Tham khảo tài liệu 'process engineering equipment handbook episode 3 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | P-262 Pumps FIG. P-281 Untimed-screw pump. Source Demag Delaval. FIG. P-282 Cutaway view of two-stage pump. Source Demag Delaval. The Transamerica Delaval CIG pump see Fig. P-282 is of the internal-gear type see Fig. P-278 . In this type of pump fluid is carried from the inlet to the discharge by a pair of gears consisting of one internal and one external gear. The gears are placed eccentrically to each other and are separated by a crescent-shaped divider that provides a sealing path for the internal and external flow paths. The internal-gear design is generally known for its quiet operation. Modification of the gear profile also provides for reduction of the trapped oil eliminating any pressure pulsations and thus reducing the noise level. The design is extremely simple and allows gear sets to be stacked into a multistage arrangement for increased pressure rating. With this arrangement the pressure loads are distributed to reduce stress on the pump components thus lengthening pump life. The design also has the inherent feature of providing for a hydrodynamic film buildup on the bearings and external gear ring that eliminates metal contact between the working parts also adding to pump life. The design also provides for double pump configurations consisting of two independent pumps arranged on a common shaft each pump having a separate discharge and sharing a common suction. The Transamerica Delaval GTS pump is of the externally timed-screw type see Fig. P-283 . The construction of this type of pump is conducive to operation on nonviscous liquids such as water that exclude the use of the IMO design. This design relies on timing gears for phasing the mesh of the threads and support bearings at each end of the rotors to absorb the reaction forces. With this Pumps P-263 FIG. P-283 Cutaway view of externally timed-screw pump. Source Demag Delaval. FIG. P-284 Cutaway view of double-end IMO pump. Source Demag Delaval. arrangement the threads do not come into contact with
