20 VALMET
Beating chromium in Yankee metallizing
Pulp Paper & Logistics
D
amaged Yankee cylinders in tissue- making machines impede production
and can have a detrimental impact on tissue quality. Cylinders with damaged surfaces are often metallized, particularly if the remaining cylinder shell is not thick enough or if further grinding may affect performance. A recognised risk with metallizing is that during the process, potentially-harmful hexavalent chromium (chromium-6) is created. Chromium is a fundamental component of almost every iron-based hard-facing alloy.
July/August 2018
Restoring the surfaces of Yankee cylinders is a vital service for the tissue making industry. Valmet has developed a new process that meets modern environmental requirements. PPL reports
It is a process that originated with UK-based Bender Machine Services, which in 2004 agreed with Metso to provide a worldwide service programme for Yankee and MG cylinder grinding and thermal spraying. Valmet – which had been
providing the market-leading Infinikote Yankee Metallizing service for more than 20 years
– recognised the potential risks associated with the thermal spraying of ferrous materials containing chromium. Three years ago Valmet embarked on a programme to develop new alloys that were better than chrome in the Yankee metallizing process. The new Infinikote-2 Yankee
Metallizing process uses alloys that contain no chromium
and generates no hexavalent chromium during application. Valmet says it is the most environmentally-safe and durable Yankee metallizing coating available.
For the safety of people and the environment Yankee metallizing is part of Valmet’s on-site field service and is carried out on the customer’s premises. The process involves grinding the surface of the Yankee and restoring it with a hard- wearing finish, and takes up to four days. “We identified the need to
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