# 14 Basic knowledges of air compressor and air?

2020-06-21 00:19:53 keepwin

## 1. What is the definition of the standard state of air?

Answer:The standard state is defined as the standard state of air when the air inhalation pressure is 0.1 MPa and the temperature is 15.6 degrees Celsius (the domestic industry definition is 0 degrees Celsius). Under the standard condition, the air density is 1.185kg/m3 (the capacity of air compressor exhaust, dryer, filter and other post-processing equipment is marked by the flow rate under the air standard condition, writing Nm3/min in units).

## 2. What is air? What is normal air?

Answer:The atmosphere around the earth, which we are used to call air. The air under the condition of specified pressure of 0.1 MPa, temperature of 20 C and relative humidity of 36% is normal air. Normal air differs from standard air in temperature and moisture content. When water vapor is in the air, once the water vapor is separated, the air volume will be reduced.

## 3. What are saturated air and unsaturated air?

Answer: At a certain temperature and pressure, the content of water vapor in wet air (that is, the density of water vapor) is limited; at a certain temperature, when the amount of water vapor reaches the maximum possible content, the wet air is called saturated air. Wet air is called unsaturated air when water vapor does not reach its maximum possible content.

## 4. Under what conditions does unsaturated air become saturated air?

Answer:What is "condensation"? And explain its phenomenon. When unsaturated air becomes saturated, liquid water droplets condense in wet air. This phenomenon is called "condensation". Condensation is a common phenomenon, such as the humidity of the air in summer is very high, it is easy to form water droplets on the surface of water pipes, and in winter morning, water droplets appear on household windows. These are the results of dew point temperature when humid air is cooled under constant pressure.

## 5. What does the partial pressure of water vapor in wet air mean?

Answer: Wet air is a mixture of water vapor and dry air. In a certain volume of wet air, the proportion of water vapor (by mass) is usually much less than that of dry air, but it occupies the same volume as dry air and has the same temperature. The pressure of wet air is the sum of the partial pressures of the constituent gases (i.e. dry air and water vapor). The pressure of water vapor in wet air is called partial pressure of water vapor, which is recorded as so. The value reflects the content of water vapor in wet air. The higher the content of water vapor, the higher the partial pressure of water vapor. The partial pressure of water vapor in saturated air is called the partial pressure of water vapor saturation, which is recorded as ab.

## 6. What is the humidity of air? How many kinds of humidity are there?

Answer:The physical quantity indicating the degree of dryness and humidity of air is called humidity. The commonly used expressions of humidity are: absolute humidity and relative humidity. Under the standard condition, the mass of water vapor in 1 m3 volume of wet air is called "absolute humidity" of wet air in g/m3. Absolute humidity only indicates how much water vapor is contained in wet air per unit volume, but it can not indicate the ability of wet air to absorb water vapor, that is, the humidity of wet air. Absolute humidity is the density of water vapor in wet air. The ratio of the actual amount of water vapor in wet air to the maximum possible amount of water vapor at the same temperature is called "relative humidity", which is commonly expressed in terms of phi. The relative humidity is between 0 and 100%. The smaller the value of is, the drier the air is, the stronger the water absorption ability is; the larger the value of is, the wetter the air is, the weaker the water absorption ability is. The moisture absorption capacity of wet air is also related to its temperature. As the temperature of wet air increases, the saturation pressure increases accordingly. If the content of water vapor remains unchanged, the relative humidity of wet air will decrease, that is to say, the moisture absorption capacity of wet air will increase. Therefore, when installing the air compressor room, attention should be paid to maintaining ventilation, reducing temperature, indoor no drainage, water accumulation, in order to reduce moisture in the air.

## 7. What is moist air?

Answer: Air containing a certain amount of water vapor is called wet air, and air without water vapor is called dry air. The air around us is wet. At a certain altitude, the composition and proportion of dry air are basically stable, which has no special significance for the thermal performance of the whole wet air. Although the moisture content in wet air is small, the change of moisture content has a great influence on the physical properties of wet air. The amount of water vapor determines the dryness and humidity of air. The working object of air compressor is wet air.

## 8. what are the methods of compressed air drying?

Answer:Compressed air can remove water vapor by pressure, cooling, adsorption and other methods, and can remove liquid water by heating, filtering, mechanical separation and other methods. Freeze dryer is a kind of equipment that can cool compressed air to remove water vapor and obtain relatively dry compressed air. The rear cooler of air compressor also uses cooling to remove water vapor. Adsorption dryer uses the principle of adsorption to remove water vapor from compressed air.

## 9. What is compressed air? What are its characteristics?

Answer: Air is compressible. Compressed air is called compressed air after the compressor works mechanically to reduce its volume and increase its pressure. Compressed air is an important power source. Compared with other energy sources, it has the following obvious characteristics: clear and transparent, convenient transportation, no special harmful performance, no pollution or low pollution, low temperature, no fire risk, no fear of overload, can work in many adverse environments, easy access, inexhaustible.

## 10. What impurities do compressed air contain?

Answer:The compressed air discharged by the air compressor contains many impurities.

• (1) Water, including water mist, steam and condensate;

• (2) Oil, including oil pollution and oil vapor;

• (3) Various solid substances, such as rust mud, metal powder, rubber fines, tar particles and filter materials, sealing materials fines, in addition to a variety of harmful chemical odors.

## 11. What is a gas source system and what parts do it consist of?

Answer: A system consisting of equipment for generating, processing and storing compressed air is called a gas source system. Typical gas source systems usually consist of the following components: air compressor, rear cooler, filter (including pre-filter, oil-water separator, pipeline filter, degreasing filter, deodorizing filter, sterilization filter, etc.), pressure-stabilized storage tank, dryer (refrigerated or adsorption), automatic drainage, gas pipeline, pipeline valve, instrument, etc. According to the different needs of the process flow, the above equipment is combined into a complete gas source system.

## 12. What are the hazards of impurities in compressed air?

Answer:The compressed air exported from the air compressor contains a lot of harmful impurities. The main impurities are solid particles, water and oil in the air. The vaporized lubricating oil will form an organic acid corrosion equipment, which will deteriorate rubber, plastics and sealing materials, plug small holes, cause valve failure and contaminate products. Saturated water in compressed air will condense into water under certain conditions and accumulate in some parts of the system. These moisture can rust the components and pipes, cause the moving parts to be stuck or worn, and cause the pneumatic components to fail and leak. In cold areas, the freezing of water will cause the freezing or freezing cracking of pipes. Dust and other impurities in compressed air will wear the relative moving surfaces of cylinders, pneumatic motors and pneumatic reversing valves and reduce the service life of the system.

## 13. Why should compressed air be purified?

Answer: As the hydraulic system has higher requirements for the cleanliness of hydraulic oil, the pneumatic system also has higher quality requirements for compressed air. The air discharged by the air compressor can not be directly used by the pneumatic device. The air compressor sucks air containing moisture and dust from the atmosphere. After compression, the temperature of the air is increased to over 100 C. At this time, the lubricant in the air compressor is also partially gaseous. In this way, the compressed air discharged by the air compressor is the high temperature gas containing oil, moisture and dust. If the compressed air is sent directly to the pneumatic system, the reliability and service life of the pneumatic system will be greatly reduced due to the poor air quality, and the losses caused by this will often greatly exceed the cost and maintenance cost of the gas source treatment device, so it is absolutely necessary to select the correct gas source treatment system.

## 14. What is the reason why compressed air is widely used in industry?

• (1) storage: It is easy to store large capacity compressed air as needed.

• (2) Simple design and control: Acting pneumatic components belong to simple design, so they are suitable for automatic systems with simple control.

• (3) Choice of sports: Pneumatic components are easy to realize linear and rotary motion of stepless speed regulation.

• (4) Compressed air generation system: Due to the appropriate price of pneumatic components, the cost of the whole set of devices is low, and the pneumatic components have a long life and low maintenance costs.

• (5) Reliability: Pneumatic components have a long working life, so the system has a high reliability.

• (6) Adaptability to harsh environment: Compressed air is largely unaffected by high temperature, dust and corrosion, which is beyond the reach of other systems.

• (7) Clean environment: Pneumatic components are clean, and there are special treatment methods of exhaust air, less pollution to the environment.

• (8) Safety: Fire will not be caused in dangerous areas. If the system overloads the actuator, it will only stop or slip.