Filters, of course, remove particulate matter from the lubricating oil, to a degree. On a two-stage filter, the first stage removes debris 10 µm and larger while the second catches particles 50 µm and larger. On cold startups when the oil is thick and slow to move, a valve lets the oil bypass the 10 µm filter. Generally, the flow rate and oil temperature, often 10 to 30°C, governs when the bypass valve begins closing for finer filtering. The main filter, the outer portion with the pass protection, handles the bulk of the oil flow.

Filters and breathers on wind-turbine gearboxes must work under conditions found in no other industrial setting. Gearbox oil, for instance, undergoes large viscosity changes due to a wide temperature span and operating conditions. And then there is potential for a high water content in the oil from humidity and condensation. Recent detailed analysis of fluid flow through a range of filter materials has led to a better understanding of conditions inside a working hydraulic-fluid filter. The work has let one filter manufacturer identify factors responsible for pressure loss in the folded material. The result is a special web technology for production of a new hybrid fabric that maintains an optimal opening of the fold channels. Thus pressure loss in the folds drops as much as 50%.

To improve filter performance, it is necessary to reduce its pressure loss. Calculations show that specific flow resistance depends on the filter materials, as well as on the structure and length of the intermediate fold gaps, the so-called fold channels. The longer a fold gap, the greater the specific flow resistance in the fold. This is because the hydraulic fluid cannot flow unobstructed through the fold gap.

The filter manufacturer says it has been able to implement the findings and confirm them in numerous trials. Reducing a pressure loss in the filter element by as much as 40% at constant flow rate means it can increase up to 65% at a specified pressure loss. This also means, depending on application, smaller filters can be used to trim weight, resources, and costs. Also, reducing the pressure loss in existing systems means the bypass circuit (it protects the fine filter on cold startups) opens less often and for shorter periods. Consequently fewer particles get through the bypass to the clean-oil side and the danger of malfunction due to non-filtered oil significantly reduces.

The low differential pressure and the high dirt holding capacity of the filter elements allow longer periods between service and improved cold-start characteristics.

Depending on application, filter elements are subject to strong flexural-fatigue stresses induced by flow-rate fluctuations. These come from rpm fluctuations of drive motors, cylinder ratios, as well as the increasing use of variable displacement pumps in modern machines.

Conventional filter elements use a metal or plastic support fabric on the out-flow or clean-oil side. A support of metal also brings the advantage of electric conductivity, but has the danger of fatigue failure. Wire fatigue then leads to wire pieces in the hydraulic fluid.  Some strength comes with plastic fabrics insensitive to flexural fatigue stresses. On their downside, such fabrics have extremely low electrical conductivity.

To counter the material-specific disadvantages, the manufacturer uses a hybrid fabric which has proven effective in years of application to support the filter material. The patented fabric consists of a mix of stainless steel and polyester fibers. This combination exploits all the advantages of metal and plastic fabrics and avoids the disadvantages of pure metal or plastic-only versions. Stainless-steel wire arranged longitudinally ensures complete dissipation of electrostatic charges, which prevents damage to the filter material and dirtier oil. The polyester fibers arranged transverse to the metal threads ensure optimal flexural fatigue strength and avoids of fatigue failure.

The structure of the filter material has been completely redesigned to contain multiple interlaminated filter and support layers. These use suitable laminating agents to improve the characteristics of the materials. In fact, it improves the differential-pressure stability of the filter material by a factor of three, relative to non-laminated materials.

In addition, a plastic sheathing shrink-fit onto the filter bellows ensures that they fit tightly on the perforated frame. This makes the filter element even more resistant to flexural fatigue-stress than conventionally manufactured filters. Improved fatigue characteristics, differential pressure stability, as well as safe dissipation of electrostatic charges significantly contribute to the long service life of the filter elements. WPE

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The new filter material, 10EX2, is available in all other common or standards filtration grades.

Matthias Jung /Product Manager for Filter Elements / Argo Hytos GmbH /www.argo-hytos.com

Author Matthias Jung

Recent detailed analysis of fluid flow through a range of filter materials has led to a better understanding of conditions inside a working hydraulic-fluid filter. The work has let our company identify the key factors responsible for pressure loss in the folded material.

The result is a special web technology for production of a new hybrid fabric that maintains an optimal opening of the fold channels. Thus pressure loss in the folds drops as much as 50%.

What we learned

To improve performance of a filter, as well as increase its dirt holding capacity, it is necessary to reduce its pressure loss. Calculations show that specific flow resistance depends on the filter materials, as well as on the structure and length of the intermediate fold gaps, the so-called fold channels. The longer a fold gap, the greater the specific flow resistance in the fold. This is because the hydraulic fluid cannot flow unobstructed through the fold gap.

We have been able to implement the findings obtained from simulations into a practical application, and have confirmed them in numerous trials. Reducing a pressure loss in the filter element by as much as 40% at constant flow rate means it can increase up to 65% at a specified pressure loss. This also means, depending on application, smaller filters can be used to trim weight, resources, and costs. Also, reducing the pressure loss in existing systems means the bypass circuit (it protects the fine filter on cold startups) opens less often and for shorter periods. Consequently fewer particles get through the bypass to the clean-oil side and the danger of malfunction due to non-filtered oil significantly reduces.

The EXAPORMAX 2 filter media is made of several layers of proprietary material supported by fine stainless-steel wire.

The performance-optimized structure of a three-layer filter material consists of various fine glass and polyester fibers. This new material matrix in the pre-filter and ultra-fine filter materials significantly contribute to improved dirt-holding capacity. For example, the dirt holding capacity can be increased by as much as 60% in a 5 μm(c) filter.

The unusually low differential pressure and the high dirt holding capacity of the filter elements enable longer time between service and improves cold-start characteristics.

Elements of filter design

Depending on application, filter elements are subject to strong flexural-fatigue stresses induced by flow-rate fluctuations. These come from rpm fluctuations of drive motors, cylinder ratios, as well as the increasing use of variable displacement pumps in modern machines.

Conventional filter elements use a metal or plastic support fabric on the out-flow or clean-oil side. A support of metal also brings the advantage of electric conductivity, but has the danger of fatigue failure. Wire fatigue then leads to wire pieces in the hydraulic fluid.  Some strength comes with plastic fabrics insensitive to flexural fatigue stresses. On their downside, such fabrics have extremely low electrical conductivity.

The FEA simulation results are for the pressure relationships in the fold of a filter element (sectional view). The perimeter of the fold is shown in black and the support fabric is shown in white. The differential pressure presses both flanks of a fold onto each other. The fold channel is only held open by the support fabric.

To counter these material-specific disadvantages, we use a hybrid fabric which has proven effective in years of application to support the filter material. The patented fabric consists of a mix of stainless steel and polyester fibers. This combination exploits all the advantages of metal and plastic fabrics and avoids the disadvantages of pure metal or plastic-only versions. Stainless-steel wire arranged longitudinally ensures complete dissipation of electrostatic charges, which prevents damage to the filter material and dirtier oil. The polyester fibers arranged transverse to the metal threads ensure optimal flexural fatigue strength and avoids of fatigue failure.
The structure of the filter material has been completely redesigned to contain multiple interlaminated filter and support layers. These use suitable laminating agents to improve the characteristics of the materials. In fact, it improves the differential-pressure stability of the filter material by a factor of three, relative to non-laminated materials.

In addition, a plastic sheathing shrink-fit onto the filter bellows ensures that they fit tightly on the perforated frame. This makes the filter element even more resistant to flexural fatigue-stress than conventionally manufactured filters. Improved fatigue characteristics, differential pressure stability, as well as safe dissipation of electrostatic charges significantly contribute to the long service life of the filter elements.

The bar charts show improvements in the EXAPOR MAX 2 filter over the previous EXAPOR MAX version. For example, the recent design holds 60% more contamination and it filters small particles.

Optimizing filter fineness

It is also important, of course, to maintain a constant and high level of oil purity over the filter’s entire service period. To meet constantly increasing user requirements, and the ever-increasing complexity of hydraulic components, the new filter elements, with material designation 10EX2, allows improving the previous 12 μm(c) filter to 10 μm(c). For particles greater than 10 μm(c) this means a four-times higher separation capacity while simultaneously reducing pressure loss, as compared with the previous 12 μm(c) media.

Lastly, preventing knock-offs

The shrink-fit sleeve on the filter bellows improves its performance, gives it a modern look, and conveys the quality of the product. The sleeve is customer-specific and individually printed. Later, all EXAPOR MAX 2 filter elements will be fitted with this feature making it easy to identify. This means that original elements can be easily distinguished from knock-offs. Thus all machine operators who value quality and safety can easily verify the authenticity of the filter elements. WPE

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How dirty is the oil? Particle counter tells

OPCom II is an optical particle monitor. It consists of a measurement cell through which oil flows, a laser, and a photo diode. The laser shines through the measurement cell and strikes the photo diode. If a particle passes through the laser beam, it reduces the detection intensity. The intensity reduction corresponds to the particle size. The unit can monitor contamination levels and purity trends in fluids. Continuous purity monitoring quickly detects changes in a machine and prompt warnings allow taking measures before the contamination reaches a hazardous level. The unit works in mineral liquids and ester liquids, polyalphaolefins.

Argo Hytos LLC
www.argo-hytos.com

Lattice met towers can reach 140m

As a capital issue in every wind energy project development, the wind resource assessment calls for in depth analysis based on the relevance and accuracy of the data collected. The company’s lattice tower family ranges from 30 to 140 m to reach the hub height of most wind turbines. The towers comply with or exceeds requirements of the latest codes. The company provides turkey operations from the design of foundations to installation of the top most instrument.

Oenko
www.oenko.com

Acumulator service kit reduces weight

Wind Kit is a portable high-pressure service unit for accumulators in hydraulic systems in turbine nacelles. The kit replaces nitrogen cylinders that weigh 140 lbs. and require 300-ft. lines that can reduce the nitrogen pressure, which should reach 4,500 psig. Based on field trials, Siemens Energy and Vestas American Wind Technology have started using this kit.

Cv International
www.cvintl.com

Vector signal transceiver

The PXIe-5644R RF vector signal transceiver has a software-centric architecture that represents a new era in which engineers and scientists can tailor FPGA-based hardware for their specific needs. Using NI LabVIEW, engineers can transform the RF vector-signal transceiver into a new instrument or customize existing functions to meet specific needs. This 3-slot PXI module is small and it performs more than 10 times faster than comparable devices and potentially replace multiple traditional instruments, providing a cost-effective way to develop and test the latest wireless standards such as 802.11ac and LTE.

National Instruments
www.ni.com

Precise wind monitoring

The 4000 series SoDAR operates around 4,500 Hz to measure a wind field to a maximum of 200-m up. The unit has a durable reflector enclosure, and the company says the 4000 series is the most accurate SoDAR commercially available. The 4000w comes with an enclosed trailer for added security in remote locations.

Atmospheric Systems Corporation
www.minisodar.com

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