Tube arrangement and furnace

A tube arrangement comprising a first metal tube, a second metal tube, a first sleeve part, and a second sleeve part,

• wherein a first end region of the first metal tube comprises a first outer threading and a second end region of the second metal tube comprises a second outer threading,
• wherein the first sleeve part is made of metal and comprises a first inner threading and the second sleeve part is made of metal and comprises a second inner threading,
• wherein the first end region is configured to be joined with the second end region via a first butt weld joint,
• wherein a first proximal sleeve end of the first sleeve part is configured to be joined with a second proximal sleeve end of the second sleeve part via a second butt weld joint, and
• wherein the first sleeve part comprises a first outer surface extending at a first acute angle to an axial centre axis of the first sleeve part and forming a first conical sleeve portion with its wide end at the first proximal sleeve end, and the second sleeve part comprises a second outer surface extending at a second acute angle to an axial centre axis of the second sleeve part and forming a second conical sleeve portion with its wide end at the second proximal sleeve end.