Abstract: A water heating apparatus having structure for recovering sensible and latent heat from flue gases generated in a heater thereof and transferring the heat to water to be heated. The apparatus has a closed circuit for liquid, such as water, in which are positioned two heat exchangers. One of the heat exchangers is positioned in the heater of the apparatus for transferring heat from a burner of the heater to liquid in the closed circuit. The other heat exchanger is positioned in a water pass-through system to heat the water therein. The apparatus has an air pass-through system for carrying flue gases from the heater out an exhaust pipe. The flue gases travel through a third heat exchanger positioned in the water pass-through system whereby sensible and latent heat from the flue gases are transferred to water in the water pass-through system, further heating the water therein.

Abstract: Forming a tubular workpiece by applying fluid pressure to the interior of the workpiece and enclosing the pressurized workpiece in a die that has a die cavity. A portion or the whole of the die cavity has its internal periphery smaller than the external periphery of the workpiece. This subjects the workpiece to compressive forming.