API RP 14E Offshore Piping System Overpressured
API RP 14E Offshore Piping System Overpressured
(OP)
This is a continutation of the previous 'Hydrotest Pressure Exceeded' discussion:
Quick Summary: The hydrotest pressure (6,500#) was exceeded for a '6 in Pipe (.562” WT) and ANSI 900 RTJ Flange' Piping System (2220# MAWP) for 15 minutes, where gaskets began to leak and the hydrotest was stopped. The previous discussion dealt with the piping only, and the problem was solved.
I am currently reviewing the flanges to see if they need to be replaced. I am currently looking at ASME Section VIII, Division 2 and trying to calculate the longitudinal, hub, and radial stresses.
Question 1: Am I going in the right direction?
Question 2: Once I get the stresses, what do I compare them against?
Please help.
Thanks,
msharptx
Quick Summary: The hydrotest pressure (6,500#) was exceeded for a '6 in Pipe (.562” WT) and ANSI 900 RTJ Flange' Piping System (2220# MAWP) for 15 minutes, where gaskets began to leak and the hydrotest was stopped. The previous discussion dealt with the piping only, and the problem was solved.
I am currently reviewing the flanges to see if they need to be replaced. I am currently looking at ASME Section VIII, Division 2 and trying to calculate the longitudinal, hub, and radial stresses.
Question 1: Am I going in the right direction?
Question 2: Once I get the stresses, what do I compare them against?
Please help.
Thanks,
msharptx





RE: API RP 14E Offshore Piping System Overpressured
Hopefully the flanges only defromed elastically and are OK.
RE: API RP 14E Offshore Piping System Overpressured
This is all being done by an offshore crew. I was informed that they replaced the gaskets and fasteners. They reviewed the flanges and pipe, and there was no deformation, but I need to provide 'calculated proof' that nothing happened.
Is it true that when the MAWP in a pressure vessel is exceeded, the only prognosis under code is to check for deformations...if none, you're okay. Since flange stresses are governed by the pressure vessel code, i would think follow the same logic.
I'm in the dark on this one.
Marcus
RE: API RP 14E Offshore Piping System Overpressured
You can calculate max stress based on the particular code that covers the pipeline or the code that the flanges were fabricated under. I should have added elastic deformation of the fasteners in my previous post.
One approach that we have used on several occasions where there was an excessive over pressure was to ask the manufacturer of the flanges for an opinion. Though our problem was with large SS flanges the manufacturer came through.
RE: API RP 14E Offshore Piping System Overpressured
Thanks.
RE: API RP 14E Offshore Piping System Overpressured
ASME Section VIII addresses this but I'm not sure about small integral flanges. Someone needs to jump in and help.
Here is one approach to checking flange rotation, EN 1591-1. You might want to get a copy.
The article by Yann Guierout.
ht
http://www.sealeng.com/ase/index.html