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October 2014

Profile: Havlik Gear – Ontario Company Is Poised To Meet The Drivetrain Needs Of The Wind Industry

Rob Borrelli
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Profile: Havlik Gear – Ontario Company Is Poised To Meet The Drivetrain Needs Of The Wind Industry

Havlik Gear in Cambridge, Ontario is one of several companies competing in the wind energy component market. During the early part of the new millennium, wind power has expanded all over North America, and in particular from a Canadian perspective, in Southern Ontario.  In the past, the large gearing market had been dominated by mining and other industries that require large, heavy pitch gearing. With a recent expansion and acquisition of key pieces of equipment, the company is well-positioned in the wind energy market as a prime supplier of gearing and related products.  

Gears used in wind power generation usually fall into two categories, namely speed-increaser gears for the actual power generation, and low-speed slewing gears for pitch and yaw mechanisms. From a design and manufacturing standpoint, there are some key differences and necessary considerations that apply to drivetrains used in wind power versus traditional applications. Most machinery operates either on or off, and the failure mode of the associated gearing is either surface failure or bending failure (crack propagation or severe overload).  Drivetrains used in wind power generation see other stresses in addition to the ones listed above, one common example is from surface stress and/or particle transfer caused by small vibrations or motions introduced to the teeth while a turbine is stopped. During this condition, lubrication systems are not necessarily functioning and the lubricant’s film strength is quickly broken down. These new scenarios are not yet quantified by existing design standards and are therefore left up to the designer and manufacturer to solve together depending on the individual case. Havlik has worked with several customers to achieve a high-quality product that meets all of the designer’s requirements while staying within the customers’ budget.

In Cambridge, Ontario, Havlik Gear operates two gear manufacturing facilities, each with unique capabilities. The newest location includes a large form gear grinder, namely a Niles ZP40. The Niles machine can grind external gears up to four meters, and internal gears up to approximately 3.5 meters depending on the proportions of the cross section. Internal gear grinding is critical to the manufacturing of gears for the wind industry. The most highly scrutinized drivetrain component usually becomes the main internal ring gear or “annulus gear” used in the speed increaser gearbox. The annulus gear typically has high power capacity with slender cross sectional proportions due to size and weight restrictions.  The result is a gear design that has absolutely no room for imperfections, is made from the highest strength material, and is subjected to best heat treatments available. There is a laundry list of processes and inspections that need to occur before a gear blank can finally be ground to an impressive mirror finish and very high AGMA or DIN quality. On average for a typical case hardened ring gear produced by Havlik, there are several inspections that occur during the process. From the raw material stage there is tensile, chemical, ultrasonic, and hardness testing. After heat treatment there is complete microstructure analysis of the case and core along with destructive testing of coupons to determine exact effective depth of case. After final gear grinding it has become necessary to chemically etch sample numbers of gear teeth with the goal of identifying areas that have been overheated by the grinding operation. The etching is done as a precaution however with advancements in gear grinding technology both in operating principal and in availability of composite grinding wheels of more favorable composition the risk of overheating has greatly reduced from what it once was. The inspections listed are in addition to the standard dimensional and gear tooth geometry checks which are standard practice.

On the economic side of the equation, Havlik uses five-axis milling machines to rough cut gear teeth within one millimeter of finished size. Gear tooth profiles are accurately milled and therefore the finishing stock is very consistent which helps to avoid heavy and light areas of grinding which can cause many issues such as cracking or variations in surface hardness and/or depth.  Five-axis milling has proven to be the greatest factor in the company’s ability to compete and remain flexible in the wind power market. Havlik Gear can produce both prototypes and production parts for its customers in a cost effective way while meeting specific quality requirements. When requested, Havlik Gear is able to provide consulting services and guidance to its customers with respect to gear design or manufacturing.  In several cases Havlik Gear has been presented with a concept or basic design and together with its customer developed that concept to a final product that is adequate for service, cost effective, and practical to manufacture.

R&D Project Shows Nacelle-Mounted LIDAR Reduces Yaw Misalignment And Improves Turbine Performance

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R&D Project Shows Nacelle-Mounted LIDAR Reduces Yaw Misalignment And Improves Turbine Performance

A collaborative research project at the Energy Department’s National Renewable Energy Laboratory has shown that the Wind Iris nacelle-mounted LIDAR from Avent Lidar Technology is an effective diagnostic tool for identifying wind turbine yaw misalignment, allowing users to improve wind turbine performance.  This is the first independent scientific field study validating the benefits of using turbine mounted LIDAR to correct rotor-induced yaw misalignment. An AEP increase of 2.4 percent has been estimated for a 7.5 degree misalignment.

The research project, supported by DOE, focused on the optimization of turbine performance using forward-looking wind LIDAR measurements, with a focus on improvement of power output by correcting yaw misalignment and a reduction in turbine O&M costs through improved load mitigation. The research was conducted in collaboration with Avent Lidar Technology and Renewable NRG Systems.

“Wind turbines traditionally rely on a wind vane mounted on the rear of the nacelle to measure the wind direction in order to control the yaw position of the turbine. Certain factors, like rotor-induced wakes, can lead the vane to measure the wind direction inaccurately. The principle focus of the project was to use a LIDAR to measure the wind direction ahead of the rotor and derive a correction function.  The correction function was shown to reduce the yaw misalignment and improve power capture in below rated power wind speeds,” said Andrew Scholbrock, field test engineer at NREL.

The study also validated the energy increase after yaw misalignment correction using the Wind Iris as an external reference sensor. The power curve improvement was measured and found to be nearly identical with wind speeds measured from the LIDAR and NREL’s reference meteorological tower. Based on the results, it is estimated that LIDAR-based yaw correction will increase the annual energy production  by 2.4 percent for a 7.5 degree static misalignment and standard reference wind speed distribution.

“Yaw misalignment correction is a hot topic in turbine O&M optimization. These field-results will give us a strong edge in a market where no other type turbine mounted LIDARs have that kind of scientific track record,” said Thomas Velociter, CEO of Avent.

NREL served as the overall project coordinator with the measurement campaign, taking place at its National Wind Technology Center in Golden, Colorado.  The LIDAR was installed on the two-bladed Controls Advanced Research Turbine (CART2). NREL performed data collection and analysis related to the use of LIDAR measurements. Avent provided its Wind Iris LIDAR for the project together and performed part of the scientific analysis related to LIDAR technology. Renewable NRG Systems was responsible for the coordination of the LIDAR field activities.

Following the evaluation of static yaw misalignment correction, NREL, Avent and Renewable NRG Systems are set to begin a new collaboration phase to explore the use of LIDAR measurements to actively control the wind turbine, through improved rotor collective pitch and yaw control.

The Wind Iris is the only industry proven turbine LIDAR for power performance verification and optimization applications. It measures the horizontal wind speed and direction at hub height from 40m to 400m upwind of the turbine, and generates accurate data to optimize wind turbine performance. It combines unparalleled operational features, validated procedures and methodologies, and has a strong track record of over 100 deployments onshore and offshore. This unique combination allows operators and owners to yield a high return on investment turbine after turbine with clear and easy to implement processes.

Dual-Stage Magnetic Filtration Shown As Effective In Reducing Fluid Contamination

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Dual-Stage Magnetic Filtration Shown As Effective In Reducing Fluid Contamination

In the fast-growing industry of wind power, new technologies for gearboxes, blades, rotors, and other major components are emerging every day but something that is often overlooked is the root cause of most turbine failures.

Gearbox and hydraulic system failures make up the highest number of failures in the wind power industry, resulting in fire, shutdown, and loss of production. In order to minimize the downtime and costs associated with replacing a failed gearbox, don’t let it fail. In order to reduce failure of gearboxes, find the root cause of the failure. In the majority of cases the root cause is contamination (mostly ferrous metals and silica dust) wearing the gearbox components prematurely. This contamination is the result of the machining process, airborne ferrous metal, break-in wear and is even found suspended in new hydraulic fluids, gear oils and glycol.  Figure 1

Research indicates that contamination under 10 microns to sub-micron in size is the most damaging to components in gearboxes, fuel, coolant and hydraulic systems.  Advancements in machining tolerances for transmissions and gearbox bearings, shafts and seals, and hydraulic valves, seals, and actuators, are now three microns in size and lower, so filtration able to remove contamination below this level is essential.

The first step in reducing this wear is to create a proactive hydrocarbon management program. In one regard ensuring that the oils, hydraulic fluids, and glycol used in the operation of the turbine are of good quality and are stored properly in a warm, dry location, closed off from the elements. The second step involves eliminating these wear particles, which is essential in maintaining the longevity of the fluids and the wind turbine.

New magnetic filtration technology developed by One Eye Industries offers the ability to remove ferrous and non-ferrous contaminants and protect the system from particles down to sub-micron levels. Traditionally, ceramic magnets have been used to filter hydraulic fluid and gear oil, but these offer minimal ability as the strength is low resulting in its inability to remove contamination below 10 microns. Another problem ceramic magnets pose is that they need to be in direct contact with the fluid to ensure the strength is not limited. This poses a contamination issue as the magnet is susceptible to vibration and temperature and can crack resulting in magnetic particles travelling through the system and attaching to metal components such as bearings. These in turn cause wear to the bearings and shafts.  

GEARBOX
There is a link between failures of lubricants and failures of equipment. Oil analysis data will detect particles of contamination and degradation and the proper use of this information can detect the chance of a failure.

In November 2013 a wind turbine company in Taranto, Italy was finding it difficult to remove contamination below 20 microns using traditional filtration. This contamination was prematurely wearing the bearings, gears, and shafts of the turbine gearbox. Alex Priori of Renox suggested installing a dual-stage magnetic filtration system to increase the filtration efficiency to sub-micron levels, protecting the system components. Figure 2

After seven months in operation, the magnetic filter removed a large amount of contamination from the gear oil. Analysis of the trapped particles indicated 48.3 percent was ferrous and 51.7 percent non-ferrous, down to 1 micron in size. “The company was amazed by how much contamination was retained by the magnetic rod,” Priori said. A bearing failure in a wind turbine gearbox can cost an excess of $500,000 plus the downtime of production. The magnetic filter has a holding capacity in excess of 12 ounces (0.34 kg) before cleaning is required.

HYDRAULICS
Hydraulic systems operate at under 1 micron tolerances, yet most traditional filtration is nominally rated to 3 microns. These ratings can be misleading, as nominal indicates that throughout a number of passes at one time a particle of 3 microns will be trapped by the filter. Patented rare earth magnetic filtration systems trap contamination to sub-micron levels at 97% efficiency.

In February 2014, a Diamond Mine North of Yellowknife in the North West Territories had a problem with dirty hydraulic fluid with an ISO of 25/24/16 on their 5500 Komatsu shovel operating with a 4500 PSI hydraulic system. Traditional filtration was not able to meet their minimum ISO standard of 18/16/13 with the limited 3-hour kidney loop filtration interval. Mark Robillard of Kingland Ford Mining Division suggested employing the OEI high flow magnetic filtration skid as it guaranteed this minimum ISO standard. Figure 3

On its trial run, fluid samples were taken before and after the unit and sent to three independent labs. Common results showed that not only had the kidney loop met the anticipated standards, but exceeded them — retaining a cleanliness level of 17/14/10. The analyzed contamination on the magnetic filter rods identified ferrous (88 percent) and non-ferrous (12 percent; mainly consisting of carbon and calcium) contamination ranging from 100-plus microns to sub-micron in size.

The diamond mine maintenance manager is very pleased with the results and is incorporating other OEI filtration solutions.   

In May 2008, Newcrest Mining’s Cracow Gold Mine was finding large amounts of metal contamination were being missed by their traditional filters, degrading the fluid viscosity in the hydraulic cooling system of their Symons 4 1/4’ Cone Crusher. After suggesting they replace one of the OEM filters with an OEI ADD-Vantage 9000 dual stage magnetic filter a 64-hour run was conducted. The amount of trapped contamination is shown in the adjacent photo. Newcrest anticipated that had this not been captured by the magnetic filter it would have found its way back to the valves, motor and hydraulic pump. As part of the continuous improvement program at this site other pieces of critical plant equipment have been identified as benefitting from magnetic filtration technology.  

COOLANT
With the price of glycol constantly on the rise, wind operators are looking at ways to reduce the consumption of this substance. Most coolant lines have no filtration, but with the employment of rare earth magnetic filtration contamination is removed to sub-micron levels leaving the glycol — in most cases — cleaner than new. Fluid life can be extended by a factor of two to three times.

From 2007 to the present, Chris Hampson has been using magnetic filtration to remove harmful contamination found in the coolant system on his  2007 CAT C15 engine. Chris was experiencing seal wear and pump wear due to ferrous metal contamination in his coolant lines. One Eye Industries suggested the installation of a one-inch Y-Strainer in line of the engine coolant circulation system. After 12,000 km, a large amount of ferrous contamination was trapped. In June 2014 at the annual PM period, Chris is still finding a large amount of contamination trapped on the rod (see Figure 3). If left in the fluid, these metal particles will prematurely wear the water pump and radiator components and degrade the quality of the glycol. Figure 4

SAFETY
Magnetic filtration offers a highly efficient, environmentally friendly solution to improve filtration capabilities. By employing this reusable, cleanable technology, the life of the components and fluids can be extended resulting in extended PM intervals, in turn reducing the risk of injury as the technician’s contact and time to and from site is reduced. This should have a positive effect on insurance costs.  Figure 5
 

Maintenance Cost Reduction Achieved Through Comprehensive Fleet Monitoring

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Maintenance Cost Reduction Achieved Through Comprehensive Fleet Monitoring
Major component repair costs are a real issue for wind farms over five years old. Taking as an example data set of six wind farms that Romax monitors, in the last 12 months there have been detections of nine failing planet bearings and 14 failing main bearings. In each case, the damage has been confirmed by inspection and repairs scheduled.  These repairs are expensive and significant cost reduction can be achieved by optimizing the scheduling of repairs. Romax customers are using InSight Fleet Monitor to realize these cost reductions.
 
Wind Turbine Condition Monitoring
Effective signal processing techniques for condition monitoring of rotating machinery have existed for decades, but applying these techniques to the wind industry presents many challenges. A large fossil fired power station may have only four large machines that need to be monitored; these machines operate in a very predictable manner, in a carefully controlled environment, perhaps with the service engineer located just a walk away. A wind farm, by contrast, comprises many turbines, with highly variable operation, located at the top of tower, often in remote locations and often with extreme ambient conditions.
 
Many independent studies have shown that predictive condition-based maintenance can significantly reduce the cost of energy from wind but, in spite of the relative maturity of condition monitoring techniques, this value is often not realized. Most owners/operators face the challenge that they have a range of different condition monitoring systems (CMS) installed, with a variety of interfaces and software tools. This makes it difficult to monitor efficiently and to a consistently high quality. Moreover, there is a shortage of the valuable expertise required to interpret the data. Software tools designed with efficient workflow in mind are essential so that wind farm owners/operators can get the most value from scarce expertise; nobody wants their valuable experts to waste time waiting while switching between turbines, or different software systems.
 
Fleet Monitor is Romax’s web-based, hardware-independent, software for wind turbine health monitoring. The software enables condition monitoring engineers to monitor an entire global fleet of turbines, whatever turbine type or CMS type, with one platform. This means that consistent alarm strategies can be applied so that lessons learned on one farm can be quickly and efficiently implemented to improve the quality of monitoring on another, without the difficulties created by moving between disparate systems. 
 
Using data from existing CMS and SCADA systems, along with lubrication and operations and maintenance data, the software is able to provide a complete picture of turbine health. Often, faults can be detected as much as 12 months in before failure. Once an incipient fault has been detected, various measures, such as main bearing life extension or turbine de-rating, may be taken to increase the component life. Multiple main bearing, or gearbox, change-outs may be scheduled together so that the crane cost is spread and the overall OPEX significantly reduced.
 
Designed with global access and collaboration in mind, Fleet Monitor enables site managers, asset management teams, and condition monitoring centers to communicate and collaborate more effectively.
 
Fleet Monitor Features
• Hardware and software independent so that all turbines can be monitored efficiently and effectively through one platform.
• Proven analysis techniques including time domain trending, FFT, envelope, Cepstrum and time synchronous averaging enable faults to be detected early so that repair costs can be kept to a minimum.
• All data stored and backed up. Many CMS automatically decimate historical data, but with Fleet Monitor no historical data is discarded.
• Libraries of tried and tested alarm rules based on Romax’s experience of monitoring over 3 GW of wind turbines mean more advanced warning and fewer false alarms.
• Remaining useful life models: these innovative prognostic techniques enable forecasts up to three years ahead, so that operations and maintenance budgets can be based on real data rather than guesswork.
• Automated alarm thresholding, which embeds best practice.
• Powerful alarm configuration enables alarms to be set against vibration, SCADA and lubrication data, resulting in confident diagnoses of the turbine condition.
• Automated reporting so that condition monitoring engineers can focus on what really matters rather than copying and pasting figures and formatting documents.
 
Networking
To use Fleet Monitor, no hardware or software installation is required because Fleet Monitor is web-based Software as a Service (SaaS). All that is required is VPN access to the site server(s). This allows Romax to fetch the data and insert it into the InSight Health Management platform automatically, see Figure 1. Open an internet browser on any device, then go to the Fleet Monitor website and you’ll be able to log-in and check the condition of your wind turbines, make rapid diagnoses and schedule inspections.
 
Case Study 1: Planet Bearing Failure Detection
In this example the vibration health index started trending in September 2013, see Figure 2. The analyst using Fleet Monitor recommended inspection. The first inspection (November) showed significant surface distress on the planet gear teeth.  The turbine could continue to operate and the trend was carefully monitored.  A second borescope inspection was scheduled in December and severe damage confirmed on a planet bearing. The gearbox was replaced in January 2014.  The site had four months warning to arrange the most cost effective repair and avoided a catastrophic failure and downtime (temperature trend or other turbine fault provided no indication).  This is typical of Romax monitoring of planet bearing failures: 3-6 months warning as the wear out from bearing spalling is slow. Aging gearboxes that have survived infant mortality issues (e.g. from poor design, poor steel or heat treatment, grind temper and so on) are commonly failing in this mode. Figure 3
 
Case Study 2: Main Bearing Failure Detection
Main bearings failures (initiated from micropitting then progressing to surface initiated macro-pitting) also progress slowly.  Figure 4 provides a typical example where the trend ran for 12 months. This is typical; Romax has not seen a case of less than three months warning and has monitored failing main bearings for 18 months before a repair was made.  At the end of useful life the condition shown in Figure 5 is typical.  Romax’s main bearing life extension technology can be applied to suspend or severely slow the failure, which offers a useful O&M strategy for sites with failing main bearings: Monitor and catch early, extend bearing life, optimize repair schedules.
 
Damaged main bearings can also be detected using SCADA data, however not nearly as early as by vibration monitoring.  For sites that have no CMS this is valuable and Fleet Monitor provides flexibility to include vibration and/or SCADA monitoring. Figure 6 provides an example in which a damaged main bearing is the outliers in SCADA temperature data.
 
Conclusion
Crane hire accounts for a large proportion of cost for a main bearing or planet stage repair; the benefits of carrying out multiple repairs with one crane mobilization are clear. Monitoring and scheduling all major component replacements in the low season reduces costs dramatically.  Romax’s proven monitoring technology is available to enable predictive maintenance with carefully optimized scheduling, worldwide, using a range of CMS hardware that is installed on the original equipment and incorporating SCADA and lubrication data.  
 

Conversation with Mike Jeffrey

Wind Systems staff
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Conversation with Mike Jeffrey

Could you tell us a little about the history of Complete Wind?

Complete Wind Corporation is currently in its fifth year of business. The origins of the company’s core management experience comes from 10-plus years of rotor blade manufacturing (600kW to 1.5MW), before it transitioned to rotor blade maintenance, inspection, and repair. CWC provides its services to wind farm owners and operators.

Geographically speaking, what is Complete Wind’s service area?

CWC is incorporated in both Canada and the United States; employing citizens in their respective countries while allowing our customers operating assets in both countries consistent services.

What is the most pressing issue pertaining to blade maintenance today?

Awareness. The CWC wind industry experience has been that the trends of rotor blade maintenance fall under reactionary measures, rather than preventative.  Increasing rotor blade inspection scope and developing a regular inspection frequency platform will allow owners and operators to identify rotor blades issues and schedule repairs as a part of a preventative maintenance program, thus managing greater control of repair expenses. Unfortunately, it has been the experience of CWC that there is little budget set aside for rotor blade maintenance at the planning stage of a wind farm. Thus, owners and operators find themselves in an undesirable position when it comes to paying for blade repairs and maintenance.

How are emerging technologies changing the way maintenance is performed on blades and other components? How do you adapt to those changes?

The larger rotors and material composition selection, such as carbon fiber, are creating challenges for inspection and repair and how it is performed. Effective data base management of the inspection findings has been aiding CWC to cope with the increase in rotor blade sizes. Drone inspection methods are supplying cost effective inspection alternatives. Also, advances in NDT technology will eventually provide the means to look for anomalies not visible to the naked eye, but there is no substitute for a hands on inspection when a potentially serious issue is found.

Looking forward, what are your expectations for blade maintenance needs?

As the industry matures, I expect there to be more emphasis placed on preventative blade maintenance as the costs associated with reactionary maintenance cannot be controlled or budgeted for.  Many of the operators will increase the scope of their technicians to encompass blade inspections at the site level and employ third party companies, like CWC, as specialists to handle out-of-scope maintenance and repair of the composite rotor blades.

Could you tell us a little about Complete Wind’s inspection services, the need for inspection, and the benefits?

At a wind farm, there are 3 basic rotor blade inspection scopes that CWC employs: Visual from-ground exterior; visual from-ground exterior and up-tower exterior; and visual from-ground exterior and up-tower interior and exterior.

Aside from identifying early stage wear-and-tear items (e.g. leading edge erosion) and force majeure issues (such as lightning strike damage), the need for inspections early in the life of a rotor blade will identify manufacturing anomalies that could lead to costly repairs later in the service life.  CWC’s extensive experience has established that 75 percent of the blades inspected have such manufacturing anomalies.

Establishing an inspection program allows owners and operators the ability to plan maintenance and budget for repairs.  Effective management of inspection findings keeps the maintenance in a preventative mode.

What other services does Complete Wind provide to its clients within the industry?

We perform rotor blade inspections, remediation, and composite repairs — both on- and off-turbine. We also do quality audits of rotor blade manufacturing facilities, technical consultation, and on-turbine dynamic rotor balancing and vibration analysis.

How often should blade maintenance or inspection be performed?

CWC has developed detailed inspection platforms for the different types of blades in the industry, but generally speaking:

  • Exterior, from-ground inspections should be performed annually. This inspection looks for damage from exterior wear, operational defects, lightning strikes, and serious manufacturing anomalies.
  • Up-tower inspections (both interior and exterior) should be performed at the end of warranty, and every two to three years thereafter. Here, inspectors again look for operational defects, wear, and manufacturing anomalies, but broaden the inspection to include both exterior and interior components.
  • The lightning protection system should be inspected according to OEM or IEC61400-24 recommendations. Primary findings commonly includes a down conductor connection, as well as inspection of down conductor connection, as well as a receptor inspection.
  • A dynamic rotor balancing inspection, testing for mass and aerodynamic imbalance, should take place when the turbine is commissioned, as well as every two to three years going forward.

What is the best advice you could give to a wind farm owner or operator regarding blade maintenance?

My advice to owners and operators is to begin planning blade maintenance and repair in January, seek out and select a blade maintenance vendor by March, so that preparations are made for the start of the warmer and typically the lower wind summer months.

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