Noise-Reduction Sealing System suits underwater construction.

Press Release Summary:

Designed to help protect marine mammals, Sealing System uses air cushion process to reduce underwater noise generated during foundation work for offshore facilities by 10 dB. System consists of 3 sealing rings that enclose external hollow pipe on upper end against column to be driven, allowing air to be compressed into middle space, displacing water. System performs at depths up to 40 m and at pressures up to 6 bar.

Original Press Release:

Freudenberg Sealing Technologies Merkel Develops Noise-Reduction Sealing System for Underwater Construction

Innovative noise reduction provides protection for marine mammals 

PLYMOUTH, Mich., – Freudenberg Sealing Technologies Merkel (Freudenberg) had a goal: less noise pollution for harbor porpoises affected in the installation of offshore wind turbine systems. Through the development of a special sealing system, Freudenberg was able to reduce the underwater noise generated during foundation work for offshore facilities by 10 decibels. 

When doing foundation work for offshore wind power stations, the noises that result can pose substantial stress for marine mammals, such as harbor porpoises, that have a very acute sense of hearing. For that reason, in 2006 the German Federal Office for the Environment commissioned a study on the reduction of noise from underwater ramming work offshore. Hands-on testing was also performed to examine various noise-reducing processes.

Five years later, the German Federal Agency for Nature Conservation followed up with a study on the status of the developments. Its findings revealed that the air-cushion process was the most effective and cost-efficient sound proofing measure. In this process, columns that are to be driven are enclosed in a hollow pipe. Inside the pipe, an air cushion is generated, resulting in a significant reduction in noise emissions.

Based on these results, Freudenberg developed a special sealing system that insulated the noise source in the water. The requirements for this sealing system are highly sophisticated and include:

- Large diameter of approximately 2.5 meters,

- Ability to perform at a depth of up to 40 meters and at a high pressure of up to 6 bar,

- Deviation in the seal gap of up to +/- 25 millimeters.

Freudenberg’s simulation and computation tools made it possible to produce an initial prototype, and subsequently develop a sealing system with specially shaped sealing elements, in a short amount of time. This sealing system consists of three sealing rings that enclose the external hollow pipe on its upper end against the column to be driven. This allows air to be compressed into the middle space, displacing water. The multilayer configuration of the seals allows for high pressures to gradually be decreased.

Media Contacts:

Cheryl Eberwein, Director, Media Relations

Office: +1 734 354 7373


Lisa Gentile, Public Relations

Office: +1 734 354 5439


About Freudenberg Sealing Technologies

The technology specialist Freudenberg Sealing Technologies is a supplier, development and service partner for customers from a variety of market segments, such as the automotive industry, civil aviation, mechanical engineering and shipbuilding, food processing and pharmaceuticals, or the agricultural and construction machinery industry. On the basis of the Simmerring® developed by Freudenberg in 1929, Freudenberg Sealing Technologies now has a broad and continuously customer-oriented product portfolio of seals. Based on detailed process knowledge, innovative development methods and selected materials, the range includes both customized individual solutions as well as complete seal packages.

Together with its partners NOK Corporation, Japan, Sigma Freudenberg NOK, India, and NOK-Freudenberg Group China, Freudenberg Sealing Technologies forms a global network which aims to supply its customers all over the world with products of the same high quality.

In fiscal 2012, the largest business group of Freudenberg generated sales of more than 1.68 billion euros and had a workforce of about 12,000 employees. The company is part of the Freudenberg Group whose business areas Nonwovens, Seals and Vibration Control Technology, Household Products and Specialties and Others generated sales of more than 6.3 billion euros in 2012 with a workforce of 37,453 in 57 countries.

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