Screw air compressor is characterized by stable gas supply, low noise, low power saving and low maintenance rate, China's screw air compressor technology has also made great progress. In the fuel injection screw air compressor, the core of the oil separator is one of the important parts. The main function of the oil-gas separator core is to reduce the oil consumption of the air compressor and ensure that the oil content of the compressed air is within 3 ppm. Air compressor manufacturers through continuous technical improvements to reduce the oil content of compressed air, the user will also choose better quality oil and gas separator core so that compressed air can meet the predetermined use standards. However, in practical application, the oil content or pressure difference of the exhaust gas may be too large, and even the combustion and explosion of the oil-gas separator may occur. How to scientifically use oil and gas separators, let's look at the rules summarized by others.
Application technology of oil and gas separator core
The oil content of the air compressor is not only related to the quality of the oil-gas separator core, but also to the design of the oil-gas barrel. The matching of the air flow rate of the air compressor and the treatment flow rate of the oil-gas separator core is also very important.
1 Matching of the oil separator with the air compressor
Usually, air compressor matching oil separator core must be greater than or equal to the air compressor outlet flow, to prevent the fine dust that can not be filtered by the air filter inhaled in the course of use, and to block the fine separation layer of the oil separator core, thereby reducing the flow of oil separator treatment, resulting in the pressure difference of the gas separator core is too large at the early stage. The most suitable type of oil separator core is more than 105% of the compressed air outgoing flow rate.
2 Service life of oil separator
Aging oil deposits, air pollutants and wear particles will affect the life of the oil separator core. The user's working condition is different, and the final pressure difference is different. In practice, the final pressure difference of the oil separator used in the compressor is 0.8-1bar, and the vacuum pump is 0.5bar. The dirt gathered on the core of the oil separator will also increase when the oil flow rate is higher. This can be measured by sewage discharge. The amount of emissions is directly related to the design of the pre separation structure of the compressor. The best value of pollutant discharge is usually about 1 grams per cubic meter. Therefore, the service life of the oil separator core can not be completely measured by time, only the final pressure difference of the oil separator core to determine the life.
3 Ensure the service life of the separator core
Proper maintenance of lubricating oil is an important condition to ensure satisfactory service life of oil separator element. Generally speaking, the service life of the oil separator is limited by the solid particle precipitates (oil oxides, abrasive particles, etc.) on the subdivision layer, which ultimately leads to the increase of pressure difference. The dirt in lubricating oil can be reduced by replacing air filters, oil filters, and by following the oil replacement cycle. In this way, the dirt entering the oil separator can be kept at a minimum level, and the maintenance cycle can be prolonged. The selection of oil has great relationship with the service life of the core of the oil separator. Only use approved, aging resistant and water insensitive lubricants. The lubricating oil with poor oxidation resistance is not suitable, even if the working time is short, it will produce a kind of jelly-like viscous sediment, which will plug the oil separator element. Higher working temperature will accelerate the aging of lubricating oil, so it is necessary to pay enough attention to cooling air volume and cooling fouling. When replacing the oil, the used oil must be completely emptied to avoid pollution of the new oil or incompatibility between the old and new oil. In very few cases, lubricants will be aged in advance due to the inclusion of gas impurities in the ambient air.
4 Fuel consumption of air compressor
Some working conditions and critical conditions affecting the oil level of air compressor oil storage tank, such as the volatilization process of oil, pre-separation and the effect of oil return system, will cause short-term or long-term increase in fuel consumption.
High oil level in oil tank can produce similar results. If the obvious isolation zone between oil and gas can not be formed temporarily or for a long time, it will damage the pre-separation of oil droplets and increase the residual oil in the air downstream of the oil-gas separator core.
When the oil temperature is low or the volatile oil is used slowly, excessive oil will cause a large number of oil bubbles to pass through the oil separation core, and the core of the oil separator will inevitably increase the fuel consumption. Under the normal operating temperature of 800℃, the fume content of some types or grades of lubricating oils can reach 10mg/m3.
5 Design of oil storage tank
The function of the oil tank in the air compressor system is to store compressor oil, colleagues buffer the flow rate of compressed air, is the separation of liquid oil in the front stage of the oil-gas separator core. Oil storage tank is the decisive factor of oil separator core treatment of oil content. The reasonable design of oil storage tank is to reduce the oil content of compressed air. If the design is improper, the oil content of the exhaust will be increased and the energy consumption will be increased. So, how can the air compressor equipment reduce energy consumption, how can the design of the oil tank be reasonable? Different brands of air compressors are designed for different oil tanks. In the design of oil tanks, the following parameters should be noted:
(1)Compressor head to understand the flow rate of air and the head of the compressor needed to fuel flow, parameters can be obtained from the manufacturer of compressor head.
(2) The velocity of compressed air before entering the tank at 7 bar pressure is within the range of V=15-25 m/s, and the diameter of the pipe from the compressor head to the tank should be calculated.
(3) When the compressed air is at 7 bar pressure, the maximum velocity in the tank is required to be V1=5 m/s. The diameter of the tank is calculated by calculating the diameter of the pipe needed for the velocity before entering the tank and the velocity in the tank. The centrifugal force, velocity and direction of the compressed air with liquid oil entering the tank are used to calculate the remaining oil content of the compressed air.
(4)The velocity of compressed air entering the core of oil separator in the oil tank is controlled at V2=0.7m/s, and the oil content of compressed air entering the core of oil-gas separator is within 5-10g/m3. The oil content of compressed air entering the core of oil-gas separator can be measured by collecting oil on the return pipe.
(5)The distance between the oil surface of the oil tank and the bottom of the oil separator core should not be less than 30 cm when calculating the fuel injection required by the air compressor. Otherwise, the oil content of the core of the oil separator will be increased, resulting in the increase of the oil content of the compressed air.
The design parameters of oil tank are calculated by referring to the treatment flow rate and oil content of oil and gas separator core of a foreign group. The flow rate is calculated according to DIN 1945 standard (at 7 bar working pressure).
Summary of problems needing attention in use
1 The pressure difference of the oil separator exceeds 1bar
During the operation of the oil separator, the normal pressure difference of the newly installed oil separator should be 0.17-0.3 bar for the first time, it is abnormal when it exceeds 0.3 bar. At this point, the minimum pressure valve of the air compressor or other parts of the air system should be checked for damage.
In the process of using the oil separator, it is abnormal that the pressure difference of the oil separator is too large in a short time, and the pressure difference of the oil separator is more than 0.8 bar. At this time, it is necessary to check whether the air system of the air compressor has short circuit phenomenon, and also to check whether the air filter used by the air compressor can filter 5-6um impurities to 95%, in 7-10um impurities to 99.8% of the effect. Otherwise the pressure difference of the oil separator will be more than 0.8bar in advance. In addition, the air compressor after the overhaul of the compressed air system and oil system clean, air compressor two major systems have no obvious fault will cause excessive pressure difference in the early use of oil and gas separator core.
In the process of using the oil separator, the separating layer can contain a certain amount of dust. When the air compressor is in constant use, a lot of dust particles less than 5 um enter the fine layer of the oil separator. Not only the flow rate of the subdivided layer is decreasing, but also the pressure difference of the oil separator is increasing. The oil separator can reach 1bar pressure difference when used normally, so the core of the separator should be replaced.
Whether the antioxidant capacity of lubricating oil meets the standards, whether it has excellent thermal stability and oxidation stability, resistance to oil decomposition and sludge production. The improper use of lubricating oil will also increase the pressure difference of the core of the separator.
2 The oil content of the separator is more than 10ppm
During the operation of the oil separator, the ideal oil content of the compressed air filtered by the oil separator should be within 3 ppm. Before using the oil separator, it is necessary to know whether the outflow of the air compressor matches the treatment flow of the oil separator core. The configuration of the oil separator core must be greater than or equal to the outflow of the air compressor. The same type of oil separator is used in different brands of air compressors, and the oil content of the oil separator is different. Because the air compressor brand is different, the design of its oil storage tank is also different, and the oil content of the oil separator is related to the design of the oil storage tank.
The oil content of compressed air is more than 10ppm/m3 min. The oil content in the oil tank and the oil temperature of the air compressor must be paid attention to. If necessary, the air compressor should be stopped for inspection. Check whether the air compressor return pipe is blocked, whether the seal is damaged and whether the oil storage tank is in a reasonable position. Usually, the amount of oil contained in compressed air can come out of the dirt.
Whether the lubricating oil used has good air release, avoid cavitation and maintain the maximum compression rate. Whether there is a low foam, carefully screened additives to ensure that the air is quickly separated, does not form excessive foam layer, whether there is excellent water distribution.
3 Combustion and explosion occurred in the separator
In the process of using the oil separator, occasional combustion or explosion occurs in the oil tank, which is not caused by the oil separator. Since the oil separator itself will not spontaneously ignite, only the two factors of kindling material and combustion-supporting gas exist simultaneously can the combustion and explosion occur.
There is also the oil separator through the gas velocity friction will produce static electricity, the greater the risk of static electricity. Therefore, producers of oil separator will have conductive sheets. Unless there is no reinforced electrostatic sheet on the flange gasket of the oil separator to conduct electricity during installation, the generated static electricity cannot be dissipated.
In the process of using the oil separator, we must prevent the fire from burning in the oil storage tank. Firstly, the conductive sheet is strengthened on the flange gasket of the oil separator, and the performance of the compressor lubricating oil used in the gasification must conform to the international standard. Secondly, the impurities of the two systems and the welding slag on the weld must be cleaned before the oil separator is installed, especially on the weld of the new machine. Because the air compressor in operation will produce high temperature and high pressure, and high-speed gas flow is easy to clean welding slag from the production of sparks by collision with metal parts. Again, always pay attention to the air compressor in the operation of the noise generated by normal, to prevent the air compressor moving parts from wear and tear caused by metal particles and metal parts produced by the collision of sparks.
Lubricants have excellent oxidation stability to prevent carbon deposition and film formation in valves and other components, which are by-products of oxidation reactions at high temperatures and pressures (such as iron oxide and hydroxides). These deposits will 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 compressor head, the mixture of carbon and rust particles can produce exothermic reaction under the action of compressed air heat, leading to fire and explosion.
4 Normal adaptation pressure is greater than 5bar
The normal air pressure in the factory can not be less than 5bar, because the treatment flow of the oil separator is calculated according to the standard 7bar pressure, and the treatment flow of the oil separator is calculated according to the DIN 1945 standard. Generally speaking, the selection of the oil separator must be arranged according to 105% or more of the air flow rate of the air compressor. The handling capacity of the oil separator is related to the pressure and velocity of compressed air used. The lower the pressure under the matching oil separator, the worse the treatment effect of the oil separator. Therefore, the oil separator must be used for a long time above 5.5 bar, otherwise the oil content of the treated air in the oil separator will be difficult to achieve the effect of 3 ppm.
Points for attention in installation
a) When installing the oil separator, a small amount of lubricating oil can be coated on the surface of the seal.
b) Install the swirling oil separator core, only by hand clockwise.
c) When installing a built-in oil separator, the flange gasket must be equipped with a conductive plate or graphite gasket.
d) When installing a built-in oil separator, pay attention to whether the return tubing extends between the central bottom 2 and 3 mm of the oil separator.
e) When unloading the oil separator, pay attention to whether there is any internal pressure.
f) Compressed air containing oil must not be directly injected into the core of the oil separator.
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