Offshore challenges
Published: 05 September, 2014
Industry speakers at National Instruments’ 2014 Offshore Measurement Summit, hosted at Robert Gordon University, Aberdeen, discussed many challenges in the industry. ODEE reports.
The keynote presentation set the scene for the event, outlining the importance of measurements in offshore applications. The summit focused around three main application areas:
• Deployed monitoring systems for automated measurements and condition monitoring
• Lab-based measurement systems for prototyping and test
• Embedded control systems for improving efficiency and solving complex challenges
For the offshore engineer, everything is more challenging, from weather impacting access to assets, logistical planning of jack-up barge schedules, corrosion, and the constant pressure to reduce the cost of extraction and increase profitability. Specifically, in the oil and gas industry, assets are aging; many were designed in the 70s and 80s and have exceeded their design life, compounding the challenge further. In complete contrast however, the offshore wind industry is heavily focused on commissioning new assets. In both cases, failures are a serious concern, with multiple sources quoting the downtime cost of a significant oil and gas asset costing greater than £350,000 ($600,000) a day. According to ‘A Guide to UK Offshore Wind Operations and Maintenance’ by Scottish Enterprise and The Crown Estate, by 2025, offshore wind operations and maintenance are expected to reach £2bn per annum.
Set against this backdrop, it is no surprise that, wherever you look offshore, measurements are prolific, and their demand and complexity are increasing in order to address these challenges. However, there is a heavy reliance on manual measurements using dials and gauges. This approach has significant limitations, the main of which is the scalability when you increase the number and frequency of measurements, and they are also prone to human error. Some would argue that chart recorders go some way to automating measurements, however mixed signal data recording, high channel count and high speed dynamic data from remote hazardous locations are not possible.
One of the main driving reasons behind the more traditional approach to instrumentation is the requirement for certification, including DNV for use in marine environments and ATEX for explosive atmospheres. This means that it can be necessary to use application specific components such as an intrinsically safe laptop that meets these requirements, but unfortunately carries a heavy price tag and offers limited functionality and flexibility. Alternatively, a completely custom solution can be developed from the ground up, however now the challenge is the high engineering development costs and time to market. Where requirements are less stringent, the offshore industry, along with many other regulated and certified industries such as energy, military and medical, are increasingly turning to customisable off-the-shelf tools in order to meet bespoke requirements, while maintaining the short time to market offered by a turnkey product.
At the summit, the area that attracted the most interest was condition monitoring and high-fidelity, deployed monitoring systems. Broadly speaking there are three approaches to maintenance:
Preventative or Scheduled Maintenance – Essentially this is being proactive, for example servicing your car every 15,000 miles or 12 months. For the offshore industry, this may include things like changing the grease in a bearing.
Run to Failure – This is a conscious decision to keep running an asset irrespective of its performance until it no longer functions. This is a perfectly valid approach if the asset is of low value or minimal impact, and ideally there is a ready supply of drop-in replacements.
Predictive Maintenance – This is the most advanced approach to maintenance and involves understanding the current condition of the asset and predicting unplanned outages.
Predictive maintenance is appealing is due to the impact it can have on increasing overall equipment effectiveness. By increasing uptime, you are producing more, and higher yield means higher revenue. It is also not about the asset being on or off, but making sure they are running efficiently and at optimal operating conditions. It is also possible to reduce operations and maintenance costs by not undertaking repairs when they are not necessary, saving money on parts and labour. Additional cost savings can be realised by optimising the activities of subject matter experts. These specialists can use their time more efficiently and focus more on understanding the condition of their assets rather than making manual rounds or undertaking maintenance tasks. Finally there are significant benefits in reducing risk. Minimising the exposure of workers to hazardous environments reduces the chance of accidents. In addition, by monitoring the condition of assets a potential catastrophic failure may be spotted and averted.
Developing a condition monitoring solution for predictive maintenance requires more than monitoring a few RMS vibration levels. In order to fully understand the current and historical performance of an asset, it is important to define a set of measurements that will enable a specialist to spot trends and changes in asset performance. One example that was cited during the keynote presentation is an application developed by National Oilwell Varco for valve leakage detection in mud pumps.
Valve leaks in piston pumps are often discovered at a late stage when the leaks are so severe that they induce large discharge pressure fluctuations and create washout damages. When a severe leak is detected, it is localised manually by listening to the fluid modules while the pump is running, but it is difficult to uniquely localise the leak and distinguish between a suction valve leak and a discharge valve leak. Human exposure to hazards is the main disadvantage of manual detection, verification and localisation. Mud pumps convert large amounts of power and often output high pressures up to 350 bar. Additional equipment in pump rooms also generates high acoustic noise pressure levels that can exceed 100 dBA and cause health and hearing damage if correct protection is not used. Valve leaks often develop quickly, so manual detection gives very little time to prepare for exchanging the defective valves after the leak is detected. If the leak source is uncertain, searching for the defective valves can be costly and time-consuming.
National Oilwell Varco developed a stand-alone module to add to the existing mud pump control system. Slightly simplified, it consists of: accelerometers (one per valve block), a proximity sensor to pick up pump speed and phase, a discharge pressure sensor, an embedded monitoring system (National Instruments CompactRIO with NI 9234 acquisition modules for acquiring high frequency vibration data), signal processing software and alarm logic implemented using NI (National Instruments) LabVIEW software running on the CompactRIO monitoring system. Based on field experience of the leak detection system, the new leak detection method offers many advantages over current practices:
• High sensitivity for early leak detection and localisation
• Remote, continuous and computer-based pump monitoring
• Increased safety through reduced human exposure to hazardous environments
• Reduced maintenance time and cost because leaky valves are localised before valve maintenance begins
As the number of assets being monitored for predictive maintenance increases from single figures, to 100’s or 1000’s, you could potentially be managing 10,000’s sensors, with the potential to deliver significant business benefits. However, implementing an enterprise-level condition monitoring system presents new challenges to overcome. These challenges include transferring, processing and storing large volumes of acquired data, managing the health of measurement nodes, deploying new firmware, and, finally, extracting actionable information from the data to plan maintenance and reduce failures.
When this topic was discussed at the summit, Duke Energy, the largest power generation holding company in the US with approximately 80 plants, was raised as an example of how to implement such a system. They faced many similar challenges to those of the offshore industry, where assets are ageing, bringing an increased risk of failure. The cost and impact of downtime is significant, and existing specialists are spread too thin and cannot analyse all critical equipment. In fact, specialists spent 80% of their time on data collection, with only 20% on analytics. To overcome these challenges, Duke Energy began a project called SmartGen, aiming to:
• Implement continuous automated monitoring
• Enable the workforce to focus 80% of their time on high-value analytics
• Deliver a system of fault diagnostics through a database
• Create a risk advisor for failure predictions
• Focus on data visualisation and integrating information together in a single location
In order to deliver and implement the measurement nodes and software infrastructure, Duke Energy partnered with National Instruments to deliver their SmartGen project. NI developed InsightCM Enterprise, a ready-to-run integrated hardware and software solution for online condition monitoring, to gain insight into operations and understand the health of rotating machinery. The suite acquires and analyses measurements, generates alarms, allows users to visualise and manage data and results, and simplifies remote management for large numbers of monitoring systems.
The system at Duke Energy is already enabling predictive maintenance specialists to receive alarms with lower thresholds than would be raised at the plant level, in order to identify changes from normal operating conditions that could result in a future failure.
Beyond condition monitoring and predictive maintenance, the summit saw many interesting applications of customised off-the-shelf hardware and software solutions. These included the development of custom control systems for subsea drilling, DNV approval of a customised off-the-shelf control system for 70-ton gripper arms used during the installation of monopiles for offshore wind turbines, and developing novel inspection tools used for internal pipeline and subsea ROV deployment. The overriding message was that the approach of using customised off-the-shelf tools to develop and deploy measurement systems offers significant advantages in terms of the power and flexibility of the tools available, along with significant reductions in the time taken to develop and commission a system.
Find out more and download the presentations from the summit at uk.ni.com/events/offshore
