This paper introduces the working principle of the steam jet vacuum pump, analyzes the main factors that affect the ability of the steam jet vacuum pump, and puts forward the troubleshooting methods, which can provide reference for its wide application. Article Aggregation: Steam Jet Vacuum Pump 1. Introduction The steam jet vacuum pump has a wide range of pumping capacity, wide working range, simple structure and no relative movement. It is a versatile vacuum equipment mainly used in degassing, bleaching, drying, deodorization, Distillation, refrigeration and transportation and so on. In particular, it has no selectivity for inhaled gas and shows superior advantages over mechanical vacuum pumps (oil pumps) in food production, petrochemicals, oil processing, polyester production and organic solvent concentration. In this paper, the influencing factors of steam jet vacuum pump are analyzed in order to provide reference for its wide application. 2, the principle of steam jet vacuum pump Steam jet vacuum pump is the use of fluid flow when the hydrostatic pressure and kinetic energy conversion of the principle of gas dynamics to form a vacuum. The water vapor with a certain pressure reaches the speed of sound through the throat radius of the Laval nozzle. When it reaches the diffusion part of the nozzle, the static pressure can be completely converted into kinetic energy to achieve supersonic speed while a vacuum is formed at the exit of the nozzle. , Is drawn into the suction chamber and mixed with the supersonic steam while entering the venturi tube and then expelled from the Venturi diffuser tube at subsonic velocities while the velocity of the mixed gas is gradually reduced and the pressure is then increased and then discharged from the vent discharge. If several injection pumps are used in series, a condenser is added between the pump and the pump to condense the steam to obtain a higher degree of vacuum. The entire steam jet vacuum pump by several pump body and condenser two major components. Pumps at all levels are composed of nozzles, baffles and diffusers. The nozzles can be single or multiple. The nozzles are made of stainless steel. Other components such as suction chamber and diffuser can be made of stainless steel, cast iron and carbon steel Other materials. 3, the main factors affecting the ability of the vacuum pump 3.1, on the work of steam and its dryness Low steam pressure and pressure fluctuations have a greater impact on the ability of the vacuum pump, steam pressure should not be less than the required working pressure, but Vacuum pump structure design has been stereotyped, too much to improve steam pressure and will not increase the amount of vacuum and vacuum. In addition, to ensure that the steam pressure supplied by the boiler is stable, it is advisable to use a boiler to provide working steam to the steam jet pump so that the steam pressure will not fluctuate and the performance of the vacuum pump will be stable. The dryness of the steam also has a greater impact on the performance of the vacuum pump, in which water will cause vacuum fluctuations, excessive water or even can not afford to vacuum, the usual practice is to install a steam separator before the drum to obtain higher dryness Working steam, while steam pipe insulation effective insulation. In order to obtain the best working efficiency, the working steam provided for the jet vacuum pump should be superheated steam of 5 ℃ ~ 10 ℃. In particular, five pumps, the steam quality requirements are very high, with traces of water may cause nozzle clogging, resulting in the fifth stage ejector vacuum but declined or no effect. 3.2, the study of the requirements of the circulating cooling water cooling water supply is insufficient, the condenser will heat, the sound of the air flow becomes larger, the degree of vacuum drops rapidly, and even the steam will return to the suction pipe. For inter-tube cold condensers, should ensure that the water supply pressure is 0.2MPa, water supply should be slightly larger than the actual amount, so the water fluctuations will be relatively stable. In addition, in order to avoid instability caused by fluctuations in water supply, it is best to use a separate circulating water system on the vacuum pump condenser water supply. Cooling water temperature is too high, the vacuum pump capacity will decline, and sometimes even can not afford to vacuum, generally not more than 32 ℃. In addition, the higher the cooling water temperature, the more steam consumption. Cooling water quality on the vacuum pump capacity is also a factor that can not be ignored, if the water quality is poor, high hardness, will cause the condenser fouling or clogging, seriously affecting the heat exchange performance, making the steam difficult to condense, thus affecting the degree of vacuum. So should ensure that the circulating cooling water is pure demineralized water. 3.3, the vacuum pump system sealing requirements of the vacuum pump at the limit state, the first stage of discharge of water is very small, sometimes not even. Therefore, the first stage pump discharge large amounts of water, it can be considered a system leak. Common causes of gas leakage are: gaskets did not install, installed the wrong or damaged, the bolts are not tightened, the flange surface damage, weld trachoma, joints (pressure gauges, vacuum gauges, etc.) are not installed. The most common method of checking leaks is that the entire system is exposed to pressurized air and painted with soap and water throughout. If there is a leak, the leak will have bubbles, and sometimes even hear the sound of the leak. The final requirement for testing for leaks is to conduct a vapor tightness test of the vacuum system (including the pump body and the leg of the atmosphere) with 0.2 MPa compressed air, with a pressure drop of 4.8% or less over a period of 24 hours. 3.4. Requirements for Nozzles The nozzle is an important component that affects the performance of the vacuum pump. The problems are: mis-fitting of nozzles, crookedness, clogging, damage, corrosion and leakage. No matter what preventive measures are taken, nozzle clogging is inevitable. On the one hand, when the steam pipe is installed, the remaining iron filings and slag in the pipe will clog the nozzle; on the other hand, when the vacuum pump system is disabled, the steam pipe is prone to rust and the rust drops and blocks the nozzle when in use. In general, the first and second stage nozzle larger aperture, easy to plug, the most easy to plug the nozzle is the first 3,4,5 level. The nozzle clogging can be confirmed by touching the temperature of the pump head and the condenser. 4, steam jet vacuum pump troubleshooting Steam jet vacuum pump in the course of the vacuum pump sometimes appear too long, the vacuum is not stable or reach the vacuum requirements of the situation, must find the cause of the failure, analysis and processing. The following fault analysis is usually performed: (1) Whether the vacuum measuring device (including the vacuum gauge, vacuum gauge, test cover) has any fault or failure; (2) Whether the working steam supply is normal and includes pressure, temperature, (3) Whether the circulating cooling water supply is normal, including water temperature, water pressure, water quantity, water quality, etc .; (4) Whether the production system is abnormal, including System leakage, excess gas generated by the system, degradation of process equipment, etc .; (5) whether the vacuum pump system itself is faulty, including pump system leakage, nozzle clogging or damage, increased pipe diameter wear and tear, Fouling, leakage or foul air leg blockage, condenser fouling blockage, suction pipe fluid and so on.