1. What are the six types of correction and adjustment items in machine installation? How to understand the allowable deviation of electromechanical equipment installation?
Answer: item: 1) flat, horizontal and vertical plane. 2) The roundness, center position and center degree of the cylindrical surface itself. 3) Smooth, horizontal, vertical and central position of the shaft. 4) The orientation of the part on the horizontal plane. 5) Elevation (elevation) of parts. 6) clearance between faces, etc.
To determine the allowable deviation of electromechanical equipment installation, the reliability of unit operation and the simplicity of installation must be considered. If the allowable deviation of installation is too small, the correction and adjustment work will be complex and the correction and adjustment time will be prolonged; If the allowable installation deviation is too large, it will reduce the installation accuracy and operation safety and reliability of the calibration unit, and directly affect the normal power generation.
2. Why can the error of square level itself be eliminated by turning around measurement?
Answer: suppose that one end of the level is a and the other end is B, and its own error causes the bubble to move to the a end (on the left) by M. when measuring the level of components with this level, its own error causes the bubble to move to the a end (on the left) by M. after turning around, its own error causes the bubble to still move to the a end (on the right at this time) by the same number of cells, in the opposite direction, which is – m, and then use the formula δ= During the calculation of (a1 + A2) / 2 * c * D, the number of cells moved by the bubble due to its own error cancels each other, which has no impact on the number of cells moved by the bubble due to the uneven level of the parts, so the impact of the error of the instrument on the measurement is eliminated.
3. Briefly describe the correction and adjustment items and methods for the installation of draft tube liner?
Answer method: firstly, mark the position of X, – x, y, – Y axis at the upper opening of the lining. Install the elevation center frame at the position where the concrete in the machine pit is greater than the radius of the outer circle of the stay ring, move the center line and elevation of the unit to the elevation center frame, and hang the piano lines in x-axis and y-axis on the same vertical horizontal plane of the elevation center frame and X and y-axis. There is a certain height difference between the two piano lines, After the elevation center is erected and rechecked, the lining Center shall be measured and adjusted. Hang four heavy hammers at the position where the piano line aligns with the mark on the pipe orifice on the lining, adjust the jack and stretcher to align the tip of the heavy hammer with the mark on the upper pipe orifice. At this time, the center of the pipe orifice on the lining is consistent with the center of the unit. Measure the distance from the lowest point of the upper pipe orifice to the piano line with a steel ruler. Subtract the distance from the set elevation of the piano line to be the actual elevation of the upper pipe orifice of the lining, and then adjust it through screws or wedge plates to make the elevation of the lining within the allowable deviation range.
4. How to pre assemble and position the bottom ring and top cover?
Answer: first lift the bottom ring on the lower plane of the stay ring, adjust the center of the bottom ring with a wedge plate according to the gap between the bottom ring and the second pond mouth of the stay ring, and then lift half of the movable guide vane symmetrically according to the number to ensure that the guide vane can rotate flexibly and tilt around, otherwise deal with the bore diameter of the bearing bush, and then lift it into the top cover and sleeve. Take the center of the following fixed leakage ring as the benchmark, hang out the center line of the water turbine unit, measure the center and roundness of the upper fixed leakage ring, and adjust the center position of the top cover so that the difference between each radius and the average shall not exceed ± 10% of the design clearance of the leakage ring. After the top cover adjustment is completed, tighten the combined bolts of the top cover and stay ring. Then measure and adjust the coaxiality of the bottom ring and the top cover. Finally, only adjust the bottom ring based on the top cover. Wedge the gap between the bottom ring and the third pond mouth of the stay ring with the wedge plate, adjust the radial movement of the bottom ring, adjust its axial movement with four jacks, measure the gap between the upper and lower end faces of the guide vane to make △ larger ≈ △ smaller, and measure the gap between the guide vane sleeve bearing bush and the journal to make it within the allowable range. Then drill pin holes for the top cover and bottom ring according to the drawing, and the top cover and bottom ring are pre assembled.
5. How to align the rotating part of the turbine after it is hoisted into the turbine pit?
Answer: adjust the center position first, adjust the gap between the lower rotating leakage stop ring and the fourth pond mouth of the stay ring, lift the lower fixed leakage stop ring, drive in the pin, tighten the combination bolt symmetrically, measure the gap between the lower rotating leakage stop ring and the lower fixed leakage stop ring with a feeler gauge, fine adjust the center position of the runner with a jack according to the measured gap, and monitor the adjustment with a dial indicator. Then adjust the level, place a level at four positions x, – x, y and – Y on the flange surface of the main shaft of the turbine, and then adjust the wedge plate under the runner to make the horizontal deviation of the flange surface within the allowable range.
6. Describe the general installation procedure after rotor hoisting of suspended hydro generator unit?
Answer: 1) pouring foundation phase II concrete; 2) Upper frame hoisting; 3) Installation of thrust bearing; 4) Adjustment of generator axis; 5) Spindle connection 6) adjustment of the general axis of the unit; 7) Force adjustment of thrust pad; 8) Fix the center of the rotating part; 9) Install the guide bearing; 10) Install exciter and permanent magnet machine; 11) Install other accessories;
7. The installation method and steps of water guide shoe are described.
Answer: installation method 1) adjust the installation position according to the clearance specified in the design of water guide bearing, the swing of unit axis and the position of main shaft; 2) Install the water guide shoe symmetrically according to the design requirements; 3) After determining the adjusted clearance, adjust it with a jack or wedge plate;
8. The harm and treatment of shaft current are briefly described.
A: harm: due to the existence of shaft current, a small arc erosion is generated between the journal and the bearing bush, which makes the bearing alloy gradually stick to the journal, destroys the good working surface of the bearing bush, causes overheating of the bearing, and even melts the bearing alloy; In addition, due to the long-term electrolysis of current, the lubricating oil will deteriorate, blacken, reduce the lubricating performance and increase the bearing temperature. Treatment: in order to prevent the erosion of this shaft current on the bearing bush, the bearing must be separated from the foundation with insulation to cut off the shaft current circuit. Generally, the bearings on the exciter side (thrust bearing and guide bearing), oil receiver base and governor recovery wire rope shall be insulated, and the support fixing screws and pins shall be equipped with insulating sleeves. All insulation shall be dried in advance. After the insulation is installed, the insulation of the bearing to the ground shall be checked with a 500V megger and shall not be less than 0.5 megohm
9. Briefly describe the purpose and method of unit turning.
Answer: Purpose: since the actual mirror plate friction surface will not be absolutely perpendicular to the unit axis, and the axis itself is not an ideal straight line, when the unit rotates, the unit center line will deviate from the center line, and the axis will be measured and adjusted by turning with a dial indicator, so as to analyze the cause, size and orientation of axis swing. The non perpendicularity between the friction surface of the mirror plate and the axis, the flange combination surface and the axis can be corrected by scraping the relevant combination surface, and the swing can be reduced to the allowable range.
Methods:
1) mechanical turning, which is driven by a set of steel wire rope and pulley with the bridge crane in the plant as the power
2) Direct current is introduced into the stator and rotor windings to generate electromagnetic force drag method – electric turning gear 3) for small units, manual turning gear can also be used to drive the unit to rotate slowly – manual turning gear 10. Briefly describe the maintenance procedure of self-adjusting water seal device with air shroud and end face.
Answer: 1) write down the position of the damaged part on the shaft, remove the damaged part and check the wear of the rusted steel wear plate. If there is burr or shallow groove, it can be polished with oilstone along the rotation direction. If there is deep groove or serious eccentric wear or wear, it shall be leveled.
2) Remove the pressing plate, record the sequence of nylon blocks, take out the nylon blocks and check the wear. If treatment is required, all shall be pressed with pressing plates and planed together, then the planing marks shall be filed with a file, and the surface flatness of nylon blocks shall be checked with a platform. The results after scraping meet the requirements
3) Disassemble the upper sealing disc and check whether the rubber round packing is worn. If worn, replace it with a new one. 4) Remove the spring, remove mud and rust, and check the compression elasticity one by one. If plastic deformation occurs, replace it with a new one
5) Remove the air inlet pipe and connector 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 leakage, it can be treated by hot repair.
6) Pull off the locating pin and disassemble the intermediate ring. Clean all components before installation.
11. What are the methods to realize interference fit connection? What are the advantages of hot sleeve method?
Answer: there are two methods: 1) press in method; 2) Hot sleeve method; Advantages: 1) it can be inserted without applying pressure; 2) During assembly, the protruding points on the contact surface are not polished by axial friction, which greatly improves the strength of the connection;
12. Briefly describe the correction and adjustment items and methods of stay ring installation?
A: (1) correction and adjustment items include: (a) center; (b) Elevation; (c) Level
(2) Correction and adjustment method:
(a) Center measurement and adjustment: after the stay ring is lifted in and placed stably, hang out the cross piano line of the unit, hang four heavy hammers on the piano line pulled above the marks of X, – x, y, – Y on the stay ring and flange surface, and see whether the tip of the heavy hammer is consistent with the center mark; If not, adjust the stay ring position with lifting equipment to make it consistent.
(b) Elevation measurement and adjustment: measure the distance from the flange surface on the stay ring to the piano cross with a steel ruler. If it does not meet the requirements, it can be adjusted with the lower wedge plate.
(c) Horizontal measurement and adjustment: use the horizontal beam and square level to measure on the flange surface of the stay ring. According to the measurement and calculation results, use the wedge plate below to adjust. While adjusting, tighten the bolts. And repeatedly measure and adjust until the bolt tightness is uniform and the level meets the requirements.
13. How to determine the center of Francis turbine?
Answer: the center of Francis turbine is generally determined based on the elevation of the second pond mouth of the stay ring. First divide the second pond mouth of the stay ring into 8-16 points along the circumference, then hang the piano line on the upper plane of the stay ring or the foundation plane of the lower frame of the generator as required, measure the distance between the second pond mouth of the stay ring and the four symmetrical points of the X and Y axes to the piano line with a steel tape, adjust the ball center, make the difference between the radius of the symmetrical two points within 5mm, and preliminarily adjust the position of the piano line, Then, align the piano line according to the ring part and the center measurement method to make it pass through the center of the second pond mouth. The adjusted position is the installation center of the hydraulic turbine.
14. Briefly describe the function of thrust bearing? What are the three types of thrust bearing structure? What are the main components of thrust bearing?
Answer: function: bear the axial force of the unit and the weight of all rotating parts. Classification: rigid strut thrust bearing, balance weight thrust bearing and hydraulic column thrust bearing. Main components: thrust head, thrust pad, mirror plate, snap ring.
15. The concept and adjustment method of pressing stroke are briefly described.
A: concept: the pressing stroke is to adjust the stroke of the servomotor so that the guide vane still has a stroke margin of several millimeters (in the closing direction) after being closed. This stroke margin is called the pressing stroke adjustment method: when the controller and servomotor piston are in the fully closed position, withdraw the limit screws on each servomotor outward to the required pressing stroke value. This value can be controlled by the number of turns of the pitch.
16. What are the three main causes of hydraulic unit vibration?
A: (I) vibration caused by mechanical reasons: 1. Rotor mass imbalance. 2. The axis of the unit is not correct. 3. Bearing defects. （2） Vibration caused by hydraulic reasons: 1. Flow impact at runner inlet caused by uneven diversion of volute and guide vane. 2. Carmen vortex train. 3. Cavity cavitation. 4. Gap jet. 5. Seal ring pressure pulsation
(3) Vibration caused by electromagnetic factors: 1. Rotor winding short circuit. 2) uneven air gap.
17. Brief description: (1) static imbalance and dynamic imbalance?
Answer: static imbalance: since the rotor of the hydraulic turbine is not on the rotation axis, when the rotor is in a static state, the rotor cannot remain stable at any position. This phenomenon is called static imbalance.
Dynamic imbalance: refers to the vibration phenomenon caused by irregular shape or uneven density of rotating parts of hydraulic turbine during operation.
18. Brief description: (2) purpose of static balance test of turbine runner?
Answer: it is necessary to reduce the eccentricity of the center of gravity of the runner to the allowable range, so as to avoid the existence of eccentricity of the center of gravity of the runner; the centrifugal force of the unit will cause eccentric wear of the main shaft during operation, increase the swing of the hydraulic guide, or cause vibration of the turbine during operation, and even damage the unit parts and loosen the anchor bolts, resulting in major accidents.18. How to carry out the outer cylinder Measurement of surface roundness?
Answer: a dial indicator is installed on the vertical arm of the support, and its measuring rod is in contact with the measured cylindrical surface. When the support rotates around the axis, the value read out from the dial indicator reflects the roundness of the measured surface.
19. Be familiar with the structure of the inner micrometer and explain how to use the electrical circuit method to measure the shape parts and central position?
Answer: take the second pond of the stay ring as the benchmark, first align the piano line, take this piano line as the benchmark, and then use the inner micrometer to form an electrical circuit between the ring parts and the piano line, adjust the length of the inner micrometer and draw along the piano line, down, left and right According to the sound, it can judge whether the inner micrometer is in contact with the piano line, and measure the ring part and the center position.
20. General installation procedure of Francis turbine?
Answer: installation of inner liner of draft tube → pouring concrete around draft tube, stay ring and spiral case buttress → cleaning and combination of stay ring and foundation ring and installation of conical pipe of stay ring and foundation ring → foundation bolt concrete of foot stay ring → assembly of single section spiral case → installation and welding of spiral case → installation of inner liner and buried pipeline in turbine pit → pouring concrete below generator floor → retest of stay ring elevation and level and hydraulic turbine center Confirm → cleaning and assembly of lower fixed leakage stop ring → positioning of lower fixed leakage stop ring → cleaning and assembly of top cover and stay ring → pre assembly of water guide mechanism → connection between main shaft and runner → hoisting and installation of rotating part → installation of water guide mechanism → main shaft connection → overall turning of unit → installation of water guide bearing → installation of accessories → cleaning, inspection and painting → unit startup and commissioning.
21. What are the main technical requirements for the installation of water guide mechanism?
Answer: 1) the center of the bottom ring and top cover shall coincide with the vertical center line of the unit; 2) the bottom ring and top cover shall be parallel to each other, the X and Y scribed lines on them shall be consistent with the X and Y scribed lines of the unit, and the upper and lower bearing holes of each guide vane shall be coaxial; 3) the end clearance of the guide vane and the tightness during closing shall meet the requirements; 4) the work of the guide vane transmission part shall be flexible and reliable.
22. How to connect the runner with the main shaft?
Answer: first connect the main shaft with the runner cover, and then connect with the runner body together, or first thread the connecting bolt into the screw hole of the runner cover according to the number, and block the lower part with steel plate. After the sealing leakage test is qualified, 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 jacked up with oil pressure, the lock nut is unscrewed, and then the rotor is dropped again, its weight will be converted to the thrust bearing.
24. What is the purpose of start-up and trial operation of water turbine generator unit?
Answer:
1) check whether the construction quality, manufacturing and installation quality of civil engineering meet 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 of the project and equipment can be found in time.
3) Through start-up and trial operation, understand the installation of hydraulic structures and electromechanical equipment, master the operation performance of electromechanical equipment, measure some necessary technical data in operation, and record some equipment characteristic curves as one of the basic basis for formal operation, so as to prepare necessary technical data for the preparation of operation regulations for the power plant.
4) In some hydropower projects, the efficiency characteristic test of water turbine generator unit is also carried out. To verify the efficiency guarantee value of the manufacturer and provide data for the economic operation of the power plant.
25. What is the purpose of overspeed test for the unit?
Answer: 1) check the regulation quality of the automatic regulating excitation device of the unit; 2) Understand the vibration area of the unit under load; 3) Check and ensure the maximum rise value of the regulating data unit, the maximum pressure rise value in front of the guide vane and the differential adjustment coefficient of the governor; 4) Understand the change law of internal hydraulic and mechanical characteristics of the unit and its impact on the unit work, so as to provide necessary data for the safe operation of the unit; 5) Identify the stability and other operating performance of the governor.
26. How to conduct static balance test of hydraulic turbine?
Answer: place two level gauges on the X and Y bisectors of the lower ring of the runner; Place a balance weight with the same weight as the level symmetrically on the bisector of – X and ‐ y (its mass can be calculated according to the reading of the level); According to the level of the level, place the balance weight on the light side until the bubble of the level is centered, and write down the size P and azimuth of the final balance weight α
27. How to pull out the thrust head during maintenance?
Answer: remove the connecting screw between the thrust head and the mirror plate, hang the thrust head on the main ditch with steel wire rope and tighten it slightly. Lift the oil pump, jack up the rotor, add four aluminum pads between the thrust head and the mirror plate in a 90 degree orientation, drain the oil and drop the rotor. In this way, the main shaft descends with the rotor, and the thrust head is stuck by the pad and pulled out for a distance. Repeat several times, control the cushion thickness between 6-10mm each time, and gradually pull out the thrust head until it can be lifted out with the main hook. After pulling out several times, the cooperation between the thrust head and the main shaft becomes loose, and the thrust head can be pulled out directly with a crane. 28. See the following table for a turning record of 1# turbine (unit: 0.01mm):
Calculate the full swing and net swing of hydraulic guide, lower guide and upper guide, and complete the above table.
Post time: Oct-21-2021
