NEWS & BLOGS

NEWS & BLOGS

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2021-01-18

What are the solutions for smoking and oil spraying in vacuum pumps?

1. Smoking: If smoking occurs right after the pump is first started up, this is normal. However, if smoking persists for an extended period, it’s abnormal. The solution: Smoking indicates that there’s a repair or leak somewhere outside the pump’s intake port—such as in the pipelines, valves, or containers. Once the leaks are located and repaired, the smoking will stop. 2. Oil喷射: This indicates numerous leaks outside the intake port, possibly even with the intake port directly exposed to the atmosphere. The solution: Seal the pump’s intake port and run the pump. If no oil is sprayed, it means there’s a leak. Alternatively, the exhaust valve flap may be damaged; check whether the exhaust valve flap is broken and replace any damaged flaps.

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2021-01-18

Maintenance methods for rotary vane vacuum pumps

1. First, you need to understand the type, characteristics, and current status of rotary vane vacuum pumps. Familiarize yourself with the usage requirements and determine the repair objectives. Before starting the repair, prepare the necessary testing tools. 2. Identify and confirm the fault. Accurate identification can save time and effort. Confirmation requires verification. 3. Eliminate the fault step by step—start with simple issues before tackling complex ones, and address easy problems before difficult ones. Avoid disassembling components that don’t need to be removed. This reduces the risk of new damage caused by lack of specialized tools or improper handling, as well as minimizing positional changes and running-in periods. Generally speaking, split-type rotors are non-disassemblable; otherwise, geometric tolerances cannot be maintained, and the rotor will become unusable. 4. For pumps containing toxic, harmful, or corrosive substances, ask the user to clean them first and provide necessary protective measures to ensure the safety and health of maintenance personnel. 5. Classification of Rotary Vane Vacuum Pump Faults It is recommended to categorize faults into operational faults and performance faults. Operational faults may include the pump failing to start, excessive pump temperature, oil leakage, water leakage, and exceeding the maximum power rating. Performance faults may include failure to meet or satisfy requirements for ultimate pressure, full-pressure limit, pumping efficiency, noise levels, oil misting, and gas ballast performance. 6. Examples of Fault Identification and Diagnosis (1) The pump fails to start. If the situation is unclear, do not attempt to start the pump immediately, as this could worsen the problem. Determine whether the pump can be turned manually or not. ① If the pump can be turned manually but does not start, possible causes include coupling failure, belt slippage, incorrect motor wiring, motor damage, or no power supply. ② If the pump cannot be turned at all or turns very heavily, possible causes include excessively low starting temperature, overly high viscosity of the pump oil, or excessive backflow due to design or manufacturing defects. Excessive backflow can also result from too-high oil levels (due to overfilling, condensation of moisture in the pump, or condensation of water flowing back into the pump through the exhaust pipe). Foreign objects inside the pump—such as welding slag or oxides from the intake pipe, debris from pump parts like vane springs, deformed vanes getting stuck, or mechanical seizure (e.g., between copper sleeves, rotors, middle walls, pump covers, stators, and bearings)—may also cause this issue. (2) Excessively high pump temperature. This refers to the highest oil temperature measured near the low-stage exhaust valve exceeding the value specified in the instruction manual. As the pump temperature rises, the viscosity of the pump oil drops significantly, increasing its saturation vapor pressure, which in turn raises the ultimate pressure and reduces pumping efficiency. It also accelerates aging of rubber components and causes thermal expansion, reducing operating clearances—especially in the thickness direction of certain non-metallic vanes and the clearance between the inner bore of copper sleeves. All these factors can compromise the reliability of pump operation. Reasons for excessively high pump temperatures may include excessively high ambient temperature, excessively high intake air temperature, failure of the intake cooling system, prolonged continuous operation at a high inlet pressure, insufficient cooling water flow in water-cooled pumps, poor design effectiveness of the circulating water system, or failure of the temperature-controlled water flow regulating valve. (3) Oil leakage. Leakage can occur at shaft seals, sealing surfaces between the oil tank and pump components, drain plugs, oil level indicators, plugged oil holes, connections between stator components and supports, gas ballast valves (e.g., 2X-8), and other areas. Causes may include aging of sealing elements, improper installation, damage or failure of seals, uneven surfaces, impurities, roughness, or porosity in castings. If the pump stops and oil flows back, it may enter the gas ballast valve; leaving the gas ballast valve open could lead to oil leakage. When making rubber gaskets yourself, always use oil-resistant rubber and follow the original design shape. If the sealing surface is too large, it won't seal tightly and may leak. (4) Water leakage can occur at pipe joints, the flat surface of the water jacket cover, drain plug screws, drain valves, etc. Leaks may also result from drilled-through water jackets, casting defects, or frost cracks. (5) Exceeding the maximum power rating. This can be caused by prolonged continuous operation at excessively high inlet pressure, excessively high exhaust pressure, foreign objects entering and causing mechanical seizure, excessively high pump temperature, too-small clearance between mating parts such as vanes, excessively high voltage, or excessive liquid returning into the pump. Such conditions can damage the motor. Try to avoid prolonged continuous operation near the maximum power rating. If there are deposits on the surface, periodically disassemble and clean them. (6) Failure to meet the ultimate pressure requirement. This can be caused by external leaks, internal leaks, blocked oil passages, poor quality or contamination of the pump oil, presence of condensable substances like moisture, distorted instrument readings, or abnormal pump operation. When external leaks are severe, white vapor may be visible at the exhaust port. There will be more bubbles at the oil level indicator, and you can feel exhaust pressure when placing your hand near the exhaust port. More bubbles will appear at the low-stage exhaust valve. Power consumption may increase slightly. In such cases, first check whether the gas ballast valve is fully closed. Since every new pump is tested for ultimate pressure at the pump outlet upon manufacture, if external leaks are present, inspect the pump outlet, pipelines, valves, and containers one by one. External seal failure, empty oil cups, or leaking plugs at oil holes can also cause external leaks. Internal leaks may arise from wear in moving clearances within the pump, the plane of the exhaust valve seat, the sealing surface of the exhaust valve, the internal shaft seal, the pump cover plane, the intake pipe, or the sealing elements of the gas ballast valve. Wear, corrosion, and mechanical seizure can increase operating clearances. When oil passages are blocked, opening the oil filling hole will reveal lighter pump noise. If the oil tank is well-sealed and you feel suction when placing your hand near the exhaust port, the exhaust valve might have failed.

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2021-01-18

How do you change the oil in a rotary vane vacuum pump?

(1) Remove the rotary vane vacuum pump from the vacuum system, raise the end of the base motor slightly, open the drain plug to release the old oil, then rotate the vacuum pump while holding your hand over the exhaust port, allowing all the dirty oil inside the chamber to drain out through the drain port. Next, add 100–500 ml of fresh oil through the inlet port, continue rotating the pump for at least 5–10 turns, and repeat this cleaning process 3–5 times. Once the heavily contaminated oil has been completely drained, reattach the drain plug, place the pump back on a level surface, and add fresh oil separately through both the inlet port and the oil-filling hole. The oil change is now complete. (2) When changing the oil, avoid running the motor for extended periods to prevent excessive and fatigued movement of the exhaust valve vanes. (3) It is strictly forbidden to use kerosene, gasoline, alcohol, or other similar substances to clean the pump without disassembling it. Note: The best time to change the oil in a rotary vane vacuum pump is when the oil temperature has been raised.

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2021-01-18

Points to Consider When Selecting a Vacuum Pump

The working pressure of a vacuum pump should meet both the ultimate vacuum and the operating pressure requirements of the vacuum equipment. Generally, the vacuum level of the selected pump should be half to one order of magnitude higher than the vacuum level required by the vacuum equipment. Each type of pump has a specific operating pressure range. Therefore, the pump’s operating point should be chosen within this range and must not be allowed to operate for extended periods outside the permissible working pressure limits. Whenever possible, the vacuum pump should be operated within its high-efficiency zone—specifically, in the region corresponding to the critical vacuum or critical exhaust pressure. Operation near the maximum vacuum or maximum exhaust pressure should be avoided. Operating in these regions not only results in extremely low efficiency but also leads to unstable operation, making the pump prone to vibration and noise. For vacuum pumps with higher vacuum levels, operating within this region often triggers cavitation—a phenomenon clearly indicated by noise and vibration inside the pump. Cavitation can cause damage to components such as the pump body and impeller, ultimately rendering the pump inoperable. Select a vacuum pump that is appropriately matched to the gas flow rate and desired vacuum level. The pump must be capable of achieving the vacuum level required for production and able to evacuate all gases generated during the vacuum equipment’s process at its operating pressure. When selecting a vacuum pump, it is essential to know the composition of the gas being pumped—whether it contains condensable vapors, particulate dust, or corrosive substances. Choose a pump that is specifically suited to the gas being handled. If the gas contains vapors, particles, or corrosive components, consider installing auxiliary equipment, such as condensers or dust collectors, on the pump’s inlet pipeline. Additionally, take into account the cost of the vacuum pump itself, as well as its operating and maintenance expenses. Where permitted by usage conditions, prioritize selecting a vacuum pump that offers excellent performance at an affordable price.

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2021-01-18

Maintenance and Usage Precautions for Vacuum Pumps

With the advancement of economy and technology, vacuum pumps are finding increasingly broad applications and playing a crucial role in various industrial processes, including vacuum filtration, vacuum water lifting, vacuum material feeding, vacuum evaporation, vacuum concentration, vacuum rehumidification, and vacuum degassing. Moreover, vacuum pumps feature a compact structure, reliable operational balance, and uniform flow rates. However, their efficiency is relatively low—primarily because the impeller consumes a significant amount of energy during the process of stirring liquids. Over prolonged use, certain components of the vacuum pump may suffer damage. When the extent of damage reaches a certain level, the pump will start emitting screeching noises and vibrations. A major cause of this issue is wear on the pump’s motor bearings or shaft. Therefore, it is essential to regularly inspect all pump components and replace any damaged parts. Additionally, if solid particles enter the pump chamber and cause blockage, this can also lead to similar symptoms; thus, it is necessary to thoroughly clean out any debris from the pump chamber. If the pump body and the motor shaft’s centerlines are not properly aligned before use, the coupling is likely to wear prematurely, eventually resulting in noise and vibration. Hence, it is critical to ensure that the pump body and motor shaft’s centerlines are accurately aligned—and replacing the coupling may also be required in such cases. Another situation that can cause noise and vibration in vacuum pumps occurs when the vacuum level becomes excessively high. In such cases, the noise tends to be particularly harsh and piercing. Therefore, if you hear an ear-piercing sound, it is highly probable that the vacuum level is too high. To address this, simply open the pump’s air relief valve to allow some air to enter the system.

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2021-01-18

A detailed explanation of vacuum pump knowledge—what do you already know about it?

Detailed Explanation of Vacuum Pump Knowledge 1. Vapor Capacity of a Vacuum Pump: The unit for vapor capacity is kg/h, which refers to the mass flow rate of vapor that the pump can remove under normal operating conditions when the gas ballast pump is running continuously. 2. Pumping Speed of a Vacuum Pump: The unit for pumping speed is m³/s or l/s. It represents the ratio of the gas flow rate passing through the test hood—when the pump is equipped with a standard test hood and operated under specified conditions—to the differential pressure measured at a designated location within the test hood. This is commonly referred to as the pump’s pumping rate. 3. Ultimate Pressure of a Vacuum Pump: The unit for ultimate pressure is Pa. It refers to the highest stable working pressure achieved by the pump under normal operating conditions, with a standard test hood installed at the pump outlet and operated according to prescribed procedures, without introducing any additional gases. 4. Backflow Rate of a Vacuum Pump: The unit for backflow rate is g/cm²·s. It indicates the mass flow rate of pumped gas passing through a unit area at the pump outlet when the pump is operating under specified conditions. 5. Pumping Speed Coefficient: This is the ratio of the theoretical pumping speed of the pump to its actual pumping speed calculated based on molecular effusion at the pump outlet.

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