dry pump of principle

Turbine dry pump is a new type of dry pump which has been popularized rapidly in recent years. Because of its superior performance, it is rapidly replacing the traditional oil seal rotary vane pump in vacuum field, especially in vacuum equipment for scientific research.

The main advantages are as follows:

(1) high compression ratio and stable pumping speed in a wide range of pressure.

(2) simple structure and high reliability;rotary-vane-vacuum-pump

(3) the working pressure range is wide and the power change is small.

The basic principle of the turbo dry pump is that the gas is compressed in the crescent compressor cavity composed of the vortex rotator and the vortex stator, the vortex stator is fixed on the periphery of the rack, an air inlet is opened on the periphery of the vortex stator, and an air outlet is opened in the center of the vortex rotator and the vortex stator. The vortex lines of the vortex stator and the vortex rotator are basically the same. The two phases are staggered 180 degrees. As a result, a series of crescent compression cavities are formed between the two vortices. When the vortex rotator rotates, one side of the crescent compression chamber moves toward the center, and its volume side continuously decreases, thus completing the suction, compression and exhaust process of the turbine dry pump.vacuum-valve

Rotary vane vacuum pump

Rotary vane vacuum pump can extract the dry gas from the sealed container. If it is equipped with a gas ballast device, it can also extract a certain amount of condensable gas. But it is not suitable for the extraction of oxygen-rich, corrosive to metals, chemical reactions to pump oil, and gas containing particulate dust.

Rotary vane vacuum pump is mainly composed of pump body, rotor, rotary vane, end cover, spring and so on. A rotor is eccentrically installed in the cavity of the rotary vane pump. The outer circle of the rotor is tangent to the inner surface of the pump cavity (there is a small gap between the two), and two rotary vanes with springs are installed in the rotor slot.

When rotating, the tip of the rotary blade keeps contact with the inner wall of the pump cavity by centrifugal force and spring tension, and the rotary rotor drives the rotary blade to slide along the inner wall of the pump cavity.

Dry vacuum pump

Oil-free dry mechanical vacuum pump (also known as dry mechanical pump) refers to the pump can start to exploit under atmospheric pressure, but also directly injected into the atmosphere, no oil or other working media pump chamber, pump limit pressure and seal vacuum pump type of the same order of magnitude or close to mechanical vacuum pump.vacuum-valve

Vacuum industry uses most mechanical vacuum pump oil, water or other polymer fluids as the working medium of the pump, cooling pump seal, lubrication, etc. With the development of science and technology and expansion of the field of vacuum application of the original mechanical vacuum pump and its extraction system, there are two urgent problems: first, the working medium pump reflux contamination is pumped container, and in many cases this reflux affects the quality of products, quantity, increase the cost of equipment maintenance. Secondly, due to the reaction materials produced in some processes, the medium of the vacuum pump deteriorates seriously, so that the pump can not work properly.

For ordinary oil-free vacuum systems, although oil-sealed vacuum pumping units have cold traps or adsorption traps, such as accessories, to prevent reflux, but can not completely solve the problem, making the system appear complex. Suitable for drying machine vacuum pump suitable type, can achieve the desired results.air-cooled-roots-vacuum-pump-introduction

How to choose vacuum pump system

The function of the vacuum pump is to remove gas molecules from the vacuum chamber, reduce the pressure of the vacuum chamber gas, so as to achieve the desired vacuum. Generally speaking, there is a wide range from the atmosphere to very high vacuum, and so far no vacuum system can cover this region. Therefore, in order to achieve different product process indicators, work efficiency and equipment life requirements, different vacuum section needs to choose different vacuum system configuration. To achieve optimal configuration, the following points should be considered when choosing a vacuum system.

1. determine the scope of work vacuum.

First, you must check to determine the vacuum degree of each process requirement. Because each process has its own vacuum range, it must be carefully studied and determined.

2. determine the vacuum limit.

On the basis of determining the vacuum degree required by the process, the limit vacuum degree of the vacuum pump system is checked, because the limit vacuum degree of the system determines the best working vacuum degree of the system. Generally speaking, the limit vacuum of the system is 20% lower than the working vacuum of the system and 50% lower than the limit vacuum of the front pump.

3. Selection calculation of main vacuum pump

S = 2.303v/tlog (P1/P2), where: s for the vacuum pump suction rate, V for the vacuum chamber volume, t to achieve the required vacuum time, P1 for the initial vacuum, P2 for the vacuum requirements.

4. vacuum volume

Check the time required to achieve the required vacuum and flow resistance and vacuum tube leakage. Considering the requirement of vacuum degree, it is necessary to maintain vacuum rate under certain technological conditions.

5. types of pumping gas and gas extraction

Check and determine the suction and exhaust types of the process requirements. If the pump gas reacts with the liquid of the vacuum pump, it will pollute the pump system. At the same time, we must consider in the pumping process to determine the appropriate exhaust time and the amount of gas generated, how to choose the vacuum pump system.

liquid ring pump of Analysis

On the basic theoretical research of liquid ring pump, domestic and foreign experts and scholars based on the relevant theory of fluid mechanics, combined with the performance characteristics of liquid ring pump, put forward their own views, and used in practical design.

After detailed analysis of various parameters of liquid ring pump, it is pointed out that in liquid ring pump, the shape and position of suction and exhaust outlet, outlet angle beta of blade and circumferential velocity Mu have great influence on the performance of liquid ring pump. One of the keys to determine the shape of the suction and exhaust windows is to determine the outer boundary of the suction and exhaust windows, and the reasonable design of the outer boundary of the suction and exhaust windows must conform to the law of motion of the liquid ring, that is, to the inner boundary of the liquid ring.

Vacuum Unit

It is assumed that the fluid is an ideal fluid and that the gas pressure acting on the liquid in the impeller is constant during the steady motion of the fluid in a working cycle. The shape of the inner surface of the liquid ring can be determined by the fluid continuity equation of the liquid relative to the radial motion. Both are equal to the liquid flow in the impeller and, for the ideal fluid, the liquid is incompressible, so the gas flow in the impeller must be equal to the liquid flow outside the impeller.

Vacuum Parts

diffusion pump of Characteristics

For the general diffusion pump, the pump body is mostly made into a straight cylinder type; for large pumps, there is also a conical cylinder or convex cavity pump body. Because the cylinder pump body is easy to process, it is widely used at present.

The pump body with a diameter of D < 250mm is made of seamless steel pipe, and the pump body of the large pump is welded by coiling a cylinder of steel plate 4 ~ 10mm thick, and the weld seam can not leak. The inner wall of the pump should be polished and nickel plated.

The pump body of the convex cavity can increase the pumping speed without increasing the size of the pump port. The convex cavity pump body changes the straight cylinder pump body into a local drum shaped convex cavity pump body. The processing method is still welded by steel plates. The bottom section of the pump is the same as the inlet diameter of the pump flange, but the pump body enlarges the pump chamber at the lower part of the inlet flange, and the enlarged diameter extends to the pump wall where the second-stage nozzle jets directly. Because of the convex cavity of the pump body, the pumping space is enlarged, the conductivity between the first and second stage nozzles is increased, and the pumping speed is also increased.

Ultra high vacuum pump oil is also a very important problem. The improper surface temperature of the pump wall makes it difficult for the oil vapor molecules colliding on the inner surface of the diffusion pump to coagulate. The surface temperature of the oil layer flowing down the pump wall is higher than that of the pump wall, so it is easy to produce re-evaporation and form oil vapor reflux. Therefore, the cooling efficiency of the pump wall is high. Generally, the pump wall is welded with spiral copper pipe or made into a water jacket form (also can be fitted with spiral steel wire in the middle of the water jacket). The cooling part of the pump is usually confined to the area where the steam flow can be ejected, so that the oil condensed from the top receives a higher degree of heat before returning to the oil pan, so that the dissolved gas in the oil is released, so as to prevent it from mixing with the oil vapor into the nozzles at all levels, affecting the vacuum of the pump.

Dry vacuum pump

Limit pressure of rotary vane pump

Soon after the rotary vane pump started to work, the lowest pressure was P'g. The pump continues to operate, because the pump temperature rises, the saturated vapor pressure of the pump oil rises, the viscosity decreases, and the inlet pressure rises slightly back to Pg. Pg is the stable minimum pressure of pump and the ultimate pressure of pump.

The ultimate pressure of the rotary vane pump is related to the type of vacuum gauge used in the measurement. The limiting pressure ratio is measured by a heat conduction vacuum gauge (thermocouple or pioglitz gauge, etc.).piston-vacuum-pump-for-various-applications

The result of measurement is about one order of magnitude. This is because the former can only measure the partial pressure of the permanent gas, and the latter measured the total pressure of the compressed gas. In China, the compressibility vacuum gauge is used to measure the limit pressure of the oil seal mechanical pump.

The pump circulation oil also affects the ultimate pressure of the pump. With the increase of the oil quantity, the better the sealing effect, the relationship between the limit pressure of the pump and the oil quantity changes, and finally reaches the saturated vapor pressure Po of the oil. In fact, there is a lot of air and water in the pump oil. When the pump oil enters the pump chamber, the air and water absorbed in the pump oil are released again. The relationship between the pump limit pressure and the oil volume is developing upwards. The general pump oil should be kept at the designated oil level, so that the circulating oil volume of the pump must be maintained. For the two-stage pump, the pump oil must pass through the low vacuum stage degassing before entering the high vacuum stage, so as to reduce the pump oil in the high vacuum stage of the degassing volume, to reduce the pump limit pressure.liquid-ring-vacuum-pump-application-process-introduction

The ultimate pressure of the rotary vane pump is related to the working temperature of the pump oil. The higher the oil temperature, the higher the saturated vapor pressure of the oil, the higher the ultimate pressure of the pump.Liquid-Ring-Vacuum-Pump-Applications