Abstract: A tank comprises a structural envelope made in a form of hemisphere with a tube connection having a ring groove in its surface. A tightening ring of the structural envelope. An elastic diaphragm made in a form of hemisphere integrated with a cylinder provided with an end projection that fits into the ring groove. A bottom is made in a form of a sphere part. A thin-walled ring with a shoulder is introduced that is mounted between the tightening ring and elastic diaphragm in the place of its end projection location. The tube flange is provided with an end projection. The tightening ring is equipped with a lateral flange providing a possibility for the thin-walled ring shoulder tightening by it to the ring projection of the tube flange. The external surface of the tightening ring and internal surface of the tube flange are made tapered in the direction from the ring groove to the hemisphere of the structural envelope above the ring groove.