scope:

Type M pumps typify gland-less type of pumps. With gland-less pumps the enclosure of the driver (motors or turbines) are integral or bolted to the pump casing (Fig. 1B) or welded to a vessel that contains the pump impeller and diffuser (Fig. 1A). In both cases the driver enclosure is at the same pressure as the pump enclosure and is to be designed as a pressure boundary item. In Fig. 1A installations, the pumps do not have a separate and distinct pump casing with inlet/outlet nozzles, volute casing, or barrel. The pump impeller and diffuser may be located within the larger pressure vessel, which supports the driver enclosure. The pump shaft exits an opening in the pump casing or the pressure vessel and couples the impeller to the driver. In Fig. 1B installations there is a regular pump casing that is to be designed to the rules of this Article (NB-3400). In addition to the motor casing, a heat exchanger may be required to cool the motor. The heat exchanger is connected to the motor casing by piping. The motor casing, piping, and heat exchanger are exposed to the same pressure as the pump casing or the vessel that contains the impeller, and their design is subject to appropriate Articles of Subsection NB.