Add a spray device to the vacuum pump for testing. The spray device is a nozzle and a diffuser tube combination device. The power source uses the original vacuum pump outlet airflow. When the initial low vacuum is started, the ejector is not put in first, and when the vacuum reaches about 15KPAa (-75KPa), the ejector is put into operation, and the program control of the system is incorporated into the DCS.

1) The working principle of technical transformation: The atmospheric ejector introduces a steam flow of about 90KPa from the exhaust side (steam-water separation box), accelerates through the nozzle to form a high-speed airflow, and drives the gas in the suction port into the pump from the suction branch pipe. , So as to increase the suction pressure in the pump, reduce the cavitation of the pump, and achieve the purpose of stable operation. The modification of the mechanical part is mainly to remove the air intake tee of the original vacuum pump unit and install the ejector assembly.

After the transformation, the pump inlet vacuum was increased from 4.0~8.0kPa to 9.0~15.OkPa (absolute pressure) to eliminate cavitation in the pump.

2) Precautions: During the installation process of the atmospheric ejector, the inlet pipe filter of the original design is moved forward due to the cutting of about 700mm on the inlet pipe. If the welding is not strong or the impurities in the pipe are not cleaned thoroughly, the inlet pipe will be blocked. And the inlet pneumatic butterfly valve (16a) is jammed and the switch does not work. Before trial operation of the entire system, it is necessary to determine whether the switch status of each pneumatic butterfly valve is correct, so as not to affect the data collection and judgment after the atmospheric ejector is put into operation. The pressure measuring points in front of the pneumatic butterfly valve (16a) should be arranged according to the actual situation. Because the pneumatic butterfly valve is not strict, it will cause a low vacuum alarm and start the standby pump. It is recommended that the pressure measuring point be taken before the inlet gate valve of the vacuum pump (on the main pipe).

When the air temperature is low, water shock will occur in the atmospheric ejector. This is because the steam drawn from the condenser condenses here and forms water droplets. When the ejector is running, the impact sound will be heard on site (the interval is very long), this problem will not affect the safe operation of the vacuum unit.