Tunnel ovens

Tunnel ovens can be used for stress relieving and annealing copper and its alloys at 500 to 900 F (260 to 480 C). Tunnel ovens are so common for paint drying that they are often assembled from standardized liber-lined, metal-encased sections that 

---

While there are small bakers who are using old ovens that consist merely of a heated box most modern ovens fall into one of three classes They are either deck ovens, rack ovens or travelling ovens. Travelling ovens are also known as tunnel ovens. 

Extrusion is the first really new technology to arrive in the food industry for many years. Tunnel ovens are a development of an oven while the sort of mixer used for the CBP process is a development of a mixer, albeit one that can apply a great deal of energy in a short time. 

The one stage of the baking process that can easily be worked continuously is baking. The bread is fed into a tunnel oven and emerges baked at the other end. 

In the next phase a spray drier converts the slip into a powder which is the raw material for pressing tiles at a pressure of more than 175 kg/cm2. The moisture content is then reduced to 0-0.5 % (m/m) in a tunnel oven with a temperature of appr. 130 °C. 

In case of single firing the sherd and glaze are fired in a simultaneous process. This is applied for floor tiles and traditionally takes place in a tunnel oven or in a quick firing process at a temperature of about 1170 °C. In case of a quick firing process the tiles are not transported through the oven in a compact way as in the tunnel oven,... 

Grid pasting. Paste of the required density and consistency is spread on to the grids by means of a specially designed machine. When expanded grids are used, the paste is applied to the expanded strip and then both sides of the pasted strip are eovered with paper, after whieh the individual plates are separated. The pasted plates are partially dried in a tunnel oven and are then stacked on pallets. 

Grid pasting. Grids are pasted in a specially designed machine. The pasted plates are then dried in a tunnel oven dryer and arranged on pallets. 

Despite its reversibility, thermopassivation reduces significantly die energy output of the battery during the first cycle. Therefore, thermopassivation is carefully avoided by drying the plates in oxygen-containing atmosphere under conditions that do not allow the plate temperature to rise above 80 °C. Usually, low-temperature drying equipment, or tunnel ovens, is used with an adequate temperature and plate flow-rate control. 

Continuous dryers, ovens, incinerators, and furnaces take any of a variety of forms such as rotary drum, tower, shaft, tunnel oven, multihearth (Herreshoff) kiln, and fluidized bed. As with all continuous furnaces, their design is very dependent on how the load(s) can be moved through the furnace (or occasionally, how the furnace can be moved over the loads). 

There are two primary pultrusion processes. In one method, the pultrusion passes through a long heated die or oven for cure. This is called the tunnel oven process. In the second method the composite is cured with radio frequency energy. This causes cure in a much shorter period of time. 

Oven types used for tack drying inclnde batch ovens, tunnel ovens, and infrared (IR) ovens. Batch ovens can be as small as a bench-top unit where panels may be inserted individually or as large as a walk-in oven that may be loaded with many panels in racks or carts. The wet panels are loaded through a door or doors that are gasketed or sealed to the operating area so that the vapors emitted are not exhansted into the work environment. 

In conveyorized tunnel ovens, panels are generally placed in slots in the cxmveyor or in racks that ride on the conveyor. The main controls are temperatnre and cxmveyor speed. Exhaust from the oven serves the same pnrpose as pnrge air and shonld be regnlated per the oven manufacturer s specification. Curing is typically nniform and is independent of panel... 

Consideration of tunnel dimensions is critical for the reflow application. Short tunnel ovens may not permit a profile adequate for attaining prescribed reflow temperature-versus-time profiles for larger, thermally massive PCB assemblies. Tunnel height dimensions must also be adequate to accommodate the tallest components or component heat sinks. Tunnel width will limit the size of the board that can be introduced to it. 

Heating in batch or tunnel ovens can be used for any of these bricks. After cooling, some bricks have completed their manufacmring cycle see the last part of this section for final procedures. Bricks for burning are appropriately stacked on kiln cars and sent to the kilns. 

---