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Annual Assessment Questions for Water Pumps in Oxygen Production Plants I. Fill-in-the-blank questions: (1 point per blank, 35 points in total) 1 When the flow rate is low and the pressure is high, reciprocating water pumps are suitable. When the flow rate is high and the pressure is low, axial or mixed-flow pumps are suitable. 2 For water pumps with high flow rates, double-suction pumps are commonly used, while multi-stage pumps are preferred for high-pressure applications. The suction head of the 3 pumps will not exceed 10 m, and for every increase of 10 m in the discharge head, the outlet pressure increases by 0.1 MPa. 4 The function of the water ring vacuum pump is to evacuate water; its working medium is air, while the auxiliary medium is water. Its working principle belongs to that of a positive displacement water pump. 5 Methods to prevent cavitation in water pumps include increasing the inlet pressure or selecting an appropriate installation height, reducing inlet resistance or enlarging the suction pipe diameter, operating at a low head, and using hard materials or epoxy coatings. 6 A water cooling tower consists of components such as a water distributor, packing, and fans, among which the packing is what increases the heat exchange area. 7 There are two factors that cool water in a cooling tower: heat exchange between the water and air, and the heat absorbed during water vaporization. In 8 centrifugal water pumps, water always enters axially and exits radially; therefore, the direction of rotation of their shafts can be determined based on their shape. 9 Check valves come in various types such as gravity or lift-type, as well as weight-activated swing-type ones; their function is to prevent the water pump from running in reverse and to stop water from flowing back. 10 The blowdown rate of an open-loop circulating cooling water system is related to the concentration ratio and turbidity. The amount of water to be added should be adjusted according to the amount of wastewater discharged and the amount of water that evaporates. Excessive water addition will cause water to be discharged through the overflow pipe, reducing the concentration ratio. 11 The concentration ratio of circulating cooling water is the ratio of the salt content in this circulating water to the salt content in its make-up water. II. True or False Questions: (1 point per question, 15 points in total) 1. The characteristic of an S-type pump is that both its suction inlet and discharge outlet are located below the axis of the pump shaft. (§) 2. The cooling process of water in the cooling tower mainly takes place in the wetting fill. (§) 3. The corrosivity of cooling water decreases as the pH value increases. (§) 4. Sulfate is a corrosive ion. (§) 5. The flow rate of a pump when operating alone is greater than the flow rate of each pump when they operate in parallel. (§) 6. As the viscosity of the liquid pumped by the water pump increases, the shaft power required by the pump also increases. (§) 7. The head of the water pump can be determined by reading the pressure gauge at the outlet of the running water pump. ( ×) 8. Increasing the concentration ratio can help reduce the amount of water treatment chemicals required, so the higher, the better. ( × ) 9. Dissolved oxygen plays both a corrosive and a corrosion-inhibiting role in circulating water. (§) 10. Installing check valves on the pressure water pipes can prevent water hammer. ( × ) 11. The values of absolute pressure and relative pressure are always positive. ( × ) 12. The shaft power of a water pump is always greater than its useful power. (§) 13. To ensure that the shaft seal does not leak, the packing gland should be tightened as much as possible. ( × ) 14. There is a drain screw hole at the bottom of the pump to allow water to be drained when the pump is stopped for maintenance. (§) 15. In addition to its function of reducing leaks, the leak reduction ring also serves to withstand wear. (§) III. Essay Questions: (Total 50 points) 1. Please list the reasons for sludge formation in heat exchangers within circulating water systems, its hazards, and the methods for dealing with it. (10 points) The sludge in the heat exchangers of circulating water systems consists mainly of dirt and microbial secretions; the dirt comes from dust in the air and suspended particles in the make-up water, while the microbes originate from the soil (2 points). A large amount of sludge accumulates on the walls of the heat exchanger in the cooler, which affects the heat exchange efficiency, reduces the equipment’s production capacity, and in severe cases forces the equipment to be shut down for cleaning. (2 points) Additionally, a large amount of sludge adheres to the surface of the heat exchanger, preventing the chemical treatment agents from reaching the equipment and thus preventing the corrosion and scale inhibition agents from functioning. (2 points) The most serious hazard associated with the accumulation of sludge is the electrochemical corrosion caused by the lack of oxygen beneath the scale, namely under-scale corrosion. This can lead to localized corrosion and perforation of the metal in a short period of time, posing a significant threat to the stable operation of the equipment. (2 points) The treatment method involves alternating the use of two different biocides to sterilize, remove algae, and disinfect the circulating water, as well as to suppress sludge formation (2 points). 2 2 What are the steps involved in chemically cleaning a running circulating water system? (10 points) Answer: Sludge stripping treatment (3 points). Removal of rust and scale (3 points). Pre-coating treatment (4 points). 3 3 The deep well pump is scheduled to be shut down due to certain issues, which will result in a disruption in water replenishment to the circulation tank for approximately 8 hours. What should be done in this situation? (10 points) Before planning the shutdown, adjust the water level in the circulating pool to the highest controllable level. (4 points) During the shutdown of the deep well pump, close the system’s drain valve and those used for non-production purposes, to ensure that the water level in the tank remains within a safe operating range. (2 points) Backwashing of the filter should not be performed unless under special circumstances. (2 points) Closely monitor the water level in the tank; in case of an emergency, immediately inform the workshop management and report to the dispatcher promptly. (2 points) 4 4 The water pump in operation suddenly stops due to a power outage, and the backup pump starts automatically. What should be done in this situation? (10 points) First, turn the self-priming pump back in the operating direction, and turn the pump that is not in use back to the shutdown position. (5 points) At the same time, disable the backup interlock for the self-priming pump and put the pump that is not in use in standby mode (after power is supplied). Workshop 5 checks the operation of valves and pumps using the PLC. (3 points) If the electric valve fails, the outlet valve should be closed manually. (2 points) Who are the main users of this pumping station? What effects do changes in water quality and water temperature have on these users? (10 points) User (5): Effects include increased resistance in the heat exchanger, scaling, and corrosion (3 points), which reduce the heat exchange efficiency of the heat exchanger; in severe cases, this can lead to shutdown failures. (2 points)