Apparatus and method for protecting the tube-sheet of a syngas loop boiler

A syngas loop boiler comprising:

• a tube bundle;
• and
• a casing that surrounds the tube bundle,
• wherein said tube bundle comprises a plurality of tubes,
• wherein one end of each of the plurality of tubes is joined to a tube-sheet provided with a plurality of tube-sheet inlet holes for inletting syngas in the boiler, and
• wherein a first tube-sheet inlet hole of the plurality of tube-sheet inlet holes is provided with:
• a protective sleeve welded at both ends to said first tube-sheet inlet hole,
• a first weld overlay placed at an inlet mouth of said first tube-sheet inlet hole, the first weld overlay encircling a first end of the protective sleeve so that the first end of the protective sleeve is welded to said first weld overlay, and
• a bore groove that contains a second weld overlay, the second weld overlay having a first end and a second end spaced from the first end in an axial direction of the protective sleeve, the second overlay encircling and directly contacting a second end of the protective sleeve so that the second end of the protective sleeve is between the first end and second end of the second weld overlay,
• wherein the second weld overlay is spaced from the first weld overlay in the axial direction of the protective sleeve.