Special Report: Real-time information optimizes condition-based maintenance

May 22, 2006
Top performers (pacesetters) in the refining industry are using real-time equipment data to prioritize and optimize their maintenance resources.

Randy Kondor, Matrikon Inc., Edmonton

Top performers (pacesetters) in the refining industry are using real-time equipment data to prioritize and optimize their maintenance resources.

The process is straightforward-real-time data determine equipment health but only inform the computerized maintenance management system (CMMS) when maintenance is actually necessary. From there, the CMMS automatically produces the work order and uses the workflow that is already familiar to all maintenance personnel.

Pacesetters take two steps to achieve this goal. First, they acquire and store real-time process data from their automation system, either a supervisory control and data acquisition system or a distributed control system. This automated data acquisition gives pacesetters consistent access to timely and accurate measurements.

Secondly, they establish a condition-based maintenance (CBM) system that uses the stored data to determine equipment health. The CBM system makes intelligent decisions regarding work orders, thus enabling maintenance workers to focus on activities that have the most impact on operations.

Automated data acquisition

Pacesetters use existing automation systems to collect real-time equipment data at regular intervals using standards-based software.

OPC is the de facto communication standard for acquiring real-time data and is based on industry-tested Microsoft technology. In fact, every automation system that can communicate with the outside world can be retrofitted with OPC.

Available since 1996, OPC has spread to every industry.

Software applications use OPC to acquire real-time data and to make the archived information available to external systems. By automating the data collection, pacesetters eliminate the slow and error-prone manual labor that is typically required; for example, reading metered data from one computerized system or measuring equipment health with standalone instruments, recording it, and then entering it into a computerized maintenance system.

Pacesetters can consequently access the latest data on demand. They are also comforted by the fact that the data were recorded exactly as they were in the original automation system, including all values and time stamps. The precision and frequency of data acquisition enables organizations to use a true CBM program.

CBM uses real-time data

Once pacesetters capture real-time data, they implement a CBM program that enables them to optimize preventive maintenance efforts. The problem with traditional preventive maintenance is that all maintenance is scheduled on a periodic, regular basis regardless of equipment usage and operating condition. Equipment that is rarely used therefore receives the same amount of maintenance as frequently used equipment.

In addition, equipment that is used under harsh operating conditions is maintained as little as equipment that operates under ideal conditions. Some equipment is therefore maintained too often, thereby increasing maintenance costs unnecessarily, and other equipment suffers undue wear and tear while waiting for its scheduled maintenance.

This situation results in high repair costs that could have been avoided and, more importantly, ignores required maintenance activities that should be performed immediately. CBM helps with the prevention of unscheduled downtime because maintenance can handle problems proactively, before they grow into more serious issues.

Pacesetters understand the key factors that influence equipment performance and, therefore, condition. Because these factors are measurable, software applications can automatically monitor them and alert maintenance only when the equipment condition demands action.

Getting started with CBM

The most obvious factor to measure is equipment runtime (or running) hours. The CBM system can determine when the equipment is running and automatically count the runtime hours by acquiring the real-time data. Once the count reaches the manufacturer-specified limits, the CBM system can immediately alert the CMMS.

Other factors such as vibration analysis, temperature readings, and fluctuating flow rates help augment the CBM system. In other words, if the operating conditions are especially harsh, these factors will alert maintenance long before the runtime hours are exceeded, which will prevent premature damage.

Additionally, equipment that operates under optimal conditions may be able to operate long past its prescribed runtime hours, thus saving undue maintenance. Although these factors provide an excellent basis for CBM, software applications can use measurement from the process itself to determine equipment health.

Process alarms

The CBM system can incorporate alarms from the automation system to help identify malfunctioning instruments. Initially, the alarms slowly stream out of the automation system. It takes keen observation (and considerable time) for the operators to recognize the pattern of repeating alarms, especially if they span multiple shifts.

By capturing these alarms, the CBM system can quickly determine if the number of alarms for a specific instrument has exceeded a preset limit during a set time period. The CBM system can then inform the CMMS that the instrument should be inspected, automatically generating a work order.

This enables maintenance to recalibrate or repair the instrument even before operations is fully aware of the problem, therefore eliminating potential hazardous operating conditions and urgency associated with unscheduled shutdowns.

Complex equipment benefits

The CBM system can associate multiple metered equipment values to calculate an overall equipment health factor. For instance, a feed-water pump might require the lube-oil pressure to be at a different reading when it idles than when it is at full capacity. Consequently, placing high and low alarm points on the lube-oil pressure may not be accurate at different operating conditions.

Process analysis software determines the relationship between the various metered equipment values and their interactions. A normal relationship between the values indicates a good health factor. An abnormal relationship indicates a poor health factor and is a warning that maintenance is required.

Pacesetters use CBM systems to monitor the equipment health factors in real time and to inform the CMMS when an abnormal relationship is detected, such as when the feed-water pump operates at 25% capacity but the lube-oil pressure is still at full capacity. This issue is typically overlooked by busy operators and frequently causes unscheduled downtime, production losses, or both.

Maintaining control loops

The CBM approach to automation assets treats control loops as though they are physical assets, which enables maintenance to trigger instrumentation work orders based on the health of the control loop. Industry studies show that although 80% of control loops could use some maintenance, only 20% are critical enough to affect process operations significantly and demand immediate maintenance.

Unfortunately, most organizations take a reactive approach and the control loops are left to perform inefficiently or are turned to manual operation, which defeats the purpose of the automation system altogether.

By implementing continuous health monitoring of critical control loops, pacesetters significantly reduce the workload of instrumentation personnel. The CBM system notifies the CMMS to focus instrumentation’s efforts on the worst instruments that have the greatest impact. This maximizes production while simultaneously reducing maintenance workload and costs.

Prioritizing activities

Pacesetters use two steps to optimize maintenance efforts. First, they automate their real-time data acquisition and storage using standards-based software applications (Fig. 1). Second, they implement CBM systems that assess equipment health based on timely and accurate information (Fig. 2).

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This enables pacesetters to prioritize their maintenance efforts by moving human and capital resources away from well-functioning equipment to areas that urgently require early attention.

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Although it might seem that pacesetters’ accomplishments are currently out of reach, most corporations are surprised to find out that these steps are easier to complete than initially perceived. With commercial off-the-shelf software and standards-based applications, such tasks can be completed economically and provide exceptional add-on value to the CMMS installations.

The author

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Randy Kondor ([email protected]) is vice-president of marketing at Matrikon Inc., Edmonton. He began his career with Matrikon in the early 1990s as product manager of the drivers division. Kondor holds a BSc Eng. CompE from the University of Alberta. He is a member of ISA.