Fitter test questions

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I. Fill in the blanks 1. The carbon content of 45# steel is (0.45%). 2. Control valves in hydraulic systems can be basically divided into three categories, namely (pressure control), (flow control), and (speed control). 3. The lubrication methods used for sliding bearings are (hydrostatic) lubrication and (hydrodynamic) lubrication. 4. The quality of gear meshing includes an appropriate (tooth side clearance), a sufficient contact (area), and the correct contact (position). 5. An excessive tooth side clearance in gear drives can easily lead to shocks and vibrations. 6. The vast majority of lubricants are classified by their (viscosity) grade. 7. The purpose of shaft alignment is to ensure the (stability) and (vibration requirements) of rotating machinery operation. 8. Sealing methods can be divided into two main categories: static sealing and (dynamic sealing). 9. The fit between the inner ring of a rolling bearing and the shaft generally adopts a (transition fit). 10. The two extreme values that permit dimensional variation are called (limit dimensions). 11. Mechanical equipment wear can be classified as energy conversion devices that convert (pressure) energy into (mechanical) energy. 12. When performing performance tests on a gear pump with a rated pressure of 25×105 Pa, and when the oil discharged by the pump flows directly into the oil tank with pipeline resistance being negligible, the output pressure of the pump is (0). 13. The 460 in VG460 gear oil refers to the (dynamic) viscosity of the oil at (40)°C. 14. The function of an oil mister is to atomize the lubricating oil and inject it into the air flow, so that it can reach the components that need lubrication along with the air flow. 15. The wear stages of mechanical equipment can be divided into (running-in wear stage), (stable wear stage), and (accident wear stage). 16. The categories of equipment maintenance are (daily maintenance), (regular maintenance), and (annual maintenance). 17. In gear drives, the methods for measuring the tooth side clearance include the dial indicator method, the lead compression method, and the feeler gauge method. 18. The algebraic difference obtained by subtracting the basic dimension from the maximum limit dimension is called the upper tolerance. 19. The ultimate goal of shaft alignment is to ensure the (coaxiality requirement) of the two shafts under (normal) operating conditions. II. Selection 1. The heat treatment process for quenched and tempered steel usually involves (C quenching + high-temperature tempering). A. Quenching + low-temperature tempering B. Quenching + medium-temperature tempering C. Quenching + high-temperature tempering 2. Among the three main components of pneumatic systems, the one that is located in the middle according to the air intake direction is (D. Pressure reducing valve). A: Water separator and air filter; B: Oil mister; C: Silencer. 3: Ordinary flat keys can be divided into three types – A, B, and C – depending on the shape of their end part (B). A: The size of the dimension; B: The shape of the end; C: The shape of the cross-section. 4. (C) Cylindrical roller bearings cannot withstand axial loads. A Self-aligning ball bearing B Tapered bearing C Cylindrical roller bearing 5. Among the methods for preventing bolt loosening, spring washers belong to the category of anti-loosening methods that utilize (A friction). A. Using friction B. Using mechanics C. Permanent. 6. The shape of the involute depends on the size of the base circle; the smaller the base circle, the more (C. curved) the involute becomes. A Straight B Inclined C Bent 7. In China’s legal units of measurement, the unit for torque is (A Newton meter). A Newton-meter B Kilogram-force meter C Kilogram-force meter 8. The function of an accumulator is ( ). A is used as an auxiliary energy source; B is used to compensate for leaks and maintain pressure; C is used to absorb hydraulic shocks; D: none of the above. 9. Belt drives transfer motion and power based on (C: the friction between the belt and the pulleys). A. Power of the main shaft; B. Torque of the driving pulley; C. Friction between the belt and the pulley. 10. Among the methods for preventing loosening in threaded connections, split pins and slotted nuts belong to the category of (B) mechanical methods for preventing loosening. A. Using friction B. Using mechanics C. Permanent. Three noun explanations: 1. Stiffness: refers to the ability of a metal material to resist deformation. 2. Pascal’s principle: In a sealed container, the pressure applied to a stationary fluid is transmitted equally and simultaneously to all points in the fluid. IV. Short Answers 1. What is the “five senses” inspection method? What is its content? "The \"five senses\" inspection method is a basic practice that involves making use of the functions of the human brain’s \"five senses\", in combination with existing knowledge and experience; these senses include vision, hearing, touch, smell, and taste. 2. What is the function of the shaft? What types can they be classified into based on the stress conditions? The shaft is an important component of machines; its function is to support the driving parts (such as pulleys, gears, sprockets, etc.) and transmit motion and torque. 3. What is the purpose of providing oil inlets, oil grooves, and oil chambers on the bearing shells? To ensure that the lubricating oil can spread over the entire working surface of the bearing, oil holes, oil grooves, and oil chambers are generally provided in the non-load-bearing areas of the bearing. Oil holes are used for supplying oil, oil channels are used to convey and distribute lubricating oil, while oil chambers serve to store oil and ensure a stable supply of it. 4. What is the function of an air reservoir in a pneumatic system? The function of the air storage tank is to eliminate pressure fluctuations, ensure the continuity of the output airflow, store a certain amount of compressed air to regulate air consumption or for emergency use in case of failures, and further remove moisture and oil from the compressed air. 5. Briefly describe the installation location of the oil filter in a hydraulic system? The pressure pipes of the oil suction pipe system of the oil pump, the bypass circuit of the system, the pressure pipes of the system, the bypass circuit of the system, the return oil circuit of the system, with a separate oil filtering circuit. 6. Explain the function and location of the emergency shut-off valve in the hydraulic system. In the event of a failure on-site, it ensures that the oil supply is cut off without stopping the pump and that any residual pressure in the hydraulic cylinder is released; it is usually installed behind the accumulator at the pump station. 7. What are the basic conditions for conducting a “five senses” inspection? Understand the equipment, be familiar with the drawings, correctly assess and master various standards, distinguish key equipment, have standard operating values, and possess extensive practical experience. 8. What are the characteristics of worm drive? What occasions is it commonly used for? The worm gear transmission features a compact design, a high gear ratio, smooth operation with no noise, and the ability to self-lock. However, its transmission efficiency is low. To reduce friction and improve wear resistance as well as adhesion, worm gears are often made from precious metals, which results in high costs and poor interchangeability; they are used in applications where a high gear ratio is required but the power transmitted is low. 9. What are the common anti-loosening methods for threaded connections? The common methods for preventing loosening in threaded connections mainly include those that rely on friction, mechanical means, and permanent solutions. Among these, methods that utilize friction include double nuts, spring washers, and self-locking nuts; mechanical methods for preventing loosening include split pins, split pins together with slotted nut stop washers, lock washers, and twisted steel wires; permanent methods for preventing loosening include end riveting, punching, bonding, etc. 10. Briefly describe the process of cleaning a fuel tank? After draining the old oil from the tank, open the cover and use non-conductive materials such as foam plastic or silk to wipe away the oil stains inside the tank. Then clean the tank with a detergent, and finally use dough or similar substances to remove any solid particles adhering to the inner walls of the tank. 11. Explain the function and location of the emergency shut-off valve in the hydraulic system. In the event of a failure on-site, it ensures that the oil supply is cut off and any residual pressure in the hydraulic cylinders is released without stopping the pump; it is usually installed behind the pump station accumulator. 12. Briefly explain why rolling mills use oil film bearings, and which roller bearings in the rolling line are oil film bearings. Due to the high load-bearing capacity of the bearings in the rolling mill support rolls (working rolls), the requirement for a long service life, a wide range of operating speeds, and certain impact resistance, oil film bearings are used. Line 1700: R1 working roll bearings, F1-F6 backup roll bearings; Line 1780: R1 working roll bearings, R2, F1-F7 backup roll bearings. 13. Why is it necessary to prevent loosening in threaded connections? All standard threaded connections meet the self-locking requirements; under static loads, such connections generally do not loosen on their own. However, under impacts, vibrations, or variable loads, or when there are significant temperature changes, the self-locking property of the threads can decrease or even disappear momentarily. When this phenomenon occurs repeatedly, it can lead to gradual loosening of the connection, and in severe cases, it may even result in serious accidents. Therefore, anti-loosening measures for threaded connections must be considered. 14. What is the function of roll balancing in rolling mills? Eliminate gaps between various components, prevent impacts, increase compression stiffness, and avoid slipping. 15. Why is clearance needed when installing gears? It compensates for gear machining errors, facilitates lubrication, and prevents the gears from getting stuck due to expansion caused by temperature rise. 16. Briefly describe the main components of air and the advantages of pressure transmission? The main components of air are nitrogen and oxygen, with very small amounts of argon and carbon dioxide. Advantages: ① Air is used as the working medium, which is easily available and convenient to handle ； ②Facilitates long-distance transportation ； ③Pneumatic action is fast and responsive ； ④Good adaptability to the working environment. 17. Analyze the reasons for water ingress into the lubrication system of oil film bearings? ① The oil film bearing is not properly sealed ； ②Steam heating tube in the fuel tank ； ③Leak in the cooling tank of the piping system ； ④There is a leak in the pipeline. 18. What are the causes of damage to rolling bearings? What are the phenomena that occur after damage? Causes of damage: It is usually due to too small a bearing clearance, poor lubrication, dirt inside the bearings, excessive weight or load, as well as incorrect assembly. Once a rolling bearing is damaged, it will cause severe vibrations during operation, produce abnormal noises, or lead to an increase in temperature. 19. What are the inspection standards for hydraulic cylinders in the various mechanisms of mechanical equipment? The dust protection mechanism is in good condition; there are no leaks or jams, the movement is smooth, and the shaft pins are properly lubricated. 20. What are the correct installation conditions for helical gear drives? The module must be equal, the helix angle must be opposite, and the pressure angle must be equal. 21. Which indicators can show the aging of oil products? ①Oil condition aging ； ②Viscosity aging ； ③Significant change in acid value ； ④Increase in impurity content ； ⑤The anti-emulsification property deteriorates. 22. Briefly describe the function of the pressure tank in an oil film bearing lubrication system ①Absorb pressure fluctuations ； ②Provides temporary oil supply to the oil film bearing in the event of a pump failure or emergency shutdown, to prevent damage to the oil film bearing