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Breakthrough technologies - PrimeDry Steel Yankee

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Breakthrough technologies - PrimeDry Steel Yankee

October 14, 2012 - 16:00

BRUSSELS, Oct. 15, 2012 (RISI) -The Steel Yankee

We start the series with a product from Andritz, thePrimeDry Steel Yankee, that is attracting a lot of attention globally as it hits all the Breakthrough Technology points on the list: improvement of quality output; energy saving; increased productivity; safety; and ease of use. Mostly used in the tissue making process, the steel Yankee is also now being ordered for graphic and speciality paper machines as its attributes of stability come to the fore.PPIspoke to Klaus Gissing, vice president, Tissue and Air engineering at Andritz about why this technology makes such a difference.

PPI: In your opinion, why does the steel Yankee stand out above existing iron cast technology?

Klaus Gissing: Iron cast Yankee dryers have been in operation for more than 100 years, as frankly, that was the best way of achieving the result. But metalizing has moved on, and working with steel gives many more advantages: less brittle, better thermal conductivity, de-bonding, and all sorts of operating properties that mean far better end results and savings for the papermaker on an operational level.

How did the Breakthrough occur?

It was clear to us at Andritz as we embarked upon the R&D with the concept of the steel Yankee that this was a winner from Day One. Our focus was initially on big and wide steel Yankee dryers where we concentrated on the welding technology, which is crucial as this is of course not cast steel and has joints. We first manufactured a 12-ft Yankee for experimental purposes and perfected the welding technique and technology so that the seams had absolutely no influence on the performance of the cylinder.

Concept to startup of the first steel Yankee was around three years.

What are the main advantages for the papermaker?

As well as improved runnability, energy savings, increased life time and security of supply one of main advantages is safety. There is a big difference in the material behaviour between steel and cast iron. Steel is a ductile material whereas cast iron is brittle in behaviour. Ductile materials can withstand much larger stratins before rupture compared to brittle ones and steel will show considerable yielding before rupture. Cast iron Yankees have been known to fail suddenly, and without warning.

In terms of energy, savings are made due to higher contact drying which is more efficient than when compared to convection drying. And the life of the Yankee will be a lot longer again due to the stability and uniform heat profile.

Another big advantage is logistics; we are able to pre fabricate the steel Yankees in our workshops and then assemble at the mill site, allowing accessibility to even the hardest to reach mills.

One of the key advantages is that we can tailor make steel Yankee cylinders to go with any machine, no matter how narrow, and we can adapt the shell width to any paper width. An added plus with the production environment is the security of supply. There is no danger of a spoiled casting and related delays or cancellations.

Success on the market: how many orders so far?

So far the PrimeSteel Yankees have been received extremely well; we have had orders for 23 of them with three of the orders being outside of tissue making in the area of graphic and speciality papers.

PrimeDry Steel Yankee
Manufacturing of the steel Yankees takes place at Andritz sites in Austria and Hungary and is handled entirely in-house without the use of any external suppliers
The Yankee is heated, coated polished and tested before transportation
In Yankee dryers, there is always the risk of explosion due to high temperature inside the dryer. Steel has proved to be much more stable as a material, but stringent tests are still made before shipping
ANDRITZ offers Steel Yankees with diameters of 12 ft, 15 ft, 16 ft, 18 ft, 20 ft and 22 ft
The steel plate thickness is up to 80 mm and must be perfectly shaped to form a cylinder. The quality of the weld seam has to be perfect
Steel Yankees have an evaporation rate 15 – 20% higher than cast iron which results in 8 - 10% better machine performance allowing producers to either increase production for the same energy input, or reduce energy consumption for the same production
Yankee cylinders – Steel versus Cast
The high-strength properties of steel enable a PrimeDry Steel Yankee to deliver higher performance than a cast iron model:
• The wall thickness of steel is less, permitting a more efficient heat transfer (evaporation rate).
• The elasticity of steel is higher, allowing for higher pressures and giving a margin of safety against thermal shocks, mechanical mistreatment (accidents), or potential explosions.
• Steel Yankees perform from day one. There is no run-in period required and no degrading of performance over time.
• Steel requires less grinding and polishing during shutdowns.
• The steel Yankee is not subject to de-rating due to thinning of the wall thickness or loss of metallic coating over its lifespan.
• The metallic coating of the steel enhances chemical coating and creping processes.
• No danger of spoiled castings in respect of delivery delays.
• Improved quality of output due to better crepe making for a more even surface temperature and a more stable coating.