Addtime： 2020-07-16 Browse times： 2326
Rotary vane vacuum pump has high cost performance, strong technical reliability and long service life, which are important factors for the continuous success of rotary vane vacuum pump for many years. Years of compression experience and excellent pumping capacity for all kinds of gases are the most significant features of this kind of pump. Since the rotary vane vacuum pump running according to the internal compression principle is oil lubricated and sealed, the main factors affecting the reliability and life of the pump are the erosion of steam and chemicals in the pump and the aging of lubricant. So, what problems should we pay attention to when we use rotary vane vacuum pump?
1、 Steam extraction
Most rotary vane vacuum pump manufacturers will specify the steam tolerance of the equipment HPA or the steam capacity of what g / h. This information refers to water vapor. When the air ballast valve is open and the vacuum pump is at the working temperature, if the inlet pressure is lower than the given value, the water vapor pumped out can not be condensed. In the drying process, the size of the pump is not determined by the pump speed according to the amount of steam, but by the amount of water collected per unit time. Therefore, it is imperative to preheat the pump for about 15 to 30 minutes using a closed vacuum side valve and an open air ballast valve to reach its optimum operating temperature (oil) (approximately 70-80 ° C). Only at the correct operating temperature can the steam be pumped out through the open valve. The delayed opening high vacuum valve can be easily integrated into the control system.
After the end of the pumping process, it is recommended to open the gas valve and let the vacuum pump continue to run for about 15 minutes, so that the residual steam in the pump can be discharged through the exhaust device. This process regenerates the working fluid to prevent standstill corrosion and possible pump failure.
The pump can be easily operated by integrating the front and rear controllers. If the system needs a pressure lower than 1 to 2 HPA, a double-stage rotary vane vacuum pump is needed. It should be noted that the steam tolerance and steam capacity of the two-stage rotary vane vacuum pump will be lower than that of the single-stage pump.
2、 Working fluid
In rotary vane vacuum pump, the working fluid (i.e. vacuum pump oil) mainly undertakes three important functions: sealing, lubricating valves and bearings, and transferring the compression and friction heat on the aluminum shell to realize the cooling of the pump body.
It is an important preventive and routine maintenance for all oil sealed vane pumps and vacuum pumps to maintain the oil level with transmission and lubricant. If the oil level drops too low, the pump system will no longer be lubricated. Due to the lack of lubrication, the pump system will be blocked, eventually leading to pump failure. If the oil level is too low, it will not be able to achieve the optimal dissipation of compression heat. Overheated pump will lead to rapid aging of working fluid, lack of lubrication and oil carbon formation will eventually lead to pump failure. Therefore, make sure that the oil level of the pump is not lower than the middle of the sight glass.
The color, viscosity and contaminants of the working fluid need to be checked regularly. If the water content in the working solution exceeds 5%, it will be milky white. This happens when the gas shock valve is closed, when the vacuum process is opened when the working fluid is still cold or when the maximum steam capacity is exceeded. The process of how the liquid turns black with the loss of working fluid. If the working fluid reaches the sixth color (from the left), it must be changed immediately. The variation range of working fluid color is suitable for P3 pump oil. In order to prevent this phenomenon, it is recommended to replace the vacuum pump oil every 12 months.
If the user is not sure whether the working fluid used is resistant to process gas, consult the manufacturer to determine the correct working fluid and pump design.
When the concentration of extracted oxygen is greater than the oxygen content in the air, mineral oil cannot be used due to oxidation and aging of working fluid. In this case, BAM certified special oil for oxygen must be used. At this time, please note that at the operating temperature of the pump, the working fluid used has a very low vapor pressure, so the required limit pressure can be achieved within the limit of the total pressure (vapor pressure of the oil).
3、 Dimensioning inlet and exhaust ducts
The nominal diameter of the inlet and outlet is designed by the manufacturer according to the maximum pump speed of the vacuum pump. Therefore, it is very important whether the nominal diameter of the inlet pipe and the vacuum pump is consistent, otherwise the pump speed will be seriously reduced due to the conductivity loss, especially in the range of molecular flow. The exhaust pipe should also be consistent with the nominal diameter of the pump. If the nominal size of the side is too small or the gas flow rate is too large, it will lead to unacceptable back pressure, which will bring continuous mechanical pressure to the vacuum pump, and lead to the increase of pump wear and failure. In addition, the noise level will increase significantly.
If the exhaust pipe extends upward, the lowest point of the exhaust pipe should be shaped like a siphon, so that the rising condensed steam in the pipe will not flow back to the pump body. The siphon can be emptied through the bottom outlet. In addition, in the exhaust pipe, the condensate separator can be installed 20-50 cm above the pump nozzle, which can also collect condensate. We do not recommend to install the filter directly on the exhaust pipe of the vacuum pump, because the heat of the pump body will be transferred to the condenser, resulting in reduced condensation effect.
4、 Adequate ventilation
Due to the compression operation of rotary vane vacuum pump, it is bound to release a certain amount of heat, so it is necessary to provide sufficient ventilation for it. If necessary, it is better to install another fan to ensure its normal heat dissipation. This is especially suitable for pumps installed in equipment or acoustic enclosures. If ventilation requirements cannot be achieved, the equipment may overheat and damage the pump.
Many of these instructions are also applicable to other types of vacuum pumps, such as roots pumps, diaphragm pumps and dry pumps.
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