Improving flex joint design to extend field life

Offshore staff

KUALA LUMPUR, Malaysia -- Flex joints are subjected to extreme demands, and failure can cost operators time and money. Mike Hogan, vice president of Oil States Industries Inc., discussed flex joint design at the second annual Offshore Asia Conference & Exhibition in Malaysia on Jan. 17.

"The purpose of the flex joint is to extend the life of the riser at the critical point where the riser terminates at the vessel," Hogan explained.

Flex joints have been used offshore since 1976, Hogan said, with 115 installed between 1995 and the present.

A failure of a single flex joint of 58 installed on a Gulf of Mexico field in 2004 led to concern about the equipment's reliability. An inspection at the field revealed 53 flex joints intact, one damaged to the point of leakage, and four flex joints damaged to the point that Oil States removed them for study and analysis, Hogan said.

"We made some very straightforward design changes to correct for failures," Hogan said.

Oil States looked at performance demands on the flex joints, including current, pressure, temperature, and vessel motion. The company learned the lesson that it needed to know all of the parameters that will affect the flex joint, Hogan said, concluding "It is important to keep an open mind in you development."

In fact, according to Hogan, analyzing this failure was a learning experience for the while industry.

One of the things the industry learned was that failure can be identified through visual inspection. "The problem previously was that nobody knew to look," Hogan said.

Now, Oil States has changed its manufacturing and testing process, and once the flex joints are installed, a visual inspection program can identify potential failures before they become serious concerns.

Identifying this issue has since led to a joint industry project, Hogan said. The JIP is working to understand how the elastomer of the flex joint responds under different operating conditions with the goal of extending the flex joint's field life.

1/18/2007