1. Field of the Invention
The present invention relates to a heater for piping in semiconductor manufacturing apparatuses and other manufacturing apparatuses, or chemical reaction processing apparatuses, etc.
2. Description of the Related Art
In semiconductor manufacturing apparatuses, chemical processing apparatuses, food product manufacturing apparatuses and other manufacturing apparatuses, heaters for piping are conventionally used to prevent solidification or deposition of a gas or liquid on inner walls of piping used for transferring the gas or liquid before processing and the gas or liquid after processing.
As heaters for piping, a contact heating-type heater for piping is known, where heating elements directly contact and heat the piping which is an object to be heated. Specific examples thereof include a jacket heater, which is fanned by embedding heating elements in a thermal insulator and a glass fabric, or the like, and is wound around the piping, a silicon rubber heater proposed in Japanese Unexamined Patent Publication No. 10 (1998)-134947 (Patent Document 1), which is formed by embedding heating elements in a silicon resin, or the like, and is wound around the piping.
Further, a non-contact heating-type heater for piping is known, where heating elements do not directly contact the piping, and a desired space is provided between the piping and the heating elements so that the piping is heated by radiation heat from the heating elements and thermal conduction by the air within the space. As a specific example, a heater for piping proposed in Japanese Unexamined Patent Publication No. 9 (1997)-017555 (Patent Document 2) includes metal plates having planar heaters attached on the outer surfaces thereof, where the metal plates form a space which is larger than the piping to enclose the piping.
With the jacket heater or the heater for piping disclosed in Patent Document 1, however, the heated piping may have temperature variation due to the positioning of the heating elements, as well as the winding position, uneven winding and uneven adhesion of the heater on the piping. Therefore, uniformity of heating of the piping is influenced by the level of skill of a worker who mounts the heater on the piping.
In addition, the jacket heater may influence cleanness of the environment in which the jacket heater is used due to dust generated from the glass fabric, etc., and the heater for piping disclosed in Patent Document 1 may cause corrosion of metal portions of the piping due to siloxane which generates from the use of the silicon resin, etc. Therefore, it is said to be necessary to consider the environment in which theses types of heaters are used.
With the heater for piping disclosed in Patent Document 2, the planar heaters do not directly contact the piping, and the piping is heated by thermal conduction by the air within the space formed between the metal plates, which are heated by the planar heaters, and the piping. Therefore, the temperature variation of the piping due to positioning of the planar heaters is reduced. However, the structure of this heater keeps a large space between the metal plates and the piping, and this results in large sizes of the parts, which may influence work efficiency during transport and mounting.
Further, during maintenance of the piping, it may be difficult to reproduce the heating performance of the heater for piping when the heater is mounted again.