For years, operating companies have outfitted their assets with monitoring equipment to ensure safety and simplify maintenance and repair. As assets age, this equipment becomes outdated and is more prone to failure. In evaluating monitoring equipment efficiency deployed on mature fields, many operators are finding it necessary to replace aging equipment.

Protecting investments

There are many considerations when choosing machinery protection and condition monitoring equipment. Foremost among these are safety, environmental compliance, production requirements, costs, and criticality to the process.

There are three primary options to choose from, depending on specific application needs.

The first option is to collect data using a handheld collection device. This approach focuses on maximizing equipment reliability and lowering maintenance expenses by collecting equipment data on a set schedule using a portable data collector. The gathered data is analyzed using software developed specifically for condition-monitoring solutions.

This approach is ideal for a small system, is inexpensive with a small upfront investment and low maintenance costs, and can be migrated easily to an integrated surveillance solution as the program grows. One of the primary drawbacks of this approach is that the data updates are less frequent and data collection is time consuming. There also is a risk of human error. Another option is to use protection monitoring systems. The safety and financial risks associated with many assets require that they be monitored continuously in real time by systems that can provide an exceptional level of performance and reliability. If a problem occurs, this type of software-based system can shut down the system immediately, helping protect the asset from further damage and mitigate damage to other connected equipment. This approach to monitoring is advantageous because the software shuts down a machine if limits are exceeded. It provides detailed information on the machine condition, which allows for precise prediction of the approximate failure time. And because it is software driven, the system can deliver data immediately for analysis. These systems call for a higher upfront investment than manual and surveillance monitoring because of their hardware and software requirements, and they require additional IT and engineering resources for system operation.

Marathon Oil Corp. has been producing oil and gas in the UK for more than 25 years. Among the company’s operated North Sea assets are the Brae Alpha, Brae Bravo, and East Brae platforms. (Images courtesy of Rockwell Automation)

A third option is an online surveillance system. An online surveillance system allows data gathering such that integration with other key production process information from the control system can be accomplished easily. Surveillance condition monitoring is ideal for data collection that must be automated due to safety concerns, limited machine access, insufficient resources, and experience. An online surveillance system is the best choice when failures can occur frequently or suddenly. This type of system also allows for rapid machinery shutdown when limits are exceeded. And continuous data collection allows problems to be anticipated by alerting the operator that a piece of equipment is experiencing problems. A condition monitoring software application serves as the core of an online surveillance system. The application can be run from handheld devices if desired to provide added flexibility.

This system works via permanently installed sensors that sample data periodically without operator oversight. As with protection monitoring systems, an online surveillance system provides detailed machine condition information so failure time can be pinpointed. The system also allows

the operator to concentrate on problem-solving instead of manual data collection. It stores and displays data immediately for analysis purposes, enables data acquisition to be scheduled frequently for earlier fault detection, and permits quick preliminary diagnosis of machines in alarm without having to manually access the machine with a portable data collector. It also reduces human exposure to dangerous situations.

The downside is that an online surveillance system costs more up front than manual monitoring because of the hardware and software requirements and requires additional IT and engineering resources to operate the system.

Identifying the problem

Marathon Oil Corp. has been producing oil and gas in the UK for more than 25 years. Among the company’s operated North Sea assets are the Brae Alpha, Brae Bravo, and East Brae platforms.

The Marathon East Brae production platform is a hub for the company’s North Sea gas production. Low-pressure operation projects are helping to maximize gas recovery and maintain high gas deliverability rates into the UK market. Keeping the platform running at optimum capacity in the harsh North Sea environment is a constant challenge. So when Marathon began to experience technical challenges with the aging vibration monitoring equipment on the platform, Paul Stewart, electrical and instrument facilities engineer at Marathon, decided it was time to look at a strategy to upgrade the system.

All of the main processing equipment on the East Brae platform is outfitted with a system that monitors and reports on the condition of the equipment based on frequency output. The system triggers an alarm if there is a problem and can shut down a piece of equipment if necessary. The problem Marathon faced was that the vibration monitoring equipment was old and had begun to require significant maintenance.

“The system was aging and rapidly becoming obsolete,” Stewart said. “Reactive maintenance requirements were increasing. We could no longer buy certain spares for the existing system, and repairing faulty items was becoming increasingly difficult due to obsolescence of electronic components.”

Marathon decided it needed an upgraded system. The company wanted a cost-effective solution that would be compatible with existing vibration probes on the machinery. If new probes were required, the cost of the upgrade and the amount of time that the equipment was out of service would be increased significantly. It was also critical that the new system communicate with the platform’s distributed control system (DCS) so the system could be managed from the central control room.

“It was important that we selected a system that would interface with all the existing systems, cope with the legacy communication standards, and be able to work with any future control system upgrades,” Stewart said.

Solution and implementation

Marathon chose Rockwell Automation because of the benefits of the company’s Integrated Architecture approach. “We could select the various components to build a system to meet our specific needs, knowing that all the components were compatible with each other and with our existing vibration probes,” Stewart said. The modular approach also allowed the work to follow a phased approach, which minimized disruption to operations.

The first phase of the work was to replace the vibration systems on the three gas export compressors. Work on the first compressor was completed as scheduled within two weeks and was performed by two engineers from the Rockwell Automation Oil and Gas Specialist team, who also designed and documented the project.

To meet Marathon’s requirements, the team installed modules from the Allen-Bradley XM Series of intelligent I/O modules.

To meet Marathon’s requirements, the team installed modules from the Allen-Bradley XM Series of intelligent I/O modules. These modules process in real time the critical parameters used to assess the health of rotating machinery onboard the platform and predict the future health of the machines.

The monitoring system was connected to Rockwell’s Allen-Bradley PanelView Plus electronic operator interface. Programmed with RSView Studio Machine Edition, the interface monitors and displays information graphically, allowing operators to view the status of their machinery more easily. The team also installed an Allen-Bradley CompactLogix PAC to provide effective communication interface to the DCS.

“The benefits were immediately apparent,” Stewart said. “We now have a much more reliable vibration monitoring system that has resulted in improved reliability and availability of the compressor.”

The controls all fit into the existing panels, which avoided additional work, reduced costs, and minimized installation time. With the PanelView Plus system, Rock-well Automation also was able to replicate the functionality and layout of the original system displays to simplify use. The new system provides additional maintenance displays, with diagnostic indications to assist maintenance personnel with fault finding.

Comments