Subsea application of the Quickflange cold flanging technology

Introduction Quickflange has developed and are delivering pipe connections to the industry which can be joined permanently to the pipes without any use of welding or other so called hot work. Operators with the need for subsea joining of pipes have stated that an equivalent connection would be sought after for use subsea, as welding at the ocean floor is highly complicated and expensive. Therefore Quickflange started to develop the technology to also apply for use at the ocean floor. This for the company, through new technology for joining of pipes at the ocean floor, to expand its product range and to contribute to a more cost efficient and safer maintenance and preparedness for leakages of underwater piping. Main problems Quickflange's existing connections were approved for up to 20 bars pressure, for small pipes and for use on a limited number of non hazardous liquids. Piping on the ocean floor has an internal pressure of several hundred bars, are large in diameter, contains hazardous liquids and gases and are exposed to greater forces. A much deeper understanding of the mechanical principles of the connection had to be developed in order to create connections that can be used on such pipes. The objectives of the development project were: - Develop the technology to be able to make connections that can withstand a test pressure of at least 750 bars - Develop the technology to be able to create connections up to 16" size - The method, the tool and the connection must in addition: - be developed to avoid that water in the cavities prevent the joining process - enable remote operated joining - withstand sea water cathodic protection without deterioration Findings/Results By utilizing proprietary methods for the calculating program Abaqus with explicit solution, it has been possible to analyze the joining process despite great local deformations occurring in the material. This has increased our understanding of the connection and pipe interaction when the metals deform elastically and plastically against each other, of the metal's elastic springback after plastic deformation, of the remaining tension in the joint and of the result in terms of leak intergrety and mechanical strength. This in turn has made possible the development of the technology to meet the requirements that apply to the joining of pipes on the ocean floor. The methods developed for nonlinear finit element analysis have been calibrated by physical tests carried out at the University of Agder, Sintef in Trondheim, and at Quickflange AS. The first scientific publication based on this work is titled "FEM simulation of cold deforming pipe into flange". The publication is a conference paper for "The 26th Nordic Seminar on computational mechanics" October 23-25 2013. Publication number 2 is published in the Journal of Material Processing Technology January 16. 2015. The title is "Numerical and experimental verification of new method for connecting pipe to flange by cold forming". We have succeeded in developing connections that has been testet to 1200 bar. We have developed connections up to 14" (diameter 35cm) pipe, and we believe the project has made us capable of making even larger connections. We have tested the leak integrity with respect to gases with good results. We have developed several methods to avoid issues regarding hydrostatic locking during the joining process. One is to separate the sealing and mechanical grip and then be able to vent out water from cavities. Another is to fill the cavities with a special material which won't be compressed by the surrounding water pressure but will collapse during the joining process. The contact pressure between moving components in the tool is up to 2 GPa (20,000 kg / cm2). This makes standard friction theory inapplicable. Friction tests and analysis have been performed at Sintef to determine the friction forces. In consultation with Professor Roy Johnsen at NTNU the challenges regarding corrosion have been solved. For example, problems related to hydrogen's impact on high-strength components in the connection when under cathodic protection have been solved by designing the connector such that these components are not subjected to strain after the installation process. Sintef has developed test equipment and has carried out pressure pulsation testing of a prototype Quickflange connection. The testing demonstrated that the connection is suited for hazardous service like for example hydrocarbon gas. We have delivered a prototype subsea connection for 4" pipe to a possible future customer, PTTEP Austalasia in Australia, for testing. This was tested by us to a pressure of 940 bars and then sent to PTTEP. We have received expert help from and worked with Statoil's Pipeline Repair System, PRS, Base on Killingoey. According to their requirements, we have developed and successfully tested a prototype Quickflange subsea connection for an actual North Sea subsea pipe.

The underlying idea of this project is to develop a faster and more cost effective method for attaching flanges to pipes subsea. This is to be achieved by developing the Quickflange cold-flanging technology of standard flanges for subsea use. The projec t goal is to be reached through research on materials properties of metals. In particular, the forces generated by the difference in spring-back effect in the pipe and flange after linear and non-linear elongation, occurring when the external forces from the hydraulic tool is released. The results from this research are to be used to extend the flanging method for pipe pressures and diameters commonly found subsea. In combination with development of tools and methods for use subsea and field tests with di vers and ROVs, subsea use of the Quickflange technology will be enabled. The main collaboration partners are The University of Agder (UiA), Det Norske Veritas, SINTEF, The University of Stavanger (UiS) and The National Hyperbaric Centre and Petrobras. T he results will have a significant impact on time consumption and costs incurred by all pipeline construction, intervention, and maintenance operations subsea. It will result in a new way of thinking when working with pipes subsea, as the operation will b e less complex, improve safety through reduced use of divers and the costs of carrying contingency equipment. This project primarily addresses Technology Target Area 7: Deepwater, subsea and Arctic production technology; Priority Area 2: Development of n ew systems for subsea installation, inspection and maintenance of equipment and pipelines, but the implications of the project are also relevant for TTA9: Health, safety and the work environment.