Abstract: How to explain the special vibrations shown in the operation of Type 100 main pumps equipped at Dayawan and Ling'ao Nuclear Power Stations has long plagued management and professionals. After analyzing several theoretical explanations, this paper analyzes the generation and development of the main pump vibration problem through the analysis of the dynamics of the vertical rotor, and proposes the precautionary measures accordingly. 1 Type and Structure of Main Pump of Reactor The main pump of a reactor is the main rotating equipment of the primary circuit of a pressurized water reactor nuclear power plant and takes on such important functions as compensating for the pressure drop of the coolant in the primary circuit and promoting the circulation of coolant. Daya Bay and Ling Ao Nuclear Power Plant operated by Daya Bay Nuclear Power Operation Company are equipped with 12 main pumps (3 units per unit) manufactured by JEUMONT-INDUSTRIES, France. Each main pump is an air-cooled, three-phase induction motor driven single-stage shaft seal unit. The machine is a vertical component, as shown in Figure 1, from top to bottom by the motor, seal components and hydraulic components of the pump, cascading arrangement of the three-stage shaft seal by the pump shaft leakage. Sealing water supplied by the fluid control system is injected between the pump bearings and the seals to prevent the reactor coolant from flowing upward while cooling the shaft seals and pump bearings. The electric pump is assembled with three radial bearings and one thrust bearing, of which two radial bearings and one thrust bearing are used to support the motor rotor and the other radial bearing is to form a pump bearing, which is a water-lubricated bearing, Alloy surfacing stainless steel journals and graphite ring sleeve composition. 2 Special Vibrations of the Main Pump of the Reactor Since the commencement of commercial operation of the two power stations, the special vibrations of the Type 100 main pump have long plagued the professional and technical personnel. These special vibration problems mainly show the following characteristics. 2.1 The main pump vibration level was significantly affected by the shaft seal water flow April 8, 2003, Ling O 1 due to commissioning RCV charge pump discharge orifice plate, resulting in the main pump shaft seal on the 3rd by 2.0m3 / h reduced to 1.7m3 / h (system design requirements shaft seal flow control at 1.8m3 / h), the pump shaft vibration from 200μm down to 150μm, then increase the shaft seal flow to 2.0m3 / h, the vibration level and rise To 190 μm. It is worth noting that the response of different main pumps to shaft seal water flow changes is completely different. For example, the shaft sealing water adjustment test of D1RCP001 / 002 / 003PO on February 22, 2000: 2.2m3 / h160μm90μm200μm 2.5 m3 / h155μm140μm180μm 3.0m3 / h155μm190μm160μm It can be seen from the above table that after the shaft sealing water flow rate increases from 2.2m3 / h to 3.0m3 / h, the vibration level of No.1 pump basically keeps unchanged and the vibration of No.2 pump shaft increases significantly , While 3 pump is significantly reduced. 2.2 The main pump of the high vibration point is constantly changing, such as: March 8, 1999, 105 after the overhaul of a circuit temperature, step-up process, recorded D1RCP002PO vibration vector changes in the cold start frequency component 160μm / 8 °. The vibration vector changes to 154μm / 104 ° when the temperature is increased and the pressure is increased to the thermal shutdown level. That is to say, the vibration direction changes by 96 °. 2.3 need to be repeated on-site balancing to reduce the vibration level Whenever the main pump shaft vibration increases sharply, the main frequency components of the change are the power frequency (accounting for 80% to 90% of the pass frequency vibration), the general approach is to stop Heap conditions for on-site balancing to reduce vibration levels.
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