Abstract: An apparatus for fabricating multi-layer spiral tubes of the type that while the webs are being wrapped in a spiral form the adjacent edge portions of the webs are welded with each other to form spiral tubes, is improved in that the apparatus has a take-up drum for taking up the wrapped webs while rotating with the leading end of the web of the first layer fixedly secured thereto, a wrapping drum having the webs wrapped therearound and including a backing section for backing a welding location of the edge portions of the web of the first layer, a plurality of web feed devices provided adjacent one another for spirally feeding the webs on the wrapping drum of the spiral tubes of the preceding layers, a plurality of wrapping devices provided in combination with the respective web feed devices for spirally wrapping the web on the wrapped drum or the spiral tubes of the preceding layers, and a drawing device for drawing from the wrapping drum the spiral tubes that are being formed continuously.

Abstract: A heater tube for use in a fluid heating device, which is used, for example, as a thermal decomposing device of hydrocarbons. The heater tube has a dumbbell shape in cross section.