SKFs Proactive Reliability Maintenance (PRM)

This article highlights a customer case from Renova in which SKF works with Proactive Reliability Maintenance (PRM), and a brief description of SKF’s products within this area.

PRM – Proactive Reliability Maintenance at Renova

As the name suggests, SKF’s Proactive Reliability Maintenance programme gets to the root of each problem and suggests measures to ensure issues do not reoccur.

SKF systematically diagnoses the causes of breakdowns through application of best practice for proactive maintenance and other processes. Under a PRM service agreement, SKF helps Renova, the Gothenburg-based waste power plant, to improve operational efficiency during measurement and maintenance activities through analysis of bearings and lubricants, among other areas.

Renova’s waste heat and power plant in Sävenäs supplies around one-third of the district heating in the Gothenburg region. The facility also produces five percent of the energy consumed in Gothenburg. Not bad when you bear in mind all this energy is generated by residual products, which could not be recycled in any other way. Waste is incinerated at the Renova plant 24 hours a day, all year round. Every tonne of waste which is burned generates 3.3 MWh of energy in the form of electricity and district heating. The waste is incinerated in three large ovens, each of which contains primary, secondary and recirculation fans. The primary fans supply air in order to maintain an even combustion temperature of 1,000 degrees Celsius, while the secondary fans allow the air to circulate around the combustion chamber. The recirculation fans dry the incoming waste which is to be incinerated. The function of the fans is fundamental to the plant’s operation. If only one fan stops working, this could cost the facility in the region of one million kronor a day. With this in mind, it is absolutely vital for the plant to maintain the operation of the fans. Thanks to a 10-year long cooperation between Renova and SKF, there are no unscheduled production stoppages.

“Previously, we may have lost around 1,000 hours of production a year as a result of emergency maintenance measures,” explains Göran Klamas, plant manager in the recycling business unit at Renova. “Reliability is now at a whole new level, with the process only stopped for scheduled maintenance. This has seen productivity increase substantially. These improvements are to a large extent due to the cooperation between Renova and SKF. At the heart of this is SKF’s PRM (Proactive Reliability Maintenance), which has significantly improved the operational stability of the plant’s rotating equipment.

Within the framework of PRM, SKF has identified and classified almost 40 critical machines at Renova, drawing up overviews in the form of reports and diagrams which indicate where additional maintenance measures are required. Measurement values give the maintenance department a clear indication of any imminent issues relating to equipment, enabling them to adopt corrective measures before unscheduled stoppages occur. “It could be misalignment, for example, which has been addressed several times on a machine without solving the underlying issue,” explains Jennie Lindahl, Service Coordinator at SKF who has performed measurements at the plant over many years. “Performing an ODS measurement (operating deflection shape) enables us to identify the reason. It could be a case of uneven ground which must be rectified, for instance. Lubricant analyses, which are primarily undertaken due to strict environmental requirements, may also help to identify operational issues. A lubricant analysis can identify reasons for downtime which are completely different to those previously assumed to be at fault. This could be faulty lubrication, water in the lubricant or an excessive bearing temperature. These types of conditions may increase the risk of hazardous chemical substances forming. The fat may oxidise, viscosity can change and oxygen may form which damages the surface of the bearings,” explains Lindahl. Essentially, this type of analysis can contribute towards preventing a breakdown. Thankfully, serious maintenance issues can be prevented through PRM. Since 2016, there has not been a single operational stoppage at the Renova plant, compared with five per year 10 years earlier. With the PRM agreement in force, only two scheduled maintenance measures were required in 2016, which is half as many as one decade earlier. The improvement in operational reliability has resulted in lower maintenance costs for Renova, freeing up resources for other investments. “Loss of production from unscheduled stoppages costs almost one million kronor a day. Operation of fans is currently reliable, which means we can devote more time to analysing more environmentally friendly, effective methods of incineration,” explains Göran Klamas.

A description of the options within condition control and vibration analysis

Periodic condition control with proposals for action

Effective preventative maintenance forms the basis for problem-free, cost-efficient operation. If this is combined with proactive approaches in which underlying causes are identified and errors rectified so they do not re-occur, then we’ve made some progress. However, adopting this method internally with positive results requires specialist expertise, investment and discipline. The periodic condition control with proposals for action service provides measurement and inspection rounds for critical equipment. The results are analysed and reported after each round, with any suggestions for improvement or further investigation included. The service is closely related to the Error-causality analysis and Machine improvement services.

Installation and commissioning of online systems for condition control

In the case of critical equipment, it is important to detect potential errors at an early stage, with condition control often an effective strategy. Certain equipment is well suited to periodical status control, however, when a breakdown progresses quickly or it is difficult to perform manual measurement, monitoring with a stationary online system can be the best solution. In the service for installing and commissioning online systems, SKF manages the entire process in the form of a project, from identification of customers’ needs and specification of the system to final inspection and submission to the customer. SKF has long experience of condition monitoring and knows what is required to create a reliable system and robust installation. Ordinarily, the solution comprises a “turnkey” system of sensors, cabling, monitoring units, software and installation. In the right environment and on the right machine, this solution quickly pays dividends.

Remote monitoring

In the case of critical mechanical equipment, it is vital to identify errors arising as early as possible in order to avoid breakdown, malfunction or unnecessary downtime. Certain equipment is well suited to periodical condition control, however, when a breakdown progresses quickly or it is difficult to perform manual measurement, remote monitoring with a stationary online system can be the best solution. Remote monitoring can also be a cost-efficient alternative to manual measurement. As part of SKF’s “Remote Monitoring” service, an online system is installed in the relevant equipment. The signals (vibrations, temperature, etc.) obtained from monitoring are transmitted to SKF via the mobile network or the customer’s local network, where data is gathered and analysed.

Where the data indicates an incipient fault, this is analysed in more detail and the customer is notified. Periodically, a review of all measurement points and a report are sent to the customer, along with the current status of the machine.

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