Special lecture on mechanical equipment: “Pumps” – Learn a little every day (19): Rotary pumps “Improve yourself””

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This post was last edited by tclz007 on 2013-12-24 at 19:36. In order to encourage more active participation in discussions and a more proactive approach to learning, the top five users each time will receive a “Proactive Learning Reward”. Some people might think that it’s terrifying to spend their working days doing nothing, performing tasks that seem like menial chores, not knowing what to do or what to learn, day after day, year after year, with no vision for their future! We must start working hard from now on; even if we learn a little knowledge every day, it will add up over time and help us enrich ourselves. We need to set clear goals – only by filling our minds first can we enrich other aspects of our lives as well. . . . . . Just spend a short ten-odd minutes every day, and you will see the future! ! ! (Anyway, I have learned it; whether you learn it or not is up to you. Apart from those experts like Hai Chuan, there are still others who know it.) . . ) Enough talk – let’s start with the basics today~~! I’ve been posting special threads for so many days now; I’m sure everyone has benefited a lot from them. Thank you all for your support~~! Welcome everyone to listen. I have started broadcasting, and I hope those who, like me, want to gain knowledge every day will listen. Let’s learn together every day and discuss~~! These past few days, many people have asked questions, and I’ll do my best to answer them all. There may be some I haven’t encountered before, but there are still plenty of people in our community who can help answer them. @AidaiAmu @hcwang12345 @YiHuXiangMing @tjdxz @YouDianDai @NewbiesPlayingHaiChuan @LoveStory @ManTianYun @zhaoqingsheng Recently, vortex pumps have been introduced; I believe those interested in pumps now have a better understanding of rotary pumps!! From now on, I’ll try to break down the knowledge into smaller parts, in smaller amounts, to make it easier for everyone to learn*~~! Someone has asked me about rotary vane pumps these past two days! Today, I’ll explain rotary vane pumps to you all~~! It might not cover everything; if you have any questions, please ask on the floor. Thank you~~! Roots pump – Physical principles of roots pumps. A roots-type pump is a vacuum pump that does not involve internal compression; its compression ratio is usually very low, which is why high and medium vacuum pumps require a pre-pump. The ultimate vacuum of a Roots pump depends not only on the pump’s own structure and manufacturing precision but also on the ultimate vacuum of the pre-pump. To increase the ultimate vacuum of the pump, Roots pumps can be used in series. The working principle of a Roots pump is similar to that of a Roots blower. Due to the continuous rotation of the rotor, the gas to be pumped is drawn in through the inlet into the space v0 between the rotor and the pump casing, and then discharged through the outlet. Since the v0 volume is completely sealed after inhalation, the gas inside the pump chamber does not compress or expand. But when the top of the rotor passes over the edge of the exhaust port and space v0 becomes connected to the exhaust side, the higher gas pressure on the exhaust side causes some gas to flow back into space v0, resulting in a sudden increase in gas pressure. As the rotor continues to rotate, the gas is expelled from the pump. In a Roots pump, there are two rotor elements in an “8” shape that are mounted perpendicularly to each other on a pair of parallel shafts; they are driven by a pair of gears with a gear ratio of 1 to rotate synchronously in opposite directions. A certain gap is maintained between the rotors and between the rotors and the inner wall of the pump casing, which enables operation at high speeds. Features of rotary vane pumps: High pumping speed over a wide pressure range ； 　　Starts quickly and can begin working immediately ； 　　Not sensitive to dust and water vapor contained in the gas being drawn in ； 　　The rotor does not require lubrication, and there is no oil in the pump chamber ； 　　Low vibration, good rotor dynamic balance conditions, no exhaust valve ； Low driving power and low mechanical friction losses ； 　　Compact design with small footprint ； 　　Operating and maintenance costs are low. 　　Therefore, Roots pumps are widely used in the metallurgy, petrochemical, papermaking, food, and electronics industries. Working principle of the Roots pump The working principle of the Roots pump is similar to that of a Roots blower. Due to the continuous rotation of the rotor, the gas to be pumped is drawn in through the inlet into the space v0 between the rotor and the pump casing, and then discharged through the outlet. Since the v0 volume is completely sealed after inhalation, the gas inside the pump chamber does not compress or expand. But when the top of the rotor passes over the edge of the exhaust port and space v0 becomes connected to the exhaust side, the higher gas pressure on the exhaust side causes some gas to flow back into space v0, resulting in a sudden increase in gas pressure. As the rotor continues to rotate, the gas is expelled from the pump. The structure of a Roots pump: Inside the pump chamber, there are two rotor elements in an “8” shape, which are mounted perpendicularly to each other on a pair of parallel shafts. They are driven by a pair of gears with a gear ratio of 1 to rotate synchronously in opposite directions. A certain gap is maintained between the rotors and between the rotors and the inner wall of the pump casing, which enables operation at high speeds. Since a Roots pump is a vacuum pump without internal compression and typically has a very low compression ratio, high and medium vacuum pumps require a forepump. The ultimate vacuum of a Roots pump depends not only on the pump’s own structure and manufacturing precision but also on the ultimate vacuum of the pre-pump. To increase the ultimate vacuum of the pump, Roots pumps can be used in series. Instructions for the maintenance of rotary vane pumps:
1. Regularly check the quality of the oil; if it becomes deteriorated, replace it with fresh oil promptly to ensure proper operation of the rotary vane pump.
2. Frequently check the oil level. If it is not within the specified range, adjust it accordingly. The oil level should be at the center of the oil gauge when the pump is running.
3. The timing for oil replacement should be determined based on actual usage conditions and whether the performance requirements are still met. Generally, for new rotary vane pumps used to transport clean, dry gases, it is recommended to change the oil every three days or so. Once no black metal particles are visible in the oil, the interval between oil changes can be increased appropriately.
4. Check whether there is any looseness in the pipes and connections of the rotary vane pump. Rotate the pump by hand to ensure that it moves smoothly.
5. Fill the bearing housing with lubricating oil, making sure the oil level is at the center line indicated on the oil gauge. The lubricating oil should be replaced or topped up as needed.
6. Under normal circumstances, the rotary vane pump should be inspected and maintained after about 80 days of operation. Check the degree of aging of the rubber seals, verify that the exhaust valve plates are not cracked, and remove any debris accumulated on the valve plates and exhaust valve seats. Clean all components inside the pump chamber, such as the rotor, vanes, and springs. Gasoline is generally used for cleaning, followed by drying. Rubber parts can be cleaned and dried with a clean cloth. Handle these parts carefully during cleaning and assembly to avoid damage.
7. After reassembly, the pump should be tested before being put into operation. It is usually necessary to run it without load for two hours and change the oil twice, as some volatile substances remain in the pump after cleaning. Only after normal operation can the pump be used for its intended purpose.
8. Start the motor. Once the rotary vane pump is operating properly, open the outlet pressure gauge and the inlet valve. Once an appropriate pressure is displayed, gradually open the gate valve while monitoring the motor’s load. During operation, the temperature of the bearings should not exceed 35 degrees Celsius above the ambient temperature, with a maximum temperature of 80 degrees Celsius. Try to keep the flow rate and head of the pump within the ranges specified on the label, so that the pump operates at its most efficient point and maximum energy savings can be achieved. When stopping the use of the rotary vane pump, first close the gate valve and pressure gauge, then stop the motor. Follow these standard procedures.
9. Within the first month of operation, change the lubricating oil every three days or so. Thereafter, change it every 20 days or so. Adjust the packing gland periodically to ensure normal leakage from the packing chamber (leakage in the form of drops is ideal). Regularly check the wear on the shaft sleeves; replace them promptly if they are significantly worn. If the pump will not be used for an extended period, disassemble it completely, wipe away any dirt, apply grease to the moving parts and connections, and store it properly (keep it well-maintained and clean when not in use).
10. When using the rotary vane pump in cold weather, after stopping the pump, turn off the drain plug at the bottom of the pump to release any remaining fluid, thereby preventing freezing and cracking. This is my dedicated post; I will continue to update it daily. Please give me your support by listening and discussing it ； If there’s any direction that needs to be explained, feel free to contact me. If many people ask for it, I’ll create a dedicated post to cover it~~! A series of special lectures on mechanical equipment titled “Pumps” – a summary post featuring new knowledge each day, continuously updated at http://bbs.hcbbs.com/thread-1256318-1-1.html. Everyone is welcome to listen; I’ve already started broadcasting these lectures, and I hope those who, like me, want to gain knowledge every day will join us to learn together and discuss~~!