Tubesheets can be solid titanium, explosively clad titanium on steel, loose lined titanium on steel, or a dissimilar metal. Solid tubesheets are used primarily in all-titanium units. Design follows conventional practice. Either explosively clad tubesheets or loose liners are used with steel or other dissimilar metal shells.
Loose liners offer economic use of material and are easy to maintain and fabricate.
When explosively clad or loose lined tubesheets are used, the tubes should be seal welded to prevent minor tubeside leakage from reaching the steel, causing undetectable corrosion. If titanium tubes are to be inserted into dissimilar metal tubesheets, as is often the case in retubing jobs, the possibility of galvanic corrosion must be considered. In actual practice, titanium tubes have been used with a variety of tubesheet materials as indicated in Table 9 for oil refinery service. Generally, titanium is more noble than most of the commonly used tubesheet materials. Galvanic corrosion might, therefore, be expected on the dissimilar metal but not on titanium.