Some aspects on the joining of titanium tubes to various tubesheet materials

The experience has shown that the roller expanded joints are unreliable, that crevices must be expected, and that corrosion will occur if the material combination is unfavourable and/or the environment aggressive enough. If the tube material has to be titanium and some facts indicate that other materials may be insufficient in water from normal cooling water supplies, it is of utmost importance to have the joint crevices sealed. The most effective method is to choose titanium or titanium clad tubesheets and seal the crevices by welding. When the explosion welding method is fully developed the same can be performed with other tubesheet materials. If this is not possible, a coating of the tubesheets can be applied to cover the joints, one condition being the projection of the tubes. It is in this case absolutely necessary that the coating is applied before any fluid has had the possibility to penetrate into the joints