Original title: How much do you know about the drying filter of refrigeration system? The dry filter is one of the most commonly used accessories in the refrigerant pipeline. It is mainly used to clean the harmful substances in the system, so as to protect the important components such as the expansion valve and compressor. The ability of the filter-drier to adsorb moisture from the refrigeration system is an important function. In the refrigerant system, many harmful substances will enter the pipeline through various ways, and the common ones are as follows: 1 Production or maintenance process At this time, the refrigerant system will be open to the outside, regardless of the length of time, there will be moisture, dust into the system pipeline, in the welding process if there is no nitrogen protection may also produce copper oxygen film, or even welding slag; 2 Fill refrigerant or refrigerant oil If there are many solid impurities and moisture in these things, they will be brought into the system and corrode the metal parts of the system; 3 When the refrigeration system is in operation In operation, when the refrigerant contains water, it will hydrolyze into acidic substances, which will corrode the metal. The mixture of refrigerant and lubricating oil can dissolve copper and bring it to the compressor to form a copper film on its metal surface, thus affecting the operation of the compressor. 4 Refrigerant oil When the temperature is low to a certain temperature, the refrigerant oil will precipitate stone toad, and for the POE oil used in environmental protection refrigerants,thin film distillation, the hygroscopicity is relatively strong, so it is easier to hydrolyze acidic characteristics. Expand the full text The existence of the above substances will seriously threaten or destroy the performance of the moving parts in the system and the cylinders and refrigeration systems that need compressed gas, so they should be removed in time. The materials that play a role in the dry filter mainly include 1. Metal filter screen: filter large solid particles (mainly used in small and medium-sized systems that are not sensitive to moisture, such as R22 and mineral oil); 2. Polyester filter screen: filter tiny particles; 3. Glass wool: filter tiny particles; 4. Molecular sieve: filter larger particles of solid impurities, mainly absorb water, which is 3-4 times that of other substances, and can also absorb acidic substances nearby; 5. Activated alumina: Absorbs water,molecular distillation systems, mainly acidic substances. 6. Activated carbon: It absorbs paraffin, but because the refrigerant oil will precipitate paraffin only when the temperature is below -35 degrees, it is not needed in the system operating at medium and high temperatures. Common desiccants have the following characteristics, which are made into two forms according to the use characteristics: 1. Small ball combination type, many small balls made of desiccant are filled in a container in the dry filter. 2. Hard filter element type. The desiccant is made into a hard filter element through a series of processes, and then installed on the fixed bracket of the drying filter. The performance of the dry filter is classified as: 1 Filtration capacity The filter screen is generally made of stainless steel, phosphor bronze or brass. 70-100 mesh is generally used to filter gaseous refrigerant, and 60 mesh is used to filter liquid refrigerant. However, the filter screen in front of the expansion valve and solenoid valve needs to use 120-200 mesh fine filter screen. At present, however, metal filter screens are generally not used, and desiccants are directly used to form tiny flow channels, nutsche filter dryer ,cbd crystallization equipment, or polyester filter screens, or glass wool, which can absorb moisture and filter, with a filtering capacity of up to 20 um (700 mesh). However, if hard filter elements are used, the filtering capacity is only 40 um (380 mesh), because it absorbs water through porous water seepage. Therefore, it is not easy to block solid impurities. When the flow rate of refrigerant is slightly larger, it is easy to wash away solid impurities. If the density of the filter element is increased, it will increase the resistance and increase the pressure loss. This is determined by its structural characteristics. 2 Moisture absorption capacity The moisture content in the refrigeration system is the smaller the better, and different systems have different States before closing, the length of vacuumizing time and the quality of refrigerant filling will have an impact, so it is difficult to determine how much moisture absorption capacity of the dryer is needed for the refrigeration products produced according to the standard process. Therefore, the general dry filter manufacturers are nominal according to the requirements of ARI710 standard. For example, the nominal moisture absorption capacity of the dry filter of DANFOSS is measured under the following conditions: (ALCO is the same, but individual parameters are different). 3 Functionality Dry filter for liquid pipe and dry filter for suction pipe (also known as dry filter for compressor burnout) can remove substances that may damage the system, but the emphasis is different. The dry filter for liquid pipe is mainly used to protect the stop valve, expansion valve and other valves, and to avoid the blockage of capillary and other throttling elements, which is the standard configuration in the refrigeration system. Because the flow rate is low here, the filtration effect is good and the pressure drop is small, followed by more protected valves. The liquid tube drying filter is usually followed by a liquid microscope. There is also a dry filter specially used to enhance the ability to clean up contaminated pipelines after the compressor burns down, which has greater moisture absorption and acid removal capacity than the normal use. The dry filter for the suction pipe mainly protects the compressor. Dry filters for suction pipes are not widely used in the industry, and there are generally two situations for formal system configuration: 1. On-site installation system: As the on-site installation is different from the factory, the on-site environment is complex and the cleanliness is poor, so it is better to install a dry filter in the suction pipe. (However, there is no installation for small and medium-sized on-site installation products such as split-type pipeline machine in China, and the quality is guaranteed by the process of the construction unit itself. Of course, this is the product of R22. I wonder if the environmental protection refrigerant has strengthened the protection in this respect.) 2. Large system: Because the cost of the compressor is relatively high, it is worthwhile to install a removable dry filter in the suction pipe to protect the compressor. In order to ensure that the pressure drop is as small as possible (the pressure drop of the suction pipe has a greater impact on the system performance), the suction pipe dry filter is generally larger than that of the liquid pipe (mainly refers to the flow capacity). Because the dry filter for the suction pipe is mainly used when the compressor is burned, it can adsorb a large amount of water and acidic substances or solid impurities in a short time, which will reduce the flow capacity of the dry filter, thus affecting its performance. Therefore, there is usually an interface near the inlet and outlet of the suction pipe dryer filter to test the pressure loss of the dryer filter. If the measured pressure difference between the inlet and outlet exceeds the following value, the dryer filter should be replaced. A sight glass with a moisture indicator is usually installed after the drying filter, and its indication is as follows: Green: no dangerous moisture in the refrigerant; Yellow: High moisture content in the refrigerant before the expansion valve. Bubble: 1) The pressure drop of the dry filter is too high. 2) No supercooling. 3) Insufficient refrigerant in the whole system. The suction filter must be replaced when the pressure drop exceeds the following values: Air conditioning system: 0.50 bar; cooling system: 0.25 bar; freezing system: 0.15 bar Installation The fluid must be installed in the same direction as the arrow on the filter label. The orientation of the filter-drier is not limited, but the following points must be kept in mind: a vertical installation with downward flow means that the refrigerant system can be drained/emptied quickly; for a vertical installation with upward flow, the draining/emptying takes longer because the refrigerant needs to be drained out of the filter-drier. Dry filter replacement conditions 1. The sight glass indicates high moisture content (Yellow). 2. Pressure drop across the filter is too high (Bubbles appear in the sight glass during normal operation). 3. The main parts of the refrigeration system were replaced. ,decarboxylation after extraction, such as a compressor. 4. Every time the cooling system is turned on ? For example, the flow port assembly in the expansion valve was replaced. Do not reuse the old dry filter. If used in a refrigeration system with a low moisture content or when it is heated, it will release moisture Dry filter replacement 1. Close valve 1 (above) 2. Suction filter 3. Close valve 4 (above) 4. Close valve 2 (above) · END · Return to Sohu to see more Responsible Editor:. toptiontech.com