth surface erosion without pitting and any other significant stress concentration mechanics taking place. Probably not too realistic for determining the effect from erosion.

 

[Engprofile]

The table you have pointed out gives an allowable stress of 9722kPa for Sch 80 steel (300mm).

When I enter this value into the formula I get a wall thickness of 73.8mm!

The values I have used are:

Pipe O.D (mm.) 300
Internal Design Pressure (barg) 52.53
Stress Value for Mat'l from Table A-1 (N/mm2) 9.722
Quality Factor ,E 0.8
Corrosion Allowance (mm) 1.58
Coefficient,Y (mm) 0.9

Can you see where I have gone wrong?

 

[BigInch]

Well it's hard to check your work w/o seeing the formula you actually used.

(type it here)-> [ ]

 

[Engprofile]

I used the online calculator here:

http://www.pipingengineer.com/online/pipewallcalc.html

 

[BigInch]

Table Reading 101 class; start with reading the column headers.

9722 kPa is the ALLOWABLE PRESSURE for 300mm sch 80,
NOT the allowable stress!

Allowable stress is 137800 kPa, put that in the online calculator.

 

[Engprofile]

Thanks for your help,
Using 137800kPa = 137.8N/mm2

I got a wall thickness of 7.7mm.

 

[BigInch]

That's roughly what I'd expect to see. I didn't check your math, but it appears that at least you're in the ball park with that number.

Cheers.