A welded tubesheet to shell joint, as shown below, is typically used for any material that can be welded together. The biggest advantage of a welded joint is that it eliminates potential air leaks on the shellside. Since the joint is welded together and tested by the manufacturer, there should be no air leaks at this joint. Some of the most common materials for this type of joint are carbon steel shell with stainless steel tubesheets. Another common option for material is a clad tubesheet. A clad tubesheet is typically explosion bonded and can vary in materials and sizes. Depending on material costs it may be more economical to use clad tubesheets for larger diameters. Another advantage for clad is you can have a dissimilar higher alloy metal such as a brass alloy on the tube side with carbon steel on the shell side and still have a welded joint.
The disadvantage of having a welded joint is that it’s harder to replace the tubesheet if needed, since it’s welded. This is less of a concern when this joint is used in a clean shell side service, which is typically the case for turbine exhaust steam surface condensers. Also, the tubesheet is not likely required to be replaced very often, if ever.