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Halogen free (natural) refrigerants Semi-hermetic compressors in so-called "hermetically sealed" systems are in this case subject to regulations for hazardous zone 2 (only seldom and short term risk). Safety demands include special devices to protect against excess pressures and speci- al arrangements for the electrical system. In addition, measures are required to ensure hazard free ventilation to effectively prevent a flammable gas mixture in case of refriger- ant leakage. Design requirements are defined by stan- dards (e.g. EN378) and may vary in differ- ent countries. For systems applied in the EU, an assessment according to EC Direc- tive 94/9/EC (ATEX) may become necessary as well. With open compressors, this will possibly lead to a classification in zone 1 ‒ which demands, however, electrical equip- ment in special flame-proof design. Resulting design criteria Apart from the measures mentioned above, propane systems require practically no spe- cial features in the medium and low tempera- ture ranges compared to a usual (H)CFC and HFC system. When sizing components, however, the relatively low mass flow should be considered (approximately 55 to 60% compared to R22). An advantage here is that the refrigerant charge can be greatly reduced. From the thermodynamic point of view, an internal heat exchanger between the suction and liquid line is recommended as this will improve the refrigerating capaci- ty and COP. Owing to the particularly high solubility of R290 (and R1270) in common lubricants, BITZER R290/R1270 compressors are charged with special oil of a high viscosity index and particularly good tribological properties. Again, an internal heat exchanger is of advantage as it leads to higher oil tempera- tures, lower solubility and therefore im- proved viscosity. Due to the very favourable temperature behaviour (Fig. 24), single stage compres- sors can be used down to approximately - 40°C evaporation temperature. R290 could thus also be considered as an alternative for some of the HFC blends. A range of ECOLINE compressors and CS. compact screws is available for R290. Due to the individual requirements a specifically equipped compressor ver- sion is offered. Inquiries and orders need a clear reference to R290. The handling of the order includes an individual agreement between the contract part- ners. Open reciprocating compressors are also available for R290, together with a comprehensive program of flame-proof accessories which may be required. Conversion of existing plants with R22 or HFC to R290 Due to the special safety measures when using R290, a conversion of existing sys- tems only seems possible in exceptional cases. They are limited to systems, which can be modified to meet the corresponding safety regulations with an acceptable effort. Supplementary BITZER information concerning the use of R290 (see also https://www.bitzer.de) o Technical Information AT-660 “Use of propane (R290) and propene (R1270) in semi-hermetic BITZER compressors” Fig. 26 R290/R1270/R22 – comparison of performance data of a Fig. 27 R290/R1270/R22 – comparison of pressure levels semi-hermetic compressor 31PDF Image | REFRIGERANT REPORT 21
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