Influence on Steam Jet Vacuum Pump and Analysis of Fault Factors

1, Introduction Steam jet vacuum pump suction capacity, wide range of work, simple structure, there is no relative movement of the components, is a widely used equipment "> vacuum equipment, mainly used in deaeration, bleaching, drying, deodorization, distillation, refrigeration And transportation, etc. In particular, it has no selectivity for inhaled gas and shows remarkable superiority to mechanical vacuum pumps (oil pumps) in food production, petrochemicals, oil processing, polyester production, and concentration of materials containing organic solvents Advantages of this paper on the steam injection vacuum pump factors were analyzed in order to provide a reference for its wide range of applications 2, the principle of steam jet vacuum pump steam jet vacuum pump is the use of fluid flow static pressure and kinetic energy conversion gas dynamics Principle to form a vacuum water vapor with a certain pressure through the Laval nozzle diameter to reach the speed of sound to the diffuser, the static pressure can be fully converted to kinetic energy to achieve supersonic velocity, while the nozzle outlet to form a vacuum, was pumping gas in the Under the effect of the pressure difference, it is drawn into the suction chamber and enters the venturi tube while being mixed with supersonic steam, After sub-sonic vent Venturi diffusion tube, while the mixed gas velocity decreased, the pressure then increased, and then discharged from the discharge port. If several jet pump in series, the pump and the middle of the condenser by adding Steam condensing, you can get a higher degree of vacuum.The entire steam jet vacuum pump consists of several levels of the pump body and the condenser composed of two parts.All the pump body by the nozzle, into the room and the diffuser composition, the nozzle can be a single , Can also be more, the nozzle is generally stainless steel, suction chamber and diffuser and other components can be stainless steel, cast iron and carbon steel and other materials.3, the main factors affecting the vacuum pump capacity 3.1, the working steam and its dry However, the structural design of the vacuum pump used has been finalized. Too much steam pressure increase will not increase the pumping pressure. Therefore, the steam pressure should not be lower than the required working pressure. Gas and vacuum.In addition, to ensure that the pressure of steam supplied by the boiler is stable, it is advisable to use a single boiler to provide working steam to the steam injection pump so that the steam pressure There will be fluctuations in the performance of the vacuum pump stable steam dryness on the performance of the vacuum pump also has a greater impact, including water will cause vacuum fluctuations, too much water or even can not afford to vacuum, the usual practice is to install soda before the separation In order to obtain the best working efficiency, the working steam provided for the jet vacuum pump should be superheated steam of 5 ° C. to 10 ° C. Especially, the grade 5 Pump, the steam quality requirements are very high, with trace moisture may cause the nozzle of the ice plug, resulting in the fifth stage ejector vacuum but declined or no effect. 3.2, the requirements of the circulating cooling water cooling water supply is insufficient , The condenser will heat, the sound of the air becomes larger, the degree of vacuum drops rapidly, and even the steam will return to the suction pipe. For the cold condenser between the pipes, the water supply pressure should be 0.2MPa and the water supply should be slightly larger than the actual amount A little, this water will be more stable fluctuations. 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, dryness, (3) Whether the circulating cooling water supply is normal, including the water temperature, water pressure, water quantity, water quality, etc. (4) Whether the production system is abnormal, including the system leakage, and the system (5) The vacuum pump system itself is faulty, including pump system leaks, nozzle clogging or damage, increased throat diameter wear, diffuser tube contraction section and the outlet fouling, the atmosphere of the legs Leakage or fouling blockage, condenser fouling blockage, suction pipe fluid and so on.