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Classic Fitter Exam Paper. Examination format: Closed-book. Duration: 120 minutes. I II III IV V Total Score Score Group: Name: Grade: Score Grader. I. Multiple-choice questions (2 points per question, total of 20 points). ) 1. The flexible rotor of a centrifugal compressor is ( ). A: When the rotational speed is below the first-order critical speed. B: When the operating speed is higher than the first-order critical speed. 2. For the gaskets used in the intermediate section of centrifugal nitrogen oxide compressors, considering the operating conditions (temperature, corrosion), the material to be used is ( ). A: Nitrile rubber B: Silicone rubber. C: Silicone rubber. 3. Machining precision refers to ( ). A: Dimensional accuracy. B: Surface geometric shape accuracy. C: Precision of the relative positions of various surfaces. D surface roughness. 4. When using lubricant, three-stage filtration should be employed; the mesh sizes for each stage of filtration are ( ). A. 60, 80, 100 B. 80, 100, 120 C. 100, 120, 200 D. 40, 60, 80 5. The higher the strength and hardness of the workpiece, the greater the cutting force. A: Larger B: Smaller C: Generally unchanged. 6. When the two sprockets are assembled with a center distance of less than 500 mm, the axial offset should be below ( ) mm. A: 1 B: 2 C: 3 7. When using a chain with an odd number of links, ( ) should be used to secure the moving pin. A: Split pin B: Spring plate C: Transition link. 8. In chain drive, as the sprockets and tooth edges gradually wear out, the pitch increases, which accelerates the wear of the chain; when the wear becomes severe, it is necessary to ( ). A: Adjust the sprocket center distance. B: Replace the sprocket center distance. C: Replace the sprocket and chain. 9. To improve the pitting resistance of gear transmissions, the ( ) method can be considered. A: Use a closed-drive system. B: Increase the center distance between the drives. C: Reduce the number of teeth on the gears. D: Increase the hardness of the gear surfaces. 10. The algebraic difference between the maximum allowable dimension of the hole and the minimum allowable dimension of the shaft being negative is called ( ). A: Interference difference B: Minimum interference C: Maximum interference Score: Grader II. True or False questions (fill in “√” for correct and “×” for incorrect). 1 point per question, with a total score of 10 points. ) 1. The thread angle for metric threads is 55 ° ( ). 2. When tapping threads, the diameter of the bottom hole should be equal to the nominal thread diameter multiplied by 1.1. ( ) 3. Molybdenum disulfide is a solid lubricant. ( ) 4 The process of subjecting steel to high-temperature tempering treatment is called quenching and tempering. ( ) The required condition for 5 rolling bearings: clearance can be divided into original clearance, installation clearance, and operating clearance. ( ) 6 For bevel gears that use the back bevel surface as a reference, the back bevel surfaces are aligned to be level during assembly, in order to ensure the correct fitting position of the two gears. ( ) 7. The contact points between two meshing gears are inspected using the coloring method; during the inspection, the driven gear is rotated while the driving gear should be lightly braked. ( ) 8. The mechanical efficiency of large piston compressors is lower than that of small piston compressors, because the proportion of frictional losses is larger in the former compared to the latter. ( ) 9. Diaphragm compressors are not hydraulically driven. ( ) 10 One-way slippage is an inevitable inherent phenomenon in belt drives. ( ) Score Grader III. Fill-in-the-blank questions (2 points per question, total 20 points.) ) 1. For the inter-segment sealing of the cylindrical inner cylinder body of centrifugal compressors, O-rings are used under high-pressure conditions; they must be used in conjunction with other components. If pressure is applied in only one direction, backup rings are used, and these backup rings are installed on the side. If alternating compression in both directions occurs, back rings should be used, with one back ring placed on each side of the O-ring. 2. The speed increase gearboxes used in compression units driven by domestic steam turbines are classified into categories based on tooth shape. They are respectively helical gears with circular tooth profiles or herringbone gears, and helical gears with involute tooth profiles or herringbone gears. 3. The performance curve of a centrifugal compressor refers to the relationship curve showing how parameters such as the machine’s efficiency, pressure, etc., change with flow rate under certain rotational speeds and inlet conditions. 4. Electrostatic precipitators are classified into and according to their internal dust collection structure. 5. The gear reduction gearbox is inspected according to the requirements for contact precision: for spur gears, the contact patch percentage is required to be % in the height direction and % in the length direction; for circular arc gears, this percentage is % in the height direction and % in the length direction after meshing. 6. When measuring coaxiality using the arc method, it is necessary to take into account various influencing factors. 7. They can be divided into four types according to the direction of the force exerted on the bearing. 8. The commonly used transmission chains are chain and chain. 9. The methods of fixing the sprocket to the shaft are fixation or fixation. 10. If the two axes of the sprocket are not parallel, it will increase wear, reduce transmission efficiency, and increase noise. Score Grader IV. Short-answer questions (5 points per question, with a total score of 45 points.) ) 1. What is a mechanical seal? How does it achieve a sealed state? What components does it consist of? 2. What are the components of the material used for the mechanical seal auxiliary sealing ring? What is its function? 3. What are the material requirements for the auxiliary seal of a mechanical seal? What are the functions of the common materials used for auxiliary sealing? 4. How is sealing achieved between the rotating ring and the stationary ring of a mechanical seal? 5. What are the principles for fixing the cylinders of turbines and compressors? 6. What components make up a turbine control system? 7. What are the hazards of vibration in steam turbine generators? 8. What are the methods for measuring the steam seal gap in a turbine? 9. What is the function of the turbine barring device? Score Grader V. Calculation questions (5 points each) A pressure vessel made of 16MnR material is to be designed, with a design pressure of p=0.8 Mpa, a design temperature of t=50°C, and an inner diameter of Di=1200 mm. Local non-destructive testing will be employed; calculate the calculated thickness of the vessel’s cylinder section.