Session: 04-01-07 Flexible Pipes & Umbilicals VII

Paper Number: 129294

129294 - Non-Metallic Clamp for Flexible Risers 

Non-metallic Clamp for Flexible Risers

Krassimir Doynov, Rachel Iwicki, Brandon Henneke

ExxonMobil Upstream Integrated Solutions

 

 

A novel non-metallic clamp for flexible risers with breached outer sheath in the splash zone has been developed, qualified, and installed to enable riser lifetime extension.

 

Flexible riser outer sheath breaches in the splash zone or aerial riser portion have been experienced by operators and reported to occur by Sureflex JIP, due to natural degradation (i.e., UV aging and fatigue), dropped objects, or blocked vent ports of riser end fittings terminated topside. An outer sheath breach in the splash zone or aerial riser portion exposes the structural carbon steel wires to rapid corrosion due to oxygen inflow at the breach location, and because existing cathodic protections are not effective above the mean seawater level. Rapid corrosion in turn decreases both riser strength resistance to pressure and tensile loads, and riser corrosion fatigue resistance, which over relatively short period of time may lead to loss of riser containment. Clamping of the breached outer sheath location has been historically used to mitigate that risk of loss of containment with the use of steel clamps of various design.

 

Over the course of few years 3 steel clamps have been installed on top of a longitudinal-seem-weld-outer-sheath repair performed at riser installation, with a new leakage discovered after each clamp installation. This experience has led to the realization that the outer-sheath stiffness transition in the vicinity of the steel clamp edge and clamp tightening have driven initiation of new breaches nearby due to the degraded outer-sheath-seem-weld repair. This realization in turn inspired the development of a novel non-metallic clamp that eliminates the sharp stiffness transition caused by metallic clamps and is cost efficient.

 

This paper describes the development, qualification and installation of a novel non-metallic clamp to enable the lifetime extension of a flexible riser described in OMAE 2023-101167. The paper presents the transition from technology readiness level TRL-1 (concept selection) to TRL-6 (system installation). It presents the logic of material selection, failure mode identification, prototyping, validation testing, system integration, installation and lessons learned.  It concludes with recommendation on scalability of the non-metallic clamp use and further developments on adding venting functionality.

Presenting Author: Krassimir Doynov ExxonMobil

Presenting Author Biography: Dr. Doynov is ExxonMobil’s Senior Principal Engineer Offshore Pipelines & Risers, with 26-year experience in the Oil and Gas Industry. His responsibilities include providing technology solutions to new Project developments, technical expertise to Operation Units, and coordinating R&D activities in Pipelines & Risers. He has been chairing the API & ISO flexible pipe standardization for 20 years.

Authors:

Krassimir Doynov ExxonMobil
Rachel Iwicki ExxonMobil
Brandon Henneke ExxonMobil