Muehlhan AG

Hamburg, Germany

Muehlhan AG

Hamburg, Germany
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News Article | February 1, 2016
Site: phys.org

Carrying out repairs on an offshore wind farm. Credit: Muehlhan AG Offshore wind farms generate energy from the raw winds out at sea. But the salty air causes them to rust. For such plants to be profitable, they have to re- main in service for at least 25 years – which is impossible without regular maintenance. In the future, the use of innovative materials and technologies will make this task less onerous and cheaper. Fraunhofer researchers are developing a protective film that will optimize the repair process and are working on the necessary inspection criteria. The energy transition is in full swing, and more and more wind parks are being constructed offshore. Many new projects are underway in the North Sea and Baltic Ocean. But the maintenance and repair of these structures presents numerous difficulties, not least because the turbines are anchored in the seabed and cannot be towed to a dry dock for maintenance like a floating oil platform. Everything has to be done on site, out at sea, whatever the meteorological conditions. This task is particularly difficult when it comes to renewing corrosion-resistant coatings. New solutions being developed by researchers as part of the collaborative RepaKorr project will make this easier in the future. "Our aim is to develop a holistic, sustainable concept for the maintenance and repair of protective systems, that will be simpler to apply and thereby reduce costs," explains Peter Plagemann of the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen. The all-round inspection and repair solution to increase the corrosion resistance of offshore wind farms is set to be ready for implementation by March 2016. It places special emphasis on those parts of a wind turbine that are not permanently submerged under water, and therefore need a particularly hard-wearing coating to prevent the formation of rust. The main contributors to the project are Sika Deutschland GmbH, which is developing new repair materials, and Muehlhan AG, which is developing novel application and analysis methods. This work is being complemented by the development of new testing concepts; current guidelines and methods are not adapted to the testing of repaired components. "There is a need for standard procedures that can be used to verify the quality of repairs," says Plagemann. Because such guidelines do not exist at present, the IFAM researchers have devised tests based on their own criteria. Another project partner, AirRobot GmbH, is investigating the idea of using drones to inspect coatings and determine what repairs are needed. Here, too, clear inspection criteria must be defined so that this process can be automated as far as possible. Until now, this job has been done by workers wearing climbing harnesses – a time-consuming and dangerous activity. The IFAM researchers are developing a protective film to prevent moisture and salt from coming into contact with surfaces that have been cleaned and prepared for recoating until such time as the actual repair coating is applied. "The challenge is that the film must adhere firmly and yet be easy to remove without leaving any residue. We're trying to find a solution that combines these seemingly contradictory requirements," says Plagemann. The Fraunhofer researchers are pursuing two ideas, one of which has been tested successfully in the laboratory. The other is in the process of being patented. "The positive effect of this protective film," says Plagemann, "is that it allows the repair process to be carried out more cost-effectively, because the critical period between preparing the surface and applying the coating can be planned much more reliably." This is a significant factor, given that the cost of maintaining and repairing offshore wind farms can easily add up to one hundred times the original construction cost over the years of operation. Whereas the metallic coating of onshore plants generally costs around 20 to 30 euros per square meter, the price can rise to several thousand euros for offshore plants. The RepaKorr project aims to considerably reduce these costs. The project partners intend to standardize the inspection process, computerize the results of individual interventions, and feed these data into existing electronic, online monitoring systems. This will help to shorten inspection and repair cycles by enabling more precise, targeted planning. Explore further: New module lowers the cost of offshore wind power


Momber A.,Muehlhan AG
EUROCORR 2013 - European Corrosion Congress | Year: 2013

The paper provides a review about the corrosion and corrosion protection of offshore wind energy devices (OWEA) with a focus on the support structure. Considered are tower structures and power transmission platforms. Firstly, special features resulting from location and operation of wind energy devices offshore are being discussed. This includes the definition of a load collective. Secondly, types of corrosion and corrosion phenomena as well as coating deterioration issues are summarized in a systematic way. Examples form site inspections are presented. Further, practical solutions to the corrosion protection of OWEA with a focus on the application of protective coating and lining systems, either organic or metallic, are discussed. Crucial issues, namely steel work quality, steel surface preparation, paint application and quality control, are discussed finally from a point of view of a surface protection contractor.


Momber A.W.,Muehlhan AG
International Journal of Advanced Manufacturing Technology | Year: 2016

The paper reports about investigations into the removal of thick organic protective coatings with rotating high-speed water jets. Ten nozzle carriers, rotating at a very high speed of 3000 min1, were applied at stand-off distances between 10 and 82 mm. Widths of the eroded sections and the percentage of completely exposed steel sections were estimated. Color-based image processing was applied for the assessment of exposed steel sections. The results reveal two types of performance. (i) Carriers with a moderate number of nozzles travelling on more than one orbit exhibit a maximum performance at characteristic optimum stand-off distances. (ii) Carriers with nozzles travelling on one orbit perform best at the lowest stand-off distance; these configurations generate notable swirl pattern (lack of overlap) in the center of the erosion path. The most effective configuration is characterized through an optimum balance between nozzle number, nozzle diameter, and nozzle orbit for a given stand-off distance. © 2016 Springer-Verlag London


Momber A.,Muehlhan AG
Materials and Corrosion | Year: 2012

The paper reviews the utilization of colour analyses for the assessment and rating of atmospheric corrosion products, whereas particular attention is spent to flash rusting. The background of flash rust formation is discussed first, along with a brief review about the composition of flash rust. The fundamentals of the HSV colour model, which is selected as a simple suitable model, are introduced. Finally, the author discusses the utilization of the suggested approach for the evaluation of steel substrate cleanliness and rust assessment. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Momber A.W.,Muehlhan AG | Marquardt T.,Muehlhan AG
Powder Technology | Year: 2016

The paper deals with a systematic investigation into the flow of copper slag abrasive particles through a metering valve. The investigation involves abrasive mass flow rate measurements, and the results are statistically interpreted based on DoE (Design of Experiments) and ANOVA (Analysis of Variance). Three process parameters are varied, namely static air pressure, nozzle diameter and valve opening. Abrasive mass flow rate increases if air pressure, nozzle diameter or valve opening increase. All three main factors provide statistically significant effects, whereby the strongest effect occurs due to changes in valve opening. Although a non-standardized quadratic regression model delivers a satisfactory agreement with experimental results, it misjudges the statistical significance of the process parameters. A standardization of the regression function omits multicollinear effects and simplifies the regression function. A standardized quadratic regression model is found to be capable to statistically describe the relationships in the scope of the evaluation effort. © 2016 Elsevier B.V..


The paper provides a review about the corrosion and corrosion protection of offshore wind energy devices (OWEA). Firstly, special features resulting from location and operation of OWEA are being discussed. Secondly, types of corrosion and corrosion phenomena are summarized in a systematic way. Finally, practical solutions to the corrosion protection of OWEA, including steel allowances, cathodic protection and coatings and linings, are discussed. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Momber A.W.,Muehlhan AG | Plagemann P.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research | Stenzel V.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research
Renewable Energy | Year: 2015

Six corrosion protection systems for offshore wind power constructions have been subjected to offshore conditions on a test site in the North Sea in three different exposure zones, namely splash zone, intermediate zone, and underwater zone. The systems included single- and multiple-layered organic coatings, metal-spray coatings, and duplex coatings. Special testing specimens were designed and manufactured and exposed to an offshore environment for three years in order to characterize particular constructive details for different corrosivity zones. The following target parameters were investigated: intensity of fouling, anti-corrosive effect, coating adhesion, coating integrity, flange corrosion, coating performance over welds, and condition of screw connections. Fouling was an issue in the underwater zone and in the intermediate zone, but it did not affect the coating corrosion protection capacity. It was found that duplex systems, consisting of Zn/Al spray metallization, intermediate particle-reinforced epoxy coating, and polyurethane top layer, provided the highest anti-corrosive effect. Mechanical damage to the coatings initiated coating delamination and substrate corrosion. Effective coating systems should be either very resistant to impact or able to compensate for corrosion of the steel. Flange connections were found to be critical structural parts in the splash zone in terms of corrosion. Notable crevice corrosion was observed at places. Except for one coating system, welds have been protected well. Welds, however, affected the corrosion of the steel inside the uncoated internal sections in the underwater samples. Coating integrity on difficult-to-coat structural parts was satisfactory for all systems. © 2014 Elsevier Ltd.


The paper reports about the assessment of deteriorated protective coatings and exposed steel surfaces on offshore wind power platforms in the North Sea and the Baltic Sea. A simple procedure for the assessment of coating deterioration and metal loss on exposed steel surfaces is developed. The procedure delivers a protection number NPNC + NS, whereby the term NC characterizes coating deterioration, and the term NS characterizes metal loss at exposed surfaces. For NP = 0, the structure is fully protected, and for NP = 2, the capacity of the corrosion protection system (protective coating combined with corrosion allowance) is completely exhausted. This number is linked to maintenance procedures. A total of 750 inspection results are reviewed and categorized. The majority of coating damages can be attributed to unsuitable constructive design and to mechanical loading. Design specifications and testing scenarios for coating assessment may be updated in order to account for special stresses in addition to corrosive stresses. Color-based digital image processing is applied for the quantitative recording and rating of coating deterioration processes and for the estimation of NC-values. Preliminary investigations reveal that color-based digital image processing opens the opportunity to evaluate fouling, top coat color changes, and early iron corrosion products. © 2016 Elsevier Ltd.


Patent
Muehlhan AG | Date: 2013-08-15

An apparatus (1) for surface treatment of an elongate object (50), such as a wire rope, while the apparatus (1) travels along the object (50), including a squeegee unit (10) for applying a deformable material, such as a coating material, comprising:


Momber A.W.,Muehlhan AG | Plagemann P.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research | Stenzel V.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research
International Journal of Adhesion and Adhesives | Year: 2016

Corrosion protection coating systems for offshore wind power constructions were subjected to offshore conditions on a test site in the North Sea. The systems included organic coatings and duplex (spray metal and organic system) coatings. Special exposure specimens were designed and manufactured and exposed to an offshore environment for three years in order to evaluate their protection performance. The adhesion in terms of pull-off strength and fracture mode was measured on coatings in the underwater zone and in the intermediate zone. All samples met the requirements for offshore ageing in terms of adhesion. An adhesion-based "corrosion protection effect" (CE) is introduced and calculated for the coating systems. © 2015 Elsevier Ltd. All rights reserved.

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