What circumstances should the dryer filter of the refrigeration unit be replaced?

The dry filter is one of the most commonly used accessories in the refrigeration piping system. It is mainly used to remove harmful substances from the system, thereby protecting important components such as expansion valves and compressors. For the dry filter, the ability to adsorb moisture from the refrigeration system is a very important function.

In the refrigerant system, many harmful substances can enter the piping through various routes. The common ones include the following:
Production or maintenance process: At this time, the refrigeration system is open to the outside. Regardless of the duration, water vapor and dust will enter the system piping. If there is no nitrogen protection during the welding process, there may even be copper oxide films or even welding slag;
Filling refrigerant or refrigerating oil: If these substances have many solid impurities and moisture, they will be brought into the system and corrode the metal parts in the system;
During the operation of the refrigeration system: During operation, when the refrigerant contains moisture, it will hydrolyze to generate acidic substances, causing corrosion to the metal. The mixture of refrigerant and lubricating oil can dissolve copper and form a copper film on the metal surface of the compressor, thereby affecting the operation of the compressor.
Refrigerating oil: When the temperature is low enough, the refrigerating oil will precipitate crystals, and for environmentally friendly refrigerants using POE oil, its hygroscopicity is relatively strong, so it is more likely to hydrolyze to produce acidic characteristics.
The presence of these substances will seriously threaten or damage the moving parts in the system and the performance of the cylinders and refrigeration system that require compressed gas, so they must be removed in time.

The materials that play a role in the drying filter mainly include:
Metal filter screen: Usually located at the front end of the drying filter, it is mainly used to intercept larger solid particles, such as metal debris or oxide scales, to prevent these larger impurities from entering the system and causing damage.
Polyester filter screen: This material is designed to capture even smaller particles. Its fine structure can effectively prevent fine impurities from passing through, ensuring the cleanliness and operational efficiency of the system.
Glass wool: As an efficient filtering medium, glass wool is good at capturing extremely tiny particle substances, providing an additional layer of protection to ensure the purity and cleanliness of the fluid passing through the system.
Molecular sieve: Molecular sieves not only can filter out larger solid impurities, but more importantly, they have excellent water absorption capacity, which is 3 to 4 times that of other conventional adsorbents. In addition, molecular sieves can also adsorb acidic substances, helping to maintain the stability of the system and extend the lifespan of the equipment.
Activated alumina: This material is mainly used to absorb moisture in the system and has a special affinity for acidic substances, effectively reducing the corrosion risk caused by the presence of moisture and also helping to control the acid-base balance of the system.
Activated carbon: Although activated carbon has the ability to absorb paraffin, since paraffin only precipitates from refrigerated oil when the temperature is lower than -35 degrees Celsius, it is not necessary to use activated carbon to deal with the problem of paraffin in most medium-high temperature operating systems. However, activated carbon is very effective for removing odors and certain organic compounds.

Common desiccants are mainly divided into two forms based on their usage characteristics and installation methods:
The ball combination type: This type of desiccant is made into small balls and filled into a container inside the drying filter. The ball combination design facilitates the filling and replacement of the desiccant, enabling flexible adaptation to different system requirements while ensuring efficient moisture absorption performance and impurity filtration effect.
The hard filter element type: Through a series of processing procedures, the desiccant is processed into a sturdy filter element shape, and then installed on the fixed support of the drying filter. The hard filter element type not only provides a stable structural support but also optimizes the contact efficiency of fluid flow, ensuring continuous and stable drying effects. Moreover, this form of desiccant is easy to replace, facilitating the efficient conduct of maintenance work.

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