Pollutant Sources and Elimination Measures of Oil Diffusion Pump Vacuum System

Oil diffusion pump pumping system, the biggest drawback is the oil vapor pollution. The main sources of pollutants in the system are as follows: (1) diffusion pump oil vapor reflux. This is the most significant source of pollution. (2) parts of the system, with the hand holding the oil in the assembly. Use oily gloves to hold, so sticky organic molecules can cause contamination within the system. (3) Pre-seal mechanical pump oil backflow. This problem is also very serious. When the inlet pressure is high, when the pressure in the transition zone (1 ~ 10-1Pa) is reached, the oil vapor of the mechanical pump can directly enter the diffusion pump to directly pollute the system. Many of the vacuum process pollution from the mechanical pump to return oil. When stopping the mechanical pump if not promptly to the pump to enlarge the air, mechanical pump oil can directly return to the diffusion pump pan. When the diffusion pump starts to poll the system more seriously. (4) The pollution caused by the deflation of the sealing material in the extraction system. In particular, artificial rubber seals, sealing grease, lubricants, also caused serious pollution. (5) When the pump is stopped and the atmosphere is enlarged, the vacuum components will stick to the steam, fume and so on in the air to cause the pollution to the vacuum system. Specific measures to eliminate the system vapor reflux: (1) increase the start-up power of the diffusion pump to shorten the pressure transition zone when the mechanical pump and diffusion pump switch. (2) Avoid the danger zone of backflow by changing the system operation technology and using the valve (to switch the transition zone). For example, a high vacuum valve that opens at a predetermined speed may be gradually turned on to ensure that the flow of gas into the diffusion pump is below its maximum displacement, and that the mechanical pumping speed, in turn, ensures the pressure at the front of the diffusion pump to So that diffusion pump can establish a job. This will avoid the appearance of a transition zone. (3) to improve the operation process, the diffusion pump heating power adjusted to the best power to avoid the phenomenon of bump oil pump; general diffusion pump in the heating process begins and closed, reflux will peak, so available at the pump port High vacuum valve to control backflow. (4) Install a liquid hydrogen trap or adsorption trap at the inlet of the diffusion pump to capture the reflux oil vapor. (5) Selection of high-quality diffusion pump working fluid.