arielrulo
Petroleum
- Aug 10, 2012
- 1
Dear All
I would like to shear an interpretation I am doing about ASME 31.8 and hear your opinion. (All references from now on is for ASME 31.8 2018 Edition)
I have this Gas pipe installed:
12 in – API 5 L Gr 70 – e: 7.9mm
Design pressure calculated by 841.1.1 is 102.9 kg/cm2g calculated with:
S = specified minimum yield strength 70000 psi
D = nominal outside diameter of pipe 12.75 in
E = longitudinal joint factor 1
T = temperature derating factor 1
t = nominal wall thickness, in. 7.9mm – 3.2mm corrosion allowance: 4.8mm (0.185in)
Hydraulic test pressure done at 99x1.25 kg/cm2g. By table 845.2.2-1 maximum operating pressure is 99 kg/cm2g.
Now well, we need to operate at 108 kg/cm2g to avoid high operations cost and is unviable to do a new hydraulic test.
So we change our design (change corrosion allowance to 1.6mm)
New maximum operating pressure calculated 137.9 kg/cm2g BUT we are limited by hydraulic test that has been done at 124 kg/cm2g. So by table 845.2.2-1 maximum operating pressure is hydraulic test divided 1.25, 124 / 1.25 : 99 kg/cm2g
Now based on 857 Uprating part of code.
Item 851.1.c) is totally accomplish.
Now we see 857.2 d) and base on that article marked on yellow (see atached file) i think we can operate at 108 kg/cm2g
What do you think about this interpretation?
Thanks in advance,
Ariel
I would like to shear an interpretation I am doing about ASME 31.8 and hear your opinion. (All references from now on is for ASME 31.8 2018 Edition)
I have this Gas pipe installed:
12 in – API 5 L Gr 70 – e: 7.9mm
Design pressure calculated by 841.1.1 is 102.9 kg/cm2g calculated with:
S = specified minimum yield strength 70000 psi
D = nominal outside diameter of pipe 12.75 in
E = longitudinal joint factor 1
T = temperature derating factor 1
t = nominal wall thickness, in. 7.9mm – 3.2mm corrosion allowance: 4.8mm (0.185in)
Hydraulic test pressure done at 99x1.25 kg/cm2g. By table 845.2.2-1 maximum operating pressure is 99 kg/cm2g.
Now well, we need to operate at 108 kg/cm2g to avoid high operations cost and is unviable to do a new hydraulic test.
So we change our design (change corrosion allowance to 1.6mm)
New maximum operating pressure calculated 137.9 kg/cm2g BUT we are limited by hydraulic test that has been done at 124 kg/cm2g. So by table 845.2.2-1 maximum operating pressure is hydraulic test divided 1.25, 124 / 1.25 : 99 kg/cm2g
Now based on 857 Uprating part of code.
Item 851.1.c) is totally accomplish.
Now we see 857.2 d) and base on that article marked on yellow (see atached file) i think we can operate at 108 kg/cm2g
What do you think about this interpretation?
Thanks in advance,
Ariel
