Overview
Aquamarine Power Ltd (APL) was a wave energy company responsible for developing a wave energy converter called Oyster. The Oyster system consisted of a Wave Energy Converter (WEC) located in shallow water close to the shore, with a bottom-hinged flap which oscillated due to wave action.
APL deployed a full-scale 315 kW Oyster 1 system at the European Marine Energy Centre (EMEC) in August 2009, followed by a second generation machine rated at 800kW, Oyster 800, in August 2011. Oyster 800 utilised double acting pistons on each side of the WEC which pumped water through a high pressure pipeline back to shore, where high pressure water drove a Pelton wheel turbine connected to an electrical generator. The flow from the Pelton wheel discharged to a header tank and returned to the WEC via a low pressure return pipeline.
APL ceased trading in November 2015, and the intellectual property was acquired by Wave Energy Scotland (WES), who propose to share relevant documents and information acquired with developers in the WES programme and the wider sector.
The documents included here capture internally produced guidance and learning records which were produced by Aquamarine Power in order to be applied to future WEC designs, and any ongoing engineering design work required on Oyster 800. They are now being shared by WES to support other WEC developers who may be facing similar issues and challenges.
Further documents will continue to be added to this collection over time.
Threaded Fastener Design
September 2020
During the design of Oyster 800, the criticality of securing fasteners was recognised in the light of experience and learning from Oyster 1. A guidance note was therefore prepared outlining recommendations maintained from the design of Oyster 1, and from new experiences gained directly from Oyster 800 or through other learning avenues. These include engagement with external specialists (notably Bolt Science and Technip Offshore Wind Ltd), specialist training (ASME PCC-1 course on bolted flange joint assembly), supplier engagement and literature review.
The only way to ensure that bolted connections will work effectively over the life of a project is through careful design engineering. Good working practices during component manufacture and joint assembly are also necessary, but if it is difficult (or impossible!) to implement the design intent correctly on site, the chances of joint failures increase significantly. It is therefore essential that the engineer understands how the joint will be made in practice and ensures the design is fit for this purpose.
The purpose of this document is to summarise Aquamarine Power’s learning in the form of guidelines for good design practice in threaded fastener connections. For the purposes of this note, bolted connections have been generalised into a small number of discrete application categories. It is intended that common approaches may be adopted for design of bolted connections within each of the categories described in this document.
Share reportStandard Bolted Connections
March 2019
This document was produced by Aquamarine Power Ltd in 2014 to record good practice for the specification of bolted connections on the Oyster 800 device, built up through experience of operation and offshore maintenance campaigns during the summers of 2013 and 2014.
Oyster 800 was installed at EMEC over 2011 to 2012 before undergoing a series of commissioning and operating trials. One area of concern was the long-term integrity of mechanical connections on the machine, which include a number of bolted and flanged connections of various sizes and functions. Operational experience shows that mechanical connections are prone to both corrosion and loosening, caused primarily by vibration.
The purpose of this document is to outline guidance to apply good design practice for threaded connections, specifically with respect to material selection and assembly techniques. The standard applications considered in this document are structural connections, hydraulic flanges, retaining fasteners, jacking screws and hydraulic fittings.
Bolt Torque Calculator
April 2019
One area of concern at APL was the long-term integrity of mechanical connections on Oyster 800, a device which included a number of bolted and flanged connections of various sizes and functions. Operational experience shows that mechanical connections are prone to both corrosion and loosening, caused primarily by vibration.
This document was produced by APL in 2014 to provide a single, standardised point of reference for bolted connection design calculations for the Oyster 800 device. The spreadsheet included data on a large variety of fastener types, materials, locking methods, lubricants, and tightening methodologies.
Outputs from the spreadsheet include required fastener tension, % yield, force range expected from tightening method, preload, bearing stress, and an indication if the design satisfies design criteria.
This document was informed by experience gained through training, design activities, and practical implementation of bolted designs during the offshore maintenance campaigns on Oyster 800 in the summers of 2013 and 2014.
The data for fasteners, frictional coefficients and tightening factors was obtained from manufacturer data, standards, and experiment, and was valid as of summer 2014. It is up to the user to be satisfied on the current accuracy of the data and standards referenced.
The spreadsheet is intended to be used as a design aid, and no liability is assumed by WES for the use of this calculation sheet.