FPSO hose reel: replacement of Single Closure Gall Thomson MBC with PetalC
In September 2021, Gall Thomson manufactured and supplied a PetalC Marine Breakaway Coupling (MBC) to an FPSO (Floating Production Storage and Offloading) with hose reel application.
The FPSO is located in the North Sea and is operated by the Anasuria Operating Company.
The task
• Replace a 16” Single Controlled Closure MBC supplied to Anasuria FPSO in January 2003.
• Installation to be performed offshore.
• Short timeline to retrofit the replacement: this to minimise impact on FPSO offloading schedules.
Making the right decision
The problem
Anasuria Operating Company had a 20-year-old 16” Single Closure Gall Thomson MBC. This provided pollution protection within the previously specified risk profile.
The previous solution was primarily designed for asset and operation protection against tanker breakout or extreme pressure surge. This MBC also offered limited environmental protection.
The vast majority of Gall Thomson Petal Valve MBCs are Controlled Double Closure. This means valves at both halves of the MBC close the upstream and downstream flows on activation.
The Anasuria FPSO is exposed to the harsh environment of the North Sea and the MBC also endures the operational stresses of hose deployment and storage between offloading reel operations.
Marine Breakaway Coupling options available
Option 1: Install new Single Controlled Closure MBC
It would have been possible to install a new 16” Single Controlled Closure MBC. This option is similar in all aspects to the original MBC installed on the Anasuria FPSO in 2003.
This type of MBC would have provided hose protection against tanker breakout and limited pollution protection as the MBC is installed after a short jumper hose (see image below).
Option 2: Install 16” Controlled Double Closure Petal17
Installing a 16” Controlled Double Closure Petal17 MBC was a possibility.
A detailed OrcaFlex analysis would have been performed to assess whether transit bolts were required.
The requirement for transit bolts depends on the offloading reel configuration, operational parameters, hose specifications and design.
Transit bolts are fitted to the MBC so that its function to activate is suspended. This means the MBC cannot be provoked to activate. Transit bolts therefore remove the risk of activation while being wound or stored on reel.
Transit bolts are removed when the MBC hose string is being deployed prior to performing an offloading operation and re-installed when the MBC is being stored onto the reel.
The use of transit bolts on an existing FPSO may require a retractable platform to perform the removal and re-installation of the transit bolts safely and efficiently.
The installed length of the PetalC is 60% less than Petal17.
More on PetalC
This reduced installed length is achieved by inserting both end profiles of the PetalC inside the hose nipples. This enables the MBC to work with the construction and strength of the OCIMF nipple hose.
The optimum solution
In this FPSO reel application, a PetalC Controlled Double Closure was installed.
Due to its unique profile and ability to take advantage of the OCIMF nipple hose design, stress on the critical breakstuds while on reel is reduced by up to 30%.
The negates the need for transit bolts.
The Double Closure specification of the PetalC also delivers Petal Valve closure for both upstream and downstream flow in an emergency activation.
Summary of options from the perspective of solution delivery
Result
16” PetalC was installed in May 2022 with the assistance of Gall Thomson.
The PetalC has been performing exactly as specified.
The FPSO owner commented:
“the PetalC ... is a more compact model of the range of MBCs manufactured by Gall Thomson and represents a technical upgrade to the previously installed MBC. The PetalC MBC is designed specifically for service where the MBC may be subjected to high loads caused by bending, such as deployment from a reeled hose string.
We can recommend the use of Gall Thomson MBC PetalC on FPSO reeling systems and other floating/subsea systems exposed to severe weather and harsh sea conditions”
Shown below: Installation of the PetalC on FPSO with OCIMF nipple hoses.
GTAC
