Analyzing wireless machine condition monitoring for offshore applications

Marty Herzog

July 14, 2014

The SKF wireless machine condition sensor collects data on three key machine conditions: temperature; overall machine condition; and rolling element bearing and has ATEX Zone 0 certification.

There has been significant interest in wireless solutions for condition monitoring in recent years, including discussion on whether wireless technologies are a viable strategy for offshore operations in exploration and production. The word “strategy” however, may be misused. While the new technology does have benefits, it should support the existing maintenance strategy and be used as a tactic in the fulfillment of a predictive or proactive maintenance program.

Properly applied, the operational and technical benefits of wireless condition monitoring provides end-users with:

Thus, these benefits suggest the usage of wireless systems will likely increase in the coming years for offshore exploration and production applications.

Wireless condition monitoring developments

Fifteen years ago, interest emerged to monitor the condition of a moving asset, such as the machining head of a metalworking machine or the axle bearings of a locomotive. Soon after, the first SKF wireless system was developed and the knowledge of how to use wireless technology in condition monitoring was enhanced. However, lack of industry standards for communications protocol and the challenges of packaging and battery life limited its applicability.

The architecture of these first systems was limited to replacement of the wired Ethernet “backbone” of the system. The field-mounted signal acquisition system still required sensors to be wired from machine to sensors. The system manages the con- version of data to digital form and then transmits it to the host PC wirelessly. This works well and there are thousands of channels of vibration data being managed in this way. However, for the oil and gas industry-specific requirements for installation in areas with hazardous gaseous environments prohibited most applications due to the requirement for packaging of the system in expensive explosion-proof enclosures.

Meanwhile, the promise of ubiquitous, low-cost process measurement sensors operating over a wide area has fuelled massive investments by wireless technology and process measurement companies. Widespread market adoption did not initially occur due to technical issues such as proprietary protocols and installation cost barriers. With recent advances in network- ing, radios, processors, sensors, and power sources it is now possible to overcome these obstacles with process measurement devices. And, with the emergence of standard wireless protocols, increasingly advanced systems have been developed to offer effective wireless systems in the process measurement domain.

Compared to process measurements (scalar, overall values), vibration monitoring (dynamic data arrays) places unique demands on wireless sensors, networks and associated components: high bandwidth, good dynamic range, low noise, higher- level processing capabilities and the ability to capture data at the right time. When operating as self-contained battery powered units, the further challenge of practical service life remained. Morever, physically mounting the sensor device directly onto a machine necessitated coping with the aggressive conditions found in the industrial environment, such as exposure to water, extreme temperatures, electrical interference, hazardous area classifications, obstructions, and physical location/distance.

Recent convergence of protocol standards coupled with new wireless condition monitoring technology developments have addressed these challenges, resulting in a viable solution. Next it is necesary to consider deployment options to gain wide acceptance.

Comparing methodologies

Condition monitoring of rotating equipment is a common throughout the oil and gas industry, with the objective to detect, analyze and diagnose machinery faults. Critical machines (tur- bines, compressors, large motors) are normally equipped with on-line condition monitoring and protection systems. Balance- of-plant equipment (motors, pumps, fans) generally are not. Yet this machine category represents well over half of the population and consumes a significant percentage of a maintenance budget. Such machines are normally monitored manually with portable data collectors because it has been impractical or uneconomical to install a permanently wired system. However, the situation has changed with the advent of a new breed of wireless condition monitoring systems that bridges the gap between the cost wired systems and inefficiencies of portable systems.

Integrating condition monitoring and process control data

Another important development has been the ability to share data with process control systems. Changes in vibration levels may be due to a change in operating conditions, and without that knowledge an incorrect diagnosis could be costly in terms of down time and lost production output.

In the past, passing data such as temperature, flow and load, between the condition monitoring system and the process control system was time-consuming and complex, involving dedicated serial communication links and cumbersome data protocol programming. Today, the emergence of OPC (OLE for Process Control) has reduced this task to a few “click and drag” operations between networked computers. This has had a significant impact on the analyst’s ability to correlate vibration changes with process conditions. All of SKF’s condition monitoring software platforms can utilize OPC.

Once data is collected, the WirelessHART gateway communicates with SKF’s wireless sensor device manager software.

A safe solution for hazardous environments

The potential to improve efficiency through condition monitoring has driven the development of a new wireless solution. The SKF wireless machine condition sensor monitors machine components in locations that are difficult to access. It achieved ATEX Zone 0 certification, which means that it can be used in hazardous environments.

The SKF wireless machine condition sensor collects data on three key machine conditions: temperature (indicative of lubrication issues, increased friction, rubbing, etc.); overall machine condition (vibrations caused by misalignment, imbalance, mechanical looseness, etc.); and rolling element bearing condition (allows damage detection and diagnosis of source as ball / roller, cage, inner or outer raceway).

A rough estimate for installation cost of online sensors in onshore applications can be as high as 15 times the cost of the accelerometer. For offshore installations, it can be higher than 20 to 30 times the cost of the accelerometer. The use of a wire- less device could equate to an approximate saving of around $1500 per measurement point.

With this new technology, users can benefit from an improved maintenance program, reduced maintenance costs, reduced installation costs and enhanced employee and machine safety. The sensor also offers compatibility with the SKF @ptitude monitoring suite, a comprehensive software suite that integrates data from a wide range of SKF portable and online data acquisition devices.

SKF wireless machine condition sensors communicate with each other, and with a wireless gateway, creating a mesh net- work. This type of network and communication protocol is ideal for monitoring rotating machinery because it can function in areas where traditional WiFi communications are not present.

Communicating via a mesh network

Communication capabilities of the SKF device include relaying data from one node to another, relaying data back to the gateway, and receiving automated commands from the wireless sensor device manager software that initiates the measurement and processing circuits to take data and transmit it back over the network. If a node is unable to receive signals directly from the WirelessHART gateway, it will instead send and receive its data through a nearby node that can pass the data to and from the gate- way – ultimately creating the mesh network.

Once data is collected, the WirelessHART gateway communicates with SKF’s wireless sensor device manager software. Data can then be automatically exported into SKF’s comprehensive diagnostic and analytic software package, where a maintenance engineer can analyze the data and determine a course of action. In parallel, the WirelessHART gateway can also send applicable data directly to the process control system for visualization and trending by operators.

Conclusion

Wireless systems will change the way we approach machine condition parameter data collection. Wireless sensors will result in much more data being acquired and, therefore, a challenge of how to analyze and manage additional data. Data reduction techniques and decision support systems have been developed to cope with this issue, thus preserving the benefit of new wireless technologies and ensuring it is supportive of maintenance strategy refinements.

Ease of deployment of wireless systems connected to process control systems will be driven by users, not by suppliers of technology solutions, and process monitoring will become more closely related to condition monitoring. The end result will be tighter integration of operating parameters and maintenance strategies where the two are adaptive to changing conditions. Eventually fully-integrated embedded sensors, using standard industrial protocols to share data, will be offered by OEMs, which will further extend the benefit of lower installation costs.

The stage has passed when early adopters installed simple systems on an experimental basis. For wireless condition monitoring, this is the end of the beginning. What engineers have been looking for is a system that is simple to install and configure, which improves on existing knowledge and allows a systemic improvement in machine reliability over a large population of machines. Data can even be analyzed remotely by maintenance engineers and the results and recommendations made available anywhere in the world where there is an internet connection.

Marty Herzog has 30 years of experience with SKF in the fields of bearing application, rotating machinery technology, condition monitoring and reliability engineering. He is currently responsible for business development and marketing for the SKF Traditional Energy Business Unit and works closely with key OEMs and end users in this sector.