Stalam: World leader in radio frequency dryers

Established in 1978, Stalam is a world leader in the development, design and manufacture of radio frequency (RF) equipment for a variety of industrial heating and drying applications, mainly for the drying to a conditioned weight of textile fibres and yarns, nonwovens, technical textiles and related products. Other important and innovative applications of the RF technology, mainly in the food industry, were introduced by Stalam in the last decade, when processes like the pasteurisation and sterilisation of either solid packaged products or viscous liquids, or the RF defrosting of frozen raw materials, were implemented for the first time worldwide on a truly industrial scale.

As a member of AEI (Italian Electronic and Electro-technical Association) and of ACIMIT (Association of Italian Manufacturers of Machinery for the Textile Industry), Stalam co-operates actively with prestigious universities and research institutes for the development of the radio frequency technology both as to generation techniques and to technological applications.

Stalam also co-operates with other leading European machinery manufacturers for the development of innovative drying and thermal processing technologies and for the supply of turn-key automated and integrated production lines.

Stalam offers the widest and most advanced range of industrial RF processing equipment, which enable their users to obtain the maximum benefits from the RF technology in terms of quality of the finished products, reduced operating costs, high flexibility and reliability.

Presently, more than 1,500 Stalam equipment are in operation in more than 50 countries, having rated power values ranging from 3 to 320 kW; from the simple, manually operated machine, to the fully automated line complete with computerized control and supervision systems.

Stalam radio frequency dryers

Stalam radio frequency dryers have  specific design and construction features, which allow users to obtain the maximum benefits from the RF technology in terms of quality of the dried products, reduced operating costs, flexibility and reliability.

The RF generators are entirely designed and manufactured by Stalam; they are of the "lumped components" type, having high efficiency (Q factor) and outstanding reliability; all components and circuits are easily and quickly accessible.

The cooling system of the triodes is made up of a double water circuit; it is designed to allow the longest possible life of the triodes and does not require periodic maintenance operations. Upon request, and as standard in some specific applications, Stalam also supplies generators fitted with a forced-air cooling system.

The RF power adjustment is accomplished by means of a semi-automatic circuit which controls the power supplied to the product being dried through a variable capacitor, located in the generator. The system does not require continuous raising or lowering of the upper electrode for RF power adjustment as the electrode is fixed or automatically positioned at pre-set heights.

The power density is as low as 5 to 14 kW(RF)/sqm of electrode surface. Therefore the heating/evaporation process is extremely gentle and the quality of the dried product is greatly enhanced.

The construction is modular, in the sense that high capacity dryers are made up of two or more drying modules, connected in series; this construction principle allows Stalam dryers to work with reduced RF power densities in all circumstances. Further modules can be added to the first at any time, so that considerable investment and floor space savings are possible.

RF 150 kW dryer

Introduced to the world markets on the occasion of ITMA 2007, Stalam's new "RF 150 kW" dryer represents, once again, a world record as to output power rated by a single RF generator in the textile industry.

The RF power distribution electrode has been adequately sized in order to maintain the lowest possible power density on the product being dried - compatibly with the purposely reduced machine dimensions - thus ensuring a gentle drying process and the highest product quality standards. Moreover, the innovative air circulation and evacuation systems assist the evaporation process maximising the moisture removal efficiency while avoiding all dew condensation problems inside the drying tunnel.

The dryer functioning is supervised by the "Twin 04+" dedicated microcontroller (PLC) specifically developed by Stalam for the reliable, safe and easy operation of its RF dryers.

The "RF 150 kW" dryer is mostly dedicated to medium and large capacity yarn package dye-houses that will have the possibility, for example, to dry over 8 tons/day of 100% cotton yarn packages in a single-generator machine which is just slightly longer than 10 m - more or less the same length of 85 kW & 105 kW dryers.

The Stalam 150 kW dryer enjoys the most favourable productivity / space and productivity / cost ratios - as to both capital investment and operating costs - improving further the outstanding economical convenience of the 85 kW & 105 kW model dryers.

Dryers for nonwovens and other textile applications

Bearing in mind that any drying process carried out by means of a radio frequency field shows outstanding energy efficiency and leads to a better quality of the dried product. Therefore, during the past decade STALAM has developed specific drying equipment suitable to process a variety of materials. Some of the most important applications within the textile industry are:

• post-vulcanisation drying of foamed latex products;
• drying of felt for clothing and for industrial uses, after impregnation, in the form of sheets and disks;
• drying of dyed elastic bands and narrow fabrics;
• drying of silk cocoons and silk wastes after carbonising;
• drying and pre-heating of defective synthetic fibres to be recycled in pellet form, in-line with the extrusion equipment;
• drying of glass fibres.