Operator Involvement Improves the Performance of a Condition Monitoring Programme

Transcription

1 Operator Involvement Improves the Performance of a Condition Monitoring Programme Henry Mikkonen Oy SKF Ab, P.O.Box 80, FI Muurame, Finland GSM: henry.mikkonen@skf.com Sulo Lahdelma Mechatronics and Machine Diagnostics Laboratory, Department of Mechanical Engineering, P.O.Box 4200, FI University of Oulu, Finland Phone: sulo.lahdelma@oulu.fi Abstract Industrial condition monitoring is typically performed by experts working in a maintenance organisation. Especially in the process industry the roles of the maintenance personnel and operators are highly separated, which in many cases lead to communication discrepancies that can impair the efficiency of the condition monitoring programme. Concepts such as TPM and its close relative LEAN emphasise the need for operator involvement in maintenance (1, 2). Regardless of the efforts, the concepts of operator maintenance or Autonomous Maintenance (AM) have not become widely accepted in the process industry. By combining operators daily machinery checks and condition monitoring, it is possible to create a natural communication channel between operators and condition monitoring experts for improved efficiency. The approach known as Operator Driven Reliability (ODR) utilises modern portable technology to enable operators to check and record machinery data as an integral part of their daily operator rounds (3). This includes visual machinery checks but also some relatively simple vibration and temperature measurements. The data are collected and stored in a database that can be accessed both by operators and the maintenance personnel. It is important to understand that technology is just an enabler for creating systematic and effective work processes. Therefore, it is vital that operator checks are carefully planned in order to support the effectiveness of production and maintenance. 1. Introduction The traditionally separated roles and tasks of operators and maintenance technicians have remained until today even though the need for closer co-operation between the two groups is evident. In spite of efforts, the concepts of so-called operator maintenance have not become widely accepted in heavy process industry. This often means that communication between the two professions is not adequate and therefore the overall performance and operating results are not satisfactory.

2 Operator Driven Reliability is a concept that is designed to overcome these challenges. The targets of the implementation have to be derived from the business goals of the company, and the whole concept has to be closely aligned with maintenance and especially predictive maintenance tasks in order to ensure that all parties are aiming at the same direction. A successful ODR project is not just about implementing technology. It is a process of creating and implementing new operating methods for the plant personnel. The project begins with defining a common understanding of what the potential risks in implementation are and how they can be mitigated. It is also essential to ensure the commitment of top and middle management and to agree key performance indicators (KPI) as well as feedback and learning processes. This paper describes the concept and implementation process of Operator Driven Reliability. It gives an overview of why and how the concept has been taken into use in industry and what the results have been as compared with the expectations. It also discusses how daily practices have changed and how operators and the maintenance personnel have perceived the new ways of working. Some ideas for future development will also be highlighted. 2. ODR Concept Operator Driven Reliability can be defined as a system of involving the equipment operators in improving reliability by having them identify potential equipment problems and failures at an early stage. The operator fixes them if they are minor and issues a repair request if they are major (4). Production operators in process industries often work close to the machinery and are the first ones to notice if something is about to go wrong. However, it may be that their observations are not reported or effectively acted upon. The maintenance personnel, on the other hand, typically include experts who specialise in diagnosing exceptional conditions, and the prediction of machine life time is based on recorded data. But instead of analyzing a problem to find the root cause, they may have to spend time making basic measurements instead. This may result in more downtime and higher maintenance costs as compared with a cross-functional approach. There are several natural reasons why traditional TPM-based operator maintenance or Autonomous Maintenance approaches have not proved successful in heavy industries. A constantly running process requires full attention from operators and allows limited time for the operators to carry out pre-planned maintenance tasks during operation. Machinery shutdowns are rare and during the shutdowns operators often have planned, process-related duties. The complexity and vast number of different process equipment lead to a large number of different maintenance tasks that often require special skills and tools. Reporting systems and structures do not usually support cross-functional communication between departments. 2

3 Operator Driven Reliability is an efficient concept that involves operators in the maintenance processes. It is a plant-wide initiative that combines people, processes and technology, but it is more a matter of how to organize the work than of technology. Similarly, it is more about making daily operator routines of checking assets more systematic instead of adding new maintenance tasks for them. For example, openness, cross-functional cooperation, communication and systematization are the pillars in ODR. This requires that the management is committed to the process right from the beginning, fostering a spirit of teamwork instead of territory protection. 2.1 Examples of operator checks ODR utilises modern mobile technology to record and store data from daily operator rounds. The data include records of basic observations, such as oil levels, asset cleanliness, readings of set or measured values etc. and can involve basic measurements of temperature and vibration levels. All the checks and measurements are carefully planned based on asset criticality. The checks are stored in database and the tasks can be downloaded to a portable handset that operators can take with them when performing operator rounds. Observations and measurements are stored and after the round uploaded to the database. Some examples of typical data are shown in Table 1 (5). Table 1. Typical operator checks that can be included in ODR routes. Data Visual checks Readings Measurements Other observations Examples Cleanliness of assets Level of oil, coolant, etc. Colour of oil Operation of belt drive Readings of manual read meters Position of manual valves Vibration velocity Enveloped acceleration Temperature Abnormal noise Leaks, smells, etc. In Figure 1, there are two examples of the screenshots of typical check points for lubrication oil. The inspections are configured in the database and downloaded to the handset. 3

4 Figure1. Examples of the screenshots of an oil level check point. The task of the operator during his field round is to choose from the pre-set alternatives the current status. The status data and time stamp of the inspection will be stored in the database and this information can even be used for trending the oil level or changes in the appearance of the oil. Figure 2 shows an example of the trend plot from the software that is based on a simple check. OK Sliding Flapping Missing Loose safety guard Figure 2. An example of a trend plot of a simple check of a v-belt drive. In this case operators record as part of their field route the status of a belt drive. From the trend plot it is easy to see when checks have been performed and if there is something to be done to prevent machinery failure. The trend is also very useful in detecting repetitive cases Improved communication One of the main objectives of Operator Driven Reliability is to improve communication between operators and maintenance. The fundamental idea is to provide operators with 4

5 corresponding hardware tools and software that condition monitoring specialists are familiar with. The results of checks and measurements are stored in the same database that the CM specialists are using and the same but a limited version of the user interface is available to operators, too. This creates a natural channel of communication between the two groups of people. Along with the highly improved quality of the data from operator rounds, the operators will also learn to speak the same language as the maintenance persons. The systems that they are using will allow operators to quantify their observations at a much higher level than before. Within a short period of time the operators will become familiar with the nominal vibration levels, will develop an idea of what the typical temperature is and learn to understand what kind of changes in behaviour are normal and what are not. On the basis of more quantitative observations, operators can create work notifications of much higher information content than before. When receiving a work notification, maintenance and condition monitoring specialists have the possibility to review operators measurements and observations from the database and to access a condition monitoring database directly. 3. Characteristics of operation Table 2 contains some characteristics of different measurement methodologies that are used in condition-based maintenance. On-line condition monitoring Operator measurements (ODR) Off-line condition monitoring Table 2. Characteristics of different measurement methods. Measurement interval Detection capability Diagnosis/ prognosis Link to machine operation Minutes to hours Days to weeks Months In on-line condition monitoring the measurements are performed by an automatic monitoring system and the measurement interval is typically some hours. An automatic measuring system of this kind is excellent in detecting exceptional situations. On-line systems also allow thorough diagnosis after an exception is detected and are therefore very reliable. The diagnosis of on-line measurements is normally performed by condition monitoring specialists and often there is also an additional screen in the control room that also allows operators to see and react to exceptions. Off-line condition monitoring measurements carried out by means of portable data collectors are usually performed and analyzed by condition monitoring specialists who work in the maintenance department. The measurements are typically performed a few times per year. This means that detection capability is not as reliable as in on-line measurements. 5

6 In the ODR concept the operators perform basic machinery checks and simple measurements as part of their normal routine operator rounds. In practice, they need very little additional work to record and measure the asset condition with the PDA. The measurements are rather simple but their frequency is much higher than in normal offline condition monitoring and therefore the capability to detect changes is much better. The diagnostics capability is very limited since the idea is to use more advanced vibration monitoring tools for the analysis after the exceptional status has been detected. 4. Applications, expectations and experiences The technology is just an enabler for creating systematic and effective work processes. It is vital that operator inspections are carefully planned to support production and maintenance effectiveness. When launching an ODR implementation project, the first step is to create a cross-functional steering group that will set up the main parameters. This can be done as a pilot project aiming at a gradual expansion as the process gains momentum. The steering group should include representatives from all levels of the professional groups involved. In addition to contributing knowledge within their area of expertise, they will serve as ambassadors when the process is up and running. 4.1 User expectations The commitment of different groups can only be achieved by being able to fulfil the expectations of each of them. Therefore, it is always beneficial to ask the people involved before launching the project what they expect from the new way of working. Operators are often concerned that the new tools may increase their work load even though in practice the expected impact is the opposite. A maintenance organisation typically expects improvements in the quality of information and hope to get rid of unnecessary routines and to release time for more challenging tasks. The production management is typically mainly interested in how the new way of operating may affect efficiency or overall costs. The expectations of maintenance management are often related to improved co-operation with the production organisation. A more detailed list of expectations is shown in Table 3. 6

7 Table 3. Expectations of different working groups. Operators Maintenance and condition monitoring professionals Production engineers & managers Maintenance engineers and managers No need to memorize how things were before since the data can be recalled from the database Ability to document and prove when things start to fail instead of just noticing the failure More even work load Interesting and reasonable tasks for field rounds, i.e. learning new things Simple working model or process Less unpredicted failures More time for high quality preventive rounds instead of fire fighting Better understanding of assets and the whole production plant. What is normal and what is not? Improved communication and feedback after findings More regular operator rounds Possibility to focus more on challenging cases Focus on tasks that require expertise Better utilization of own time by having more time for problem solving Improved process understanding by better communication with operators More precise information from operators that help in tracking changes Improved production efficiency Less unplanned shutdowns and shorter planned shutdowns Knowledge exchange between maintenance workers and operators Systematic and more interesting way of working for operators Improved documentation and learning from best practices Deeper asset and failure mode understanding Better care of assets Documentation of knowledge to future generations Better planning of maintenance strategy together with production Better work planning through an increased number and quality of work notifications More focus on predictive maintenance Better utilization of maintenance experts More accurate information for root cause analysis Elimination of continuous failures 4.2 Considerations regarding ODR Implementation There are a number of factors that have to be mapped and decided from area boundaries for data collection, timetables and key performance indicators (KPI). The latter is extremely important because one key to success is that there are goals for the process and that the goals are known by everybody involved. That is why this step is preferably taken through a workshop, where everybody can share information and opinions. Another important step is the asset criticality analysis (6), where assets are rated according to their relative importance in the plant. One method is to divide them in classes, where the most critical one includes assets where a breakdown will result in a shutdown of production. This is not only crucial for production security, but also for optimizing the inspection schedule for maximum reliability and minimum effort. 7

8 The inspection routes should be planned according to the location and criticality of the assets. The routes have to be tested and adjusted and alarm limits defined for the measurements. Finally, all members of the professional groups involved need some theoretical and practical training before the ODR process is up and running. 4.3 Case: ODR implementation in a power plant A power plant in Finland has already been using ODR methodology tools and processes for their machinery reliability for several years. In addition to regular checks, cleanings and measurements, a number of maintenance process development initiatives have been completed based on these checks, such as the development of a lubrication programme based on the measurements. Today there are close to 1000 measurement points and the average measurement interval is about two weeks. There is clear evidence that the ODR operation has improved the status and performance of assets. For example, readings of vibration and temperature have decreased and the Mean Time Between Failures (MTBF) has improved. Figure 3a) shows a graph of the development of the average level of enveloped acceleration ge from all measurement points. The decrease has been significant, which is an indication that the lubrication status of bearings has improved and also suggests that the bearings themselves are in better condition. Figure 3b) shows a trend in the average vibration level (vrms) of the plant. Similarly, it has gone down dramatically. This of course is clear evidence that the assets are in better condition but also indicates that the dynamic loads in the machinery are dramatically lower, which means that the life time of bearings and other mechanical components has increased. 9,00 8,00 7,00 6,00 5,00 4,00 3,00 2,00 1,00 0,00 ge mm/s Enveloped acceleration (ge) Vibration velocity in mm/s (v rms ) a) b) Figure 3. Decreasing trend in the average level of enveloped acceleration (ge) and vibration velocity (v rms ) after the implementation of ODR. Figure 4 shows a trend in average asset temperature. The decrease over the couple of years has been significant. The decrease in temperature of course is connected with lower vibration levels. However, it is noteworthy that the decreased temperature means significantly less energy consumption and also reduces lubricant lifetime significantly, which is very beneficial from the environmental point of view. 2,00 1,90 1,80 1,70 1,60 1,50 1,

9 C 50,00 45,00 40,00 35,00 30,00 25,00 20,00 15,00 10,00 5,00 0, C Lin. ( C) Figure 4. Decrease in average temperature after the implementation of ODR. In addition to the above-mentioned benefits, there is clear evidence that the unplanned shutdown hours have decreased by more than 50% in six years, which confirms that the decreased vibration and temperature levels are connected with asset lifetime and proves that in this case ODR has improved asset efficiency. 5. Conclusion Operator involvement in performing machinery checks and basic measurements can be a major contributor in improving the efficiency of maintenance. However, the success in the implementation of new practices requires commitment from operators, the condition monitoring team as well as operations and maintenance management. Since operators are making checks and measurements much more frequently than normally is the case in condition monitoring, the detection of exceptions will improve. The use of modern tools also improves the quality of data significantly as compared with traditional operator rounds. This data are much more valuable for maintenance in many ways, as they can be used for diagnostics, help detect recurring events and in general give a significant amount of feedback for maintenance planning and for continuous improvement. When operator data become reliable and quantitative, they enable condition monitoring specialists to shift their focus from routine measurements to more challenging cases and thus help them support development and continuous improvement processes. Today there are numerous practical examples of how operator involvement can significantly improve maintenance efficiency in the process industry. The processes in implementing the ODR model are well defined and mature. However, there are still development needs in defining more accurately the co-operative practices between condition monitoring measurements and operator measurements. In the long term this will enable further optimization of the tasks and roles of these groups. 9

10 References 1. S Nakajima, TPM Development Program: Implementing Total Productive Maintenance, Productivity Press, p. 2. R Smith, B Hawkins, Lean Maintenance: Reduce Costs, Improve Quality, and Increase Market Share Elsevier Inc., p. 3. J Markkanen, A Numminen and Å R Malm. Improved Productivity with Operator Driven Reliability, Maintworld, Vol. 3, no. 2/2011 pp R Gulati, J Kahn and R Baldwin, The Professional s Guide to Maintenance and Reliability Terminology, Golf Publishing Company, p. 5. H Mikkonen and J Markkanen, Improved Production and Maintenance Efficiency by Operator Driven Reliability (ODR). To be presented at Comadem Helsinki, Finland 11,-13. June, p. 6. H Mikkonen and S Lahdelma Practical Considerations on Selecting Assets for Condition Monitoring, 9th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, London, UK. 11p. June