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Improve the Operation Stability of 150NW-78 × 2 Low Drainage Pump
Improve the operating stability of 150NW-78 × 2 type low-water-repellent pump (in Chinese) Holding Co., Ltd. Ma Tau Power Plant, Handan 056044, Hebei, China) Abstract: Through the frequency conversion modification of 150NW-78 × 2 low-water-repellent pump, the axial seal water system, Low cavitation pump cavitation, poor sealing effects of packing caused by excess dissolved oxygen, bearing vibration exceeded, impeller wear and bearing burned defects, improve the health level of the pump. Key words: low plus drainage pump; rotor; shaft End of the seal; Frequency conversion adjustment Abstract: such as pump crossion at low-load operation, extra O2 rate caused by bad packing seal, bearing vibration, impeller wear, bearing burned have been solved by means of multi-frequency regulation improvement and sealing water improvement and rotor stability improvement of 150NW-78 × 2 type LP heater drain pump. Health level has been improved. Keywords: LP heater drain pump, rotor, shaft seal, multi-frequency regulation1 Equipment Overview A power plant # 5, # 6 units for the former Soviet Union to produce 200MW units, # 8 units for the East Steam Turbine Factory production 200MW units, each unit configuration 2 sets of low dredge pumps, a spare, One for operation, and the other for three sets of 4 low-plus units numbered # 4, # 3, # 2, # 1 low, # 4 low added to # 2 low added, # 1 low added to the condenser Hydrophobic use of gravity self-flow way, # 2 low after the hydrophobic by low plus drainage pump hit the condensation jellyfish pipe. Low plus drainage pump horizontal horizontal open centrifugal pump, model 150NW-78 × 2, flow 82.8m3 / h , The head of 145 meters, the minimum Nose remaining 3 meters, speed 2970r / min, shaft power 55Kw. The pump stator sub-components from the pump and pump cover, the pump body and the pump cover is divided into two spiral pressure chamber, phase error 180 ° arranged to balance the radial force; rotor components from the inducer, impeller, shaft and sleeve and other components, the axial force of the impeller symmetrically arranged to achieve balance; rotor at both ends supported by 2 2310 bearings, the free end of the set 2 Disc 7310 bearings to withstand the residual axial thrust. All bearings using thin oil lubrication, while the cooling chamber in the bearing body through the cooling water to assist in cooling .2004 has been low Plus the replacement of the shaft end of the drainage pump for BP424 10 × 10 graphite carbon fiber packing (working temperature ≤ 650 ℃, working pressure ≤ 2.1Mpa, linear speed ≤ 20m / s), extending the packing life .2 main problems And Cause Analysis 2.1 Severe cavitation of flow passage components Since the unit was put into operation in 1976, the 150NW-78 × 2 low-added water-dredging pump basically meets the operation requirements of the unit. However, as the unit depth is peak-shaved and the frequency of variable operation is increased (At present, the unit operates in the load range of 120MW to 200MW, and will operate at low or no water level when the load is less than 170MW.) The frequency and degree of fluctuation of increasing or decreasing the water level of # 2 are correspondingly increased, Low water level or no water level status. Because # 2 is a constant speed pump, it can not meet the minimum NPSH requirement for low added water pump when # 2 is added to low or no water level. In addition, In addition to the main components of the low-added water pump, the primary impeller and the secondary impeller are made of ZG1Cr18Ni9 with good anti-cavitation ability. The pump body, pump cover, inducer wheel hub, bearing body and seal ring are all HT20- 40), inducer (Zhsi80-3) and sleeve (# 45) material grade are lower.As the pump often Cavitation at low water level or no water level, coupled with low cavitation resistance of the main components of the pump group, low pump plus pump in operation 2 to 3 years (5 years as an overhaul cycle), the pump cover, pump Shell inlet and outlet side of the flow channel leaves, induction wheel vane and bushing shell and other large areas appear penetrating cavitation pit, honeycomb distribution.2.2 shaft seal water system set unreasonable BP424-type packing The heat generated by the friction with the pump shaft during operation needs to be cooled by the cooling water outside the packing room. The low-added water-repellent pump packing adopts the self-cooling with the low water-repellent outlet of the pump set itself. The cooling method has the following disadvantages: 1 150NW-78 × 2 Low Drainage Pump Cooling water system design requirements: In order to make the shaft end packing work properly, will not be burned, you must cooling the filling chamber cooling water, lubrication, cooling water is designed to re-water, Flow rate 1 ~ 2m / h, temperature 2.2.2 Low added water pump shaft cooling water system design requirements Cooling water on the shaft end packing has a sealing function, when the unit load is lower than 170MW when the low water level is low, low water pump Cavitation will occur and cut off, this time the outlet pressure fluctuations between 0 ~ 1.56Mpa , The export of water on the shaft seal packing effect is very poor, or even ineffective, the air will enter the pump through the shaft end packing, and finally into the deaerator, affecting dissolved oxygen supply.According to statistics below 170MW load water dissolved oxygen Up to 40μg / L, exceeding the eligibility of less than 7μg / L. 2.3 poor rotor stability caused by excessive vibration bearings, impeller wear 2.3.1 rotor sleeve lock positioning poor reliability of the pump set on both sides of the pump shaft A single sleeve lock the mother positioning, lock the mother of M39 × 1.5, the outer diameter of ¢ 49mm, length of 28mm, the thickness of the lock sleeve on one side of the lock, easy to cause loose nut after long-term operation, the thread tip in the axial force Under the blunt, shaft lock lock sleeve, impeller failure, causing the rotor axial movement, the impeller wear .In view of the lock sleeve lock loosening caused by repeated wear and tear of the impeller, the rotor assembly in the sleeve lock Thread glue to prevent the lock sleeve locking loose caused the defect, but the effect is not obvious, after running a period of time the high temperature thread adhesive gradually loosening.2.3.2 Locking the sleeve lock mother, the rotor component positioning failure, the impeller, inducer wheel axial Occurrence of movement, the axial low pressure side seal clearance decreases, the impeller, The guide wheel and the seal ring, the shaft sleeve and the pump shell touch each other, and the seal friction rubs against the axial bond, the glue and the bond, the glue enters the radial seal gap, causing wear, the gap becomes larger, the hydrodynamic action of the seal ring is weakened, Increase, macroscopically the pump outlet pressure instability, bearing vibration value exceeding 0.06 ~ 0.07mm.2.3.3 impeller, induced wheel single static balance, small rotor static imbalance after stack phenomenon, resulting in Bearing vibration excessive movement of the pump.3 Measures to improve low-water pump to change the frequency adjustment operation # 2 Low-water-adding low-density water pump to adjust, due to the low water pump for the frequency pump, low water level # 2 in the unit low load To avoid the pump cavitation operation, the inverter can be retrofitted under the condition that the original equipment (pump and motor) is not changed, and the output of the low-added drain pump group is changed according to the low added water level The modification method is as follows: 3.1.1 Adjust the system with a single loop so that the # 2 low water level adjusting system can be automatically added to the water level transmitter for adjusting the feedback (drill a ¢ 10mm hole, then ¢ 16 × 3mm signal tube as a liquid level signal EJA110A-DMS4A-92NA-type water level transmitter), as the original water level measurement for the electrical contact mode, the need to increase the measurement of balance containers (housing 3/5 at a ¢ 10mm hole, then a ¢ 100 × 5mm, high 200mm Of the balance container and ¢ 16 × 3mm signal pipe connected to the steam level signal to the water level transmitter.) 3.1.2 2 sets of low water pump in a variable frequency adjustment transformation can be switched knife switch select "workers Frequency "and" Frequency "mode, select" Power Frequency "state, the low plus drain pump start and stop operation will start and stop the pump through the contactor in the electrical switchgear, at this time low plus drain pump to power frequency operation; select" Frequency "state, the operation of low dredging pump start-stop will control the start-stop of the pump through the start-stop of the inverter in the frequency converter cabinet.Electrical sends a pair of nodes to the DCS from the low- Down the frequency conversion operation of the drain pump .3.1.3 retrofit settings low plus drainage pump power frequency operation, pump and DCS interface signals (including the pump status signal, start-stop signal, current signal, etc.) is still using the original water pump signal unchanged ; Frequency conversion operation, the pump and DCS interface signals provided by the inverter .3.1.4 Low plus drainage pump no matter in Frequency or frequency can be achieved under the state of the SCS logic, A and B with a low dredging pump DJS01 (DJS02) single operation / linkage; alternate mode selection; run pump accident tripping, associated standby pump .3.2 shaft seal water system to improve the low sparse Pump shaft seal, cooling water, self-cooling by the pump outlet to improve the way from the condensate pump outlet header condensate cooling to meet the design requirements (condensate pump outlet parameters: pressure 1.2 ~ 1.6Mpa, temperature 40 ℃). 3.2.1 The low water pump outlet pipe cooling water pipe cut off, sealing and welding dead .3.2.2 from the condensate jelly tube access ¢ 16 × 3 pipe for the low water pump shaft cooling water. Low plus water pump Set the valve on the cooling water pipe for system disassembly (system diagram attached) .3.3 rotor stability improvement 3.3.1 improve the material grade rotor parts replacement, improve the low water pump parts and components