Originally operated in the Hutton field, located in the North Sea, the Hutton TLP (Tension Leg Platform) structure was the first of its kind to be constructed and installed anywhere in the world.
Construction started in 1982 by ConocoPhillips at Highland Fabricators. The Hutton TLP is unlike any nearby oil platforms, as when in situ, it had no massive underwater steel structure. Instead, 16 steel tethers help to anchor the platform to the ocean floor.
The structure was designed for a minimum service life of 20 years in a water depth of 148 metres (486 feet). The North Sea posed a challenge as it is considered to be extreme and hostile and as such requires a high-performance coating system to be specified.
During construction, we recommended using Interzone 1000, a newly formulated glass flake epoxy for the tubular splash zone sections. Construction began in 1982 and the project went on to consume 40,000 litres of protective coating for the tubular sections.
In 2011, the first assessment of the Hutton TLP took place. Interzone 1000 was reported to be in excellent condition after almost 30 years in an ISO 12944 CX environment.
Chris Jordan, Coatings Specialist for ConocoPhillips during construction of the Hutton and with more than 40 years’ experience of surveying in the North Sea said at the time of inspection:
“It is clear that after nearly 30 years in service, the high loaded glass flake epoxy applied on the tubular splash zone sections of the Hutton TLP hull is performing very well. Even areas subjected to abrasion from topside equipment such as pumps, ropes and chains are in excellent condition considering the lifetime… I would consider a glass flake epoxy, as used on the Hutton TLP, to offer the best corrosion protection for the splash zone of offshore assets.”
11 years after the initial assessment, and with the support of Nerida Decommissioning, AkzoNobel conducted a second assessment of the coating system to independently verify and report the results. Interzone 1000 meets the ISO 24656 specification standard on the use of a minimum 20% lamellar, non-micronized glass flake epoxy for category V corrosion protection, which is the highest performance category and the lowest breakdown factor for the entire lifetime expectation.
ISO 24656 provides an important guidepost for aligning coating system performance to international standards. The second inspection helped to determine the performance of the coating system and the following results were found:
- Visual Inspection: A visual inspection of the steel showed no sign of coating breakdown, there was also no evidence of defects or cracking even when inspected under 40x magnification.
- Adhesion: Checks were performed in accordance with ISO 4624 using a self-aligned automatic adhesion tester – adhesion was shown to be between 11-13Mpa which is well above industry expectations. The mode of adhesion failure in the tests occurred between the system layers indicating a higher degree of adhesion between the coating system and substrate.
- Electrochemical Impedance Spectroscopy: An EIS test was conducted which is used as a non-destructive technique to determine a coating’s barrier properties and potentially indicate substrate corrosion processes under the film. Impedance measurements were recorded and it was reported that the EIS results were in a high order of magnitude and indicate that the coating is continuing to act as a barrier.
Andreas Hoyer, Global Energy Key Account Manager at AkzoNobel, spoke about Hutton TLP and the use of Interzone and stated:
“It really demonstrates why Interzone is so widely specified and chosen to protect offshore assets. The performance of a coating system is a result of its whole formulation, where careful selection and optimisation of all raw materials combined with technical know-how and expertise help to deliver what really matters - proven performance on offshore assets, and in-service. This is the reason that the Interzone range delivers differentiated performance versus others and continues to be the coating of choice for protecting the Energy industry’s offshore assets, whether they be in oil and gas or within the energy sector.”
With the long-term projection of growth in the offshore wind energy industry in particular, the findings provide greater certainty for owners, engineers and specifiers on the choice of technology to protect and deliver against lifetime expectations. The Interzone epoxy technology continues to be one of the best solutions for fabricators and applicators to apply and supports HSE goals when compared to alternative technologies.
Reflecting on the 40-year off-shore performance track record of Interzone 1000, AkzoNobel reinforce the message that its epoxy solutions remain the trusted and go-to technology for meeting lifetime performance expectations. The TLP upon decommissioning, was then moored in Scotland and then it made its final journey to Queen’s Dock at the Port of Cromarty Firth where work to break the structure down was undertaken by Nerida Decommissioning. In its lifetime, the Hutton TLP was proof of Interzone’s performance and quality.
Focus product: Interzone 1000
Year of project: 1982
Project size: 40,000 litres