1. What are the six calibration and adjustment items in the machine installation? How to understand the allowable deviation of electromechanical equipment installation?
Answer: Items:
1) The plane is straight, horizontal and vertical. 2) The roundness of the cylindrical surface itself, the center position and the center of each other. 3) Smooth, horizontal, vertical and center position of the shaft. 4) The position of the part on the horizontal plane. 5) The elevation (elevation) of the part. 6) The gap between the surface and the surface, etc.
To determine the allowable deviation for the installation of electromechanical equipment, the reliability of the unit operation and the simplicity of installation must be considered. If the allowable installation deviation is too small, the correction and adjustment work will be complicated, and the correction and adjustment time should be extended; the installation allowable deviation must be specified If it is too large, it will reduce the installation accuracy of the school unit and the safety and reliability of operation, and directly affect the normal power generation.
2. Why can the error of the square level meter itself be eliminated by the method of turning head measurement?
Answer: Assuming that one end of the level meter is A and the other end is B, its own error causes the bubble to move to end A (on the left) the number of grids is m. When using this level to measure the level of the component, the error of the level itself causes the bubble to end A ( On the left) move m grids, after turning around, the inherent error makes the bubble still move the same number of grids to end A (right now), in the opposite direction, which is -m, and then use the formula δ=(A1+A2)/2* In the calculation of C*D, the internal error causes the number of cells to move the bubbles to cancel each other, which has no effect on the number of cells that the bubbles move because the parts are not level, thus eliminating the influence of the instrument’s own error on the measurement.
3. Briefly describe the correction and adjustment items and methods for the installation of the draft tube lining?
Answer method: First, mark the X, -X, Y, -Y axis positions on the upper mouth of the lining, install an elevation center frame at the position where the pit concrete is larger than the outer radius of the seat ring, and move the centerline and elevation of the unit to the elevation On the center frame, the X-axis and Y-axis piano lines are hung on the same vertical horizontal plane as the elevation center frame and the X and Y axes. The two piano lines have a certain height difference. After the elevation center is erected and reviewed, the lining center will be carried out. Measurement and adjustment. Hang four heavy hammers at the position where the piano line is aligned with the mark of the upper nozzle of the lining, adjust the jack and stretcher so that the tip of the heavy hammer is aligned with the mark of the upper nozzle, at this time the center of the upper nozzle of the lining and the center of the unit Unanimous. Then use a steel ruler to measure the distance from the lowest point of the upper nozzle to the piano line. Use the piano line to set the elevation and subtract the distance to obtain the actual elevation of the lining upper nozzle. Within the allowable deviation range.
4. How to carry out the pre-installation and positioning of the bottom ring and top cover?
Answer: First, hang the bottom ring on the lower plane of the seat ring. According to the gap between the bottom ring and the second hole of the seat ring, use a wedge plate to adjust the center of the bottom ring first, and then hang in half of the movable guide vanes symmetrically according to the number. The guide vane rotates flexibly and can be tilted to the surroundings, otherwise, the bearing hole diameter will be processed, and then the top cover and sleeve will be suspended. The center of the fixed leak-proof ring below is used as a benchmark, hang out the center line of the turbine unit, measure the center and roundness of the upper fixed leak-proof ring, and adjust the center position of the top cover, so that the difference between each radius and the average should not exceed the design gap of the leak-proof ring ±10%, after the adjustment of the top cover is completed, tighten the combined bolts of the top cover and the seat ring. Then measure and adjust the coaxiality of the bottom ring and the top cover, and finally adjust only the bottom ring based on the top cover, use a wedge plate to wedge the gap between the bottom ring and the third hole of the seat ring, and adjust the radial movement of the bottom ring. Use 4 jacks to adjust the axial movement, measure the clearance between the upper and lower ends of the guide vane to make △large ≈ △small, and measure the clearance between the bushing of the guide vane and the journal to make it within the allowable range. Then drill pin holes for the top cover and bottom ring according to the drawings, and the top cover and bottom ring are pre-assembled.
5. After the rotating part of the turbine is hoisted into the pit, how to align it?
Answer: First adjust the center position, adjust the gap between the lower rotating o-ring and the fourth hole of the seat ring, hoist the lower fixed o-leak ring, drive in the pin, tighten the combination bolts symmetrically, and measure the lower rotating stop with a feeler gauge. The gap between the leak ring and the lower fixed leak-proof ring, according to the actual measured gap, use a jack to fine-tune the center position of the runner, and use a dial indicator to monitor the adjustment. Then adjust the level, place a level on the X, -X, Y, and -Y four positions of the flange surface of the turbine main shaft, and then adjust the wedge plate under the runner to make the flange surface level deviation within the allowable range.
6. What are the general installation procedures after the rotor of a suspended turbine generator set is hoisted?
Answer: 1) Pouring foundation phase II concrete; 2) Hoisting of upper frame; 3) Thrust bearing installation; 4) Adjustment of generator axis; 5) Main shaft connection 6) Adjustment of unit axis; 7) Thrust bearing Force adjustment; 8) fix the center of the rotating part; 9) install the guide bearing; 10) install the exciter and permanent magnet machine; 11) install other accessories;
7. Describe the installation method and steps of the water guide tile.
Answer: Installation method 1) Adjust the installation position according to the specified clearance of the water guide bearing design, the axis swing of the unit and the position of the main shaft; 2) Install the water guide shoe symmetrically according to the design requirements; 3) Determine the adjusted clearance again Afterwards, use jacks or wedge plates to adjust;
8. Briefly describe the hazards and treatment of shaft current.
Answer: Hazard: Due to the existence of shaft current, there is a small arc erosion effect between the journal and the bearing bush, which makes the bearing alloy gradually stick to the journal, destroy the good working surface of the bearing bush, cause overheating of the bearing, and even damage the bearing. The bearing alloy melts; in addition, due to the long-term electrolysis of the current, the lubricating oil will also deteriorate, blacken, reduce the lubricating performance, and increase the temperature of the bearing. Treatment: In order to prevent the shaft current from corroding the bearing bush, the bearing must be separated from the foundation with an insulator to cut off the shaft current loop. Generally, the bearings on the exciter side (thrust bearing and guide bearing), the base of the oil receiver, the recovery wire rope of the governor, etc. must be insulated, and the support fixing screws and pins must be insulated. All insulators must be dried in advance. After the insulator is installed, the bearing-to-ground insulation should be checked with a 500V shaker to be no less than 0.5 megohm
9. Briefly describe the purpose and method of turning the unit.
Answer: Purpose: Since the actual friction surface of the mirror plate is not absolutely perpendicular to the axis of the unit, and the axis itself is not an ideal straight line, when the unit is rotating, the center line of the unit will deviate from the center line. Measure and adjust the axis to analyze the cause, size and orientation of the axis swing. And through the method of scraping the relevant combination surface, the non-perpendicularity between the friction surface of the mirror plate and the axis, and the combination surface of the flange and the axis can be corrected, so that the swing is reduced to the range allowed by the regulations.
Method:
1) Use the bridge crane in the factory as the power, the method of dragging by a set of steel wire ropes and pulleys-mechanical cranking
2) Direct current is applied to the stator and rotor windings to generate electromagnetic force dragging method — electric crank 3) For small units, it is also possible to manually push the unit to rotate slowly — manual cranking 10. Brief description belt Maintenance procedures for air shrouds and end-face self-adjusting water seal devices.
Answer: 1) Note the position of the spoiler on the shaft and then remove the spoiler, and check the wear of the stainless steel anti-wear plate. If there are burrs or shallow grooves, they can be smoothed with oilstone in the direction of rotation. If there is a deep groove or severe partial wear or abrasion, the car should be leveled.
2) Remove the pressure plate, note the order of the nylon blocks, take out the nylon blocks and check the wear. If you need to deal with it, you should press all the pressing plates and plan them together, then file the planed marks with a file, and use the platform to check the surface flatness after the nylon block is combined. The result after repairing is required to reach
3) Disassemble the upper sealing disc and check whether the rubber disc is worn out. If it is worn out, replace it with a new one. 4) Remove the spring, remove the mud and rust, check the compression elasticity one by one, and replace it with a new one if plastic deformation occurs.
5) Remove the air inlet pipe and joints of the air shroud, disassemble the sealing cover, take out the shroud, and check the wear of the shroud. If there is local wear or wear and tear, it can be treated by hot repair.
6) Pull off the positioning pin and disassemble the intermediate ring. Clean all parts before installation.
11. What are the methods to realize the interference fit connection? What are the advantages of the hot sleeve method?
Answer: Two methods: 1) Press-in method; 2) Hot-sleeve method; Advantages: 1) It can be inserted without applying pressure; 2) The protruding points on the contact surface are not worn by axial friction during assembly. Flat, thus greatly improving the strength of the connection;
12. Briefly describe the correction and adjustment items and methods of seat ring installation?
Answer:
(1) Calibration adjustment items include: (a) center; (b) elevation; (c) level
(2) Correction and adjustment method:
(a) Center measurement and adjustment: After the seat ring is hoisted and placed firmly, hang out the cross piano line of the unit, and the piano line has been pulled above the X, -X, Y, -Y marks on the seat ring and on the flange surface Hang the four heavy hammers respectively to see if the tip of the heavy hammer is consistent with the center mark; if not, use lifting equipment to adjust the position of the seat ring to make it consistent.
(b) Elevation measurement and adjustment: Use a steel ruler to measure the distance from the upper flange surface of the seat ring to the cross piano line. If it does not meet the requirements, the lower wedge plate can be used to adjust.
(c) Horizontal measurement and adjustment: Use a horizontal beam with a square level gauge to measure on the upper flange surface of the seat ring. According to the measurement and calculation results, use the lower wedge plate to adjust, adjust and tighten the bolts. And repeat the measurement and adjustment, and wait until the bolt tightness is even and the level meets the requirements.
13. Briefly describe the method of determining the center of the Francis turbine?
Answer: The determination of the center of the Francis turbine is generally based on the second tangkou elevation of the seat ring. First divide the second hole of the seat ring into 8-16 points along the circumference, and then hang out the piano wire on the upper plane of the seat ring or the base plane of the lower frame of the generator, and measure the second hole of the seat ring with a steel tape. The distance between the four symmetrical points of the mouth and the X and Y axes to the piano line, adjust the ball center device so that the radii of the two symmetrical points are within 5mm, and adjust the position of the piano line initially, and then align the piano according to the ring component and the center measurement method. Line so that it passes through the center of the second pond, and the adjusted position is the center of the turbine installation.
14. Briefly describe the role of thrust bearings? What are the three types of thrust bearing structure? What are the main components of the thrust bearing?
Answer: Function: To bear the axial force of the unit and the weight of all rotating parts. Classification: rigid pillar thrust bearing, balance block thrust bearing, hydraulic column thrust bearing. Main components: thrust head, thrust pad, mirror plate, snap ring.
15. Briefly describe the concept and adjustment method of the compaction stroke.
Answer: Concept: The compression stroke is to adjust the stroke of the servomotor so that the guide vane still has a few millimeters of stroke margin (toward the closing direction) after being closed. This stroke margin is called the compression stroke adjustment method: when the controller When both the servomotor piston and the servomotor piston are in the fully closed position, retract the limit screws on each servomotor outwards to the required compression stroke value. This value can be controlled by the number of turns of the pitch.
16. What are the three main reasons for the vibration of the hydraulic unit?
Answer:
(1) Vibration caused by mechanical reasons: 1. The rotor mass is unbalanced. 2. The axis of the unit is not straight. 3. Bearing defects. (2) Vibration caused by hydraulic reasons: 1. Water flow impact at the runner inlet caused by uneven water diversion of the volute and guide vanes. 2. Carmen vortex train. 3. Cavitation in the cavity. 4. Interstitial jets. 5. Pressure pulsation of the anti-leak ring
(3) Vibration caused by electromagnetic factors: 1. The rotor winding is short-circuited. 2) The air gap is uneven.
17. Brief description: (1) Static imbalance and dynamic imbalance?
Answer: Static imbalance: Since the rotor of the turbine is not on the axis of rotation, when the rotor is at a standstill, the rotor cannot remain stable at any position. This phenomenon is called static imbalance.
Dynamic unbalance: refers to the vibration phenomenon caused by the irregular shape or uneven density of the rotating parts of the turbine during operation.
18. Brief description: (2) The purpose of the static balance test of the turbine runner?
Answer: It is to reduce the eccentricity of the runner’s center of gravity to the allowable range, so as to avoid the eccentricity of the runner’s center of gravity; the centrifugal force generated by the unit will cause the main shaft to produce eccentric wear during operation, increase the swing of the water guide or cause the turbine Vibration during operation can even damage the parts of the unit and loosen anchor bolts, causing major accidents. 18. How to measure the roundness of the outer cylindrical surface?
Answer: A dial indicator is installed on the vertical arm of the bracket, and its measuring rod is in contact with the measured cylindrical surface. When the bracket rotates around the axis, the value read from the dial indicator reflects the roundness of the measured surface.
19. Familiar with the structure of the inner diameter micrometer, explain how to use the electrical circuit method to measure the shape of the parts and the center position? Answer: First find the piano wire based on the second hole of the seat ring, and then use this and the piano wire as the benchmark. Use the inner diameter micrometer to form an electrical circuit between the ring part and the piano wire, adjust the length of the inner diameter micrometer, and draw a circle along the piano line, down, left, and right. According to the sound, it can be judged whether the inner diameter micrometer is in contact with the piano wire to make the ring part. And the measurement of the center position.
20. General installation procedures for Francis turbines?
Answer: Installation of draft tube lining → pouring concrete around draft tube, seat ring, volute buttress pier → seat ring, foundation ring cleaning, combination and seat ring, foundation ring tapered pipe installation → foot seat ring foundation bolt concrete → single Section volute assembly → volute installation and welding → machine pit lining and buried pipeline installation → concrete pouring below the generator layer → seat ring elevation and level re-measurement, determination of turbine center → lower fixed leak-proof ring cleaning and assembly → lower fixed Stop-leak ring positioning → top cover and seat ring cleaning, assembly → water guide mechanism pre-installation → main shaft and runner connection → rotating part hoisting installation → water guide mechanism installation → main shaft connection → unit overall cranking → water guide bearing installation → Installation of spare parts → cleaning and inspection, painting → start-up and trial operation of the unit.
21. What are the main technical requirements for the installation of the water guiding mechanism?
Answer: 1) The center of the bottom ring and the top cover should coincide with the vertical center line of the unit; 2) The bottom ring and the top cover should be parallel to each other, and the X and Y engraving lines on them should be consistent with the X and Y engraving lines of the unit. The upper and lower bearing holes of the guide vane should be coaxial; 3) The clearance of the guide vane end face and the tightness when closing should meet the requirements; 4) The work of the guide vane transmission part should be flexible and reliable.
22. How to connect the runner and the spindle?
Answer: First connect the main shaft with the runner cover, and then connect with the runner body together or first pass the connecting bolts into the screw holes of the runner cover according to the number, and seal the lower part with steel plate. After the sealing leakage test is qualified, Then connect the main shaft with the runner cover.
23. How to convert the rotor weight?
Answer: The conversion of the lock nut brake is relatively easy. As long as the rotor is lifted up with oil pressure, the lock nut is unscrewed, and the rotor is dropped again, its weight is converted to the thrust bearing.
24. What is the purpose of starting the trial operation of the hydro-turbine generator set?
Answer:
1) Check the construction quality of the civil engineering construction, whether the installation quality meets the design requirements and relevant regulations and specifications.
2) Through the inspection before and after the trial operation, the missing or unfinished work and the defects in the engineering and equipment can be found in time.
3) Through the start-up trial operation, understand the installation situation of hydraulic structures and electromechanical equipment, and master the electromechanical
Post time: Oct-14-2021
