Structure Analysis of Feedwater Pump in Supercritical Unit

Structural Analysis of Feedwater Pumps in Supercritical Units (1) Overall Structure Due to the large unit capacity of supercritical units and the improvement of unit parameters, the requirements for high-pressure feedwater pumps are further raised, and the requirements for safe and reliable feed pumps are high efficiency and controllability Well, when asked for a short service. At present, the world's supercritical units with high-pressure feed pumps are double-shell cylinder, multi-stage centrifugal pump, instead of or rarely using single-shell multistage centrifugal pump. Cylindrical water supply pump shell can be permanently welded to the water supply pipe, the pump (pump core) is pumping type, the type of water pump for high pressure and high pressure, suitable for thermal shock, for load changes in the unit . Pump cylinder is a horizontal center support, with a strong rigid single base or common base. High-pressure side of the pump seal generally used metal wound gasket seal. Large bolt disassembly generally use the provisions of the torque wrench or electric heating device, convenient and reliable. Impeller and pump shaft for the interference fit, with the key to transfer torque transmission, the shaft is a rigid shaft. There are two kinds of structures in the world: one is the original American Byron Jackson (referred to as 8.J company, now with Flowserve, IDP, Adrich, etc. Company restructuring for the Flcwserve Pump Division, referred to as FPD company) as the representative of the internal pump for the axial split volute in the open structure, including Japan's EBARA now (that is, the EBARA original production). MITSVBISHI (that is, Mitsubishi Pump) and so are the introduction of the United States 8.J's original pump manufacturing technology. The other is the internal pump radially divided multi-step segmented structure represented by German KSB pump valve company, including the British Vail Pump Company, the Swiss Sulzer Pump Company and the former Soviet Union (now Ukraine) Radial split multi-stage structure. Manufacturing Technology. The other is the internal pump radially divided multi-step segmented structure represented by German KSB pump valve company, including the British Vail Pump Company, the Swiss Sulzer Pump Company and the former Soviet Union (now Ukraine) Radial split multi-stage structure. Manufacturing Technology. The other is the internal pump radially divided multi-step segmented structure represented by German KSB pump valve company, including the British Vail Pump Company, the Swiss Sulzer Pump Company and the former Soviet Union (now Ukraine) Radial split multi-stage structure. The high-pressure feed pumps used in the United States are all internal pumps, which are axially split open multi-stage centrifugal pump structures. Shenyang Pump Co., Ltd. and the United States FPD co-production of HDB-type pumps for Huaneng Qinbei Power Plant. (2) The internal pump is a scroll-type axial split high-pressure feed water pump structure represented by the United States FPD tubular double-shell pump axial split volute structure of the high-pressure boiler feed pump, multi-year operation proved: the pump special Suitable for high pressure or extra high pressure boiler feed water, and can be safe and reliable operation under variable load, allowing frequent start and cold start, able to withstand thermal shock, and ask the gap wear is small. Mainly by the outer cylinder, pump cover, the volute, rotor, bearing the five components. The internal pump (pump core) is a volute-type axially split feed pump compared with a radial split-section feed pump, the main advantages are: 1) the volute pump has a high flow rate over a wide range Efficiency, and the flat performance curve, which is a significant advantage for high-pressured high-pressured feed pumps requiring relatively small changes in outlet pressure for high power and frequent flow regulation. 2) The volute-type water pump allows larger water clearance angle without affecting the hydraulic performance of the pump. It can be said from the perspective of hydraulics that the instability of the pump at non-designed flow rate is reduced, and the pressure ripple Also low. 3) The laryngeal tongue in the volute can reduce the erosion of high-speed liquid and reduce the impact of abrasion damage. 4) The test shows that the volute-type pump is not particularly sensitive to the axial displacement of the impeller in the scroll chamber, which is also an advantage compared with the multistage pump with multi-stage diffuser vanes. 5) Constructed of two identical, semi-volute castings, which require only light load bolts to be tightened, are easy to dismantle and assemble, requiring a shorter assembly and maintenance time than a segmented multistage pump. 6) The double volute symmetry design offers the possibility of applying deflection deflection of rotating parts (rotors) to the lower volute because the pump shaft is operating in a land-locked condition. This will ensure that all the rotation gap to maintain the necessary concentricity and improve the reliability of high-speed pump operation. 7) After all the rotating parts are assembled in high-speed dynamic balance, the rotor part can be removed directly without disassembling the lower part of the volute, then the volute can be assembled to ensure accuracy and save time and reliability. 8) In case of emergency, the rotor part can be quickly lifted out of the volute and fitted with a spare rotor. The radial and axial clearances are easy to measure, easy to maintain and short in time. 9) Volute-type internal pump The impeller on the rotor is placed back-to-back relative to each other. As a result, the water thrust (ie axial force) generated by the pump during operation is self-balancing and the first-stage impeller adopts double-suction impeller. There is no need to use a small gap, high pressure drop prone to accidental balance device (such as balancing disc or balance drum). Considering the existence of residual axial force and the axial positioning of the rotor, a thrust bearing with a relatively low load capacity is provided, which results in a higher safety factor for the feed pump (10). Because the axial thrust balances with the impeller set , The maximum pressure of the pump is concentrated in the center of the rotor and the discharge side wall through the rotation gap, which is about 50% of the total pressure head. The rotation of the gap is uniform, the pressure drop per unit length equal, so the normal wear and tear, there will be no small pressure drop in the small area, that is, all gaps wear equal opportunity, so to ensure the smooth operation of the pump. 11) Since the volute-type internal pump is composed of two semi-volutes completely symmetrical from top to bottom, the volute-shaped tongue into 180. Precise positioning, the pump radial force generated in the self-balancing, enhanced rotor stability. 12) The use of back-to-back impeller of the volute pump can be run at speeds 6000 ~ l0000r / min reliable operation, and thus meet the supercritical and ultra-supercritical thermal power units on the ultra-high pressure water pump (the general outlet pressure at 29 ~ 40MPa) needs.