"RF" and "RFA" series dryers

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More than 1,200 "RF" (Radio Frequency) model dryers, the well known conveyorised STALAM dryers sold all over the world since 1981, are presently in operation for the drying to a conditioned weight of yarns in packages and cakes, and of worsted fibres (tops) in bobbin and bump form.
Almost all combinations of natural, artificial and synthetic fibres, as filament fibres or worsted and spun, pure or blended, in every count and form (worsted slivers in bobbins and bumps, weighing from 3 to 25 kg; yarns wound on plastic cones or stainless steel springs, either compressed or not, and cakes wrapped in polyester hose) can be dried perfectly, down to the desired residual moisture level, with outstanding efficiency and quality results. Such outstanding results cannot be achieved with any conventional hot air drying system.

Tops can be dyed and centrifugally hydroextracted using standard basket-type (movable or fixed) carriers or directly on centrifugable spindles. Yarn packages, after dyeing, can be hydroextracted one by one after removal from the dyeing carrier, or directly on centrifugable spindles, or may be simply pre-dried in a pressure (rapid) dryer. All handling operations can be carried out manually, assisted by partial automation or with fully automated systems.
In the "RFA" (Radio Frequency Assisted) series dryers, the RF treatment, duly controlled in the different phases of the drying process thanks to a special design of the RF application electrodes, is combined with a conventional warm air circulation system, either generated by steam-fed heat exchangers or recovered from the cooling circuit of the RF generator (in case of air cooled dryers).

Recently, some interesting innovations have been introduced in the "RF" and "RFA" series dryers, like the extensive use of stainless steel inside the drying tunnel, a new conveyor belt tracking and tensioning system, the modular type polypropylene conveyor belt, the multi-position upper electrode system, the new electronic board to control the RF generator’s working parameters and the PLC with related software for fully automated operation.
STALAM’s latest "RF" and "RFA" model dryers allow savings in operating costs up to 5-10% compared to other standard RF dryers available in the market.

"RF 105 kW" and "RF 150 kW" dryers

Download data-sheet "RF 105 kW" (208 Kb)
Download data-sheet "RF 150 kW" (188 Kb)

In the past several years, many efforts have been dedicated by STALAM to the development, in exclusive co-operation with the world’s leading supplier of vacuum RF tubes, of new, more powerful and even more reliable generators, which have enabled our company to present - on the occasion of ITMA ’99 - the first textile dryer equipped with a 105 kW output power RF generator, either with water cooling or air cooling system and - on the occasion of ITMA ’07 - the dryer with a single 150 kW output power RF generator.
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 "Fortec Twin04+" dedicated micro-controller (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 model dryers.

The new 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 economic viability of the 85 kW 105 kW model dryers.

"TCRF" series dryers

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The "TCRF" (Thermo-Controlled Radio Frequency) model dryers represent the outcome of the researches carried out by STALAM in co-operation with Messrs. LORIS BELLINI as to the RF drying at a controlled temperature of yarn packages and tops in bobbin or bump form, and can surely be considered as the most sophisticated batch-type textile dryers available worldwide.
In the "TCRF" dryers a suitable air flow, forced through the product while submitted to the RF field, makes it possible to control the product's internal temperature: in more detail, the RF energy supplied endogenously causes the evaporation of the water within the product, and the air flow passing through quickly evacuates the water vapour, thus avoiding a temperature increase above a certain value, duly pre-set by the operator. An automatic weighing system stops the drying cycle automatically when the desired final weight has been reached. All working parameters and dryer operations are set and automatically controlled through a PLC.
"TCRF" dryers with 1 or 2 trolleys specifically designed for yarn packages, and a dryer model with 2 trolleys suitable for both tops and packages, are available.

Thanks to the accurate drying temperature control, the "TCRF" dryers are particularly suitable for: bleached and optical whitened fibres (such as chlorite bleached wool tops - also after anti-shrinking treatment - and cotton/acrylic blended yarns in light and pastel shades), cotton and viscose yarns dyed with direct dye-stuffs, both fixed and unfixed, and, generally speaking, for all products whose quality parameters are negatively affected by prolonged thermal treatments or by temperatures above a certain limit.
"TCRF" dryers allow a remarkable reduction of overall drying costs: average electricity savings are of 10-25% compared to the standard radio frequency technology, depending on the product being dried; moreover, the ease of loading and unloading of the trolleys contributes to reduced labour costs. The "TCRF" dryers are also predisposed to be integrated into fully automated dyeing plants with robotised handling systems for dye-columns.

"RF/C" dryer

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An great innovation that STALAM has disclosed to the world markets for the first time at ITMA ‘03 is the "RF/C" model dryer, a continuous type radio frequency dryer for yarn package columns.
This equipment has a drying chamber constructed with fully screened product inlet and outlet apertures, placed adjacent to each other at the front of the dryer. The RF generator is conveniently located above the drying chamber. In line with the apertures, the drying chamber is dotted with two pairs of vertical electrode plates, such that the yarn package columns enter in the first pair of electrode plates and return out through the second pair of electrode plates.
The package columns are carried in and out from the drying chamber by a carousel system, which is made up of a series of individual supports holding the columns upright and at the same time sliding on lateral rails. The drive system transfers the columns in stepped movements, where the pitch of each step is 250 mm, corresponding to the maximum possible diameter of the yarn packages. The step pace is adjustable according to the drying requirements specific to the product such as: yarn type, package weight, moisture content, etc.
The product loading and unloading station is located at the front of the dryer. In this position the operator - or a robotised handling device - can load the wet columns directly from the hydroextractor (with or without dye-spindles, according to the dyeing and hydroextraction equipment in use) and unload the dry ones to the finished product station.

All running parameters of the equipment (RF power, carousel speed, etc.) are set by a SIEMENS S7-200 series PLC via a touch-screen operator panel.
Besides all the well-known benefits of the radio frequency technology, this revolutionary drying equipment has several important advantages, specifically related to ease of product handling and the simplified logistics within the dye-house, as detailed below:
yarn packages can be processed in the form of columns throughout the entire dyeing - hydroextraction - drying sequence of operations, thus reducing drastically the labour requirements within the dye-house and minimising the risk of yarn spoilage due to repeated handling of individual packages;
loading and unloading of columns take place at the same (front) side of the equipment, therefore both operations can be carried out at the same work position. This function can be either manual (the operator can lift and transfer the columns with the assistance of a simple counterweight lever) or by means of a fully automated handling system;
the step movements of the carousel and the designed single loading / unloading station make the implementation of a robotised column transfer system extremely compact, simple, and cost effective, unlike similar current systems presently utilised to automatically load and unload other drying equipment;
yarn package columns can be handled and transferred to the dryer with or without the (eventual) movable and/or centrifugable stainless steel dye-spindles: this depends on the dyeing and hydroextraction equipment used. Moreover, package columns of any height up to 1800 mm can be fed to the dryer, in any desired random sequence, as they come out from the various size / type dyeing machines. The dryer is therefore suitable to be integrated within any existing or yet-to-be-established dye-house, irrespective of the dyeing machines’ make, type or size;
the equipment, like all other STALAM dryers, is modular so that more drying chambers / generators (typically two or three) can be installed in-line to form a single high-capacity “drying station”, yet within a relatively limited floor-space area.

"RFA/HP" dryer

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On the occasion of ITMA ‘07, STALAM has introduced to the world markets a revolutionary drying equipment named "RFA/HP", specifically designed for yarn packages, which combines the RF technology with a forced air circulation system through the product in a conveyorised type dryer.
It is the first time worldwide that a passing-through air flow can be obtained in yarn packages in a continuous throughput industrial drying equipment, thus enabling the “RFA/HP” dryer to exploit at all times the maximum RF power delivery compatible with each specific yarn type. On the contrary, in batch type dryers, the RF power naturally tends to drop as the product gets dried, thus reducing the productivity and the overall efficiency of the process. That is why the “RFA/HP” dryer has the highest hourly productivity among all RF dryers (standard type or combined with forced air circulation, including those using steam to heat up the air) having the same size RF generator, yet at a reduced drying temperature.
The air forced through the product is heated up to the desired temperature, set through the PLC by the operator according to the product to be dried, generally in the range 60°C to 80°C, without using any external (additional) energy source, but just recovering the heat dissipated by the RF generator cooling system.

Both the RF energy and the warm air forced through the product contribute to water evaporation and the same air flow quickly removes the water vapour. This combined process, other than being extremely efficient, enables a precise control of the product’s internal temperature, thus optimising the drying quality results.
The performance (effectiveness) of the air flow in both cooling down the RF generator and evaporating the water from the product can be greatly enhanced by fitting a heat pump in the system, so that the ambient air is treated in 4 distinct phases before being forced through the yarn packages: filtering, cooling and dehumidifying, heat recovery from the RF generator, heat recovery from the heat pump.
The heat pump is particularly suitable when the dryer has to be installed in hot and/or humid environments, that would otherwise make it necessary to provide the water cooling system on the machine and where, sometimes, even a water cooling tower or a chilling plant is unavoidable. In these cases, not only the use of water and related cooling or chilling equipment can be avoided, but also the heat dissipated by both the generator and the heat pump can be fully recovered for the drying process. This is the reason why the “RFA/HP” dryer has the lowest energy consumption among all RF dryers (standard type or combined with forced air circulation, including those using steam to heat up the air) per kg of dry product.

The air coming from the cooling system of the generator, at the desired temperature level, is forced through the product, while submitted to the RF field, by one or two high-head centrifugal fans, each controlled by independent inverters to cope with all different yarn package types and working conditions of the equipment.
The packages are conveyed through the drying tunnel on plastic holders fixed to stainless steel plates that, when passing under the RF-fed electrode, become a “floating” bottom electrode, ensuring a safe and efficient RF power delivery to the yarn. The plates are conveyed by means of stainless steel chains with a stepped movement, that enables the plastic holders, duly fitted with special seals, to stop in the positions where the ducts have the connectors blowing or sucking the warm air through the product. After drying is completed, the packages are brought back by the conveying system to the loading / unloading position in front of the dryer.
The operation of the dryer is fully automatic and managed through a SIEMENS Simatic S7-200 PLC equipped with an ESA VT595W LCD touch-screen operator panel, where all different “recipes” for various yarn package types can be stored and recalled. Bar code scanner for product identification, modem connection for on-line communication and trouble-shooting, etc. are all optional features that can be implemented upon request.
The outstanding features and performance of the “RFA/HP” dryers can be considered a real break-through in the yarn dyeing sector and demonstrate once again that STALAM is the most innovative and far-sighted manufacturer of RF drying equipment for the textile industry worldwide.