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1. Working principle of the water ring vacuum pump: The water ring vacuum pump is used to draw in gases that contain no solid particles, thereby creating a vacuum in the system being evacuated. The working medium is usually plain water at room temperature; if appropriate materials are used, it can also be employed for pumping other working media such as acids and alkalis. The impeller of a water ring vacuum pump is mounted eccentrically within the pump body. Before starting, a certain amount of working medium is filled into the pump. As the impeller rotates, the water is subjected to centrifugal force, forming a rotating water ring against the walls of the pump body. The blades and the side plates on either side (also known as distributors) create a sealed chamber. During the first half of the rotation cycle (when passing through the suction port), the volume of this sealed chamber gradually increases, allowing gas to be drawn in through the suction port. During the second half of the rotation cycle (when passing through the exhaust port), the volume of the sealed chamber gradually decreases, causing the gas to be expelled through the exhaust port; some water is also discharged along with the gas. After the discharged water vapor is separated in a gas-liquid separator, the water can be reused. 2. Startup and operation of the water ring vacuum pump: 1) Before starting, especially for pumps that have been out of use for a long time, it is necessary to manually rotate the coupling several times to ensure that the rotor can rotate freely. All water inside the pump must be drained before starting it ； 2) Oil level and oil quality – are they normal? ； 3) Fill the water tank to 2/3 of its capacity ； 4) Close the intake valve ； 5) Turn the pump supply valve 2-3 times (this can be adjusted according to actual conditions; strive to minimize power consumption) ； 6) Turn on the power switch (before starting it fully, test the motor first to check whether the rotation direction is correct) ； 7) When the pump reaches ultimate vacuum, open the valve on the intake pipeline, and the pump begins to operate normally ； 8) Adjust the water temperature in the tank promptly, ensuring that it does not exceed 40 degrees℃ ； 9) Adjust the packing gland so that water drips out in drops. When the vacuum pump operates at extreme vacuum levels, explosive noises may occur due to physical phenomena taking place inside the pump; however, the power consumption remains low. If explosive noises are heard as the power increases, it indicates that the pump has failed, and the pump should be stopped for inspection at that point. III. Parking: 1) Close the intake valve ； 2) After shutting off the pump’s water supply valve to stop the water flow, the pump should not be stopped immediately; it should continue to run for 1-2 minutes to allow some of the working fluid to be discharged ； 3) Turn off the motor switch. IV. Maintenance: 1) The packing should be tightened regularly to allow water to drip out, but not in large amounts; oil-impregnated asbestos rope should be used as the packing ； 2) Regularly check whether the vacuum gauge readings, oil level, as well as the vibration and noise of the pump are normal ； 3) Regularly check the temperature rise of the pump bearings; their operating temperature should not be 35°C higher than the surrounding temperature, and the actual measured temperature should not exceed 70°C. Two-thirds of the space inside the bearing housing should be filled with grease. For bearings in normal operation, oil should be added 3–4 times per year, the bearings should be cleaned at least once a year, and all the lubricating oil should be replaced ； 4) The water tank should be kept clean, free of any foreign objects. 3. Maintenance steps for water ring vacuum pumps: 1) Remove the guard, loosen the motor and its bolts, as well as the set screws holding the motor in place; move the motor towards the pump to loosen the belt (for coupling-driven pumps, disconnect the coupling). 2) Remove the V-belt, loosen the bolts securing the pulley; tap on the taper sleeve to loosen the pulley, then lift it up. Use a flat tool to wedge into the cracks in the taper sleeve in order to widen them, and pull the taper sleeve out. 3) Remove the bearing cover and the bolts that secure the bearings; loosen the bearing brackets, and use set screws to push both the brackets and the bearings out. 4) Loosen the flanges at the pump’s inlet and outlet, remove the bolts that hold the pump in place, and take out the pump’s foot bolts. Gently strike the end cover with a copper rod to separate it from the pump body, then move the end cover horizontally out of the way. 5) Remove the cylinder, secure the rotor, remove the other bearing cover, loosen the nuts holding the thrust bearing in place, pull out the thrust bearing, and remove the bearing bracket; use set screws to push the bearing out along with the bracket. 6) Lower the rotor, remove the disc from both end caps, and take off the check valve. 7) Clean the rotor, the two discs, and the end caps; clear the return holes and clean the check valves; replace them if they are worn or damaged. 4. Inspection and testing of various components: 1) Check for wear and corrosion on the impeller; replace it if the wear or corrosion is severe ； 2) Measure the bending of the shaft; the value at the middle of the shaft should be < 0.05 mm ； 3) The surface of the disc must be free from defects such as rust spots, cracks, and pitting; its roughness should be ≤ Ra1.6. 4) Before assembling the bearing, it is necessary to ensure that there are no defects such as pitting, scars, or burrs, and that it can rotate freely; after assembly, the radial clearance should not exceed 0.03 mm. 5) Packing seal: During installation, it is necessary to ensure that the water seal ring is aligned with the water holes in the sealing chamber; the packing dimensions must be correct, with cuts that are parallel and even, and no looseness present. The cuts should form a 30° angle with the axis of the shaft ； When compressing the packing, the packing joints should be staggered; typically by 120° ； The clearance between the gland and the shaft is (0.4–0.5) mm. 6) Mechanical seal: The perpendicularity of the contact surface between the gland and the gasket to the axis centerline is 0.02 mm ； The radial clearance between the gland and the shaft is 0.75–1.00 mm, and the thickness of the gasket between the gland and the sealing chamber is 1–2 mm ； The sealing compression amount is 3 mm greater than the shaft play ； The rotation direction of the mechanical seal ring spring should be opposite to that of the pump shaft ； 7) The parallelism between the motor pulley and the vacuum pump pulley is 0.4 mm. 8) The gap between the impeller and the disk is 0.4–0.5 mm. 5. Common faults and their solutions: 1) Insufficient pumping capacity: (1) Excessively large gap ； (2) Air leakage at the filler area ； (3) High water ring temperature ； (4) Air leakage in the piping system. 2) Decrease in vacuum level: (1) Air leakage in the piping system ； (2) Filler air leakage ； (3) Excessive clearance between impeller and gap ； (4) The water volume is not large ； (5) Frictional heating of the parts causes the water ring temperature to become too high. 3) Vibration or noise: (1) Friction caused by foreign objects inside the pump ； (2) Leaf drop ； (3) Cavitation ； (4) Loose fasteners.