Energietechnik Essen GmbH – a member of the Georgsmarienhütte Group – bases its capabilities and skills on continuous research and development as well as on experience reaching back to 1811. The Energietechnik Essen GmbH develops, produces and supplies safety-relevant high-tech products, mainly for manufacturers of power generation machinery. When the first turbo-generator was built at the start of the 20th century, the Essen-based company supplied the retaining rings. Retaining rings are placed on the ends of the rotors to fix the copper coil against the centrifugal forces created by the high rotational speeds. The oldest documents in the company's archive relating to non-magnetisable retaining rings date back to 1901. Energietechnik Essen GmbH uses two remelting units, one electroslag remelting unit and one pressurised electroslag remelting unit, to produce the materials for retaining rings.