Using Natural Frequency Response Monitoring (NFRM) to Reduce Inspection Costs for Ageing North Sea Platforms
EVENT: Offshore Europe
1 Sep 2017
The offshore industry is faced with a tough financial market, requiring innovative solutions in order to reduce costs and increase operational efficiency. This includes solutions to ensure that maintaining the structural integrity of North Sea platforms is achieved as cost-effectively as possible without increasing risk or compromising safety.
Regular general visual inspection of fixed platforms for structural damage, by ROV fly-by, is a commonly used technique. There are two main concerns with this technique. Firstly, these inspections are costly to perform and secondly, damage may occur shortly after a scheduled inspection and go undetected until the next inspection. Both of these concerns are addressed through real-time structural monitoring. This uses automation of frequency detection and signal processing in order to avoid equipment and personnel mobilisations and provide immediate notification of potential damage. Inspections can then be conducted only when required and targeted at a specific area of interest, resulting in a significant reduction in overall integrity management costs. A platform monitoring system can be used on both manned and unmanned platforms and can be installed during construction or retro-fitted to an older installation.
A platform monitoring system, also known as Natural Frequency Response Monitoring (NFRM), works by measuring the natural frequency response of the platform under wave loading. The structural failure of a member will alter the natural frequency of the platform and the monitoring system will detect the change and alert the Operator. Prior to implementing this technique a screening study of the change in platform response following damage to critical members is necessary in order to ensure that incidents will be reliably detected
This paper presents a case study of a NFRM screening study prior to installation of the system on a North Sea platform. The structural analysis used to confirm the suitability of the NFRM system and the method for specifying the monitoring system itself are described. An indicative cost of procuring and installing the NFRM system is also presented.
Authors
Phil Ward
Technical Manager, UK
About
Phil has over 15’ years of offshore energy experience and is technical manager of 2H’s Edinburgh office. In this role, he is responsible for the growth of 2H’s business in the Greater Edinburgh and Central Belt areas of Scotland, particularly in the offshore wind sector.
Phil started his career with Jee Ltd. before joining 2H in Aberdeen in 2011. During his time at 2H, Phil has held numerous roles from engineer to director. Phil led 2H’s presence in Aberdeen for five years before relocating to 2H's Houston office in 2019 with the goal of cross-populating experience with shallow and deepwater systems.
Phil has project management and technical leadership experience on a variety of projects from concept through to life extension, including the use of field data to verify subsea systems for continued use, subsea wellhead fatigue mitigations, and design optimisation of platform wells and deepwater production risers.
Phil holds a master’s degree in Engineering from Cambridge University, and is a Chartered Engineer and Member of the Institute of Mechanical Engineers.
Elaine Whiteley
Principal Engineer, UK
About
Elaine is a principal engineer in 2H’s Edinburgh office. She graduated from Heriot Watt University with a Masters degree in Structural Engineering and has 14 years’ experience in the offshore energy industry. She has been a Chartered Engineer and Member of the Institute of Civil Engineers since 2017. Elaine began her career with 2H in Aberdeen before relocating to Houston in 2019 to broaden her experience with various riser systems. She has experience across the industry, including shallow water platform conductors, steel catenary risers (SCRs), top tensioned risers (TTRs), seawater intake risers (SWIRs), fixed offshore wind, and local component FEA. She has worked across all phases of offshore projects from concept development through to detailed engineering, delivery, operation, integrity management and life extension and also has hands-on offshore experience.
B. Taylor
Pulse Structural Monitoring