Application skills of air compressor using oil and gas separator

Application skills of air compressor using oil and gas separator

Abstract: The application technical requirements of the oil-gas separation core used in air compressors, and the problems that occur during the use of the oil-gas separation core are analyzed, and the matters to be noted before installation.

Keywords: application of oil and gas separator, problem analysis; matters needing attention Chinese Library Classification Number: TH457 Document Identification Code: B

1 Introduction

Power gas is inseparable in the modern machinery industry. Air compressors were not used in many industries in my country before the ages, and they were not widely used in factories and machinery until the ages. During the year, oil-injected screw air compressors were the most widely used. The main characteristics of screw air compressors are stable air supply, low noise, power saving and low maintenance rate, meeting environmental protection requirements, and making up for the deficiencies of piston air compressors. The ratio of using screw air compressors in industrial power has greatly increased. While continuously introducing foreign technologies, my country is also constantly researching new technologies. As a result, there are more and more domestically produced screw air compressor factories to meet the needs of the market industry. The domestically produced screw air compressors are not only sold domestically, but also continuously sold abroad. This represents my country's screw air compressor The machine technology has taken a big step forward.

The oil-gas separation core in the oil-injected screw air compressor is one of the important components. The main function of the oil-gas separation core is to reduce the oil consumption of the air compressor and ensure that the oil content of the compressed air is within 3ppm. Manufacturers of air compressors continue to make technological innovations to reduce the oil content of compressed air, or choose better quality oil and gas separation cores. However, part of the effect during use is not very ideal, and the oil content of the air is too large or the pressure difference is too large; serious combustion and explosion.

2 Application technology of oil-gas separation core

The oil content of the outlet gas of an air compressor is not only related to the quality of the oil-gas separation core, but also related to the design of the oil drum. It is also important to match the outlet flow of the air compressor with the processing flow of the oil-gas separation core.

2.1 Matching of oil-gas separation core and air compressor

Under normal circumstances, the oil and gas separation core of the air compressor must be selected to be greater than or equal to the outlet air flow of the air compressor to prevent the fine dust that cannot be filtered by the air filter sucked in during use from blocking the fine separation layer of the oil and gas separation core , Thereby reducing the processing flow rate of the oil-gas separation core, causing the early pressure difference of the oil-gas separation core to be too large. The most suitable choice for the supporting oil-gas separation core is more than 105% of the compressed air outlet flow.

2.2 The service life of oil and gas separation core

Aging oil deposits, air pollutants and worn particles will affect the service life of the oil-gas separation core. Different users require different final pressure differences. In actual use, the final pressure difference of the oil-gas separation core for the compressor is 0.8-1bar, and the vacuum pump is 0.5bar. The dirt accumulated on the oil-gas separation core will also increase at higher oil flow rates. This can be measured by sewage flow. The blowdown volume is directly related to the pre-separation structure design of the compressor. The best value of sewage discharge is generally about 1g per cubic oil. Therefore, the service life of the oil-gas separation core cannot be measured by time. Only the final pressure difference of the oil-gas separation core determines the service life.

2.3 Methods to ensure economical service life of oil-gas separation core

The correct maintenance of lubricating oil is a prerequisite to ensure a satisfactory service life of the oil-air separation core. Generally speaking, the service life of the oil-gas separation core is only limited by the solid particle deposits (oil oxides, worn particles, etc.) on the fine separation layer, which eventually leads to an increase in pressure difference. The dirt in the lubricating oil can be reduced by replacing the air filter, oil filter and observing the oil replacement cycle. In this way, the dirt entering the oil-gas separation core can be kept to a minimum, which is beneficial to extend the maintenance and maintenance cycle. The selection of oil has a great relationship with the service life of the oil-gas separation core. Only use those approved, anti-aging and water-insensitive lubricants. Lubricating oil with poor oxidation resistance is not suitable. Even if the working time is short, it will produce a jelly-like viscous sediment that will block the oil-gas separation core. Higher operating temperature will accelerate the aging of the lubricating oil, so sufficient attention must be paid to the cooling air volume and the fouling of the cooler. When changing the oil, the used oil must be completely drained to avoid contamination of the new oil or incompatibility between the new and old oils. In rare cases, the lubricating oil will age prematurely due to the inclusion of gas impurities in the ambient air.

2.4 Fuel consumption of air compressor

Some working conditions and critical conditions that affect the oil level of the air compressor oil tank, such as the oil volatilization process, the effect of the pre-separation and the oil return system, will lead to an increase in oil consumption in a short or long time. For example, a blockage of the oil return pipe will cause the separated oil to accumulate on the dry end of the oil-gas separation core. The magnitude of the accumulated oil is related to the amount of accumulated oil.

Excessive oil level in the oil storage tank will have similar consequences. If a significant isolation area cannot be formed temporarily or for a long time between oil and gas, it will damage the pre-separation of the oil droplet separation effect and increase the air downstream of the oil and gas separation core. The residual oil rate in the

When the oil temperature is low or the slower volatilization lubricant is used, excessive refueling will also cause a large amount of oil foam to penetrate the oil separation core, which will inevitably increase oil consumption. In the case of a normal working temperature of 800C, the oil fume content of certain models or brands of lubricants can reach 10mg/m3.

2.5 Design of oil storage tank

The function of the oil storage tank in the air compressor is to store the compressor oil; buffer the flow rate of the compressed air; it is the separation function of the front stage liquid oil of the oil-gas separation core. The oil storage tank is the decisive factor for the oil content of the oil-gas separation core. The reasonable design of the oil storage tank is to reduce the oil content of the compressed air. If the design is unreasonable, the oil content of the compressed air will increase and the energy loss will be increased. How can the equipment of the air compressor reduce energy consumption? How can the design of the oil storage tank be considered reasonable? Different brands of air compressors have different oil storage tanks. The reasonable design of oil storage tanks should pay attention to several parameters:

(1) To understand the air outlet flow rate of the compressor head and the fuel injection flow rate required by the compressor head, the parameters can be obtained from the compressor head manufacturer.

(2) The flow rate of compressed air before entering the oil storage tank at a pressure of 7 bar is required to be within the range of V=15-25m/s. At this time, the pipe diameter from the compressor head to the oil storage tank needs to be configured.

(3) When the compressed air is at a pressure of 7bar, the maximum flow rate within the storage tank is required to be V1=5m/s. At this time, the required pipe diameter and the flow rate inside the storage tank must be calculated for the flow rate before entering the storage tank. What is needed is the diameter of the storage tank. The centrifugal force, speed and direction of compressed air with liquid oil entering the oil storage tank are used to calculate the remaining oil content of the compressed air.

(4) The flow rate of the compressed air in the oil storage tank entering the oil-gas separation core is controlled at V2=0.7m/s, and the oil content of the compressed air entering the oil-gas separation core is within 5-10g/m3, which can be in the oil return pipe The oil collected on the upper to measure the oil content of the compressed air entering the oil-air separation core.

(5) Calculate the fuel injection volume required by the air compressor, and the distance between the oil level of the oil in the oil storage tank and the bottom of the oil-air separation core cannot be less than 300mm. Otherwise, the oil content of the oil-gas separation core will be increased, resulting in an increase in the oil content of the compressed air.

The design parameters of the oil storage tank are calculated with reference to the processing flow rate and processing oil content of the oil and gas separation core of the German "MANN+HUMMEL" group, and the flow rate is calculated according to the DIN1945 standard (under 7bar working pressure).

3 Analysis of problems that need to be paid attention to when using oil-gas separation core products

3.1 The pressure difference of the oil-gas separation core is too large (>1bar)

In the process of using the oil-gas separation core, the normal pressure difference of the newly installed oil-gas separation core for the first time is 0.17-0.3bar. If it exceeds 0.3bar, it is abnormal. At this time, check the minimum pressure valve of the air compressor or other air Whether the parts of the system are damaged.

In the process of using the oil-air separation core, the pressure difference is too large in a short period of time. It is abnormal for the pressure difference of the oil-gas separation core to be greater than 0.8 bar. At this time, check whether the air system of the air compressor is short-circuited. , Also check whether the air filter used by the air compressor can filter 5-6um impurities to 95%, and 7-10um impurities to 99.8%, otherwise the oil and gas separation core will have a pressure difference in use in advance; Above 0.8bar. In addition, whether the compressed air system and oil system of the air compressor have been cleaned after the overhaul, and the two major systems of the air compressor have unobvious failures, which will cause the oil-air separation core to have excessive pressure in the early stage of use.

In the process of using the oil-gas separation core, the separation layer can contain a certain amount of dust. When the air compressor is continuously used, there are many dust particles less than 5um into the fine separation layer of the oil-gas separation core. The processing flow rate of the fine separation layer is continuously decreasing, and the pressure difference of the oil-gas separation core is also increasing. The oil and gas separation core reaches a pressure difference of 1 bar in normal use, and the oil and gas separation core needs to be replaced at this time.

Whether the anti-oxidation ability of lubricating oil meets the standard, whether it has excellent thermal stability and oxidation stability, and resists oil decomposition and sludge generation. Improper use of lubricating oil will also increase the pressure difference of the oil-air separation core.

3.2 The oil content of the oil and gas separation core is too large (10ppm)

During the use of the oil-gas separation core, the compressed air containing liquid oil is separated by the oil-gas separation core with an ideal oil content of less than 3ppm. Before using the oil-gas separation core, it is necessary to understand whether the air compressor's outlet flow matches the processing flow of the oil-gas separation core. The configuration of the oil-gas separation core must be greater than or equal to the air compressor's outlet flow. The oil and gas separation cores of the same model are used on air compressors of different brands, and the oil content of the oil and gas separation cores is different. Because different brands of air compressors have different oil storage tank designs, the oil content of the oil and gas separation core is related to the design of the oil storage tank, and the flow design of the oil storage tank is calculated according to the DIN1945 standard.

In the process of using the oil-gas separation core, the oil content of the compressed air: 10ppm/m3min or more, you must pay more attention to the oil volume in the oil storage tank and the oil temperature of the air compressor. If necessary, stop the air compressor for inspection. Check whether the oil return pipe of the air compressor is blocked, whether the seal is damaged, whether the oil volume of the oil storage tank is in a reasonable position, and other related parts are checked. Under normal circumstances, the oil content of compressed air can be clearly seen from the sewage.

Whether the lubricating oil in use has good air release, avoid cavitation, and maintain the maximum compression rate. Whether there is a low foam, carefully selected additives to ensure that the air separates quickly, will not form an excessive foam layer, whether it has excellent water separation.

3.3 The oil-gas separation core appears to burn or explode (smoke, burnt smell)

In the process of using the oil-gas separation core, occasionally there will be burning or explosion in the oil storage tank, which is not caused by the oil-gas separation core. Since the oil-gas separation core itself does not catch fire naturally, it will burn and explode only when the two factors of fire and combustion-supporting gas exist at the same time. Also, the oil-gas separation core will generate static electricity through the friction of the gas flow rate. The greater the static electricity, the greater the danger. So manufacturers that produce oil and gas separation cores will install conductive sheets. Unless there is no reinforced static sheet on the flange gasket of the oil-gas separation core during installation, the static electricity generated cannot be dissipated outside. When the static electricity generated by the oil-gas separation core cannot be dissipated to the casing, the oil-gas separation core is equivalent to a storage battery. The glass fiber of each layer is equivalent to the material in the fusion, and the storage capacity can reach more than 10,000 volts. The fire is generated at the position closest to the metal parts, and the principle is the same as the ignition of our family's gas stove.

In the process of using the oil-gas separation core, it is necessary to prevent fire in the oil storage tank. First, reinforce the conductive sheet on the flange gasket of the oil-gas separation core. Generally, manufacturers use stapler nails as the conductive sheet. This is not feasible, because the gasket will be pressed into the asbestos gasket when the flange is reinforced. If the static electricity cannot be dissipated, it is best to use an aluminum film sheet to cover the surface of the gasket, so as to ensure that the static electricity can be dissipated. The performance of the vaporization amount of the compressor lubricating oil used must meet international standards. Secondly, the impurities of the two systems and the welding slag on the weld must be cleaned before installing the oil-gas separation core, especially the welding slag on the weld of the new machine must be cleaned. Because the air compressor generates high temperature and high pressure during operation, and high-speed gas circulation, it is easy to remove the clean and dirty welding slag, and produce sparks when it collides with metal parts. Thirdly, always pay attention to whether the noise emitted by the air compressor is normal or not, and prevent the moving parts of the air compressor from being worn and sparks caused by the collision of metal fruit particles and metal parts.

Does the lubricating oil have outstanding oxidation stability to prevent the formation of carbon deposits and paint films on valves and other parts? These substances are by-products of oxidation reactions (such as iron oxide and hydroxide) under high temperature and high pressure conditions. These deposits can cause serious damage to air compressors, reduce efficiency and increase maintenance costs.

Whether the lubricating oil can prevent fire and explosion accidents, in the exhaust pipe of the compressor head, the mixture of carbon deposits and rust particles can undergo an exothermic reaction under the action of the heat of the compressed air, leading to fire and explosion.

3.4 Normal adaptation pressure of oil-gas separation core (>5bar)

In the process of using the oil-gas separation core, it should be noted that the air pressure normally used in the factory cannot be <5bar. Because the processing flow of the oil-gas separation core is calculated according to the standard 7bar pressure, and the processing flow of the oil-gas separation core is calculated according to the standard of DIN1945. In general, the selection of the oil-gas separation core must be configured to be more than 105% of the air compressor's air flow rate. The processing capacity of the oil-gas separation core is related to the pressure and flow rate used. The lower the pressure under the matched oil-gas separation core The treatment effect of the oil-gas separation core is worse. Therefore, the oil-gas separation core must be used above 5.5bar for a long time, otherwise the oil content of the processing air of the oil-gas separation core will not reach the effect of 3ppm. The table of correction coefficients under other pressures is as follows:

4 Installation considerations

A) Apply a small amount of lubricating oil on the surface of the seal when installing the oil-air separation core.

B) The spin-on oil-gas separation core only needs to be tightened clockwise by hand during installation.

C) When installing the built-in oil and gas separation core, the flange gasket of the oil and gas separation core must be installed with conductive sheets or graphite gaskets.

D) When installing the built-in oil-gas separation core, pay attention to whether the oil return pipe extends between 2-3mm from the center bottom of the oil-gas separation core.

E) When removing the oil-gas separation core, pay attention to whether there is still residual pressure inside.

F) The compressed air containing oil cannot be directly injected into the oil-air separation core.

5 Conclusion

The application technology of the oil-gas separation core mentioned in this article and the analysis of the problems that will occur during the use process have the effect of increasing the oil content of the air compressor and reducing the cost of the air compressor. It is suitable for data reference for the manufacture of oil storage tanks of air compressors, and is especially suitable for equipment maintenance and has reference significance for equipment fault diagnosis. The problem analysis and precautions presented in this article are helpful for training materials for operators in the air compressor industry.