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Web dryers are primarily designed for the converting industry, where manufacturers take a simple material such as paper, film, foil, non woven or fabric and convert it into a commonly used product such as adhesive tape, wall covering, aerospace material, or flexible packaging.

Radiant Energy Systems designs and manufactures custom web dryers and ovens that convert gas, electricity or steam into efficient process heat for industrial drying, curing and heating applications. These dryers can heat one or both sides of a web in single or multi-pass configurations. We offer the following types of web dryers:

Design considerations for Web Dryers

To design the right dryer for each application, the following considerations must be taken into account:

  • Type of dryer most suitable for the application
  • Source of energy
  • Direct or indirect heating
  • Materials of construction such aluminized steel or stainless steel
  • Easy access for threading and maintenance
  • Location of heating apparatus skid
  • Special considerations for clean room environments

For all types of web dryers, length is a function of:

  1. Line speed
  2. Substrate weight
  3. Coating thickness
  4. Amount of water or solvent in the coating
  5. Temperature and velocity sensitivity of the coating and the substrate

For the past thirty years, Radiant Energy has designed and built hundreds of process heating systems for a variety of applications across many industries. Our engineers have over 100 years of combined experience building these systems. This experience, combined with our lab, rental heater program and pilot line testing, ensures that your installation is a success.

Hot Air Impingement Web Dryers

Hot air impingement web dryers are the most common convection oven design used in the converting industry. Air can be heated up to a desired temperature using any form of energy such as gas, oil, electric or steam. Hot air is delivered by a high-pressure blower to nozzles, where it impinges onto the product at a controlled temperature and velocity to deliver a high rate of heat transfer. After delivering energy to the coating and the web, the air returns to the heat source for reheating and re-circulation through the dryer.

Certain processes might require nozzles not only on the coated side of the web but on the back side as well. There are several types of nozzle designs, but the two most common are tapered nozzle and mail box designs.

The web is carried through the oven supported on idler rolls (which may or may not be driven) or as is common in the textile industry, on a tenter frame. These techniques keep the web at a good tension, which is an important factor in the design of web dryers.

Impingement web dryers offer the following advantages:

  • Uniform heating
  • Gentle drying
  • Energy efficiency
  • Long life
  • Good for water- or solvent-based coatings

Flotation Web Dryers

Flotation web dryers have nozzles on both sides of the web. The bottom nozzles not only provide drying, but also support the web so that no support idlers are required, making these dryers ideal for applications where the web is coated on both sides.

The special coanda nozzle design used in flotation web dryers creates a pad of air, and the web moves through the nozzles in a sinusoidal wave pattern, providing good tension control and web stability.

Flotation web dryers offer the following advantages:

  • Great for webs coated on both sides
  • Essential for webs where any scratching is unacceptable, such as optically clear films
  • Uniform heating
  • Drying from both sides reduces the dryer length
  • Energy efficiency
  • Long life
  • Good for water- or solvent-based coatings

Through Air Web Dryers

Through air web dryers are ideal for heating and drying permeable products, including non wovens, carpets, and fabrics. These web dryers are also used for making products like sound deadening mats for automobiles by melting low-melt adhesive fibers blended with recycles fibers such as shoddy and cardboard.

Through air web dryers pull the heated air through the entire thickness of the product, resulting in extremely high rates of energy transfer. The design of the dryer may be horizontal with the web carried on an open mesh conveyor, or circular with the web going around a rotary drum with holes to pull the air through the web.

Through air web dryers offer the following advantages:

  • Great for drying coatings on porous webs
  • Essential for efficiently heating thick and permeable webs and melting the low melt binder fibers
  • Extremely high rate of heat transfer reduces the dryer length
  • Energy efficiency
  • Long life

Interstation Web Dryers for Inkjet, Flexo and Gravure Presses

As printed images get more complex, the number of stations in printing presses increases. So does the need to dry the ink after each station so next color can be added without any issues. Interstation dryers, also called BCDs (between color dryers), dry the inks just enough on the surface so that the next color can be applied.

Available space for web dryers between print stations is often quite tight, whether it’s a CI (Central Impression) Press or Station Press. And with press speeds increasing every day, it is a challenge for the dryer supplier to accomplish more drying in less space.

Radiant Energy Systems has developed several web dryers for this specific application. Our interstation dryers, such as Dortmann 8000, offer unique ways to dry inks or coatings at a rapid rate. Using low temperature but high velocity air, these web dryers prevent shrinkage and distortion in thin and temperature-sensitive films such as PE. In some cases, IR lamps are added to provide additional drying in the tight spaces.

Our web dryers for printing presses offer the following advantages:

  • Great for drying inks and coatings on paper, film or foil webs
  • Fit in tight spaces
  • Extremely high rate of drying reduces the dryer length
  • Energy efficient, do not need large amounts of compressed air
  • Low temperatures do not distort films
  • Short residence time prevents registration issues

Infrared Web Dryers (Electric and Gas)

As a complete process heating systems supplier, Radiant Energy’s engineers are equally experienced with both infrared heating systems and hot air systems for the web converting industry. Radiant Energy Systems has been at the forefront in combining the two technologies to design web dryers that are short, efficient and more economical.

Infrared dryers offer one major advantage over the hot air ovens – a significantly higher rate of heat transfer. For the right application, using infrared can reduce the dryer length to one third of the length of a hot air oven. But of course, not all applications would qualify for that kind of reduction.

Our infrared systems are designed with electric infrared heaters, which may be short, medium or long wavelength, or gas-fired medium wavelength heaters. Gas IR heaters are twice as intense as electric. The choice of heater technology and energy source for web dryers depends on:

  • The application
  • Energy source available in the plant
  • Cost of electricity vs gas

Infrared web dryers offer the following advantages:

  • Great for drying inks and coatings on paper, film or foil webs
  • Fit in tight spaces
  • Extremely high rate of heat transfer reduces the dryer length
  • Can be zoned across the machine direction for better uniformity
  • Available in wide widths with cut off capability for running narrow webs
  • Multiple zones provide versatility at a reasonable cost

Infrared Air Web Dryers

Radiant Energy Systems pioneered the concept of using infrared and air simultaneously. This innovative design expanded the use of IR web dryers to applications previously not considered possible. Combining infrared with air makes drying gentler and prevents issues such as blistering or skinning. While infrared provides the energy to heat the coating, the air provides scrubbing action to break away the boundary layer. With this technology, many coatings can be dried and cured without the need for long hot air ovens.

Infrared air web dryers can be used as pre-dryers, installed in front of an existing hot air dryer to increase the line speed, or as a complete drying system.

Infrared air web dryers offer the following advantages:

  • Great for drying adhesives, inks and coatings on paper, film or foil webs
  • Combining air and infrared makes drying efficient and gentle
  • Can be zoned across the machine direction for better uniformity
  • Available in wide widths with cut-off capability for running narrow webs
  • Multiple zones provide versatility at a reasonable cost
  • Can be used as a pre-dryer or for complete drying

Infrared Pre-Dryers to Increase Speed on Existing Coating Lines

Infrared pre-dryers are one of the best value-added systems in the industry. Many coating lines are limited in their run speed due to insufficient capacity of the web dryer. This deficiency often results when a dryer originally sized for solvent-based coatings is being used for water-based coatings, which require more drying.

To fix this problem with existing web dryers, you could add another convection zone, but that would require a longer space and cost a great deal of money.

This is where an infrared pre-dryer shines. By adding a pre-dryer, typically 3 to 5 feet in length, you may be able to increase your line speed by up to 50%. These pre-dryers are installed after the coater and before the oven and provide a lot of sensible heat to the coating so that evaporation starts as soon as the coated web enters the dryer.

Pre-dryers, which may be infrared only or infrared air, offer the following advantages:

  • Great for increasing speeds on existing lines drying coatings, adhesives and inks
  • Combining air and infrared makes drying efficient and gentle
  • Economical way to get additional production from existing dryers
  • Will fit in limited spaces between the coaters and hot air dryers
  • Easy to install