Should you take action quickly and minimize the damage, or wait until the system crashes? Operators have to ask themselves this question when they start thinking about how to lower operating costs as part of a long-term operating and maintenance concept for their wind turbine.
The days when operators could simply leave their systems running until the crash at the bitter end are forever in the past, not least due to the attitudes of insurance firms. As the latest wind turbines continue to grow in size, costs for repairs for major damage skyrocket, and operators are often left to cover a large portion of the costs due to the stipulations for depreciation in insurance contracts. In addition, the damage, which usually comes without warning, also causes long downtimes and drops in production while the operator waits for spare parts to be delivered and cranes to arrive.
Clearly, a new strategy is needed. Nowadays, insurance firms no longer cover all of the damage and downtime without further ado, and the increasing complexity of the turbines makes repairs more and more difficult.
Classic concepts are outdated and no longer able to take account of the demanding technology behind current wind turbines; fortunately, GEO mbH offers cost-saving operating and monitoring concepts for modern wind turbines.
If we take a look at other industries, it is easy to see how such challenges are faced. Prevention is the buzzword when it comes to avoiding major costs. Wherever the initial signs of damage go unheeded, resulting in major subsequent damage and possibly complete production stops, it is standard procedure to take a protocol of the status of the system, make an unbiased assessment of it, and include this assessment in the overall maintenance managementin the overall maintenance management. Preventive maintenance has long been a buzzword in the wind industry; it plays a large role in lowering the operational costs in the long-term.
Manufacturers, insurance firms, and operators now all agree that there is no way around preventive maintenance anymore. After all, unplanned downtimes as a result of now malfunctions or damage -- especially to mechanical components in the drive train -- no longer have to be accepted as inevitable; rather, modern measurement technology can be used to provide appropriate monitoring and enable preventive maintenance.
Online condition monitoring systems can be used to constantly keep an eye on the status of bearings and gear boxes so that mechanical damage can be detected quickly. In combination with a manufacturer-neutral monitoring center, this monitoring system serves as the basis for long-term maintenance management to provide preventive maintenance for the main components in a wind turbine.
Wear and damage to the roller bearings and gear boxes in a drive train can be detected very quickly and localized by means of a condition monitoring system.
In combination with professional data analyses and system assessments, maintenance can then be planned according to wind conditions, downtimes as a result of a wear reduced, ongoing maintenance costs lowered, and the optimal availability of the system attained.
When condition monitoring systems (CMS) are used, insurance firms offer much better conditions. Measurement data can be archived for the long term for later documentation in case the operator needs to provide the system manufacturer with evidence during the warranty period.
In particular, the independent use of CMS to separately document the service life of a wind turbine is especially beneficial when full-service contracts are signed with system manufacturers; risks can be more easily covered both at the end of the contractual term or beforehand if the contract is terminated before it expires or if the manufacturer goes bankrupt or is taken over.
But it also helps to know exactly what the status of major components is even if the wind turbine is a small, old system whose damage insurance firms no longer cover completely due to depreciation. For such turbines, the provisions that have to be set aside to cover the deductibles in insurance policies are considerable. GEO mbH's "safe&win" concept demonstrates this fact clearly; no wonder a growing number of banks are interested in the concept.
After all, everyone involved benefits from accurate early detection of damage and preventive maintenance.
The successful implementation of condition monitoring requires high-quality diagnoses and proper measures to reduce and remedy damage regardless of the manufacturer.
A CMS is only as good as the competence and experience of the monitoring staff. A great amount of experience is required to precisely assess changes in conditions. It is just as important to assess the valuable monitoring information in the overall context along with other details such as visual inspections or oil and oil filter analyses in order to decide which maintenance measures must be taken.
GEO mbH is the market leader among manufacturer-independent service providers in the field of condition monitoring. It has comprehensive expertise and many years of experience in the monitoring of wind turbine oscillations. Currently, the Company constantly monitors more than 70 wind turbines from all major manufacturers. All leading German insurers of wind turbines recognize GEO mbH as a monitor; the Company is also ISO 9001 certified. Queries have also been placed from other European countries.
As a reliable, competent partner, GEO covers the entire spectrum of permanent online monitoring for wind turbines from the individual planning of a monitoring concept for each individual product to purchase options during project processing and interesting lending models that go easy on your liquidity for the financing of condition monitoring systems.
Furthermore, turnkey complete installations and the initiation of systems and wind farm networks for the transmission of measurement data are also part of our portfolio.
Another of GEO's specialties is completely autonomous additional power supply components for the system and measurements of power signals; these services are also part of our complete packages, which offer a lot of value for your dollar. These systems constitute a completely neutral monitoring solution that does not endanger warranties.
Once the system has been configured for the specific turbine, the operator of the turbine receives monthly reports based on this neutral monitoring. These reports include recommendations of what actions should be taken based on detailed diagnoses of the measurement data.
GEO is a reliable partner thanks to the numerous cases of system damage to systems detected and remedied at minimal cost.
The following case illustrates the early detection and remedy of damage based on condition monitoring for a high-speed output output shaft on the generator -side bearing of a two megawatt wind turbine. If this damage had gone undetected, it would have posed considerable danger to the operation of the wind turbine.
Figure 1 shows the steeply rising characteristic curve typical of this damage starting at a normal level around 15 m/s to a peak seven times greater at around 100 m/s. Generally, this curve is completed within a couple of months or even weeks as we will see in another case study below. In our first case, the damage increases very quickly within only a few days; here, permanent online monitoring is crucial to detect this damage.
Once this increase in damage has issued an automatic alarm to the condition monitoring center, a diagnosis engineer studies the frequency-selective analysis of the envelope spectrum shown in Figure 2 to trace the damage back to the cage for the high-speed output shaft bearing on the generator side .bearing.
The shaft is immediately inspected, and the inspector confirms that the steel cage has indeed cracked under pressure as shown in Figure 3.
The condition monitoring center, the operator, and the wind turbine manufacturer then worked together closely to replace this bearing within two days, thus preventing subsequent costly damage and ensuring the further smooth operation of the turbine.
Replacing the damaged damaged bearings only cost the operator around 5,500 euros.
If the turbine had not been constantly monitored and this damage had remained undetected between two servicing intervals, the shaft would have been displaced, resulting in a grinding of the teeth, potentially ruining them.
The 5,500 euros for repairs based on condition monitoring appear quite inexpensive compared to the approximately 105,000 euros for a new gear box -- and that does not even include such concomitant costs for a crane, logistics, etc.
Another recent example of damage shows how important it is to have constant monitoring for a wind turbine. In this example, there was damage to the toothing in a 1.5 megawatt gear box.
As operation continued, the damage became so great that a gear wheel had to be replaced.
Even as the damage was being monitored based on measurement data from the condition monitoring system and the gearbox was being inspected, an optimal date for the replacement of the components was set at the earliest possible time in coordination between condition monitoring experts, the operator, and the wind turbine manufacturer. This remedy came just in time, as the damage to the teeth shown in Figure 6 during replacement illustrates. Such a toothed wheel would not have held up for the entire service life of the turbine.
It must be also kept in mind that, had the condition monitoring system not been used, this damage would have gone undetected between the semiannual servicing intervals, resulting sooner or later in total damage to the gearbox. Furthermore, the condition monitoring system provided irrefutable documentation of the history of the damage over several months.
Turbine operators should compare the costs of a condition monitoring system to the much greater expenses for the damage that can be caused if none is used.
Here, 13,500 euros was spent on specific maintenance instead of 105,000 euros for a complete, new gear box -- not including the costs of a crane and other damage that simply cannot be assessed.
We also have to keep one thing in mind: condition monitoring is more than assessment of characteristic curves and traffic lights, as many of the systems sold would have us believe. The dynamics and physics behind condition monitoring are far too complex to be represented accurately by such simple means. Only experts can make detailed analyses and assessments of oscillation data. Without such expert knowledge, costs that could have easily been prevented are quickly incurred when inaccurate diagnoses lead to improper maintenance.
In other industries, investments in neutral monitoring and maintenance of machines and systems have long been standard practice to reduce operating costs considerably, with a quick return on investment. Unfortunately, the wind industry still does not seem to have taken account of this fact, especially if we consider that only 400 to 500 of the approximately 17,000 wind turbines currently in operation in Germany have condition monitoring systems.
And yet, the potential savings make it clear that classic turbine management and maintenance concepts are no longer the best solution for the cost-optimized operation of wind turbines.
High time to make proactive investments to prevent the high and growing expenses of reactive maintenance! Whether your turbine is an old one or a new multi-megawatt turbine with a full-service contract, independent early detection always pays.!