Refrigeration Piping Materials
Type of the material selected for the pipelines refrigeration application depends on the size of I. characteristics of the system, the type of refrigerant used and the cost of materials and labour. To the refrigeration system to function properly and efficiently pipelines connecting its components must be properly sized and installed. The correct pipe sizes ensures that the refrigerant passes through the system without creating excessive pressure drops. Remember from earlier chapters that the pressure loss change the saturation temperature and specific volume die refrigerant to reduce the system's operating efficiency.
Reduction of pressure that occurs as a refrigerant passes through the tubes, caused by the friction produced by the pipe inner surface roughness, viscous forces in the refrigerant and oil, and changes in piping height, along with changes in velocity, caused by the fittings and valves. Using the correct diameter pipes minimizes pressure drop in the line, increasing the efficiency of the system. Proper installation procedures, make sure that the oil can die peacefully return to the compressor crankcase, prevent liquid refrigerant from returning to the slugs compressor and the weakening of the vibration of the compressor, so they are not transmitted over the building.
The materials most commonly used refrigerant pipes of carbon steel, aluminum and copper.
All of these metals, which are suitable for General halocar-Bon refrigerants. Steel is most often used in applications where the size of the pipes more than 6 inches (15 cm) internal diameter ID and ammonia (R-717) refrigerant system. Aluminium is used mainly in complete units of low to moderate power. It is not often used in the field to connect components together because it is not easy to bend or solder. Copper pipes have the advantage of weight easier, more corrosion resistant and easier to install than carbon steel. In addition, it's easier to bend and soldering than aluminum pipes. So most experts will use copper pipes and pipelines installation and repair of equipment in the field.
Copper pipes manufactured for use in air-conditioning and refrigeration equipment labeled ACR (air Conditioning, refrigeration). It is available in sizes from % to 6 in (0,3 up to 15 cm) in outside diameter (od). ACR tubes and pipes to be kept clean and cleaned gases before nitrogen. After tubes, pipes and primed with nitrogen, the ends are closed plastic caps. Nitrogen decreases formation of oxides inside the tubing during soldering. Cover seal inside the tube of air, moisture and other contaminants that would otherwise transfer into the receiver before using it. The service is good practice dictates that whenever a piece of ACR tubes, pipes and cut from the roll or length, the cap be placed on the rest of them die pipe to continue to protect the die unused tubes.
ACR pipes and pipelines is measured in relation to its OD. This measurement method differs from the method used for the classification of pipes and plumbing pipes made applications. As steel pipes, plumbing pipes and fittings, measured with respect to their internal diameter (ID). Plumbing piping is also different from the ACR pipeline is that it is not purged with nitrogen and closed before leaving the factory. Additional costs for cleaning and sealing is not justified for sanitary applications, since they do not require a level of purity that refrigeration do. Plumbing piping can be cleaned and washed with water or chemical solution for the removal of oils, scale and other impurities before the system is commissioned.
Copper pipes, which was annealing plant is called soft-drawn pipes. The annealing process heats formed tubes, until it is red-hot, and then allows it to slowly cool down to ambient temperature. This process changes the molecular structure die material, stress, leading to cracking in non-annealing pipes. Hard-drawn copper pipes and pipelines are not burnt, so he remains tight. Consequently, it cannot be bent, compact or flared without fractures and cracks in the skin. Annealing leaves tube softer, which allows him to be formed, shaped, broke out, and compact. Soft-drawn pipes are available in size from y8 to 1% (0.3 to 4 cm) OD, in coil lengths of25,50 and 100 feet (8,16 and 32 m). Hard copper tubes are available in the form of straight sections 8, 10 and 20 feet (2.5,3 and 6 m).
Copper ACR pipes and pipelines is available in two different wall thickness: Type-K and Type l, Type- this thick-walled pipes having a wall thickness of which varies from 0.049 in V2 OD tube to 0.120 for 3% per ML pipelines. K-type thick-walled pipe are used in refrigeration engineering, in which a system is exposed to aggressive fluids and environments. Its walls diickness increases die long-term safety and reliability of these applications. Type-L tube, most often used in the typical for refrigeration applications. The average wall thickness that varies from 0.035 for 1/2 ML tubes for 0.100 3% in the OD of the pipe. Type-M tube is also available. This tube is not classified ACR, because of its thickness of the wall is too small for use in high-pressure system. It can be used for water supply, sewage, and other HVAC/R and distribution systems.
Steel pipe is used exclusively with ammonia (R-717) refrigerant. Copper and its alloys, may not be used in these systems, so as refrigerant attacks of non-ferrous metals when moisture In the system. Steel pipe is also available in different wall thickness is called a schedule. Schedule 80-thick-walled pipes with a thickness that varies from 0.068 in 1/2 ID in the pipe 0.280 within 6 ID in the pipe. Schedule 40 medium pipe wall thickness that varies from 0.095 in 1/2 ID in the pipe 0.432 within 6 ID in the pipe. Smaller diameter steel pipe is connected by means of the threaded and flanged fittings. Larger diameter steel pipes are joined together by welding die seams to die in the field, using arc welding...