At least one glass tube has an azimuthal wall thickness deviation WTD of not more than 6.0%, the azimuthal wall thickness deviation being determined based on a lowest wall thickness value and a highest wall thickness value measured within a cross-section of the at least one glass tube, the azimuthal wall thickness deviation WTD being calculated according to the following formula:

[00001]$WTD=100-\left(\frac{\mathrm{lowest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}{\mathrm{highest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}*100\right)\%.$

The present invention relates to a method for cooling a space around a sleeve shaft, a device for guiding a fluid along an outer surface area of a sleeve shaft, a sleeve shaft including such a device, and a refractory tube with such a sleeve shaft inserted. The present invention also relates to a system including such a device, which system may also include such a sleeve shaft and such a refractory tube.

The present invention relates to a method for cooling a space around a sleeve shaft, a device for guiding a fluid along an outer surface area of a sleeve shaft, a sleeve shaft including such a device, and a refractory tube with such a sleeve shaft inserted. The present invention also relates to a system including such a device, which system may also include such a sleeve shaft and such a refractory tube.

An inlay for a sleeve shaft for collecting particles originating from a material of the sleeve shaft at least in part, at least one fluid being flowable through the sleeve shaft along an axial direction which is parallel to a main extension of the sleeve shaft, the inlay includes at least one first wall section and the inlay is inserted or insertable at least in part into the sleeve shaft such that at least one part of the first wall section has a radial distance from at least one first area of an inner surface of the sleeve shaft, and, hence, that the inlay together with the first area of the inner surface of the sleeve shaft encloses at least one volume domain, which volume domain is limited in the axial direction by a limiting element.

An inlay for a sleeve shaft for collecting particles originating from a material of the sleeve shaft at least in part, at least one fluid being flowable through the sleeve shaft along an axial direction which is parallel to a main extension of the sleeve shaft, the inlay includes at least one first wall section and the inlay is inserted or insertable at least in part into the sleeve shaft such that at least one part of the first wall section has a radial distance from at least one first area of an inner surface of the sleeve shaft, and, hence, that the inlay together with the first area of the inner surface of the sleeve shaft encloses at least one volume domain, which volume domain is limited in the axial direction by a limiting element.

A system for use in a glass drawing process includes: a tensioning element; a refractory tube having a tubular element and a surface element, the refractory tube being configured so molten glass runs onto a contact surface area of the refractory tube during a glass drawing process, the contact surface area of the refractory tube being allocated at least in part on the surface element, the surface element covering at least one surface of an end section of the tubular element, and the surface element projects at least in part over the end section of the tubular element, at least one portion of the part of the surface element projecting over the end section of the tubular element being connected at least in part to the tensioning element; and a carrier that carries the refractory tube and is connected with the refractory tube in a non-rotating manner.

A system for use in a glass drawing process includes: a tensioning element; a refractory tube having a tubular element and a surface element, the refractory tube being configured so molten glass runs onto a contact surface area of the refractory tube during a glass drawing process, the contact surface area of the refractory tube being allocated at least in part on the surface element, the surface element covering at least one surface of an end section of the tubular element, and the surface element projects at least in part over the end section of the tubular element, at least one portion of the part of the surface element projecting over the end section of the tubular element being connected at least in part to the tensioning element; and a carrier that carries the refractory tube and is connected with the refractory tube in a non-rotating manner.

An apparatus for forming glass tubes is provided. The apparatus includes a Danner-pipe, a heating device, and a heating chamber having the Danner-pipe and the heating device arranged therein. The Danner-pipe is inclined with respect to a horizontal plane by a Danner-angle. The heating device is inclined with respect to the horizontal plane by a heating-angle. The Danner-angle and/or the heating angle are in a range of 1° to 45°.

An apparatus for forming glass tubes is provided. The apparatus includes a Danner-pipe, a heating device, and a heating chamber having the Danner-pipe and the heating device arranged therein. The Danner-pipe is inclined with respect to a horizontal plane by a Danner-angle. The heating device is inclined with respect to the horizontal plane by a heating-angle. The Danner-angle and/or the heating angle are in a range of 1° to 45°.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300° C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.