chartered engineer - EA - qualification error

3D modeling and FEM simulation

Andrew Palmer

Famous subsea pipeline text.

by Andrew Palmer and Roger A. King

the world authority on marine pipelines

Subsea Pipeline Stability Standards Review

1.0           Subsea Pipeline Stability Standards Review

1.1             PETRONAS technical standards - PTS 31.40.00.10

The PTS offer the traditional static analysis.

1.2             British Standard - BS8010-2:2004

Generally, BS8010 follow the DNV RP E305 & DNV OS F101

1.3             ASME\ANSI B31.8

ASME B31.8 recommends the traditional static analysis.

1.4             API recommended practice 1111, 4 Edition, Dec-2009

API use AGA research (PR-178-516 & PR-178-717) for on-bottom stability analysis. The AGA research defines 3 levels for stability analysis.

Level1: static analysis with single airy wave

Level 2: static analysis with wave spectrum and embedment

Level 3: dynamic analysis with random wave kinematics

Level 3 is similar to DNV code. AGA use Lstab software for stability calculations.

1.5             TOTAL General Specification, Submarine pipeline system, GS PLR 100

GS PLR 100 suggests DNV or equivalent codes.

1.6             DNV

DNV published DNV RP E305 in 1988 and considered pipeline stability for static and dynamic and generalized methods. DNV developed this standard in DNV RP F109. DNV commonly used for stability of submarine pipeline

1.7      Conclusion

DNV RP F109 is considered as a best code for stability calculation and this report is based on it.

CALM buoy simulation with two types of chain

12 graph shows the response of buoy with lighter chain and 678 graphs shows it with heavier chain

12 graph shows the response of buoy with lighter chain and 678 graphs shows it with heavier chain

 

12 graph shows the response of buoy with lighter chain and 678 graphs shows it with heavier chain

Tight Flange strange failure

Tight flanges normally are used for connection two pipe under water without welding. Tight flange is locked to pipe by it's gripper and sealed with a internal rubber sealing. below figure shows the typical Tight flange. the gripper and seal are activated by flange bolts while tightening of flanges bolts.

 

please pay attention, tight flange has not been made by oceaneering

 This failure was strange and intricate because Tight flange was hydrotested before using  .

it was unprecedented . tight flange was failed from back side!!!. it was not normal. why ? . the rubber seal was emerged. almost of bolt was broken.

all bolt and nuts have certificate and sample of them was tested. 

 

the stress analysis of tight flange didn't show any failure

tight flange was located in the rupture point of 4 inch pipeline.

 

Up to now, the reason of the failure is unknown.