Diffusion pump gas pumping system
The composition of the pumping system of the diffusion pump:
The front-stage pump of diffusion pump pumping system can be combined with roots pump-rotary vane pump, roots pump-sliding valve pump, single rotary vane pump or roots pump. The oil diffusion pump pumping system has the advantages of simple structure, convenient operation, long service life and low price. It is the most widely used vacuum acquisition equipment at present.
The diffuser pump system can be properly equipped with some sensors, when in case of operating errors or leakage of the system, poor cooling, and the lack of diffusion pump fluid, these sensors can signal the system to be switched off or make the system in a safe state. The pneumatic valves and solenoid valves in the vacuum system should be able to act immediately when the equipment fails, so that the system is in a safe state. When compressed air or power fails, all valves except the purge valve of the crude pump should be closed. The crude pump bleed valve should be opened to prevent mechanical pump oil from returning to the rough pipe. A flowmeter can be installed at the outlet of the diffuser cooling water pipe instead of the inlet. With the help of the flow meter signal, the system controller can cut off the power supply of the diffusion pump, and close the high vacuum valve and the front pipe valve.
A water filter is used at the inlet of the diffuser cooling water pipe to prevent fouling and water plugging, and to avoid premature overhaul. The temperature of the pump wall and the pump oil can be detected by the thermostatic switch and the heat sensitive switch installed on the outside of the pump shell of the diffuser pump, and the liquid surface of the working fluid can be monitored. The set value on the thermocouple or the pin controller gives the automatic controller signal when the vacuum chamber is leaking, so that it closes the high vacuum valve and disconnects the power supply at the front stage when there is an excessive front stage pressure. Many liquid nitrogen devices are equipped with sensors with low liquid level alarm and turn off the high vacuum valve when the refrigerant is exhausted.
Because the diffusion pump has no running parts, the maintenance is simpler. The general pump should be replaced with a new oil after the use of 500h. When oil is changed, maintenance is carried out at the same time. Maintenance is to thoroughly clean the pump core, pump body, remove the fouling on the oil pan, and blow the rust out of the cooling pipe with compressed air. If the heater is a general bare electric furnace, it will be replaced once with 500h. If it is a closed heater, the life of the heater can be greatly extended, and it is not necessary to replace it regularly until it is replaced.
The diffusion pump usually uses KSl to KS3 diffusion pump oil, and the normal use is about half a year. In order to reduce the oil return rate, 274~275 silicone oil can be used. Under normal working conditions, the oil will be changed for another 2~3 years. The correctness of the assembly and adjustment of the diffusion pump will directly affect the performance of the pump. The parts should be cleaned and kept clean before assembling. Before assembly, the parts must be thoroughly dried. When assembly is not used directly to touch the core of the pump, the assembly of the pump core must be correct and must not be skewed to any side. After assembly, the distance between the nozzle and the wall of the pump is measured. When you are in the tank, you should measure the oil well outside and do not look at the depth, so as to ensure that the amount of oil meets the requirements.