Abstract: A shutter for large pressure vessels comprises a lid assembly (Y) constituted of a seal plate (1) formed of a flexible material of a size fit for the opening of a pressure vessel and a multitude of beam members (2) attached to the outer surface of the plate (1) and extending widthwise. The beam members are connected to the seal plate in such a manner as to be parallel to each other along a reference line for connection, extending in the widthwise direction of the seal plate, and advance or retreat while flexing along a guide member (7) having at least one bending portion (71). The guide member extends between a closing position (A) disposed in front of the opening portion and a storage position (B) disposed on an outer housing of the pressure vessel, so that the assembly can be housed in a relatively small space. This shutter is most suitable for use on a medical autoclave and a retort for food processing.

Abstract: A multi-pipe once-through boiler having at least one row of a plurality of circumferentially arranged pipes on which a plurality of fins are arranged in such a manner that the fins are in contact with the flow of the combustion gas in a substantially parallel maner. Elements are provided for increasing the heat transfer effect, such as slits in the fins, or an inclined arrangement of the fins, or pipes without fins at the region near to the inlet of the combustion gas passageway, are provided. Furthermore, a heat insulating member for decreasing operational noise as well as a cleaner device for blow-cleaning the combustion gas passageway are provided.