Brief analysis of roller heating methods

Most of the rollers on the machine do not need to be heated, but a few rollers do, which we call heating rollers.

Heated rollers are widely used in preheating, drying, shaping, laminating, embossing, embossing, compounding and other production processes in papermaking, printing, printing, copying, textile, rubber, plastic, chemical fiber and other industries. They are mainly used for product Heating and thermal processing. The roller is heated in some way, and the product running on the roller is heated by the rotation of the roller.

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According to different heating methods, heating rollers can be divided into two categories: fluid heating and electric heating. Among them, fluid heating mainly includes three media: thermal oil, water, and steam; electric heating is mainly divided into two types: direct heating by electric heating tubes and electromagnetic induction heating.

1. Thermal oil heating roller

This is the most commonly used type of heating roller. Most of the heating rollers currently in use are heated with thermal oil. The advantage is that the structure is relatively simple and the cost is low. The disadvantage is that it is easy to scale after long-term use, resulting in uneven temperature; limited by the properties of the heat transfer oil itself, the temperature cannot be too high (generally not higher than 250°C); an external oil pump is required for circulation and the roller is connected through a rotary joint. Not only is extra energy wasted, but there is also a hidden danger of oil leakage.

2. Water heating roller

The roller structure of the water heating roller is similar to the thermal oil heating roller, and the cost is also low. Limited by the water temperature (not exceeding 100°C in an open system), the roller surface temperature is difficult to exceed 80°C. If ordinary tap water is used, there will also be scale problems on the inner wall of the roller; there will be additional energy waste in the external water pump circulation.

3.Steam heating roller

The steam heating roller is connected to an external steam pipe through a rotary joint to pass steam into the roller for heating. The roller has a simple structure and low cost. Similarly, due to the rapid rise of steam pressure with temperature, the roller temperature is not too high (generally no more than 180°C). With the national restrictions on the use of boilers, the number of steam heating rollers is declining rapidly.

4. Electric heating roller

Electric heating mostly uses electric heating rods as the heat source, so in theory the roller can be heated to a very high temperature. The electric heating rod in the existing electric heating roller is not in complete contact with the roller, so there are two ways of heat transfer: conduction and radiation. If the problem of reasonable heat transfer is not dealt with, the uniformity of the roller temperature is often poor. For this reason, many manufacturers have oil holes in the roller wall and pour thermal oil into them. In this way, the roller temperature can be made more uniform through the heat equalizing effect of the thermal oil. However, if the heat consumption is particularly large, the uneven phenomenon will still be serious. In addition, there will be other problems when pouring thermal oil, which will be discussed in detail later.

5.Electromagnetic induction heating roller

This is the most technologically advanced type of heating roller and was invented by Japan Teden Co., Ltd. in 1964. After more than 50 years of development, the company still monopolizes the high-end heated roller market. China's electromagnetic induction heating roller with independent intellectual property rights was successfully developed by Shanghai Lianjing Company in 2009. It not only broke Japan's monopoly, but also reached the world's leading level. The electromagnetic induction heating roller can not only achieve a very high roller temperature (above 400°C), but is also clean and energy-saving. After embedding good temperature equalization technology, good temperature uniformity can also be achieved. Therefore, electromagnetic induction heating roller is an ideal heating and processing tool for many high-end materials. At the same time, due to its complex structure, its cost is bound to be high. This is also the biggest obstacle limiting the large-scale application of electromagnetic induction heating rollers.