Ian Taylor, Corus Northern Engineering Services and Dr Steve Lacey, Schaeffler Limited, UK
Most of us wouldn’t dream of not insuring a high-cost item, such as a car or home, against unforeseen loss or damage. We always take out a risk management policy, which invariably helps us sleep better at night.
Power generation and energy companies also need to adequately protect themselves and their high-value capital goods, particularly critical plant and heavy machinery, against costly breakdowns. After all, depending on the industry, lost production time can result in hundreds of thousands of pounds of losses per day until the problem is rectified.
Although the cost of a machine component, such as a bearing or motor, is small compared with the total cost of the machine, the cost of downtime and any consequential losses resulting from a bearing failure, are often very significant.
Of course, every company has a maintenance department to deal with situations like these, but often, because of time and resource constraints, the maintenance team becomes reactive, fire-fighting problems around the plant as they occur. There are no predictive maintenance systems and there is little preventive maintenance sometimes there is no maintenance strategy at all.
There are no excuses for this today. Numerous technology safeguards are available that are relatively inexpensive, compared with the cost of downtime. Enlightened companies are using the latest condition monitoring and predictive maintenance systems, including bearing vibration monitoring, acoustic emissions monitoring and thermography, to protect plant and machines. Less forward-thinking firms need to take heed.
Plant and maintenance managers need to justify any expenditure on condition monitoring systems and services to their finance director or managing director. A risk management approach is often the most effective way of doing this.
CNES’s acoustic emissions monitoring system, Aquilla AE Pro
Ask your finance director: What will it cost the company in lost production if I lose that critical machine for five hours? Or what would you be prepared to pay as an insurance premium to secure the running of the power plant and protect it against unforeseen breakdowns? The response is likely to be illuminating.
One of the finance director’s responsibilities is to ensure that the company’s assets are protected. Risk assessments should be carried out regularly to establish what effect breakdowns would have on critical machines and equipment. The severity and likelihood of breakdowns on particular machines should be assessed and given a corresponding risk value. Those with the highest risk scores should be given priority by the maintenance team and be protected using a condition monitoring device.
Of course, companies can protect their plant without using condition monitoring or predictive maintenance systems, for example, by holding more stock of a business-critical component, such as a gearbox, bearing, coupling or shaft. When a breakdown occurs on a machine, the component that caused the breakdown is available to hand, ready for the maintenance team to fix the problem.
However, as well as incurring increased stockholding costs, the company runs the risk of the stock deteriorating or becoming obsolete over time. Companies should therefore reduce the risk of unexpected failures by implementing suitable condition monitoring systems on rotating plant and machinery. This should not be seen as capital outlay, but as insurance against the risk of lost production.
So what is the true cost of a bearing failure in each of your critical machines? By installing a predictive maintenance system, the customer picks up a problem early. During the next convenient downtime, the maintenance team can remove and replace a bearing with minimum disruption and at minimum cost, and also avoid the risk of breakdown damage to the equipment.
Maintenance engineer using an acoustic emissions monitoring system to assess the condition of hydraulic pumps
Condition monitoring also prevents maintenance teams replacing components unnecessarily and introducing new and unrelated problems. Maintenance staff should be using condition monitoring systems to predict when failures are likely to occur and plan replacement during plant shutdown periods. In too many companies, parts are changed on a time basis rather than on a condition basis because the maintenance team considers this to be the safest option. However, this introduces further risk, because whenever there is human intervention problems can occur at start-up or when re-commissioning.
Most companies work in a breakdown culture that is reactive rather than proactive. But rather than boasting about how rapidly engineers can repair or replace components and get a machine back in operation, maintenance teams should be asking themselves: How can we prevent problems occurring in the first place? Condition monitoring is the most effective solution. An old adage from the textiles industry is: “The best loom tuner [mechanic] is the one sat down doing nothing.”
Established in 2005, the PRAXIS partnership between Schaeffler (UK) Ltd and Corus Northern Engineering Services (CNES) is helping to prevent costly plant downtime in many industries across the UK and overseas, including nuclear and other power generation sectors.
Schaeffler UK is a member of the Schaeffler Group, one of the world’s leading manufacturers of rolling bearings and automotive components, marketing three world class brands, INA, LuK and FAG. The group has 66 000 employees at more than 180 locations around the world. FAG Industrial Services (F’IS) is a separate support division offering maintenance management and condition monitoring equipment and services for a wide range of applications across all industry sectors.
CNES is a global engineering support organisation with UK bases at steel-making plants in Teesside, Scunthorpe, Rotherham and Workington. Part of the Corus Group, the company uses a ‘toolbox’ of techniques to help customers of all sizes and from every industry sector maintain their output, efficiency and profitability by providing a detailed and accurate assessment of their plant assets.
CNES uses a range of non-intrusive techniques, including acoustic emissions monitoring, thermographic imaging, vibration monitoring, laser alignment, lubricant technology and remote visual inspection. CNES also offers structural design, project management, training, electrical, process control, machining, fitting and weld reclamation services.
Corus is Europe’s second largest steel producer, with revenues of £9.7 billion and crude steel production of 18.3 million tonnes in 2006, primarily in the UK and the Netherlands. Corus is a subsidiary of Tata Steel, the world’s sixth largest steel producer.
The PRAXIS partnership gives customers access to a unique and comprehensive range of condition monitoring products and services, including handheld and fixed systems, vibration monitoring systems, acoustic emission monitoring, endoscopy and thermal imaging equipment, as well as oil analysis and contract patrol monitoring services.
Training services are also offered, so that the customer can get the most out of the equipment, analyze the results and take the most appropriate corrective action. The focus here is on customers being trained to take complete ownership of their condition monitoring strategy and its implementation.
The combination of the specialist skills of the two partner companies is key to the success of PRAXIS. Schaeffler UK provides the specialist bearing knowledge and vibration monitoring expertise, while CNES contributes its operational engineering know-how and toolbox of condition monitoring techniques and services. This means that PRAXIS engineers have a portfolio of hardware and software systems for a variety of different applications and can provide support for the installation, commissioning, monitoring and maintenance of complete condition monitoring systems. This often includes an initial plant survey, followed by equipment specification, supply, installation, consultancy, data interpretation and trending.
PRAXIS combines the best of both companies in one tailored condition monitoring package. Normally, power generation companies would have to deal with two condition monitoring companies for separate condition monitoring problems. With PRAXIS they can source everything they need from acoustic emission to vibration monitoring and thermography from a single source, safe in the knowledge that PRAXIS engineers have many years of experience in the fields of both engineering and condition monitoring.
For more than 25 years, engineers at Corus have been using condition-based monitoring to accurately predict maintenance requirements and maximise steel-making plant availability. With a detection capability beyond that of other methods, CNES’s acoustic emissions monitoring system, Aquilla AE Pro, is a unique fixed system that is particularly effective at slow rotational speeds. Typical applications include the monitoring of the large tilting vessels used in steel making, bucket wheel excavators and heavy cable reeling or pipe laying machines.
Horses for courses
When it comes to monitoring the condition of critical, slow-moving (0.25-80 rpm), high-capital-value plant and machinery, companies really need to consider the benefits of acoustic emission monitoring particularly where there are fluctuating load conditions and where a breakdown would have a significant impact on plant production.
Monitoring acoustic emissions is certainly not a new method of monitoring high-capital plant and machinery. The technique has been around since the early 1990s, but more companies should be using it. Acoustic emissions are the high-frequency stress waves generated by the rapid release of strain energy that occurs within a material during crack growth, plastic deformation or phase transformation. Acoustic emission monitoring systems use surface-mounted transducers to detect these stress waves, which lie within the 25 kHz to 1 MHz frequency range.
Many companies rely on vibration monitoring systems to check the condition of critical plant and machinery, but this method is not as accurate as acoustic emission monitoring, especially when it comes to slow-speed, fluctuating-load applications.
Vibration monitoring is effective on high-speed motors, fans and pumps. The equipment is cost-effective and easy to use, and the data is easier to interpret. However, where components or machines rotate at less than 80 rpm and operate under fluctuating load conditions, or only move through a part revolution, it is more difficult to collect meaningful data from vibration monitoring.
Acoustic emissions monitoring equipment is highly sensitive to machine faults, but it is also immune to audible noise and low-frequency background vibration. According to CNES, the problem is that many engineers are not fully aware of how acoustic emission monitoring systems can help them reduce plant maintenance costs and improve machine availability. Also, many companies simply do not possess the necessary skills in-house to interpret the data from acoustic emissions monitoring, so they continue to use vibration monitoring or other devices.
In a further development, CNES has introduced Aquilla AE Pro IMON, a new semi-portable system for acoustic emissions monitoring. The system is ideal for use on plant that doesn’t warrant a fixed system, but still requires more than the instantaneous data collection provided by the handheld systems used in patrol monitoring.
Vibration monitoring expertise
The other side of the partnership, Schaeffler UK, has a product portfolio that includes a wide range of vibration monitoring hardware, including FAG ProCheck, the company’s new online monitoring system that detects plant or machinery faults early, preventing costly breakdowns and reducing plant downtime.
E.ON Kernkraft uses Schaeffler’s FAG Vibrocheck to monitor the condition of plant at its nuclear power stations in Germany
The system, which was developed in partnership with National Instruments, helps companies monitor vibration levels on critical rotating plant or machinery, including electric motors, drives, bearing arrangements, gearboxes, pumps, generators, ventilators, fans and excavators.
FAG Vibrocheck control panel
Schaeffler UK also recently launched its FAG Detector III system, a handheld vibration and temperature monitoring and balancing device that now comes with RFID technology. This enables automatic identification of measuring points on plant machinery and equipment, eliminates operator error and results in more efficient data collection.
A remote condition monitoring system from Schaeffler is helping a nuclear power plant monitor more than 90 electric motors, pumps and fans, providing early warning of impending failures and helping to keep plant availability high.
E.ON Kernkraft in Germany is using the FAG VibroCheck online condition monitoring system. Since its initial implementation in 2003, FAG VibroCheck has on several occasions identified damage to bearings, imbalance in fans and unstable machinery at an early stage, enabling the maintenance team to order the necessary spare parts and resources and plan the replacement of the damaged part within the regular maintenance schedule or shift.
The latest condition monitoring technology allows the remote monitoring of key plant
The condition monitoring system is ideal for monitoring the condition of critical rotating machinery and components, such as gearboxes, bearings fans and pumps. Using selective frequency monitoring, FAG VibroCheck automatically detects imbalance and misalignment in rotating plant and machinery, as well as damage to individual bearings and gears. Selective frequency monitoring enables the detection of even minor damage or defects at an early stage, since these will cause an increase in the amplitude of the characteristic frequencies. FAG VibroCheck also uses demodulated signal analysis, as this is ideally suited to shock pulses.
The system enables the monitoring of up to 2048 measuring points and can be easily integrated into a plant’s existing systems. Remote monitoring is possible, and alerts can be sent via email or SMS text message to appropriate individuals.
At E.ON Kernkraft, 226 separate measuring points are being monitored by the condition monitoring system, which provides the maintenance team with information on the condition of rolling bearings, gear sets and shafts, and on imbalanced rotors in fans and pumps.
Although 12 staff at E.ON are trained to use FAG VibroCheck, the company also has a teleservice contract with F’IS, which includes an online remote monitoring service for the plant and technical support by F’IS vibration monitoring specialists, who can help analyse and evaluate recorded data.
For example, the condition monitoring system at E.ON Kernkraft recently detected bearing damage in a pump at an early stage. This damage was then confirmed by visual inspection and the bearing replaced in plenty of time by the maintenance team. If left undetected, the bearing damage would have led to the failure of the pump, resulting in secondary damage to the housing and shaft.
As a subsidiary of E.ON Energie, E.ON Kernkraft is a major contributor of electricity generation in Germany. The company operates six nuclear power stations in Bavaria, Lower Saxony and Schleswig-Holstein and is involved in a further five plants. The company employs around 2500 staff and generates a total annual output of 8500 kW, making the company a leading international generator of electricity.
E.ON Kernkraft’s Grafenrheinfeld nuclear power plant in Germany was commissioned in 1981. The pressurised water reactor is rated at 1275 MW and is cooled by two 143 m-high natural draught cooling towers. The plant generates electricity for base load applications.
The working availability of the plant at this site has to be high, at more than 90 per cent. This is not only for safety reasons (to protect personnel entering hazardous areas) but also to ensure efficient maintenance of plant and machinery. Failure of individual components or machines can cause costly secondary damage or shutdown of the complete plant, resulting in lost production.