DNV’s latest revision to Offshore Standard for Submarine Pipeline Systems, DNV-OS-F101, will be the pilot for a new approach to rule development, competence management, communication and application.
The update represents more than the inclusion of the latest industry experience and research. DNV now has an in-house, web-based tool for recording changes on a continuous basis to enable interpretations (FAQ), documentation and revisions. The revision will be used to pilot test the system, called DNV Code Manager.
“Our standards are regularly updated to reflect new technology and knowledge, and we now have the opportunity to keep better track of revisions and the reasons behind them,” said Leif Collberg, senior principal engineer for pipeline technology at DNV. “We received over 1,000 comments from industry stakeholders during the development of the 2012 release of the standard. With Code Manager, we will be able to make such feedback available both internally and externally much quicker.”
DNV OS-F101 provides acceptance criteria and design procedures for offshore pipelines. The first version of the standard was introduced in 1976 and it has been systematically updated since then. In 2009, the American Society of Mechanical Engineers gave DNV the Global Pipeline Award, the industry’s most prestigious global award, emphasising the status of DNV’s pipeline standard. Currently 65% of all new projects globally are designed to it.
DNV OS- has been specified in accordance with the ISO 13623 standard, which specifies requirements and gives recommendations for the design, materials, construction, testing, operation, maintenance and abandonment of pipeline systems used for transportation in the petroleum and natural gas industries.
“In isolation, it is very hard to convert the goal-based requirements of ISO 13623 into practical solutions,” said Collberg. “You have to have more guidance and that is what we offer with DNV OS-F101.”
Limit-state-design principles with safety classes linked to consequences of failure are employed in the standard, which is complemented by 14 Recommended Practices (RPs), giving detailed advice on how to analyse specific technical aspects according to stated criteria. As a minimum, a code should ensure safety levels that are acceptable to society, Collberg said.
“For an ‘off-the-shelf’ pipeline design, any of the internationally recognized codes fulfil this criterion. Most are experience-based, using an allowable stress format where all failure modes are covered implicitly in a few simple design formats,” he said.
“However, for pipeline designs where there is limited field experience – such as high-pressure or high-temperature, deepwater, uneven seabed or pipelines in ice-infested areas – only a limit state-based design code with links to fabrication, installation and operation phases can ensure an acceptable safety level,” he said.
The catalyst for the latest revision to DNV OS-F101 has been the need to align of the standard with the latest release of ISO 3183, which specifies requirements for the manufacture of seamless and welded steel pipes and the new ISO concrete coating standard ISO 21809-5. In addition, DNV has incorporated recent industry experience and drawn a closer link between risk analysis and design requirements.
The concept development and design premise section has been reorganized in chronological order. The section on pressure control systems has been slightly restructured and pressures are defined and generalized so that the control system is no longer limited to pressure alone. Instead, it has been extended to all critical operational parameters, such as temperature, content and minimum pressure. The term operating envelope has been introduced for this purpose.
The installation section is now termed “Construction – Offshore,” as it includes pre-installation as well as post-installation activities. This section is based on several workshops with Statoil. The section is now more balanced concerning the extent of these activities and is organized in chronological order. In addition to the reorganization, de facto changes in this section relate to marine operations and equipment qualification.
Another key change relates to nondestructive testing (NDT) and automated ultrasonic testing (AUT). As this has been a less mature area in terms of technology compared to other parts, the experience gained over the last five years and from the new DNV-RP-F118 on the qualification of AUT systems has led to some updates.
Now interpretations of general inquiries from the industry will addressed to by FAQs stored and linked to the applicable text. Code Manager therefore facilitates uniform interpretations and fosters discussion between users. The system also enables background discussions and reports to be accessed directly from the standard’s text.
Revisions can be continuously included in the online “live” version, based on feedback gained at meetings with customers. As soon as DNV believes it needs to be communicated more widely, a new hearing version is generated.
In the future, DNV’s clients will be able to subscribe to the service to develop company-specific notes – for example, outlining the company’s use of the standard and any associated clarifications and interpretations that have been used.
Continuum Of Research
DNV has established a dedicated pipeline committee that meets twice a year. and from time to time guests are invited to discuss specific subjects. The committee talks about current needs in the subsea pipeline industry and helps monitor the development of new codes and standards. With this in mind, a number of joint-industry projects (JIPs) have been established, which draw from the most competent resources worldwide. The committee reviews and updates progress on these projects as part of its work. Committee members represent operators, including BP and Shell, contractors such as Subsea 7 and Technip, regulators, academics and manufacturers.
Colin McKinnon of Wood Group/JP Kenny is chairman of the committee, which last met in April.
“Probably one of the most important outcomes of our meeting was an acknowledgement that research kept confidential for too long is essentially wasted research,” McKinnon said.
“Although research has to be funded, and the current model in many countries is that industry has voluntarily to provide this funding, it is clear that the results must be made public as soon as reasonable. A two-year moratorium, to allow the funding companies to have some of the technological rewards from their investments, was seen as acceptable, longer delays were not,” he said.
Code Manager will facilitate more timely dissemination of research, and it is DNV’s policy to make the details of JIPs it is involved in openly available through its website.
Some JIPs that DNV is managing relate to CO2 pipelines, spiral-welded pipelines, high-integrity pressure protections systems (HIPPS) and pre-commissioning of pipelines with industry partners, such as Dong, ConocoPhillips, Inpex and Saipem. In some JIPs, contractors are also sub-contracted to carry out work in which they are specialists.
DNV’s leading-edge approach to standard development has seen it partner in many significant pipeline construction projects, including the Blue Stream gas pipeline completed in 2005. This pipeline delivers Russian natural gas to Turkey across the Black Sea. The offshore section runs at depths of up to 2,150 meters in an aggressive hydrogen sulphide environment. This necessitated the use of high-grade, corrosion-resistant steel pipes with internal and external polymer coatings. The project additionally involved pipeline stress testing and intellectual cut-ins.
More recently, DNV’s standard has been used for the Nord Stream project, which came online last year and consists of 48-inch, twin pipelines, which transport natural gas over a distance of 1,224 km through the Baltic Sea. DNV started supporting the project in the late 1990s and verified the Nord Stream conceptual/FEED study and the design, fabrication and installation of pipeline to DNV-OS-F101.
The project’s challenges included development of the heaviest ball and gate valves ever produced as well as risks specific to the Baltic Sea environment such as corrosion control in brackish waters, pipelaying on an irregular seabed with soft soils, and interference with fishing activities and ship traffic. The fact that the Baltic Sea contains obstacles, such as sea mines from the first and second world wars and shipwrecks posed additional installation risks.
DNV’s recently established oil and gas office in Perth, Australia is participating in that country’s mega gas projects. Chevron’s Wheatstone project is a complex development with a dual-jacket-mounted central processing facility offshore and a 44-inch trunkline to shore. The calcareous soil conditions and the region’s exposure to cyclones mean stability design is a demanding exercise in which the cost involved for various stabilization measures is substantial.
Wheatstone introduces the hub concept to Australia, allowing not just Chevron but other companies to supply LNG through Wheatstone infrastructure. The offshore platform, Australia’s largest, will connect with an onshore plant at Ashburton North via a 225-km trunkline.
Micro-tunneling technology will be used to bring the trunkline to shore, minimizing environmental impact. About 200,000 metric tons of line pipe is required for the trunkline which will be Australia’s largest in terms of diameter.
The complex infrastructure will be tied together by a network of pipelines and chemical supply lines which are being built to DNV-OS-F101. Australia’s national standardisation body adopted the standard for submarine pipelines with only minor amendments. The authority requires an independent third party to validate offshore developments, addressing the design of the safety-critical elements and confirming the use of appropriate codes and standards.
For Inpex’s Australian Ichthys project, DNV is verifying the overall facilities, including field infrastructure, such as floaters, subsea equipment, the flexible pipeline system, the export pipeline and the LNG plant. A 900-km export pipeline will bring gas from the field, where there is both a central processing facility platform and a floating production, storage and offloading (FPSO) unit, to an onshore plant in Darwin.
Knowledge Transfer For The Future
DNV continues to support industry developments, such as Fluor’s cryogenic LNG pipeline technology that can be used to transport the LNG to an offshore terminal. The use of 9% nickel steel is a new technology and was verified to fulfill the requirements of DNV OS-F101, especially regarding fabrication aspects such as welding. Pipeline safety philosophy and safety criteria given in DNV OS-F101 were applied as part of the design methodology to validate the overall technical safety level.
“DNV’s transparent and fully independent approach to verification, certification, quality surveillance and marine operations helps reduce and manage risk,” Collberg said. “Historically, verification and certification have been carried out with varying scope, depth of involvement and transparency.”
There will always be a need for developments and enhancements in order to guide and support the industry in relatively uncharted territories such as the Arctic, ultra-deep waters, or projects with challenging fluid composition and long tie-back solutions, he said.
Author: Wendy Laursen is a freelance maritime journalist based in New South Wales, Australia.