Siempelkamp Maschinen- und Anlagenbau GmbH & Co. KG

Vulcanizing plants for steel cord and textile conveyor belts: Siempelkamp shortens the length of a line by 10 - 20 percent

The new vulcanizing plant for steel cord and textile conveyo
When manufacturing steel cord and textile conveyor belts Siempelkamp trusts in two innovations: the uniform tension of the steel cables embedded in a rubber compound and the even pressure distribution in the vulcanizing press. The new design principle makes plant components that were considered essential in the past now dispensable. Thus, Siempelkamp reduces investment costs and, at the same time, improves process safety during vulcanization.

Modern measurement and control technology as well as Finite-Element simulations have made two innovations possible that lower the costs of buying and operating vulcanization lines for steel cord and textile conveyor belts and also improve process safety.

Tension control reduces costs

During uncoiling of the steel cables which are to be embedded in the rubber compound, Siempelkamp measures the initial tension of each cable and controls each of them individually with up to 260 brake motors. Each motor tightens one cable with a force of up to 4000 N. This control ensures the uniform tensioning of all steel cables across the entire width of the belt. The control also compensates for the different angles in which the steel cables are running over the combs for different belt widths.

With the new concept Siempelkamp reduces costs in several places: Since the steel cables are already tensioned during uncoiling, a separate cable tensioning system becomes obsolete. The tension of the steel cables is, due to the individual controls, the same over the entire length between the creel and the pull-roll stand. Therefore, Siempelkamp can replace the compactor lorry with a stationary compactor station. This lowers investment costs, saves room inside the production hall and reduces maintenance.

Multi-piston concept guarantees consistent vulcanization parameters
Siempelkamp also uses a new principle for its vulcanizing presses. The design engineers did not strive for a press with higher mechanical rigidity, but for one that would distribute pressure evenly onto the belt. Instead of using a few large cylinders, as in previous press designs, Siempelkamp uses six times as many smaller cylinders with the new multi-piston presses.
These cylinders distribute pressure more even onto the belt. The hotplaten is flexible at pressures of up to 25,000 t (27,558 US tons) and is able to adjust to unevenness in the green rubber belt and therefore, provides a significantly improved pressure distribution.

The new design effects the productivity of the entire plant: Presses with a length of up to 23.5 m (77 ft) are possible.
At a given belt length, longer presses require a lower number of pressings. This represents a great advantage because heating times can be 30 to 90 minutes long.

The even pressure and temperature distribution guarantees that the vulcanization parameters are maintained over the length of the belt, which is an invaluable benefit if one considers that conveyor belts are several hundred meters long.

The improved process safety furthermore allows to better keep the necessary tolerance values and thus, save material.

The world's strongest vulcanizing presses in the rubber and plastics industry were put into operation by Siempelkamp at Fenner Dunlop in Australia in July 2009 and at Shandong Aneng in China in August 2009. This press design is equipped with 156 cylinders which provide a total press capacity of up to 25,000 t.