Abstract — The integrity of the mooring system is critical for the safe station-keeping of any floating structure. For motion dependent wave energy converters, the additional requirement is to provide sufficient compliance to allow the power take-off working principle to function. This paper presents the physical testing carried out as part of the MARINET2 test programme. The mooring system design for the Calwave wave energy converter is tested in order to validate the actual physical performance of the mooring system. The tests are carried out at the Dynamic Marine Component Test facility (DMaC), capable to replicate the forces (up to 30 tonnes) and motions (up to 1m / 30°) with submersed test specimens of up to 6 meters length. The tests explore the Minimum Breaking Strength (MBS) as a primary measure of integrity, but will also perform repeated cyclic loading, simulating low-cycle fatigue behaviour of the mooring system. The tests also assess the mooring response and integrity under simulated Accidental Limit State (ALS) conditions, where the device’s power take-off will be locked and the mooring loads are expected to increase considerably. A key finding of the tests is the importance of the termination pattern and quality, which has a direct influence on the mooring MBS. The static and dynamic stiffness for the tested HDPE belts is also determined. The paper will be of interest to technology developers, mooring designers and stakeholders concerned with the integrity, durability and validation of offshore mooring systems. Keywords—Reliability, Component Testing, Mooring, Shock Load, Tension-tension test. I. INTRODUCTION OORING systems are one of the most important sub-systems for floating offshore structures, as they warrant the safe station keeping of the installation. Thus, the design and testing of mooring systems has to take into account the technology development status. According to [1] technologies can be classified regarding their technology status (Proven, Limited field history, new/unproven) and their application (known, unknown). The assessment yields a technology class range from 1 - 4: 1. No new technical challenges 2. New technical uncertainties This work was supported through the MaRINET2 programme (http://www.marinet2.eu/) through funding from the European Union Horizon 2020 Framework Programme (H2020), grant agreement no 731084. P.R. Thies is the corresponding author: P.R.Thies@exeter.ac.uk. Together with P. Halswell and L. Johanning he is working in the 3. New technical challenges 4. Demanding new challenges Class 1 and 2 represent well established, demonstrated mooring systems with a track record in the field and multiple monitored installations. For many floating wave and tidal energy technologies the ‘application’ has to be classed as ‘new’, as there often is not sufficient field experience with a complete system. This classes the mooring system as category 2 and above, depending on the technology status itself. If the mooring system itself has limited field history (class 3) or is in itself new (class 4) additional design and test work is required to identify, quantify and validate the new technical aspects and challenges. This is a reoccurring issue and as a result dedicated component testing is increasingly used in order to physically test the behaviour and load capacity of sub- systems in general and mooring components in particular. This paper reports the specifications and results for a tension-tension test, carried out on mooring belts. The belts constitute the critical component of a taut mooring system for the CalWave wave energy converter [2]. The paper is structured as follows. After the introduction, the test objectives, methods and specifications are described in section II. The results regarding the Minimum Breaking Strength (MBS), dynamic response and shock loading behaviour are presented in section III. The test outcomes will be discussed regarding the specific taut mooring design as well as wider technology assessment findings for the sector (section IV). II. TEST OBJECTIVES AND SPECIFICATIONS The aim of the mooring component tests were to validate the design assumptions for a taut mooring system. The critical component was identified to be a High Density Polyethylene (HDPE) mooring belt. Relevant work in the literature includes the seminal paper by Banfield and Casey [3] on the evaluation and testing of mooring fibre ropes and their application for in the marine renewable energy sector [4]. Ocean Technology group at the College of Engineering, Mathematics and Physical Sciences at the University of Exeter, Penryn Campus, Treliever Road, TR10 9FE, UK. M. Lehmann is with CalWave, 1387 Scenic Avenue, Berkeley, CA 94708, United States. Philipp R. Thies, Peter Halswell, Marcus Lehmann and Lars Johanning Integrity and Reliability Testing of a HDPE Taut Mooring System Belt M