Controls, Infrared radiation borders visible light

Medium and Hi-Velocity Transco (Convection) Ovens

All objects are surrounded by a relatively still layer of air which acts as an insulator around the object. This layer of air is known as the boundary layer. When drying a finish on the surface of an object the vapors pass from the finish to the surrounding boundary layer of air which becomes heavily saturated with the vapors.

The principle behind Fostoria-Transco high velocity air drying is to impinge high velocity heated air against the finish to be dried through a series of slot nozzles at velocities up to 13,500 fpm. The high velocity air continuously removes the stagnant boundary layer of air surrounding the finish and replaces it with fresh heated air to dry the finish. This reduces the insulating effect of the boundary layer to an absolute minimum and enhances the transfer of heat into the finish. Because the finish is dried faster, the substrate is heated less, reducing the energy required and minimizing a variety of undesirable effects caused by heating the substrate.

In a Fostoria-Transco high velocity dryer heat is added only in quantities enough to pace the curing reaction of the finish. Air temperatures are generally in the 400° to 500°F range resulting in product temperatures in the 200°F range. It should be understood that Fostoria-Transco dryers are not ovens. Temperatures outside the direct path of the nozzle flow are moderate. Thus, the dryers provide drying or curing, but not cooking or baking.

To facilitate the large volumes of air being moved in the dryer, an exhaust plenum and blower are provided to draw the air away after impingement. Frequently, the exhaust air can be ducted to another drying stage for additional energy savings. The exhaust air may also be returned to the heat source and recirculated with only a small percentage being exhausted and most of the heat reclaimed.

For high velocity air drying to be effective, nozzle velocities should exceed 6,000 fpm. Fostoria-Transco high velocity dryers are available with velocities up to 13,500 fpm and our medium velocity dryers are in the 6,000to 9,000 fpm range. The key to obtaining these air velocity levels lies with the horsepower of the fan motors as well as the design of the dryer air floe system and slot nozzles. There are some drying applications which may require lower velocities such as thick coatings, skinning and blistering problems and special shaped parts. Whatever the application may be, it is important to match the dryer velocity with the particular drying requirements of the applications.

Advantages of High Velocity Air Drying

Energy Efficient
Energy is the key element in most industrial processes. Fostoria-Transco dryers inherently minimize the energy required to dry a finish. Unlike conventional convection dryers which require heating up an entire chamber, the heat in high velocity dryers is directly impinged onto the finish. This enhances the transfer of heat into the finish and significantly reduces the amount if heat required. The temperature outside the direct path of the nozzle flow is moderate. Also, high velocity dryers utilize only enough heat to pace the curing reaction of the finish, relying instead on continuous air impingement for drying.
Any Energy Source
Fostoria-Transco dryers can utilize gas, oil, high and low pressure steam, electric and electric infrared as heat sources. Steam, in some cases, can be provided by waste-fueled boilers
Faster Drying ... Less Floor Space
High velocity air drying is one of the fastest methods for drying a finish. Fostoria-Transco dryers will allow faster line speeds than conventional dryers for the same finish drying requirement. If the line speed is fixed, then a Fostoria-Transco dryer will occupy less space (line length) than a conventional dryer for the same finish.
Versatile ... Any Finish Requirement
Fostoria-Transco dryers are custom designed to insure that the ideal temperature, nozzle spacing and air velocity are used based on the characteristics of the particular finish and substrate. The dryers can be used on a variety of solvent based coatings as well as high solids and catalyzed coatings. They are especially well suited for drying waterborne coatings. The dryer controls are fully adjustable, so in many cases the same dryer can be used for a variety of different coatings. Among the primary products for which Fostoria-Transco dryers are successfully used are: hardboard, wood, paperboard, metal, paper and fabric. These may be webs, sheets, or flat or shaped parts.
Safer ... Lower Operating Temperatures
Since Fostoria-Transco dryers evaporate solvents at lower temperatures than conventional dryers, they are safer to operate. The high volume air flow which is characteristic of the dryer's operation continuously removes solvents from the dryer to maintain a safe atmosphere.
Better Quality Finishes
The high volume, low temperature air drying in Fostoria-Transco dryers completely removes solvents from a coating for a superior finish. The solvents are removed before the coating surface hardens resulting in an extremely durable, blister-free finish. Also, all inlet and recirculated air is filtered prior to being heated and impinged on the surface finish. All of the air in the dryer enclosure then is free from dust and dirt particles to Insure clean, quality finishes.
Lower Operating Costs ... Low Maintenance
High velocity air drying has proven to be among the fastest, most efficient methods for removing solvents from a coating. By shortening time cycles and line lengths while reducing the energy required for operation, Fostoria-Transco dryers reduce operating costs. Maintenance costs are kept minimal since the dryers are designed to permit easy access and service of component parts.

Design Features
While each Fostoria-Transco dryer is individually designed to meet the drying requirements of a particular application, all of the dryers are equipped with certain standard design features which assure their operating efficiency and dependable performance.

The dryer enclosure is constructed of heavy duty aluminized steel panels which are insulated with up to 6" of high temperature insulation. This insures that the heated air is confined within the dryer enclosure and directed to the product.
Optimum design slot nozzles impinge the heated air onto the product. The spacing and sizing of these nozzles is dependent on the air velocity requirements of the application. The nozzles are designed to impinge an even, direct path of air flow onto the product to provide thorough, uniform product drying.
Access doors extend the full length of both sides of the dryer to permit easy access to the dryer chamber for maintenance purposes. The access doors on one side of the dryer are hinged in such a way that they serve as explosion relief panels for safety purposes.
Negative pressure is always maintained within the dryer enclosure to eliminate the possibility of any of the heated air escaping through the dryer entrance and exit openings
A heat recirculation system continuously recycles the heated air after it is impinged onto the product. Only a small percentage of the air is exhausted and most of the heat is reclaimed. The heat recirculation system insures that Fostoria-Transco dryers provide maximum energy efficiency.
A complete closed-loop control system to maintain the continuous, efficient operation of the dryer is provided. This system operates by monitoring the temperature of the heated inlet air and automatically modulating the temperature of this air to maintain a given set temperature within the dryer. Additional controls usually provided with the control system include interlock disconnect switches, purge timer, automatic ignition, overload protection and flame proof. Other special control devices can be incorporated with the dryer control system as required.

Laboratory Testing Facilities
Complete laboratory testing facilities are maintained at our Fostoria, Ohio headquarters. Here, customers are invited to send in or bring their product samples and finishing materials for testing on our laboratory equipment. Our testing laboratory is fully equipped with both high velocity air drying equipment and gas and electric infrared equipment along with accurate control and measuring devices. This makes it possible for us to determine the best solution for our customer's application problem and make sound heating equipment recommendations based on the results of the tests. Please click on Laboratory Testing.

Fostoria Industries, Inc.
1200 N. Main • Fostoria, Ohio 44830
419-435-9201 • 1-800-495-4525 • Fax: 419-435-0842
email@fostoriaindustries.com