20100318 Weekly Questions for the Moving Equipment Technology Exchange Area – Issue 43

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This post was last edited by yxmqh on 2010-3-18 at 13:37. It is the 43rd installment of the theoretical question competition in the Mobile Equipment Technology Exchange Forum; to make it easier for participants to answer, the question types are multiple-choice and true/false, with the total number of questions increased to 25. Reply method: Hide reply! For easy scoring, leave a blank every 5 questions. For example: AAAAA BBBBB CCCCC. The method for hiding such content can be found at http://bbs.hcbbs.com/thread-492556-1-1.html. Any instances of spamming, plagiarism, or disruptive behavior will result in double deductions in points; in severe cases, posting will be prohibited outright. We ask all forum moderators to provide their support, and we also urge all users to supervise one another and abide by the forum’s rules conscientiously, while actively participating! Scoring method: 1 point per question; those who answer correctly to 20 questions or more will receive an extra charm reward! The top 30 participants will receive more points! True or False: 1. The ignition point refers to the lowest temperature at which a combustible substance, in the presence of sufficient air, will catch fire upon contact with a heat source, and will continue to burn even after the heat source is removed. ( ) 2. The upper tolerance and the lower tolerance are collectively referred to as limit dimensions. ( ) 3. The code for the basic deviation is represented by Latin letters, with uppercase letters indicating shafts and lowercase letters indicating holes. ( ) 4. Based on the relative position between the tolerance zones of the hole and the shaft, fits can be divided into clearance fits and interference fits. （ ） 5. In malleable cast iron, the graphite exists in spherical form. ( ) 6. Tempering determines the machinability and service life of rigid parts. （ ） 7. Stress-relief annealing is primarily used to eliminate stress concentrations in cast steel and forged steel. ( ) 8. The height vernier caliper belongs to the marking tools. （ ） 9. The dividing head can only be installed in horizontal or vertical positions; it cannot be used to draw reference lines when installed at an inclined angle. ( ) 10. Pitch is the distance between two corresponding points on the pitch diameter line of adjacent teeth. ( ) 11. If a bolt breaks and remains stuck inside the screw hole, it can generally be removed by drilling a hole in the bolt. ( ) 12. Excessive key clearance is mainly caused by long-term wear; during maintenance, it is necessary to measure the actual dimensions of the shaft slot and the hub, and then re-fit the key according to those actual dimensions. ( ) 13. The occurrence of key rolling is mainly caused by low precision in the fit between the keys, a large gap between the keys and their grooves, as well as an overly tight fit between the shaft and the hole. （ ） 14. A sealing structure with a throttle sleeve in the packing gland allows the high-pressure medium to have its pressure reduced after passing through the throttle sleeve, thereby enabling the packing to operate under medium-pressure conditions. ( ) 15. After the mechanical seal is installed, it is necessary to manually rotate the shaft to check that it turns smoothly. ( ) 16. When replacing the shaft of a centrifugal pump, it is necessary to check its dimensional dimensions, bending degree, and roundness; it can only be used after these checks confirm that it is in good condition. ( ) 17. When the requirement for contact between the grouting layer and the equipment base surface is low, shrinkage-free concrete is advisable. ( ) 18. When the bending direction of the centrifugal pump impeller is the same as the direction of its rotation, it is called a backward-curving blade. （ ） 19. The oil level in the bearing housing of a centrifugal pump is generally higher than that of the rolling elements. ( ) 20. The higher the discharge pressure of a steam reciprocating pump. Its traffic will also be greater. （ ） 21. Shielded pumps use lubricating oil to lubricate the bearings. （ ） 22. During operation, the driven screw in a triple-screw pump is driven by the driving screw. ( ) 23. Marking refers to the use of marking tools to draw the outline of the area to be processed, or points and lines that serve as references, on the blank or workpiece. ( ) 24. The function of a rolling bearing cage is to reduce friction and wear between adjacent rolling elements. （　） 25. The head of a multi-stage pump is the sum of the heads generated by each individual impeller. ( ) Published reference answers: Wrong Right Wrong Wrong Wrong Wrong Right Wrong Right Right Wrong Wrong Wrong Wrong Wrong Wrong Right Wrong Right