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Zap-Lok® connection in offshore use | Successful approval thanks to the best connections | Technology | Issue 11 • April 2018 | Line Pipe Global

Line Pipe Global

Issue 11 • April 2018

Zap-Lok® connection in offshore use

Successful approval thanks to the best connections

Just how important not only technical but also personal connections can be has been illustrated yet again by the offshore approval of the Zap-Lok® system for oil and natural gas pipelines in the Dutch North Sea.

Generating new products and partnerships on the basis of good business relations was the idea behind Offshore Day 2014 in Siegen. Forty-four employees of pipe-laying and further processing companies along with representatives of international energy companies came together at the time for an exchange of ideas on the subject of offshore applications.

Dr. Benjamin Chapman of NOV-Tuboscope presented the Zap-Lok® connection process in which the pipes are not welded but pressed firmly together. Over long distances, this process is not only quicker but also less expensive than conventional welding processes. In a study in 2013/2014, he demonstrated that the Zap-Lok® method is on a par with conventional welding methods in the offshore sector as well.

In the auditorium at the time was Peter Mather from Dutch engineers Smart Engineering B.V., a longstanding project partner of Mannesmann Line Pipe. He was so interested by the subject that he used his contacts with Dutch energy supplier Oranje-Nassau to have the process presented there. Oranje-Nassau Energie B.V. (ONE) is one of the biggest Dutch private companies in the exploration and production of oil and gas.

Successful cooperation between Smart Engineering, ONE and Mannesmann Line Pipe

Building on the project successfully realized in 2014, that of connecting the natural gas production platforms P11E and P15F in the Dutch North Sea, ONE, Smart Engineering and Mannesmann Line Pipe agreed at short notice to qualify the Zap-Lok® process for offshore applications. Pipe size 2019 x 12.7 mm in steel grade L360 FBN was chosen, this being a standardized size/grade combination of offshore companies in the Netherlands.

Extensive program of tests

In mid-2016, the experts of Smart Engineering B.V. developed an extensive program of tests to obtain the approval of the Zap-Lok® connection for offshore applications. Following consultation with ONE and Mannesmann Line Pipe, the program was entrusted to Salzgitter Mannesmann Forschung (SZMF) in Duisburg. Concurrently, Mannesmann Line Pipe had already supplied bare pipes conforming to the agreed specification to NOV-Tuboscope in Gladbeck, where the Zap-Lok® connections for the test pipe strings were produced. At SZMF in Duisburg, the pipes underwent the bulk of testing, with supplementary tests being performed at RWTH University of Aachen.


Peter Mather, Smart Engineering (center), Michael Bick (left) and Nils Schmidt, Mannesmann Line Pipe, monitored certification from beginning to end.

Watch this animation of the laying unit developed by Cortez Subsea.


Approval within a year

Weekly reporting by Smart Engineering made the entire qualification process transparent from beginning to end and ensured an outstanding flow of information among everyone involved. On completion and after evaluation of all test findings, the approval for offshore suitability under defined conditions was granted by Dutch certifier Bureau Veritas (B.V.) under the official supervision of the ‚Staatstoezicht op de Mijnen‘ in mid-2017.

Nils Schmidt, Regional Sales Manager at Mannesmann Line Pipe, not only devised Offshore Day in Siegen in 2014, but was also the lead contact for Smart Engineering and ONE in all matters relating to the project. »The fact that we were able to obtain approval in such a short time is undoubtedly a reflection on the mutual trust among all project partners and our good relations with the Group‘s own research department in Duisburg,« says Schmidt summing up.

Efficient laying process

The Scottish pipe installer Cortez Subsea meanwhile developed a module that is docked onto the NOV-Tuboscope connecting unit and can be installed on pipe-laying ships in a procedure taking half a day‘s work. The Zap-Lok® connecting unit is automatically loaded with pipes and can theoretically operate around the clock.

  The certification process and how the Zap-Lok® connection works

Obtaining certification

At Salzgitter Mannesmann Forschung GmbH (SZMF) in Duisburg, a Mannesmann Line Pipe affiliate, the pipes underwent various resonance, fatigue and burst tests. The load limit was also determined and cyclic hydrostatic pressure tests and corrosion tests were carried out. Charpy V-notch tests and hardness tests as well as macroscopic studies of samples from the various tests were performed over and above this.

The axial tension and epoxy curing of the lining were tested at RWTH University of Aachen, which has a special unit with a test capacity of 12 meganewtons. All the findings from the tests performed under various loads and special conditions were evaluated by the participating parties and brought together in a final report. The approval for offshore suitability under the defined boundary conditions was awarded by Bureau Veritas (B.V.) in the Netherlands in mid-2017.

Further information on the Zap-Lok® process can be found on the PDF.

How the Zap-Lok® process works

Zap-Lok® is a connection system patented by NOV-Tuboscope that dispenses with the welding of the pipes. The line pipes are connected by press-fitting, which is suitable for all conventional pipeline applications (gas sour/non-sour, oil, water) and for offshore and high-pressure pipelines. Pipes in diameters of 60.3 to 323.9 mm (2 3/8 to 12 ¾" ) can be used.

In downstream processing of the pipes on the machines developed by NOV-Tuboscope, one pipe end is shaped as a bell and the other as a so-called pin. During laying, the pin end is coated with the two-component epoxy compound and then pressed into the bell end.

Since welding and the X-raying of the welds can be dispensed with, up to 300 pipes can be laid per day using the Zap-Lok® method.

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