A tube shield has a cylindrical shape and adapted to be attached with refractory cement (R) around an outer peripheral surface of a boiler tube (T). The tube shield has at least two tube shield parts for surrounding the boiler tube (T). The shield parts has complimentary parting surfaces for defining a gap between abutting complimentary parting surfaces of adjacent shield parts when the shield parts are attached with refractory cement (R) around the boiler tube (T). Each shield part encloses 140-220° of the total circumference of the boiler tube (T). Each complimentary parting surface is configured in a dovetail form such that one shield part is locking into the other shield part with dovetail protrusions (DP) located in dovetail slots (DS) in the other shield part.