Abstract: An expansion tank with an improved diaphragm seal includes a seal for the joint between the flexible diaphragm and either an optional. non-flexible diaphragm or the tank wall, the providing of a seal support that prevents collapse, delamination, or tearing of the 5 tank shell wall. The tank shell may be formed of two substantially hemispherical domes joined together, either directly or at the two ends of a substantially cylindrical section. One of the segments forming the shell of the expansion tank, further comprises an extension lip, extending inwardly of the tank and around the entire circumference of the inner surface of the shell wall, located substantially near the junction of two of the sections 10 forming the tank. This extension lip may be made from the same material as the tank wall, or may be part of a separate circumferential connector interconnecting two of the sections of the tank wall.

Abstract: An improved expansion tank is provided for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell formed of two substantially hemispherical domes joined together, either directly or at the two ends of a central, substantially cylindrical section, and a flexible diaphragm located internally of the tank and secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section holding a gas under pressure and a fluid-tight section for holding an aqueous liquid under pressure. The improvement comprising diaphragm coupling ring formed as a discrete part of the diaphragm tank that can be fabricated independent of the domes and any cylinder. The diaphragm coupling ring provides a robust, leak-proof seal with the diaphragm, so that it can be connected onto an inner surface of an expansion tank in a separate, secondary operation.