^ A glimpse into Siedentop’s Rotainer pickling system: the components are sprayed with the bat pickle in a closed container system. Image: Oliver Farys.

By Jutta Thiel, frische denken, Germany

Pickling is an essential process, yet it remains an inconvenient issue for many stainless steel processing companies. It is said to be toxic, environmentally hazardous, subject to tight restrictions as well as expensive. While these shortcomings do apply to traditional bath and spray pickling, modern pickling systems using the Rotainer principle avoid them entirely.
Developed by the German company Siedentop, the EU-patented Rotainer systems for stainless steel pickling are computer controlled, which improves the pickling result while also saving resources. The systems are designed as closed containers so that no toxic gases may escape into the ambient air. Consequently, there is no need for evacuation and cleaning of the air, which is a common obligation when applying conventional pickling methods.
Siedentop’s system uses nozzles to spray bath pickling acid on the stainless steel parts to be processed. Even complicated surfaces and cavities are treated perfectly. Every processing step – from degreasing to pickling, passivation, rinsing, and air washing – are carried out as a fully automated programme. The computer-controlled pickling process saves time and ensures consistently high pickling quality. At the same time, the Rotainer pickling principle reduces the quantity of pickling agent. It requires a maximum of 900 litres of pickling agent. The Rotainer principle is also leading in terms of accident prevention: the Siedentop system works with nitric acid-free pickling acid. Operators do not come in contact with acid during the pickling process.

Pickling long stainless steel tubes 

Siedentop’s new technology has also been developed into a pioneering pickling system for long stainless steel tubes that may be installed without prior legal approval in most countries. It provides a cost-effective alternative to conventional tube pickling and offers resource-saving and fast pickling processes.
The fully automated tube pickling system Tube Blue Rotainer is built as a closed container system. It uses nozzles to spray bath pickling acid on the tubes. A hoist-rotation lift specially designed for tube pickling then raises the tube bundle to be pickled to an optimal position, ensuring that all tubes are uniformly coated with the bath pickling solution. The tubes within individual bundles may also have different diameters.
As both pickling systems can be operated with less than 1,000 litres of pickle, companies in most countries needn’t ask for legal authorization to install the system. “Depending on the country, legal approval procedures may take up to several months,” reports FriedrichWerner Siedentop, founder and managing director of Siedentop GmbH. “However, when facing harsh competition, a business can’t put an investment on hold for so long.”

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