January 2013

OEM’s, service companies and end-users have an abundance of gear lubricant products available for use in wind-turbine gearboxes. Many OEM factory-fill products come with two- to five-year warranty periods. Pricing is usually the main concern to the customer when it’s time to choose a lubricant once the warranty period has ended or the factory-fill lubricant has reached the end of its useful life. What should be of concern is the performance level of the lubricant and how it relates to the wind turbine gearbox and more importantly, how it protects the environment the wind turbine/farm they reside in In addition, a lubricant company should also provide all the necessary support such as on-site inspection, free condition monitoring and advice on add-on components such as lubricant filtration systems, wireless monitoring devices and mechanical insurance, whether they provide these services themselves or through a contracted service company.

Safety and the Environment
Unexpected lightning strikes, generator set malfunctions and other mechanical and electrical system malfunctions have the potential to ignite lubricants that are on board a wind turbine’s nacelle. This potential is elevated when standard mineral oil-based products are used. Synthetic wind turbine lubricant technologies such as Total’s Carter SH 320, Carter SE 320, and Carter SY 320 help reduce the risk of fire and explosion when system malfunctions occur. They should be strongly considered where long fluid life, safety and environmental protection are paramount.

In Europe and North America, Fire protection agencies such as CFPA E & NFPA have recently added wind turbine and outbuilding fire protection standards. These standards are the CFPA E No 22:2010F “Wind Turbine Fire Protection Guidelines” and NFPA 850 std., titled “Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations,” 2010 Edition. These codes provide detailed recommendations for wind turbine generating facilities fire protection requirements.

A single turbine may contain up to 200 gallons of oil. The transformer at the base of each turbine may contain another 500 gallons of oil. In rural areas even a spark can easily develop into a large fire before discovery is made and fire-fighting can begin. Damage from fire accounts for up to 20 percent of wind power insurance claims.

Leading Causes of Turbine Fires
Lightning strikes are the leading cause of wind turbine fires. This is primarily brought about by their exposed and often high-altitude location and the height of the structure — turbines are now being built that are up to 320 feet tall.

Mechanical failure or electrical malfunction also accounts for a significant percentage of fires that can be fueled by hydraulic fluid and lubricants in the nacelle, which itself are constructed from highly-flammable resin and glass fiber. Internal insulation in the nacelle, which can become contaminated by oil deposits, adds to the fuel load.

Electrical equipment is another high-risk area. Capacitors, transformers, generators, electrical controls, and transmission equipment all have the potential to catch fire, as do Supervisory Control and Data Acquisition (SCADA) systems. There is also the risk of fire due to loose or broken electrical connections or the overloading of electrical circuits.

Braking systems also pose a particularly high fire risk. Overheating can cause hot fragments of the disc brake material to break off, rupturing hydraulic hoses and resulting in highly combustible hydraulic fluid being expelled under pressure and coming into contact with the hot disc brake fragments. Hydraulic pumps and connections have also been known to fail, allowing the fluid to erupt into flames when it comes into contact with a hot surface.

Synthetics based on PAO, PAO/ester, Polyolester and Polyalkylenglycols provide high flash points and low volatility, which provide a wider margin of safety in regard to fire protection. The following table (Table 1) illustrates this increased level of protection for both gear fluids and hydraulic fluids.

Environmental Protection
Total Specialties believe that we should all strive toward minimizing the negative impact we have on our environment in regard to the amount of pollution generated in our day-to-day lives, whether at work or at home. We proudly support and specify the use of our biodegradable lubricants whenever possible. Total defines biodegradation as the chemical breakdown or transformation of a substance caused by organisms and their enzymes.  Further, in regard to what defines a biodegradable lubricant, we utilize either ASTM D 5864 and/or OECD 301 B, which are standard test methods for the determination of aerobic-aquatic biodegradation of a lubricant, which specifically defines degradation of a lubricant from 60 percent to 95 percent within nine to 28 days.

Biodegradable Terminology
Primary biodegradation — is defined as a minimal modification of a substance by microorganisms that cause a change in some measurable property of the substance.
Ultimate biodegradation — is the degradation achieved when a substance is totally utilized bymicroorganisms resulting in the production of carbon dioxide, methane, water, mineral salts, and new microbial cellular constituents. This term usually refers to vegetable oil-based products
Readily biodegradable — Using the ASTM test method D 5864 or OECD 301 B, 60 percent or more of the test material carbon must be converted to CO2 in 28 days. Usually associated with lubricants that are glycol or ester-based whether synthesized from renewable resources (Oleochemical) or synthetic esters, (class HEES) such as Total Biohydran SE-series.
Inherently biodegradable — is a classification of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) in any test of biodegradability. This term is usually associated with mineral oil-based products due to their low degree of biodegradation in ASTM D 5864 or OECD 301 B (Typically less than 40 percent). Products that are classified as inherently biodegradable are also pollutants and if disposed of in the environment are subject to fines, clean-up regulations, and long-term remediation.
Mineral-based formulae are not biodegradable. Applications where biodegradability is of importance, such as offshore service or areas mandated by governmental, state or local law, mandate the use of  esters — specifically polyolesters (such as Total Carter SE 320) and polyalkyleneglycols (such as Total Carter SY 320).

Synthetic Lubricant Overview
Synthetic chemistries provide energy efficiency and energy conservation which are of major concern today. Synthetic lubricants formulated for general industrial applications typically utilize some combination of PAO (polyaplhaolefin), Diester, Polyolester, alkylnaphthalene, and PAG (polyalkyleneglycol)-oil soluble type. These synthetic basestock chemistries bring certain attributes that can maximize performance in relation to the mechanical components operation. Synthetics provide enhanced thermal-oxidative resistance, improved lubricity, heat dissipation, and wider operating temperature range, when compared to mineral oil-based products. The use of synthetics provides performance-level gains over longer periods of time as compared to mineral oil-based products. For example, a typical ISO 320 mineral oil-based product lasts 2-3 years in most wind turbine applications. Synthetic basestocks such as polyalphaolefins (PAO), due to their “non-polar” nature, are excellent at separating from water, which is attractive in many applications where water has the potential to migrate into the lubricant — such as rotary screw compression applications and Industrial gearbox operating in humid conditions. Esters, such as diesters, triesters and especially polyolesters, due to their polar nature and molecular bonding strength, provide excellent thermal-oxidative stability, which is very attractive in high heat, closed system applications such as aeroderivative turbines. Of special interest to the formulator, PAO’s and esters have opposing reactions in regard to compatibility properties in relation to most commonly used elastomers and seals. A balance between the two can provide a compatibility characteristic that is favorable to the applications seals, gaskets, and coatings especially in elevated temperatures and pressures. Some formulations may also contain low amounts of high molecular weight “thickeners” such as polyisobutylene (PIB), polyalkyl methacrylates (PAMA), or polymeric esters in order to build viscosity to the required ISO level.

In regard to synthetics, the standard basestock chemistry that has the most wide spread usage in wind turbine gear applications today is PAO with addition of polyolester. The addition of polyolester, usually a TMP (trimethyolpropane)-type, is mainly an aid for additive solubility, contaminant dispersion and in combination with PAO provides the required compatibility profile. This PAO/ester-blend utilizes a combination of low molecular weight and high molecular weight polyalphaolefin species. Since they contain high molecular weight polyalphaolefins, they do not require polymeric thickeners such as some mineral oil-based products. Shear rates are very low for products that use high molecular weight PAO. For instance, PAO 40 when blended with PAO 4 showed to have only a 0.5 percent viscosity loss in the KRL 20-hour tapered bearing shear test. Comparatively, certain polyalkylmethacrylates blended with PAO 4 can lose up to approximately 6 percent.

Typical additive chemistry for wind turbine gear lubricant utilizes extreme pressure and anti-wear additive package that usually contains some combination of sulfur, phosphorus and boron along with antioxidants, anticorrosives and defoamants. The PAO basestocks offer low pour point, high flash point, in addition to excellent thermal-oxidative stability, shear stability, and demulsibility properties which are all considered paramount in regard to performance properties in typical wind turbine service. PAO’s molecular structure also provides a high inherent viscosity index. The high viscosity index is directly related to the molecular chain structure which is “comb-like.” Though its structure resembles a hydrocarbon (since it is synthesized) it contains no wax or other undesirable chemicals that are particularly found in group one and group two mineral oils. Typical viscosity index for an ISO grade 320 PAO-based product is in the range of 145 to 160. The high viscosity index provides wide operating temperature range and indicates the amount of “molecular density load” or hydrodynamic film provided between metal surfaces under elevated pressure and temperature. The molecular structure of polyalphaolefins provides very low order of volatility, especially with the high molecular species. This low order of volatility relates to low levels of fluid loss in high-temperature, high-pressure applications which lessons the call for “top-off” or “make-up” oil. For comparison, low molecular weight polyalphaolefin has approximately a 12  percent weight loss in volatility (Noack) testing. Whereas, the equivalent viscosity mineral oil yields 14 to 23 percent weight loss. Another detriment of using mineral oil based products is the deleterious byproducts from oxidative breakdown that they leave behind in lubrication systems and mechanical parts. These byproducts are usually in the form of varnish and/or coke. These remnants will eventually be solubilized by the ester contained in the PAO formulation. The inherent low pour points of PAO/ester gear formulations offer “clean operation” and energy efficiency at low temperature start-ups and during standard operations.  Of importance, most well-formulated PAO-based products do not use viscosity improvers in the formulation. Comparatively, most mineral oil-based formulations utilize viscosity improvers. As stated earlier, wind turbine gear formulations require a high degree of shear stability which most viscosity improvers cannot provide.

PAG’s and POE’s, such as Total’s Carter SY 320 and Carter SE 320 respectively, provide excellent thermal stability, low order of volatility, and high flash points. Their molecular structures have excellent effect on lubricity, solvency, and biodegradability. This is very attractive since it effectively lowers the carbon footprint in regard to its manufacturing process. Many polyolesters are manufactured using vegetable-derived renewable content some high as 85 percent. Both polyalkyleneglycols and polyolesters attribute their high level of polarity to the inclusion of oxygen in the hydrocarbon molecular structure. As far as physical properties go, they have much higher specific heat and thermal conductivity profiles as compared to mineral oil. Specific heat and thermal conductivity are a measure of how well a lubricant absorbs and dissipates heat. They have the ability to carry more heat away from the friction sites in a gearbox such as bearing surfaces and at the gear-teeth contact site.

Coefficient of friction and thermal conductivity properties improve with this type of molecular structure. Coefficient of friction is the lubricants ability to improve mechanical efficiency through minimizing the friction (or wear) between moving parts. Thermal conductivity is a measure of the lubricant’s ability to absorb heat than dissipate the heat away from the mechanical friction sites such as the gear teeth and bearings found in wind turbine gearboxes. Both properties have a positive impact on operating temperature. It is well known that cooler running mechanical components last longer.

Synthetic lubricants are the clear choice for protecting not only the mechanical components of a wind turbine but also our environment. 

Everyone is familiar with the problems associated with poorly balanced rotating equipment. When buying new tires for a car, you would not think of having them installed without first having them balanced.  An unbalanced tire creates vibration forces that can be felt throughout the entire vehicle. A balanced tire is created when a small weight is placed opposite the “heavy spot” on the tire. This small weight is the difference between a bouncy, dangerous ride and a smooth one. The same can be said about a rotor on a wind turbine. A wind turbine rotor that is not balanced creates vibration forces that affect the mechanical life and operating performance of a turbine. Therefore, an acceptable level of wind turbine rotor balance should be established and measured as a part of any in-situ blade repair, blade replacement, wind turbine commissioning, end-of-warranty inspection, or reliability centered maintenance program. Figure

Problems Caused by Unbalanced Turbine Rotor
An unbalanced wind turbine rotor results from a mismatched weight distribution of the individual blades that make up the rotor. There may be several consequences of an unbalanced rotor on a wind turbine.

First, in light winds, a turbine may have trouble coming on line or may be operating in portions of the revolution as motor rather than a generator, both leading to potential loss of revenue for the wind farm operator. An unbalanced rotor accelerates and decelerates during each revolution. The turbine experiences loss of power during half of the rotor rotation and gain of power during the second half of rotation. The controller sees this as a satisfactory condition to stay connected. The solution is to properly balance the rotor. However, achieving a precision balance on a wind turbine rotor is easier said than done and falls outside of the skill set of most wind farm maintenance personnel as well as those who are specifically employed by general industry to balance rotating equipment.

Secondly, a wind turbine with an unbalanced rotor will lose some of its low wind production capability. For any given level of unbalance, it requires power to rotate it at a given shaft speed. This power requirement robs the rotor of speed for a given wind velocity and delays its synchronization with the utility. Consequently, it will require more wind velocity to achieve synchronization as compared with a balanced rotor. Again, an unbalanced rotor results in a loss of revenue potential for a wind farm operator which could have been realized otherwise by an acceptably balanced wind turbine rotor.

Third, the out of balance rotor continuously applies fluctuating loads to all of the mechanical components of a wind turbine (e.g. main shaft, main bearings, gear box, drive train support structure, yaw system, tower, bolts and even the foundation). In order to visualize the effect of the unbalanced force on a rotor, remember the unbalanced ceiling fan that operates on high speed and wobbles uncontrollably. If there wasn’t a flexible mounting to the ceiling, these forces would eventually cause the ceiling fan to fall as was the case when the flexible mount was not an installation requirement.  The rotor weight of a ceiling fan is on the order of ten’s of pounds. The rotor weight of a wind turbine can be greater than 72,000 lbs. However, there is no flexible mounting for the wind turbine rotor.  The mechanical structures which support the rotor are designed to keep the rotor in a fixed location. These constantly fluctuating loads add to the fatigue loading and shorten the mechanical life of these systems. Remember, fatigue life is finite. When you use it up through these wildly fluctuating loads, it’s gone. You unknowingly spend fatigue life on an unbalanced rotor which could have otherwise been spent on producing revenue. Premature expenses and loss of production will be incurred by the wind farm operator through the replacement of a major component or entire system as a result of this fatigue failure.

Rotor unbalance is a leading contributor to the need for frequent and costly maintenance action on yaw systems and fastening hardware. The unbalanced force on the rotor causes a reaction on the yaw system twice per revolution, accelerating the wear on the yaw gear teeth through impact loading and adding to the fatigue loading of the tower shell and mounting bolts.  Yaw brakes are used to limit this impacting on the gears. However, the brakes do nothing to limit the loads transferred to the tower. For perspective, a typical turbine will have over 100 million of these “two per revolution” loading events in its life. That’s a lot of pounding and stressing on your machine components.

Causes of Wind Turbine Rotor Unbalance
Rotor unbalance results from an unmatched weight distribution between each of the blades on a rotor. Each blade on a hub produces a moment or a torque on the main shaft. The moment or torque can be represented as a weight mounted on a weightless arm at some distance from the centerline of rotation (main shaft). Ideally, the moments of each blade on the rotor are equal around the center of rotation. When these moments are identical, there is no net unbalance force on the rotor. The moment of a blade is the product of the distance of its center of gravity to the center of rotation and its total blade weight (see Figure 1).

It is for this reason that efforts are made to match the blades as closely as possible during blade manufacture.

Any changes which affect the weight distribution of the blade will affect the moment of a blade and, consequently, the balance quality of the rotor. Significant changes in blade moment can result from everything from manufacturing to blade repair. Examples of issues leading to blade repair are: structural cracking, gel coat cracking, lightning damage, gun shot damage, shipping damage, storage damage, ultraviolet environmental degradation, etc. Changes in blade moment may also happen during “normal” operation. Examples that produce changes in weight distribution and total blade weight are: oil and grease from pitch systems, wind erosion, water absorption, internal debris accumulation from poor construction, animals/nests from unprotected ground storage. Examples which produce unequal blade moments at time of manufacture are:  poor production techniques, weak construction process controls, inconsistent manufacturing tools, etc. Over the twenty-year design lifespan of a wind turbine, there is a high probability that a wind turbine rotor will be operating with a higher degree of unbalance than desired — caused by any combination of these factors. Perhaps most concerning is that without good analysis, an operator may never know the extent of your balance problems.

Balance Quality
The international ISO 1940-1 standard is a widely accepted standard for selecting rigid rotor balance quality.  It effectively grades and describes acceptable limits of rotor unbalance as a function of its rotating mass and rotational speed.

The lower the grade number, the better the rotor is balanced.  For example, an ISO balance quality G0.4 would apply to a spindle of a precision grinder while an ISO G1600 would apply to the crankshaft of a large two-cycle, rigidly mounted engine.  While a rotor balance quality standard has not been adopted by the wind turbine industry, an ISO G16 or better may prove to be a practical and acceptable target.  G0.4 is achievable with tight blade manufacturing tolerances and/or dynamic field balancing.

The chart above is an adaptation of the ISO 1940-1 standard for the area of wind turbine rotor operation.  To use the chart above, you would select the desired balance quality and the maximum operating speed of the wind turbine rotor.  At the point where the operating speed intersects the desired balance quality line, find the corresponding value of “e” on the y-axis.  Multiplying this value of “e” by the total weight of the rotor will give you the maximum amount of residual rotor unbalance allowed for the desired ISO balance quality.  For example, if a rotor weighed 5,000 lbs and was operating at 60 rpm, for a G16 balance quality, it could have no more than approximately 500 in-lbs of residual unbalance. This is equivalent to one blade having an “extra” weight of 2 lbs located 250 inches away from center of the hub.

Rotor Balance — Static Blade Balancing
All three blades must create the same moment around the center of rotation when mounted on a wind turbine hub. This is accomplished by weighing the blades and then adding calculated weights such that each blade exhibits the same moment around the center of rotation. The inherent assumption is that if the blades are balanced, the assembled wind turbine rotor will be balanced.  There is a phrase for those who ASSUME.

A generally accepted balancing practice for a blade repair shop or for field determination of blade balance requires weighing the tip and root ends of each blade through the use of flexible straps supporting the blade at prescribed distances and a crane weighing scale. Root and tip weights are then matched to the heaviest root and tip measurements by adding the appropriate amount of weight. This process makes the total blade weights the same and the moments of the roots and tips the same around the center line of rotation. Statically balancing the blades in this fashion will produce equal blade moments. However, it does so with more weight than is necessary. It will not only effectively increase the mass of the rotor more than required but will place additional bending fatigue on the blade as this corrective weight at the tip has to be supported against gravity every half revolution of the rotor. This extra weight is operationally counter-productive. Figure 2

Dynamic Rotor Balancing
For general industry, rotating equipment (fans, pumps, gears, motors, etc.) can be balanced using a transducer (displacement, velocity, acceleration) and a shaft reference to measure the response of the shaft supporting structure or the shaft itself to the unbalance forces in relationship to a physical location on the shaft. The rotational speed of general industry equipment is typically above 600 rpm. The process involves recording the amplitude response, typically with an accelerometer, at the turning speed (1X rpm) of the rotor and its relationship to a physical shaft reference. A trial weight is then added to the rotating object and the new 1X rpm amplitude response and shaft reference relationship is measured. By knowing the response to the trial weight, a corrective weight solution can then be calculated to nullify the unbalance. 

This same principle can apply to wind turbine rotors and several companies offer corrective balancing of wind turbine rotors using this method. However, employing this method for wind turbine rotors is risky at best. The typical speed of a wind turbine rotor is below 60 rpm or 1 Hz and falls into a range of limited usable sensitivity for most standard transducers and associated data acquisition equipment. The reduction in sensitivity will necessarily limit the level of balance quality which can be achieved. The accessibility of the main shaft, where the 1X rpm amplitude response is measured, presents an issue as it may be elevated off of the ground by distances as great as 300 feet. Safety protocol may prevent personnel from being in this area during operation. Data acquisition is further complicated by the presence of non-steady wind and spurious structural responses which may limit data collection to periods of low wind. While several companies may balance a turbine rotor with this method, a simple assessment or validation of rotor balance using these methods may be cost prohibitive. As compared with static blade and static rotor balancing, a better rotor balance quality can be achieved dynamically within the limits of the traditional balancing instrumentation employed, technician skill level, and other factors.

Frontier Pro Services utilizes Dynamic PowerPro Balance™, a patented method and instrumentation to dynamically assess the degree of wind turbine rotor unbalance and provide for a corrective solution. This proprietary method does not employ the traditional sensors used in balancing and is not subject to the inherent sensitivity limitations. The technology performs throughout the motoring and generation range of the turbine. Furthermore, this technology allows both cost effective assessment and correction unattainable by traditional methods. As such, balance quality can be assessed and realized as a part of any in-situ blade repair, wind turbine commissioning, end-of-warranty inspection, or reliability-centered maintenance (RCM) program. The balance assessment can be made without any installation of trial weights and does not require turbine down time. While Frontier Pro Services targets to achieve a balance quality of G16, the utilization of this technology, as well as the process of installing the corrective weights internally to the blade, has enabled final balance qualities of G0.4.

Conclusion
Wind turbines are highly engineered mechanical devices designed to have balanced rotors. Unacceptable levels of rotor unbalance accelerate mechanical fatigue on everything connected to it — bearings, shafts, pitch systems, gearboxes, generators, yaw drives, towers, and even foundations. This excessive fatigue loading will cause performance issues on start up and shut down. Unbalanced rotors result from manufacturing, blade repairs, or blade alterations as well as events which can occur during operation. There is no debate; the cost of accelerated mechanical wear, delayed startup, and wind turbine motoring are real. Like a silent cash register, your costs accumulate on every sub-optimal turbine, every day. Precision rotor balancing can drastically reduce the continuous profit drain on your operation.

While static blade balancing is designed to achieve a balanced rotor, it will not achieve the objective due to measurement and process errors. Additionally, static blade balancing requires that the blades be removed from the rotor, which is expensive, time consuming, and risky. Traditional dynamic balance assessment and correction doesn’t provide the precision necessary to get optimal results.  Thus, the best way to assure peak performance is to utilize Frontier Pro Services’ Dynamic PowerPro Balance system.  As a part of overall reliability and performance management of a wind farm, establishing acceptability criteria for rotor balance is essential for blade repair, wind turbine commissioning, end-of-warranty inspection, or reliability-centered maintenance program.  Management of rotor balance quality can now be cost effectively realized through the services and technology of Frontier Pro Services. 

It is widely believed in the wind industry that improvements in yaw control can only produce a small improvement in output power. This belief simultaneously exists with an acknowledgment that attempting to measure wind characteristics in the turbulent post-rotor wind is problematic.

BlueScout Technologies has shown, on a variety of turbines, that power increases can be achieved when improved wind angle information is fed into the yaw control systems of turbines. However, this early work typically uses the legacy control strategy of the turbine. In truth, turbine manufacturers have invested considerable time and thought into developing yaw control strategies that compensate for the errors of the post-rotor measurement system. However, those strategies typically include long averaging times and allow considerable variance in yaw before correcting the yaw angle of the turbine.

Accurately measuring the incoming wind properties, with dramatically reduced noise, means that different control strategies can be considered for yaw control. Put simply, beyond the gains achieved by simply feeding better information into the legacy control system, how much extra power can really be generated by employing control strategies that take advantage of the improvement in wind information?

This work takes real data from an operating turbine under the yaw control of the BlueScout Optical Control System (OCS). The summary describes the methodology used in the simulation and the results of the parametric study for the two control parameters of wind direction moving average time and yaw direction threshold. Power performance increases and turbine yaw actuation times are presented. For unlimited yaw activity, a power increase of about 6 percent is demonstrated. If yaw activity is limited to 8 percent, it was found that an additional 3 percent power gain may be achieved with settings for the site/turbine installation evaluated in the study at a moving average time for the wind direction of 60 seconds and a yaw direction threshold of 8 degrees.

Methodology
A simulation was developed in order to estimate optimal control parameters for the OCS. The simulation and model were developed in MATLAB and Simulink, the model being presented in Figure 1. The design of this controller model was based on existing turbine yaw algorithms: The system utilizes a moving average of the wind direction as measured by the nacelle anemometry and begins yawing when the moving average exceeds a specific threshold. The turbine continues to yaw until the moving average of the direction error is zero degrees. Both the moving average time and the direction error threshold are parameters in the simulation.

The input to the simulation is the sum of the OCS measured wind direction on an operational wind turbine (wind direction relative to the nacelle) and the turbine nacelle position. This sum is a measure of the wind direction relative to north, and represents the wind field to which the turbine is exposed in time. The data utilized to run these simulations is real data from an installation of a BlueScout OCS on an operational turbine. The data set includes OCS variables, such as wind speed and direction, as well as the nacelle orientation and power production.

The simulation models how this actual turbine will react to this changing wind field based on the turbine’s yaw rate, and the two parameters of moving average time and yaw error threshold. The output of the simulation is the yaw actuation of the turbine and an estimate of the local wind direction error to which the rotor is exposed. The yaw actuation data allows for calculation of number of yaw events and time yawing. The wind field measurements from the OCS upwind of the turbine are propagated to the turbine assuming a constant convection velocity equal to the mean velocity of the sample data being processed. Utilizing the wind from north data and the current simulated nacelle position, and assuming the time to convect to the rotor from the OCS measurement locations, a local rotor wind direction error can be calculated. This data allows for statistics of the instantaneous yaw error and estimates of power production to be determined. Power production is modeled as the cos3 of the local rotor wind direction error. This relationship comes from the argument that the effective wind speed for power production is the cube of the normal component of the wind to the rotor. The relative power production is proportional to cos3 of the wind direction error, so the cos3 of the convected wind direction error is the metric for performance increase in this study.

Results
A parametric study was conducted using the simulation for a variety of moving average times and yaw threshold values. The simulation assumes that the power produced by the turbine is proportional to the cos3 of the wind direction error at the rotor, so this value is used as the metric for power performance improvement. Results of this study can be seen in Figure 2 and Figure 3. Figure 2 demonstrates how the cos3 of the yaw error varies with the two-parameter settings. Figure 3 demonstrates how the fraction of yawing time changes with the two-parameter settings. In looking at these curves, as the moving average time is decreased and the yaw dead-band is tightened, both the relative power captured and the amount of time yawing increase. This is as expected: the turbine is more accurately tracking the wind, especially smaller turbulent scales, such that the local rotor wind direction error is reduced, but at the cost of much more yaw actuation. Figure 2 also demonstrates that there is an upper limit to this benefit in power capture given the upwind nature of the measurements. Once the moving average time becomes small enough, the phase lag this introduces is smaller than the convection time from the OCS measurement volume, such that the controller is introducing an error by yawing too soon. This is more evidence that these studies should be more rigorous in being done at specific speed regimes, and that the parameter settings will probably be optimized with a scheduling routine to account for this phase issue.

Given these results, a recommend set of parameters where there is moderate power performance gain, while limiting the increase in yaw actuation, would put the moving average time around 60 seconds, and the yaw direction threshold at 8 degrees. This would be an increase in power performance of roughly 3 percent while changing the time yawing from about 5 percent of time yawing to roughly 8 percent. Again, performing this study while focusing on differing wind regimes would be beneficial, as a representative power curve showing the relative increase with scheduled parameters could also be developed.

Note that this is optimization of the OCS. The OCS has greatly improved performance over legacy control systems with existing nacelle anemometry at any of the parameter settings in the range demonstrated in this study.

Discussion and Further Work
The results presented here are mean results over all wind speeds. The model for power performance of the cos3 of the wind direction error is only applicable below rated power. The performance increase may vary depending on wind speed. The simulation could be run taking speed regimes in to account, which may lead to scheduling of parameters for different wind speeds.

This simulation is run using local wind data and turbine characteristics. Parameters may vary by time of year (seasonal weather patterns), or by nominal wind direction (local properties – terrain, etc. – which may affect turbulence), as well as for turbine model (unique yaw rates). A schedule of parameters could be developed if optimal parameters were found to vary for these changing conditions (such as scheduling by wind sector). Historical MET data from the original site assessment could be utilized to do this work, but this would ignore the local affects the turbine has on the inflow wind. The data used for this study had the benefit of an OCS installed on an operational wind turbine, so blockage/induced flow effects are present in the real inflow measured data.

This simulation is based on a simple turbine control algorithm. More advanced algorithms could be developed and implemented. The same processes as described in this study could be utilized, where the Simulink model has more capability. More complexity could also be added for scheduling yaw rates (variable yaw rate machines), as well as scheduling the given parameter settings. The overall algorithm could also be modified, where the simple on/off relay model is replaced. Manufacturers could also modify the physical yaw actuation systems to allow for different control strategies, such that the controller is not limited by the amount of time yawing. This research is currently ongoing in order to best utilize the novel optical control system. Implementation of such algorithms is relatively simple, as these are simply software changes in existing control hardware implementations. 

Since the inception of the Industrial Revolution, machinery reliability has become increasingly important. In more recent times, it has become obvious that every aspect (from design and purchase through the operation, continuous evaluation, and maintenance) must be scrutinized for means to keep machinery performing effectively and efficiently. Each time a machine or system goes down, revenue and profits take a hit. One of the most important means of maximizing a machine’s performance and operating time is to increase its reliability. Over time, condition monitoring and predictive maintenance technologies have proven to do just that. New innovations have been developed to harness these technologies and to remotely evaluate and analyze machinery and system performance at an affordable price.

IMPROVE YOUR MACHINERY RELIABILITY
From the beginning, vibration analysis has been the tool of choice for identifying and analyzing machinery problems. Today, vibration analysis has gone through numerous advancements to become an exacting, reliable and cost effective means for achieving machinery reliability. The next phase of maintenance is to enhance machinery reliability by marrying the standard process parameters (such as temperature and pressure) with the advanced dynamic predictive factors such as high resolution vibration spectra. This complex combination offers invaluable analytics for a detailed picture of the health of each machine. Merging these enhanced diagnostic abilities to the Internet’s 24/7 accessibility and the latest products are making the industrial world a much smaller place. Suddenly no matter where you are located, you will have instant access to experts from around the globe to aid you in resolving your machinery problems at a moment’s notice. This vision is not only possible but, with Vibration Specialty Corporation’s Protect Wireless online monitoring and evaluation system, it has become reality.

VSC’s extensive condition monitoring and hardware/software development experience has enabled them to create Protect Wireless. Protect Wireless is a game changing, online monitoring and analysis system for every piece of rotating machinery, especially wind turbines. It merges predictive maintenance and condition and energy monitoring, with every other process-related vital sign, to provide a complete picture of machinery conditions at any instance.

Condition monitoring and predictive maintenance provide critical information that turns the tide on machinery reliability. In fact, the Federal Energy Management Program states that predictive maintenance programs offer a return-on- investment (ROI) of 10:1, while reducing maintenance repair costs by 25-30 percent, eliminating breakdowns by 70-75 percent, reducing downtime by 35-45 percent, and increasing production by 20-25 percent . All of this occurs because machinery faults are able to be seen well before they can cause a failure. As a result, you have the luxury of time on your side to resolve the impending problems and plan maintenance actions at the most convenient time. These remarkable predictive maintenance performances can improve even further with increased data resolution/accuracy, enhanced signal processing techniques, and more on-line data collection and evaluation.

TECHNOLOGY — The World at our Fingertips
Our world is experiencing new technological advances each day. We have become an instant gratification society by receiving current information on our friends, breaking news, sports scores, and even live video right on our smartphones.  These continual updates keep us totally apprised of our constantly changing world, making us far more informed of conditions around the globe.

Protect Wireless was designed with this same concept in mind. This communication model that keeps us up to date with world events also transforms how we monitor and analyze equipment. Protect Wireless was created so experts are no longer needed on site to evaluate machinery. The goal has been to eliminate the cost and time consuming requirements of experts that take days to come on location with their advanced equipment. This new model brings the data and email/text alarm alerts to any computer or smartphone via the Internet. Just like everything else in today’s society, personnel can be notified of any deteriorating conditions in machinery as it happens.

Protect Wireless takes data collected on a machine and wirelessly transmits it anywhere around the globe, virtually in real time. The system consists of one coordinator and one or more satellites that are located near the equipment/machinery and are directly wired to the sensors. Beyond that, the system is wireless. The system can take in virtually any type of sensor and even incorporate existing SCADA/PLC wired data into the process. Each Protect Wireless Satellite comes with numerous options to fit varying needs and budgets. Figure 1

One of the different options that Protect Wireless offers is the ability to select between one to eight simultaneous or synchronous data collection channels. The fewer collection channels you have, the lower the cost and the fewer multi-channel analytics that can be performed. However, even with a one-channel system, you can conduct advanced real-time FFT analysis that can paint a clear picture of the machine condition.

The data collection section is attached to one or more multiplexers, each offering 32 input channels. These can be joined together to offer more than 100 total input channels per satellite. The multiplexers have several different advanced options as well. It will suffice to say the standard multiplexer can provide ample information to accurately evaluate equipment cost-effectively from anywhere.

After the hardware gathers data from the sensors, it is initially processed and analyzed by each satellite. Subsequently, it is wirelessly broadcast at a 2.4 GHz 802.15.4 industrial standard frequency to the Protect Wireless Coordinator. The coordinator then translates and communicates the information to a local computer.

At the computer, the information is displayed through the software’s simple image-based user interface that provides machine and sensor hotspots. For instant problem recognition, the colors change based on the severity of the detected faults. Clicking on a colored hotspot launches a new level, revealing additional analysis details for quickly evaluating the situation. In a simple picture, the software’s mid-level screen distinctly reveals the specific part of the equipment and sensors that are in alarm. One mouse click on the alarming icon allows immediate access to information with trends, statistics, and historic and real-time raw data from each sensor. Figure 2

HIGH RESOLUTION — CRITICAL DETAILS
Protect Wireless is ideal for wind turbines for many reasons. First, the high resolution data is similar to high definition television which allows the viewer to crisply see the individual grass blades on a football field or the blemish on an actress’s face.  VSC’s high resolution data works exactly the same way. Specific fault frequency peaks can be identified earlier than in the past, resulting in quicker solutions and less damage. Secondly, the wireless communications are simpler to install, so you can quickly get set up permanently or even for temporary testing. Further, simultaneous multi-channel data collection (up to eight channels) along with the instant Internet connectivity provide an expert remote diagnostic capability and keeps you informed of any alerts.

Protect Wireless has an exceptional high definition accuracy with 24-bit resolution. This is critically important as it detects wind turbine faults early. Normal monitoring systems have 16-bit or lower resolution, which causes the noise floor to be raised. This instrument noise blocks the machinery signals. Wind turbines, like other slow rotating machines, typically have lower vibration levels. Low-amplitude data can be buried in the instrument noise, making it difficult to identify bearings faults which are inherently lower signals.

Dropping the noise level enables the system to offer logarithmic scaling which amplifies the low-amplitude signals, so that even the lowest incipient bearing or other critical fault can be seen. This factor is extremely important considering that current practices often have difficulty identifying bad bearings. By the time the identification takes place, it is simply a matter of time before the bearing totally deteriorates. With early detection, there may be actions possible to avoid a complete failure and extend the bearing life appreciably.

WIRELESS COMMUNICATION — SIGNIFICANT ADVANTAGES
Wireless communication has a huge advantage over wired systems for wind turbines. Only minor wiring is necessary from the satellite to the machine sensors. Once the satellite and sensors are installed in the wind turbine, the signal goes wirelessly from there to a centrally located coordinator. This provides for ease of installation and gets 24/7 machinery monitoring online quickly.  Once online, each wind turbine turns into an intelligent machine that relates when there is a problem.

Data from the Protect Wireless system is accessible instantly through the Internet and received at the other end, almost in real time. This means that you can view and analyze current data regardless of the turbine’s location in the world.  All processing, trending, correlating, etc. can be performed to give the user immediate knowledge of the equipment and component conditions. This is invaluable when immediate assessments are required to make economical decisions regarding maintenance. Figure 3

One unique benefit of Protect Wireless is that it allows offsite and onsite personnel to quickly connect with experts from around the globe to remotely review, analyze and consult on the data via computer or smartphone. In the past, analysts and engineers needed to be onsite to diagnose machine problems. Protect Wireless has changed this. This system, with advanced hardware, offers detailed phase analysis across couplings and shafts for additional analytics to promote predictive diagnostics. In addition, the system’s distinctive ability to gather eight simultaneous channels of data is invaluable to engineers analyzing the data, because all of the data is collected at exactly the same instant. Engineers can relate each sensor’s amplitude, frequency and movements to all others involved for a comprehensive picture of how each part is moving in relation to other parts as well as the entire system. This operational deflection shape (ODS) similarity provides a third dimension to your online monitoring, enabling you to determine the total and relative movement of the structures and machines in your system. Figure 4

All of this information empowers the analysts to identify explicit machinery faults, and recommend specific inspections, tests and repairs to help resolve the issue. No matter where you are, the information is always at your fingertips. Faults are found early and decisions can be made quickly to resolve issues well before they have time to deteriorate and compromise your operation.

DATA — A WEALTH OF KNOWLEDGE
The ultimate value of this smart system goes well beyond finding specific machinery problems and energy losses, but lies in the data generated. This data holds a wealth of information which, when mined for analytical significance and correlations, can predict future operational, process, environmental and maintenance issues. Different data combinations may produce advanced diagnostic insights that were not considered possible before. This information could reveal an unlimited world of new solutions. This intelligent world will also feed off itself — blending old with new data and new sensors — to yield a profound understanding of our most perplexing problems. 

As onshore wind power expands, suitable sites will become scarcer in the long term. By identifying further suitable sites in forested regions, decision-makers plan to increase the number of potential sites. However, forested sites demand a differentiated approach to address the complex topography, turbulence caused by wind flow, national regulations and stakeholders’ sometimes extremely diverse interests. Under what conditions are forest wind farms feasible and profitable?

The land area in Germany that is fully suitable for harnessing the power of wind amounts to around 8 percent. This percentage rises by 4.5 percent if suitable forested sites are included and by a further 10 percent if nature conservation areas are added. These are the conclusions of the “Potenzial der Windenergienutzung an Land” (Potential of onshore wind power) study, which the German Wind Energy Association (BWE) reissued in March of this year. On the other hand, 78 percent of Germany’s land area is unsuitable for producing energy from wind, as these areas are too close to infrastructure or residential zones or inappropriate from the perspective of nature conservation.

Given this, space on farmland, fields and meadows may soon be at a premium because the percentage of suitable land area identified by the BWE does not actually take into account wind conditions, ownership conditions and geographical features. When all these aspects are taken into consideration, the locations that are actually suitable for wind farm realization and profitable operation amount only to a few percentage points of Germany’s land area.

Paradigm Shift: Forests No Longer ‘No-Go Areas’
In light of the above, sites located in various types of forests are increasingly moving into the focus of local councils, owners/operators and investors. At some locations, high energy yield is promised by the wind conditions high above the tree tops. The decision makers in the German state governments have also become aware of this fact. They are now increasingly differentiating between biotopes and economically used forests, which enables them to identify locations that offer ideal wind farm conditions in intensively cultivated commercial forests. After North-Rhine Westphalia published its new wind power decree last summer and now also permits forested wind sites, Baden-Wuerttemberg also passed new regulations in late May which govern the harnessing of wind power in forest areas. The paradigm shift is evident: public bodies no longer categorically exclude forested sites. Instead, after impartial analyses and assessment of wind conditions and profitability and after weighing the individual interests of all parties, suitable forest locations can now be identified and developed.

However, up to a height of around 90 meters (i.e. around three times the height of the trees themselves), the trees increase turbulence to critical levels. This in turn causes vibrations of the rotor blades, exposing them to significant stresses and adversely affecting the stability and service life of the turbines and their components. In view of this, forested sites require hub heights of at least 120 meters to avoid rotor blades operating in the layer of increased turbulence above the tree crowns. Mature technology does exist and suitable wind turbines have been available on the market for some years. Yet forest locations must offer higher profitability than wind sites situated on open land, as yield — which depends largely on the rotor diameter — can only be increased by using larger rotors, which in turn require higher hub heights to avoid the zone of increased turbulence. In view of these greater heights, this involves increased purchase, design and construction costs and therefore requires a differentiated profitability analysis.

Higher Wind Turbines, Higher Investment Costs
In this situation, the upstream procedures for wind resource analysis are all the more important. After all, on-site wind measurement, which supplies fundamental data for site-related wind resource assessment and profitability analysis, is one of the basic requirements for the licensing and approval procedure, and therefore must realistically map the wind profile up to hub height. The German Federation of Wind Power and Other Renewable Energies (Fördergesellschaft Windenergie und andere Erneuerbare Energien, FGW) require long-term measurements carried out with a cup anemometer on a measurement mast. However at heights of over 100 meters, the design and construction of such a measurement mast is relatively expensive.

Instead of a wind measurement mast that reaches up to hub height, a smaller measurement mast can be used and the data measured by this mast complemented with additional measurements carried out by other systems. The FGW standard, for example, recommends a measurement mast that extends to at least two-thirds of the hub height. In this case, a LIDAR (light detection and ranging) system can be used to measure and complement the missing wind data from higher atmospheric layers. A LIDAR system installed at ground level enables wind velocities and directions to be measured at heights of between 40 and 250 meters. Measurement points in a vertical direction can be defined at a resolution of approximately 20 meters.

LIDAR Systems Suitable for Complementary Measurement
The equipment sends vertical, ultra-short laser pulses into the atmosphere. The photons emitted by the system are scattered by aerosols and dust particles in the air flow. The backscattered photons are collected on the LIDAR telescope and registered by a highly sensitive detector. The LIDAR system uses the received light signals to make high-precision calculations of wind direction and velocity based on changes in frequency and signal runtime (Doppler effect). In combination with the simultaneously determined exact reference data of anemometer measurements, the wind profile can be extrapolated up to the heights of the upper tip of the rotor blade. The data thus offer a reliable basis for subsequent wind-resource assessments and profitability analyses, enabling the possible energy yield to be forecasted and quantified with maximum accuracy.

Another challenge faced in the assessment of potential wind sites concerns the often complex topography. Most of the high-wind areas that offer high yields are not located in lowland forests, but on minor mountain ranges. However, unlike lowlands, hills, valleys, open strips and other geographical obstacles have a significant and widespread influence on wind conditions at a site. Depending on the direction of the wind, these influences can vary massively, causing “jet effects” or interactions among wind turbines (wakes).

The Simulation Model — Critical for Yield Prediction
In view of the above, the framework conditions require careful selection of a suitable simulation model for the calculation and prediction of potential and yield based on wind measurements. While two-dimensional simulations, such as the “Wind Atlas Analysis and Application Program” (WAsP) of the Technical University of Denmark in Risø, is sufficient for lowland areas, they produce excessive errors and standard deviations when applied to complex and hilly terrain. As a result, yield predictions and profitability analyses can no longer be used as reliable and bankable reports but are reduced to mere forecasts that involve a high level of uncertainty.

By contrast, 3-D simulation tools such as WindSim enable the inclusion of complex topographic data from GIS systems, ensuring that wind conditions are described with a sufficient level of accuracy. This ensures an improved data set used as basis for potential analysis and yield prediction. TÜV SÜD’s experts review whether complex calculations using more elaborate 3-D simulations make sense for a potential wind site, also considering economic perspectives. The experts must answer the following question: Is 2-D simulation sufficient or is the terrain so complex that a 3-D simulation is required?

Given this, in the run-up to modelling TÜV SÜD’s wind power experts use RIX analysis to describe and assess the terrain over an area of 20 x 20 kilometers. The experts also carry out detailed calculation and examination of gradients in a radius of 3,500 meters around the wind turbine. The result, known as the ‘ruggedness index’ (RIX), is rated on a 15-point scale which indicates the percentage of the surroundings of the wind turbine that exceed a defined gradient. For values from 0 to 5, 2-D simulations are fully suitable. For values between 6 and 10, correction factors and adjustment parameters must be taken into account when 2-D simulation is used. 3-D simulations therefore already offer advantages at these values. For calculations in forested regions, for example, the hub height can be reduced by virtual methods. However, if the RIX value exceeds 11, application of a 3-D simulation is recommended.

Conclusion
On principle, wind turbines of the 2nd generation with hub heights of around 140 meters and rotor diameters of over 100 meters are suitable for harnessing the power of the wind even at greater heights. However, compared to sites located in lowland areas the necessary assessments involve more work and are more complex and cost-intensive. TÜV SÜD’s wind experts apply state-of-the-art methods to measure, check and assess the profitability and wind conditions of potential wind farm locations. In these activities, they profit from their long-standing experience with project-related wind reports and own studies, such as the modelling and calculations carried out for the wind atlases on behalf of the German states of Baden-Wuerttemberg and Hesse. 

Wind energy is becoming increasingly competitive compared to conventional sources of energy. Particularly emerging and developing countries decide to use this technology.” This is the conclusion of a study by Sustainable Business Institute (SBI, Oestrich-Winkel, Germany) that the World Wind Energy Association (WWEA) presented at an international conference in Cairo, Egypt, in early November 2011. These findings are confirmed by the development of wind energy over the past decade: According to the WWEA Wind Energy Report 2010, the capacity of this sector rose from 24GW in 2001 to 197GW by the end of 2010. As a result of the financial crisis, however, the capacity of new plants installed declined in 2010 for the first time in the past 20 years. Despite this, all experts expect investments to rise again significantly in 2011. “We will end this year at the record 2009 level at least, and in 2012 the global wind industry will grow at a double-digit rate,” predicts Thorsten Herdan, Managing Director of Power Systems at VDMA, the German Engineering Federation.

WWEA experts expect that capacity might increase to 600,000MW worldwide by 2015 (from just under 200,000MW today) and even rise as high as 1,500,000MW by 2020. Wind turbines now produce 430TWh of electricity each year — more than the entire electricity demand of the United Kingdom. All in all, wind energy covers 2.5 percent of the global demand for electric power. The global wind energy industry will continue to develop rapidly. According to “Internationales Wirtschaftsforum Regenerative Energien (IWR),” a German-based renewable energy industry institute, China has taken the lead on this road. In 2010, the industry as a whole failed to meet the new installations record set in the previous year. Figure 1

About 35,800MW of wind energy capacity was newly installed in 2010, which represents a decline by seven percent with respect to the previous year’s figure of about 38,000MW. As wind energy markets continued to become increasingly international, the focus kept shifting to non-European markets. With a capacity of nearly 16,500MW newly installed, China remains the biggest wind energy market in the world. New installations of wind power plants nearly halved in the U.S. as new capacity installed reached only about 5,100MW. India comes third (2,100MW), followed by Spain and Germany with 1,500MW each. By the end of 2010, the wind turbines installed around the globe had a total capacity of about 195,000MW (2009: 160,000MW). With a total of more than 42,000MW of capacity installed, China outpaced the U.S. (40,000MW) to become the new global wind energy champion. Germany remains in the third place (27,000MW). The fourth and fifth ranks are held by Spain, which has 20,000MW, and India with its 13,000MW.

In some countries, wind energy is now contributing significantly to power supplies. Denmark leads this ranking, at 21 percent, with Portugal and Spain following at 18 and 16 percent respectively, and Germany in the fourth rank, at nine percent.

Particularly ambitious targets are being pursued by Denmark, which plans to generate 50 percent of its electricity from wind by 2030.

The worldwide market for wind turbines again proved to be very robust in 2010: Around the globe another 37,600MW were added to the capacity installed. China took the lead yet again, adding 18,900MW — or more than half of all the additional capacity installed. Additions in Germany totaled 1,550MW. “The wind industry is becoming a major player in the world energy markets,” states WWEA Secretary General Stefan Gsänger. “Despite the momentary dip, the trend that the installed wind capacity more than doubles every three years remains unbroken.”

The share that wind energy contributes to the electricity mix is generally growing across the board. “The manufacturers of wind energy systems have a vital role to play in transforming electricity generation in Europe. According to expert forecasts by manufacturers of the different power generating technologies, by 2030 wind energy will account for nearly 25 percent of total power generation in the 27 EU countries,” says Gerd Krieger, Deputy Managing Director of Power Systems at VDMA. By 2030, the experts expect wind energy capacities to increase three-fold in Germany and even five-fold in the EU. “Plant retrofitting, which was largely irrelevant to date, plays a major role in this development,” Krieger points out. The Global Wind Energy Council (GWEC) equally projects very positive developments for wind energy until the year 2014. “Outside of Europe, too, we are expecting strong growth in wind energy, especially in markets that are already growing fast, such as China and the U.S., and also in Latin America and Africa. We expect new construction to rise from 38.3GW to 62.5GW per annum in the next five years, giving a total installed energy capacity of more than 400GW by 2014. Our longer-term forecasts suggest that by 2030, between 25 and 30 percent of global electricity needs will be covered by wind power,” says Angelika Pullen, GWEC Communications Director. Offshore installations will be one of the core issues on this road. This is demonstrated, for example, by the keen interest the maritime industry is showing in offshore wind energy activities, which range from special-purpose vessels for offshore wind farms to the production of steel towers and rotor blades.

A Maritime Future for Wind Energy
Experts expect that the potential of off-shore wind energy plants will be exploited more intensively in the future because the wind blows stronger and more consistently at sea. Offshore wind turbines have been Europe’s domain to date. In terms of installed capacity, the United Kingdom (688MW by the end of 2009) and Denmark (663MW) are in the lead, followed by the Netherlands, Sweden and Germany. According to an overview by “Internationales Wirtschaftsforum Regenerative Energien (IWR),” a German-based renewable energy industry institute, the U.K. intends to add approximately 10,000MW more to this. And Germany is aiming high as well: The German Maritime and Hydrographic Agency BSH in Hamburg has granted permissions for 23 offshore wind farms in the North Sea and four in the Baltic Sea. Permissions for another 54 new wind farms in the North Sea and nine in the Baltic have been applied for. The total capacity of all German projects exceeds 27,000MW. Figure 2

The U.S. energy ministry DOE also estimates that, by the end of 2030, 30,000MW of wind energy capacity may be installed in American territorial waters. Numerous projects are additionally being planned for the Great Lakes. According to the U.S. wind energy association AWEA, projects with a capacity of more than 5,000MW have already been applied for or are in different stages of planning or development. To speed up these projects, 10 U.S. states have formed an offshore wind energy consortium that is to coordinate initiatives for new projects and expedite their realization. The Cape Wind Project off the coast of Massachusetts is to play the pioneering role. This is a large-scale project comprising 130 wind turbines with a total capacity of 420MW. The cost of the investment amounts to $1 billion. According to a study by Stanford University and the University of Delaware, the wind energy potential off the U.S. Atlantic coast is about 330,000MW — which if fully harnessed would more than cover the energy demand of the East Coat states. One needs to remember here that the U.S. East Coast states consume about three-fourths of the total energy used by the nation. “The technology is proven, effective and available,” stresses U.S. Secretary of the Interior Ken Salazar.

Wind energy is booming and will maintain its high growth rates. It is also becoming more demanding, though. There is a trend for plants to grow in size and performance, and offshore conditions are particularly demanding. This applies not only to turbines and rotor blades, but to towers and foundations as well. Against this background, the requirements on the systems and materials being used keep increasing. Accordingly, chemical solutions that are customized to suit specific uses are gaining importance. In the past years, BASF, the world’s biggest chemical company headquartered in Ludwigshafen, Germany, had developed such solutions in various fields, thereby building a strong position in the wind energy industry that it intends to reinforce in the years ahead.

Rotor Blades and Wind Turbines
BASF developed new epoxy resin systems for fiber-reinforced composites, for example, that sell by the Baxxodur® brand and are highly suitable for the production of rotor blades for wind turbines: They allow for significantly shorter cycle times and so increase productivity. Rotor blades are growing ever bigger since a blade with twice the length covers an area that is four times the size and thus can capture four times as much energy from the wind flow. At the same time, however, a blade with twice the length is generally four times as heavy. While a 30-meter blade weighs 4 to 5 tons, a 60-meter one weighs in at nearly 20 tons. In spite of these increasing weights, the technical limits have nowhere near been reached, particularly thanks to the use of new materials such as carbon fiber composites. There are design concepts for 70-meter blades and test rigs for blades of up to 90 meters. At around 60 meters in length the possibilities for glass fiber reinforcement have been pretty much exhausted. Beyond this, carbon fibers tend to be used, but they cost around five times as much. Figure 3

New Epoxy Systems Boost Productivity
Limits at the top end are not set by the materials, however, but rather economic in nature since the profitability of a turbine increases only up to a point with rotor diameter. While larger turbines are of course more efficient, they are also more expensive in terms of transport and erection so that their profitability is influenced by many factors that matter significantly in rotor production. BASF sells a broad range of curing agents, accelerators and additives for professional epoxy resin processing. The company recently expanded its range by developing tailor-made epoxy resin systems for the manufacture of rotor blades.

Meanwhile, the epoxy resins for blades have been approved by Germanischer Lloyd. Engineers are increasingly replacing conventional composites based on polyester resin by more resilient fiber-reinforced materials based on epoxy resins in order to reach the material properties required for rotor spans in excess of 100 meters. BASF has succeeded in developing innovative epoxy resin systems that, on the one hand, allow the long processing phase needed to produce ever larger rotor blades and, on the other hand, deliver short curing times in order to reduce cycle times. “In this way individual cycles can be reduced by around 30 percent,” explains Dr. Gregor Daun, who is responsible for epoxy systems in BASF’s Intermediate division.

The forces that act even on a 40-meter blade are enormous. On top of weight loads of around 70 kilonewton (the equivalent of five Volkswagen Golfs) and the rotational-speed-dependent outwards-acting centrifugal force, it is particularly the tangentially acting wind forces, which are dependent on wind speed, that can produce flexural moments of some 6,000 kilonewton-meters at the blade root, which corresponds to the leverage of 11 Volkswagen Golfs on the blade tip. To meet these requirements, epoxy resin systems are typically used with mainly glass fiber mats being inserted for reinforcement. Rather than being interwoven, these glass fiber layers are laid out next to one another or stacked in multiple layers and secured with a few threads in order to minimize fiber bending. Alongside this carbon fibers are also used, but in much smaller quantities as they are not only more expensive but also available in limited quantities only. Other materials such as aramid or basalt fibers have played no part as yet. In the manufacture of large blades the fibers or fiber mats are soaked with two fluid components, the resin and curing agent, that reacts with each other when heated in a shape-defining mold to form a very strong polymer. The entire system comprising the matrix and fibers makes a fiber composite material that delivers the necessary mechanical stability.

There are basically four different techniques for impregnating the fibers. In laminating the dry mats are impregnated manually one after the other using rollers dipped in the epoxy resin systems. Infusion technology uses a vacuum to suck the epoxy resin systems into the dry mats laid up in the mold. The third possibility is to soak the mats outside the mold and let them pre-cure to semi-rigid state before laying them up in the mold for final curing (prepreg technology). For round, longish components the fibers are impregnated and wound onto a mold before being cured using thermal energy (filament winding technology). Using these four technologies it is normally possible to manufacture all of the main components of a rotor. This includes in particular the thick multi-layer blade root that transfers the force to the hub as well as the internal load-bearing structure of shear webs, spar caps or hollow sections that take up the major part of the forces acting along the length of the blade. The third component is the outer shell of the blade, which is basically hollow. This shell performs the aerodynamic function and is either molded along with or bonded to the root and internal structure. Figure 4

The modern infusion systems used in the wind energy sector consist of two components, the resin and a curing agent. Amine formulations are typically used for curing since they are well suited to the requirements of mechanical stability and processing. The new BASF systems also use this class of substances. Immediately before the infusion both components are mixed together at a predefined ratio. At this moment the potlife, or processing time, clock starts ticking because the reaction between the two components begins slowly and increases at higher temperatures. However, in order for infusion to work well the viscosity of the system has to be correct. For this reason so-called reactive diluents, which reduce the viscosity but at the same time form part of the cross-linking reaction, are included in the formulation. The actual cross-linking or curing of the resin is achieved by the amines reacting with the epoxy groups to form a three-dimensional network. This reaction is dependent on the reaction temperature, but can be influenced by the use of additives such as accelerators.

Latent Curing Agents Square the Circle
Turbine manufacturers, who are now concentrating on offshore plants, are for the most part targeting the use of large blades exceeding 50 meters in length in order to make most effective use of the more consistent wind flow out at sea. In the case of large structures such as the outer skin of such huge blades, processors using infusion technology face a dilemma. On the one hand, the epoxy resin system should react slowly in order to completely fill the mold before it begins to gel. On the other hand, however, the epoxy resin system should react rapidly once heated so that the mold can be released for the next blade as quickly as possible. BASF developed a chemical route — first slow and then fast — that uses so-called latent systems to square this circle. Here, some of the curing agents are activated thermally on passing a threshold temperature, having previously been “dormant.”

These latent curing agents from BASF can be easily adjusted to simplify handling during the entire process. The bottom line is higher quality, better process stability and a lower scrap rate. Up until now, depending on external factors such as temperature several curing agents had to be mixed. In this respect as well, the Baxxodur system offers significant advantages because it can be used over a considerably greater range of temperatures. This means that the curing agent mixes do not have to be adjusted every day. Not the least of the advantages is that stocks are much easier to manage because only a single curing agent needs to be stocked. In addition, BASF is working on further improvements in the core mechanical properties and in fiber matrix adhesion.

Other engineering plastics also have a major role to play in future blade construction. Because the dimensions of rotor blades keep increasing, these are getting heavier, too, with the glass fibers used currently adding significantly to their weight. Engineers are accordingly thinking intensively about replacing these fibers with much lighter carbon fibers. This has been tried out in China for the spar caps that ensure load transmission. These tests show that much thinner layers are possible, greatly reducing the weight of blades. In this arena, BASF offers its Ultrason E branded polyethersulfone (PESU), a high-performing plastic material. This thermoplastic material features exceptional impact resistance, is resistant to chemicals and suitable for components that are exposed to high thermal strain. Yet, while they are high-strength materials, carbon fiber composites are also brittle. Adding Ultrason® E 2020 P SR will make the system tougher. Two options are available: The plastic material either comes as a powder which is distributed homogeneously in the epoxy mix, or it is spun into a fine mat that is inserted between the laminate layers.  Figure 5

Coating Systems for More Than 30,000 Rotors
Whereas internal rotor blade stability is one part of the story, their outward protection is the other part. The general rule here is that the coating systems must be matched precisely to the blade production process for the blades to perform perfectly for a long time. Since the mid-nineteen-nineties, Relius Coatings GmbH & Co. KG in Oldenburg, Germany, which is part of BASF’s Coatings division, has been developing coatings for rotor blades that are effectively protecting more than 30,000 blades. Product development focuses clearly on a long service life. The entire portfolio is highly suitable for application on glass-fiber reinforced plastics, GRP, used for rotor blades. It comprises gel coats, putties and topcoats. The two-component coatings based on polyurethanes (PUR) are either low-solvent or solvent-free products and therefore meet current VOC limits.
The coating systems being marketed under the new RELEST® brand excel by their well-balanced set of properties, which includes:

• Very high abrasion resistance for durable surface protection,
• Very high elasticity, which minimizes the risk of stress cracking,
• Excellent UV stability, ensuring colors stay the same for years,
• Eco-friendliness (compliance with VOC limits).

All coatings are obviously matched perfectly to the different production processes being used. And another point applies to all systems: The products of the RELEST® Wind brand, from gel coats, to putties, to topcoats, sustainably support the production of environmentally benign energy.

Since the rotor blades are exposed to exceptionally severe weathering, they need to be protected against humidity and light, for example, by application of a gelcoat. Putties are used to smooth minor surface unevenness. Then, to protect edges against wear and tear an edge protection coating is applied, and topcoat application is the final step in the coating process.

BASF provides customers with tailor-made solutions for each of these process steps: The solvent-free two-component polyurethane gel coats it offers as RELEST Wind ProcessCoat and RELEST Wind Gelcoat are VOC-compliant and feature convincing properties like long potlife, fast curing and re-coatability, and excellent abrasion resistance. They are available for different blade production processes. Figure 6

RELEST Wind Putty Porefiller serves as a pore stopper. To complete its portfolio BASF also sells a viscoelastic putty known as RELEST Wind Putty Contour. It can be sanded after just one hour and is suitable for manual or machine processing. For a high-quality surface finish, exceptionally fast-drying topcoats are available by the name of RELEST Wind Topcoat, alternatively as water-based or high-solids formulations.

Ongoing product development is crucial because plant operators specify demanding performance standards. BASF works continually to improve its products. The company presented two novelties at JEC 2011 in Paris, Europe’s major composites trade fair: The new RELEST Wind ProcessCoat is an exceptionally efficient solution for coating rotor blades. Effective protection against erosion and UV radiation is essential in this application. It is the kind of protection that you get from RELEST Wind ProcessCoat, which was developed to meet these precise requirements and incidentally, by its low product use, helps to reduce rotor blade weight and optimize the process. In addition, the RELEST Wind RepKit will be showcased, a system for repairing rotor blades. Along with all the materials and tools necessary for repairs, this kit also comprises an extensive application training seminar. The new RELEST Wind RepKit has been designed for stationary use on the ground or on wind turbines.

“BASF has decades of experience, through its RELIUS COATINGS subsidiary, in supporting the industry as a coating systems partner. Mature solutions are therefore available to the wind energy industry for turbine towers as well, whether those ‘legs’ are made from concrete or steel,” says Dr. Achim Gast, who is responsible for BASF’s Industrial Coatings Solutions Business Management.  Topcoats based on two-component polyurethane systems (as high-solids or water-based formulations) guarantee weather-resistant, non-reflecting surfaces. The coating material features active anti-corrosive properties, thereby enabling a long service life. BASF’s extensive experience in marine coatings adds to its expertise in supporting complex offshore projects, an area that is becoming increasingly important. Moreover, equipment installed at the entrance and inside wind power plants requires equally efficient protection against exposure to weathering, which may be extreme in some cases. Environmentally friendly polyester powder coatings ensure optimum resistance against corrosion and chemicals for machines, stairs, doors and lightning protection systems.

Durable Foundations? Not Without Construction Chemicals
Safe and durable foundations are vital to the erection of wind turbines, and this applies equally to onshore and offshore installations. Offshore power plants are nowadays typically built on either monopile foundations, where a single pile is driven into the rocky or sandy seabed; as so-called tripod foundations featuring three piles; or by using concrete caissons for foundations that rest on the seabed due to gravity. Eighty percent of the installations erected to date are monopile structures. The choice of design depends on the conditions in which the specific wind farm is built such as the nature of the seabed, the water depth or its distance from the shore. For deep-water installations, which are increasingly moving to the focus of attention in the North Sea area, engineers tend to prefer new systems with four or six legs (known as jackets) or floating designs for even deeper waters. The booming wind energy industry, with its increasingly larger installations, need products of the highest quality in this particular field that help reduce construction times. BASF’s Functional Solutions business offers a broad portfolio of construction chemicals. BASF Construction Chemicals is a global leader in the development of concrete admixtures like plasticizers, retarders or accelerators.

Admixtures enhance the ease and efficiency of placing concrete. They also increase the stability and service life of concrete structures. The portfolio includes specialty grouts, which play a crucial role in the construction of wind turbines.

BASF has developed a special product, known by the brand name MASTERFLOW 9500, that is designed specifically for the construction of offshore wind turbines. This grout formulation guarantees excellent results in terms of strength and fatigue resistance. Its compression strength can be as high as 140 megapascals, and the modulus of elasticity, up to 50 gigapascals. The product was tested extensively by the independent universities of Aalborg, Denmark, and TU München, Germany. The grouting mortar was found to meet the strict fatigue resistance standards of the Det Norske Veritas (DNV) classification body and is the first grout to have been certified for use in offshore wind turbine construction. It even allows processing in the most adverse conditions, which include temperatures as low as 2 °C and underwater processing without any segregation issues. Another positive effect is reduced dust formation during processing. This grout is free of autogenous shrinkage and features good volume stability. MASTERFLOW® 9500 allows pumping over long distances of more than 200 meters or for rather long times — yet another processing advantage.

By its characteristic properties MASTERFLOW 9500 ensures high cost efficiency: It reduces installation times because the required strength builds up fast even at a low temperature.

“In the past, offshore wind farms used to be built in two construction phases, with the foundations being erected in the first phase and the rest of the power plant following in the second phase. Investors and project designers would rather shorten the time of installation to a single phase, with foundations being erected in the winter and the turbines being installed earlier the next summer. However, this is feasible only if the grouting mortar cures fast and builds strength at low temperatures of less than 5 °C. It is precisely what you achieve by using MASTERFLOW 9500,” says Luc Westhof, a graduate engineer who is responsible for special-purpose construction materials for wind turbine towers and foundations within BASF’s Construction Chemicals Europe division.

The product takes only five hours to set in standard conditions and nine hours at low temperatures. The long processing time (up to four hours) reduces the risk of interruptions and product being wasted. Short construction times eventually enable wind farms to be brought on stream faster, and the construction equipment required can be released faster for other projects. As a result, the use of MASTERFLOW 9500 produces foundations featuring excellent durability and a high capability to absorb dynamic loads.

The new mortar was used for the first time in October 2009 in the Danish Storebælt wind farm, which comprises seven Vestas wind turbines and was connected to the grid just in time for the opening of the Copenhagen Climate Conference in late 2009 thanks to the use and fast curing of MASTERFLOW 9500. The first large-scale commercial project using MASTERFLOW 9500 is the Rødsand II wind farm in Denmark. This farm was erected in the Baltic Sea, off the south coast of the island of Lolland, on behalf of E.ON. It comprises 90 wind turbines made by Siemens, each of which has a capacity of 2.3MW. About 50 tons of MASTERFLOW 9500 were used to build the turbines, with up to three turbines being grouted per day. The Siemens equipment has already stood the test of time in the Rødsand I wind farm that was started up in 2003 and consists of 72 of these turbines. The combined Rødsand I+II farm is today the largest Danish offshore wind farm. MASTERFLOW 885 was used to build it at the time, another BASF grouting mortar designed specifically for installing machinery, equipment and assemblies that need to take up dynamic loads on concrete floors. As MASTERFLOW 9500 is even more suitable for offshore use, however, it was selected for the new project.

MASTERFLOW 9500 also provided the basis for a new product development that BASF is launching this year under the name MASTERFLOW 9300. This is a special grouting mortar for onshore wind turbines that includes metallic admixtures and nanotechnology features.

Specially Designed Grouting Mortars for Onshore Turbines
The new grouting mortar also offers a response to the growing number of cracks in wind turbine foundations that have appeared with increasing frequency in the past three years. About 30 percent of all plants installed in Germany, for example, develop this type of problem in the first three to five years. These issues can be traced to a range of different reasons: They may be due to dynamic loads and variations in loads on the one hand, and on the other hand design errors and, above all, the ever larger dimensions of wind turbines have a role to play. These insights are among the factors that have resulted in special requirements being made on grouting mortars. These include, for example, optimum filling of all cavities in order to achieve perfect load transmission, guarantee a long service life and facilitate uninterrupted generation of energy. Other requirements are fast installation, which reduces costs, and a safe, durable structure that features top strength, guarantees volume stability throughout its service life and shows excellent fatigue resistance despite all the load changes it has to absorb.

MASTERFLOW 9300 meets these standards exceptionally well, thanks to its characteristic profile. The product expands while it is being placed, filling all cavities. It is free of autogenous shrinkage in the curing phase and even continues to expand, ensuring perfect load transmission while the turbine is operational. At a temperature of 20 °C, its can be processed for at least three hours, and drying shrinkage is less than 0.5 millimeters per meter. Efflorescence, exudation or sinkage have not been observed. The flow properties have been improved again, compared to MASTERFLOW 885. Air void content and porosity are remarkably low compression strength after 28 days is at least 120 megapascals — which means that MASTERFLOW 9300 outperforms MASTERFLOW 885 by more than 50 percent in this respect. To allow fast installation of wind turbines, it is essential that the grouting mortar build strength quickly.

MASTERFLOW 9300 achieves a compressive strength of 50 megapascals — this criterion determines the moment when the turbine anchor bolts are tightened — within 24 hours at a temperature of 20 °C. At a temperature of just 2 °C, the product takes two days to reach this minimum level of 50 MPa. This translates into time-savings in wind farm construction, as turbines can be erected in poor weather conditions as well. In formulating MASTERFLOW 9300, BASF resorted to the best available plasticizer technology and even included nanotechnology for cement-type mortars. This product, too, was tested by Aalborg University and TU München University and has been certification tested by DNV. 

High-Performance Lubricants for Wind Turbines
In the course of the Cognis acquisition BASF again expanded its wind energy portfolio, entering the arena of lubricants for wind turbines. The industry essentially needs three types of lubricant, gear lubricants, hydraulic fluids, and greases. BASF supplies its customers with both high-performance, synthetic gear lubricants (based on POA technology) and high-performance, synthetic hydraulic fluids.

The performance requirements in the global wind industry are severe and the demands on performance increase every year. “Developing and proving a new formulation represents a significant commitment to innovation and to the development of the wind industry in general,” explained Mark Hesseling, Global Strategic Marketing Manager at BASF. Once a particular formulation has passed a long list of fundamental specifications it is field-tested in conjunction with the wind turbine and gearbox OEMs. High-performance synthetic base oils are increasingly preferred over conventional mineral oils. One of the reasons is that customers place particular emphasis on long drain intervals since oil changes on wind turbines tend to be complicated and expensive affairs. In fact, their cost typically exceeds the cost of the actual oil many times over. While solutions based on mineral oil last no longer than one or two years in operation, high-performance oils from BASF have a much longer useful life.

Low temperature viscosity is another major criterion. While high-performance lubricants from BASF stay liquid and stable at extremely low temperatures down to minus 50 °C, mineral-oil-based formulations as a rule do not withstand temperatures below minus 20 °C. “We worked to improve low-temperature viscosity to reach excellent results in turbines located in the harshest environments, anywhere in the world,” Hesseling said.

To meet the ever-increasing demands in wind turbine applications these high-performing synthetic basestocks are complemented with special additives. In developing BASF’s high-performance gear lubricants, for instance, our scientists focused especially on minimizing wear and micropitting in the gearbox, the most expensive component of a typical wind turbine.

By combining its know-how in oil basestocks, performance additives, and finished lubricant formulations, BASF continues to invest in the innovation necessary to participate in this exciting and challenging industry.

The wind energy industry remains on the road to success, and materials from BASF play a major role in this development by enabling ever-higher performance, raising productivity and improving durability. Tailor-made materials will be crucial in the future, too, as we continue to see wind energy plants increasing in size and offshore installations becoming more popular. We will continue to expand our product range in this field because we are convinced that wind energy has the capabilities we need and must be developed further. 

In recent years, the growing emphasis on finding alternative power sources that are renewable, affordable and sustainable have caused tremendous growth in the wind energy industry. Wind turbines, though basic, have key components that are difficult to access and expensive to maintain.

Machinery reliability in wind turbines is especially tasking as poor lubrication practices can cause failures in system gearbox, hydraulic systems and bearings, which are costly to fix. Maintaining clean oil is one of the best investments a company can make to prevent problems, yet contamination often remains an overlooked factor behind premature machinery failure and diminished lubricant life.

To increase scheduled time between maintenance, reduce cost of lubrication replacement, and protect the system from failure, the prevention and treatment of contamination — from the time oil enters a facility until it leaves — is key.

The Problem: Contamination
Two primary types of contamination include dirt and water.

If the atmosphere is contaminated (and most are to some degree), the oil is probably dirty and lubricant quality is compromised. Particulate contamination, once inside an operating system, will accelerate the generation of new contaminants. These contaminants damage critical components and act as a catalyst for oxidation, further degrading lube condition.

If the atmosphere is particularly humid or has frequent temperature fluctuations, the oil is probably moisture-laden and lubricant quality is compromised. Often, plant wash-down activities are responsible for inducing conditions that lead to moisture ingression and corrosion.

The good news is that these factors, which work together to threaten equipment reliability, can be effectively controlled with some preventative maintenance techniques. The best and easiest way to exclude contaminants is to avoid practices that risk exposing lubricants to contaminants.

A multi-faceted program that includes some simple proactive steps will conquer contamination.

The Goal: The Right Targets
Every application is unique — and what’s right for one environment isn’t what’s needed for another. There are a number of sources in which to refer in order to get a bit of help. Noria Corporation, Reliability Web and other publications and manufacturers offer a wide variety of published and training materials that can get you well on your way. To complete an introductory survey, you can visit www.descase.com/contact to request an complementary online self-assessment.

Options
It has been said that prevention is the best cure. Ideally, all of us would have a brand new plant and machinery and begin with a solid program of preventative measures that would ensure the longest life for our equipment and oil. That, of course, never happens. Once you know how big the problem is, you can combine several options to help bring the current situation in line with your cleanliness targets, and add components that will help keep your oil clean and “dry.”

Reservoir filters:
Today’s options for restricting the ingression of contaminants are a far cry from yesterday’s open tube turndown pipes that did little more than keep the birds out (Table 1). Proper installation and maintenance of contamination control breathers can significantly reduce ingression of airborne contaminants.

Breather filters:
The breather filter continues to be at the top of the list for preventative maintenance and conquering contamination. Conventional vent ports or breather caps provide little or no protection. They are typically rated at 40 micron and offer no means of capturing moisture. Retrofitting these ports with breathers will provide 24/7 protection against uninvited contaminants, both dirt and water (see Table 2). Clean lubricants extend the life of equipment, and lower the total cost of ownership with lower oil, repair, downtime and maintenance costs (a search for “Lubricant Life Extension Table” on the internet will show a number of sources of information).

Breathing starts the same day the machine is put into operation or a static tank is filled. The correct approach to preventing dirt and moisture damage is to proactively control ingress points. Since the most common point of entry is the conventional vent port, installation of desiccant breathers is imperative.

Breathers are essential to the health of machines and lubricants. A properly fitted and maintained breather is a critical step toward reliability optimization. Combining breather use with other contamination control tools, such as mechanical seals, proper sampling techniques, downstream filters and appropriate lubricant storage/dispensing systems will increase the overall level of maintainability and increase the chances of meeting or even exceeding life expectancies.

In-line / Off-line filtration:
In-line and off-line filtration (sometimes referred to as bypass, kidney-loop, or auxiliary filtration), consists of a motor, pump, filters, and proper hardware connections. Fluid is continuously pumped out of the reservoir, through the filter(s), and back to the reservoir. In-line is, of course, a permanent part of the overall system. An off-line filtration loop has the extra advantage of being relatively easy to retrofit on an existing system that has insufficient filtration. Also, the off-line filtration device can be serviced without turning off the main system.

Filter Carts Capture Contaminants:
A hand cart is a portable, off-line filtration system used to filter fluid inside the reservoir. It is a transfer cart when used to move lubricants from a drum to a reservoir. In either mode, it is an economical solution to off-line filtration requirements.

Filter carts should be used to remove particles and moisture, thereby preserving the working life of the oil. They are not just a tool for emergency remedial measures when dealing with contaminated lubricants and hydraulic fluids. To avoid cross-contamination of fluids, make sure there is a dedicated filter cart for each type of lubricant in use. Filter carts should be fitted with quick disconnects and with particle removal and water — absorbing filter elements. Filter carts should be part of a routine that includes new oil filtering, transferring, and dispensing oils.

New oil filtering, you may ask? Many plant personnel feel new oil is clean enough to use right away. However, many new fluids have initially high contamination levels. Fluids should always be filtered before being put into service. Contamination, both particulate and water, may be added to new fluid during processing, mixing, or handling. This contamination can be removed with the use of a filter cart. They are the ideal way to pre-filter and transfer fluids into reservoirs.

Where To Look: Savings Everywhere
Area #1 – Storage:
Many improvements to your storage procedures can be made with minimal cost. A little time spent simply reviewing your current storage and handling procedures can be informative and useful.

Some simple procedures to improve your storage maintenance operations:

• Stored oil should be kept indoors.
• Add breathers to vented storage containers.
• Controlling temperature is important for proper drum storage. Drums “breathe” as the internal pressure increases and decreases with temperature variations. Moisture and other contaminants are forced into the drum when the internal pressure decreases. It is recommended to store drums or containers in enclosed, temperature-controlled storage facilities.
• Shielding storage containers from dirt and moisture is another procedure that will keep your cleaned and filtered oil in good condition. Be as careful with pumps and transfer containers as with your storage containers. This will minimize the chances of cross-contaminating with other lubricants and introducing contaminants into machines when filling.

Area #2 – Handling:
Some simple procedures to improve handling maintenance operations:
• Transfer hoses should be equipped with quick-connects to prevent contamination of the hose from the environment, provide leak-free connections to tanks and reservoirs and allow a method for off-line filtration.
• All oil-dispensing equipment, including tanks, drums, pails, hoses and reels, should be clearly labeled to avoid cross-contamination of products.  Color-coding is helpful in avoiding cross-contamination.
• The use of an industrial filter cart is one of the most economical ways to protect your system from destruction caused by contamination.

Area #3 – Equipment:
Nearly every industrial application is a candidate for a contamination control solution. Gearboxes, pumps, turbines, transformers, hydraulic systems… all of them can be looked at as an opportunity to save money through the reduction of downtime, increased oil life (and decreased oil replacement and disposal costs), and increased machinery life and reliability. Examining seals, ensuring the application has the correct sized breather for the application and environment, and the regular filtration of oil can extend the life as much as  four times what a non-systematic approach would yield, saving tens if not hundreds of thousands of dollars.

The Payoff: Money In The Bank (And Budget)
Contamination control is the single greatest opportunity for gains in the average lube program. Significant gains in machinery reliability can be made with minimal investments.

Your program’s effectiveness can be measured through the following metrics:
• Maintenance of targeted ISO cleanliness codes
• Reduction in moisture levels (% or ppm) measured by Karl Fischer titration
• Lubricant life extension, extended drain intervals
• Extension of MTBF (mean time between failures), decreased unscheduled downtime
• Cost savings (e.g. reduced component repair, decreased oil disposal expense, decreased oil purchases)

There is an inverse relationship between lubrication quality and maintenance costs. Financial gains can be made by implementing procedures which maximize lubrication effectiveness.

There are a good number of documented examples of the effectiveness of using these methods. Maintenance publications and textbooks list case studies from plants around the world that have brought “youth” back to their equipment. There’s the case of the water treatment plant in Ohio that saved money by just adding one type of breather to their equipment, or the bulk storage application that went from an ISO cleanliness rating of 21/19/17 to 18/16/14 with a 20 percent reduction in moisture by using these methods, or the mobile equipment that went over 30,000 hours without needing an oil change.

The Bottom Line
Tribological losses can be greatly reduced through proper lubrication maintenance which effectively starts with breather protection, off-line filtration, and oil sampling. In today’s competitive market with ever climbing oil prices, it is more important than ever to maintain system integrity and extend equipment life.

By utilizing options outlined above and implementing several contamination control techniques, maintaining clean, dry lubricants is easier than ever.