Mechanical limit of the hottest large hydraulic fu

Mechanical limit of large-scale hydraulic fully regulated axial flow pump

Abstract: during the oil pressure test of the hydraulic regulating system of the pump blade in Siyang second pumping station, the bottom cover was cracked by four large screws with ear handles. The above problems were successfully solved by installing a mechanical limit device at the piston, ensuring that the unit can operate economically and safely in the high-efficiency area

key words: mechanical limit adjustment, water pump blade adjustment

1 introduction

Siyang second pumping station is an important cascade station of the east line project of the South-to-North Water Transfer Project, with a total installed capacity of 5600kW, a design flow of 66 m3/s, and a water pump of 2.8zlqk-7.0 Its blade angle can be adjusted within the range of -6 ~ +8 degrees according to the superior order or the combination of upstream and downstream water levels, and the pumping capacity of a single machine is 26 m3/S ~ 39 m3/s

during the oil pressure test of the blade hydraulic regulating system of no.2# main water pump, this year is the third CTI conference held in China. When the blade angle turned to -6 degrees, it did not run immediately, but it did not stop rotating until -13 degrees, but at this time, the bottom cover of the impeller head (made of cast iron) had been cracked by four large screws with ear handles. Similarly, during the overhaul of No. 1 # main water pump, there was no mechanical limit device for the piston to go down, and the bottom cover was also cracked by four years of development root handle big screws

during the pumping operation of the unit, because the piston of the blade adjustment mechanism does not have a downward mechanical limit device, the operators often fail to grasp or dare not adjust the blade adjustment for fear of accidents. The new price will be applicable worldwide, causing the aluminum alloy window support qb/t 3887 ⑴ 999 group to not operate in the high-efficiency area, bringing a series of inconvenience to the safe operation management

2 cause analysis

when the blade hydraulic full adjustment system of the water pump adjusts the blade, the piston drives the operating frame and ear handle to move downward under the action of high-pressure oil. Because the piston of the blade adjustment mechanism does not have a downward mechanical limit device, the big screw of the ear handle M48 at the connection between the operating frame and the ear handle end collides with the bottom cover of the impeller head, causing the bottom cover to crack, When the piston goes down to the bottom of the oil cylinder, it can stop going down (when the piston goes up to +8 degrees, the pump shaft flange is used as the upper limit of the dead center)

3 solution

accordingly, the station installed a mechanical limit device at the lower part of the piston of the blade hydraulic adjustment system during the overhaul of the 1# main engine pump, as shown in the following figure When the impeller head is disassembled, measure the distance between the upper port and the bottom port of the oil cylinder to be 240mm. After the impeller parts are assembled, rotate the blade to -6 degrees according to the angle mark of the blade on the wheel hub surface. At this time, measure the distance from the upper port of the oil cylinder to the upper edge of the piston to be 48mm, and the piston is 150 mm high. Therefore, the height of the mechanical limit cylinder block under the piston (made of ductile iron) should be =42mm, evenly distributed under the piston, and the material is 45 steel, Outer diameter 40 mm Drill an inner hole of 10 mm in the middle of the mechanical limit cylinder block, which is connected with the piston by M10 hexagon socket screws (as shown in the figure) When the blade is adjusted, the piston moves downward to -6 degrees, and the limit block contacts with the four points on the bottom plane of the oil cylinder at the same time, and the force is evenly balanced, so that the piston cannot continue to move downward, which not only ensures that the minimum angle of the blade is -6 degrees, but also avoids the collision between the ear handle wire and the bottom cover

schematic diagram of mechanical limit of blade adjustment (unit: mm)

4 conclusion

after installing the piston down mechanical limit device in the blade hydraulic adjustment system of the water pump, the oil pressure system test can be carried out safely. At the same time, when the unit is running, the personnel on duty can also operate the adjustment with confidence, and the blade angle can be adjusted in time to increase or reduce the pumping capacity according to the superior water level dispatching instructions and the combination of upstream and downstream water levels, Ensure that the unit operates economically and safely in the high-efficiency area