Plug header is the most commonly used up to 350 bar working pressure. The plug holes opposite each tube allows expansion of the tube in the tube sheet, mechanical cleaning and plugging in case of leakage. Seal welding or strength welding can be provided for high partial hydrogen pressure resulting in a less expensive solution than pipe header. Generally used for over 200 bar pressure.

Cover plate is used for fluids with high fouling factors and upto 40 bar maximum when frequent mechanical cleaning is needed. It is also used for very corrosive process fluids so as to periodically check corrosion allowance. Special cover plate headers using welded gaskets are provided for hydrogen service in hydro-cracking plants.

Welded bonnet type is used in some special services such as Ammonia condensers, Freon condensers and Vacuum Steam condensers. One advantage of this design is the fully welded construction which provides perfect sealing required for such applications.
 

A large circular manifold is used in some cases where the allowable pressure drop is very low. This large manifold ensures an equal distribution of fluid flow in the tubes. The tube sheets are directly welded to the manifold. This type is used for vacuum steam condensers and refrigeration units
 

Pipe headers are used for working pressure over 200 bar. The U bend tubes are welded to weldolets on the pipe. The welds are heat treated and X-ray tested.