TECHNICAL BULLETIN hydrocarbons

Transcription

1 TECHNICAL BULLETIN hydrocarbons

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3 SUMMARY Introduction: Hydrocarbons 4 I. Properties 4 II. Lubricants 9 III. System Design 10 IV. Safety Aspects 14 V. Retrofitting 17 VI. FAQs (Frequently Asked Questions) 17 VII. References 18 VIII. Glossary 19

4 INTRODUCTION: HYDROCARBONS The use of hydrocarbon (HC) refrigerants R600a (isobutane) and R290 (propane) as substitutes of HCFC s (hydrochlorofluorocarbons) and HFC s (hydrofluorocarbons) continues around the globe. R600a and R290 have ozone depletion potential (ODP) factors of zero (0.0) and a fraction of the global warming potential of those refrigerants they are intended to replace. The process of replacement for CFC (chlorofluorocarbon) in all products worldwide started in 1996 with the Montreal Protocol, initially in developed countries and then extended to other nations. The fluorocarbons like R12 (used as refrigerant) and R11 (used as blowing agent in the foam insulation) have been phased out in most of uses, considering that feasible alternatives like R134a and hydrocarbons are widely available. In 2007 Meeting of Parties (signer countries of the protocol), the Montreal Protocol was updated to adopt control measures also for the HCFC s, establishing reduction targets in quantities for consumption and production until the complete elimination of these refrigerants. This process has already started in several countries, having a successful example in Europe R600a is in use with safety for years in domestic appliances. Hydrocarbons have acceptable toxicity levels; however, they are flammable. Neither of these refrigerants are drop-in replacements for HCFC s or HFC s. There are significant differences between R600a and R290, and the non-hc refrigerants that must be considered in handling, processing and application. Tecumseh cannot control the final use and application of the compressors it sells, nor can Tecumseh guarantee that compliance with agency standards will eliminate all risk of fire. However, we do urge all OEM s to use care in the selection and use of such compressors and to obtain appropriate certifications from recognized testing agencies concerning compliance with all standards. I. PROPERTIES Formula and Composition Refrigerant Formula Chemistry Name Critical Temperature C ( F) Molecular Weight (kg/kmol) Boiling Point C ( F) R12 CCl 2 F 2 Dichlorodifluoromethane 112 (233.6) (-21.6) R134a CF 3 CH 2 F 1,1,1,2-Tetrafluoroethane 101 (213.8) (-15.5) R600a CH(CH 3 ) 3 Isobutane 135 (275) (11.1) R22 CHF 2 CI Chlorodifluoromethane 96 (204.8) (-41.4) R290 CH 3 CH 2 CH 3 Propane 96.8 (206.2) (-43.8) Source: ANSI ASHRAE Standart 34, TECHNICAL BULLETIN - HYDROCABONS

5 With the above characteristics, R290 works as a substitute for R22. As it has a boiling point very close to R22, the propane allows that the evaporator project be similar to the original. Pressure temperature table Temperature Pressure PSIA (kpa Abs.) C ( F) R600a R134a R (-40) 4.1 (28.3) 7.4 (51.2) 16.1 (111.0) (-30) 5.4 (37.4) 9.9 (68.0) 20.3 (140.3) (-20) 7.0 (48.6) 12.9 (88.9) 25.4 (175.1) (-10) 9.0 (62.3) 16.6 (114.7) 31.4 (216.3) (0) 11.5 (79.0) 21.2 (146.0) 38.4 (264.5) (10) 14.3 (98.9) 26.6 (183.6) 46.5 (320.4) -6.7 (20) 17.8 (122.5) 33.1 (228.4) 55.8 (384.8) -1.1 (30) 21.8 (150.3) 40.8 (281.2) 66.5 (458.4) 4.4 (40) 26.5 (182.7) 49.7 (343.0) 78.6 (542.0) 10.0 (50) 31.9 (220.1) 60.1 (414.6) 92.3 (636.4) 15.6 (60) 38.2 (263.1) 72.1 (497.1) (742.5) 21.1 (70) 45.3 (312.1) 85.8 (591.6) (861.0) 26.7 (80) 53.3 (367.6) (699.0) (992.8) 32.2 (90) 62.4 (430.3) (820.6) (1139) 37.8 (100) 72.6 (500.5) (957.3) (1300) 43.3 (110) 83.9 (578.8) 161.1(1111) (1477) 48.9 (120) 96.6 (665.8) (1281) (1672) 54.4 (130) (762.1) (1471) (1884) 60.0 (140) (868.3) (1682) (2116) 65.6 (150) (984.9) (1914) (2369) Source: Data Refprop 6.01 Environment characteristics The ozone layer The ozone layer is located in the stratosphere, with 13 to 20 kilometers of altitude and contains approximately 90% of atmospheric ozone. It is one of the main barriers that protect us from the ultraviolet (UV) radiation, however it is vulnerable from chemical products known as organohalogen compounds that contain fluorine, chlorine and bromine in their composition. 5

6 The chlorofluorocarbons (CFC s) contain the element chlorine, which is the main responsible for depletion of the ozone layer. These highly stable compounds are capable of surviving around 150 years and migrate to the stratosphere completely unmodified, where the ultraviolet rays reach them with great intensity, releasing the chlorine that, consequently, catalyze a chain reaction capable of breaking down the ozone molecules: CFCl 3 + uv CFCl 2 + Cl Cl + O 3 ClO + O 2 ClO + O Cl + O 2 The greenhouse effect and the global warming The presence of gases in the atmosphere (water vapor, CO2, methane, etc) maintains the energy from the sun and keeps the temperature on Earth positive. The greenhouse effect occurs when additional gases (CFCs, HFCs, HCs) besides the existing ones in the atmosphere cause an increase in average global temperature. The scheme of this process is given below: A B D C A: Absorption of radiation emitted by the sun in the atmospheric layers B: Reflection of solar radiation (approximately 30% of absorbed radiation) C: Retention of solar radiation reflected by the gases that cause greenhouse gases (CFC, HFC) D: Solar radiation released to space The cycle formed by the arrows B and C is responsible for raising the temperature in the layers nearer the surface. Two indicators of how the refrigerants behave in relation to aggression to the environment are the ODP (Ozone depleting Potential) and GWP (Global Warming Potential). 6 TECHNICAL BULLETIN - HYDROCABONS

7 As shown in the table below, both the R600a and R290 do not affect the ozone layer (ODP = 0) and, moreover, their GWP values are much lower than R12, R134a and R22. Refrigerant ODP GWP (100 years TH*) R R134a R600a R R *Time Horizon Source: IPCC Comparative between evaporating temperatures (-41.4) (-44.0) (-21.6) (-15.5) (-11.1) R12 R134a R600a R22 R290 REFRIGERANT TEMPERATURE o C ( o F) Toxicity The refrigerants mentioned in this bulletin have similar values of TLV (Threshold Limit Values), which is a value that defines the maximum concentration of toxic gases in the workplace, without affecting those exposed to this environment. This way, the same care that should be taken when handling other fluids must also be taken when handling the R290 or R600a, such as: Work in ventilated rooms; Avoid direct inhalation; Avoid contact with skin; Avoid contact with fire. Flammability The flammability of a fluid is defined by lower and upper explosion limits, LEL (Low Level Explosion) and UEL (Upper Explosion Level) respectively. LEL and UEL represent the minimum and maximum fluid concentration in the air, where it could cause the spread of flame in the presence of an ignition source. Refrigerant LEL (% Volume) UEL (% Volume) Ignition Temperature C ( F) R12, R134a, R22 Non-flammable Non-flammable - R600a (860) R (878) Source: ACRIB 7

8 Due to the fact that the hydrocarbons have low toxicity and are flammable, they are classified as A3 according to ASHRAE Standard 34: INCREASING TOXICITY SAFETY GROUP Higher Flammability A3 B3 Lower Flammability A2 B2 No Flame Propagation A1 B1 Lower Toxicity Higher Toxicity INCREASING TOXICITY Refrigerant Safety Group (ASHRAE) R12 A1 R134a A1 R600a A3 R290 A3 Source: ANSI ASHRAE Standart 34, 2007 The aspects shown above imply the adoption of certain precautions and procedures in the operation and maintenance of products designed for hydrocarbons, which will be shown in following chapters. Compatibility with materials According to the chemical characteristics of each refrigerant, its compatibility with lubricating oils and other components of the refrigeration system, like the filter dryer, must be considered. The hydrocarbons are compatible with all common elastomers and plastic refrigeration materials used as valve seats, seals and gaskets. Materials such as natural rubber, silicone, PP, PVC, PVDF, EPDM and CSM are not suitable for use with the hydrocarbons: Compatible Neoprene (polychloroprene) Viton (fluoropolymer) Nitrile rubber HNBR PTFE (Teflon - Polytetrafluoroethylene) Nylon Incompatible EPDM (Etilenopropilenodieno) Natural rubber Silicone Rubbers Source: ACRIB Tecumseh always recommends consulting the manufacturer or distributor, due to the variety of available components. 8 TECHNICAL BULLETIN - HYDROCABONS

9 Purity The refrigerants must contain a low level of contamination. The presence of impurities can cause: Moisture: acids / saturation filter / capillary blockage; Reduction of cooling capacity; Increasing on energy consumption; Increasing on work pressures (overheating). For hydrocarbons, the specifications of purity are determined according to international standards. Considering the DIN 8960 standard: Criteria Specification Moisture Purity 99,5 % mass Non-condensable gases 1,5 % (vapor phase vol.) Humidity 25 (mg/kg) Remark: The refrigerants R600a (isobutane) and R290 (propane) must be specific for use in refrigerating systems, due to the levels of purity and moisture listed in the table above. II. LUBRICANTS The using of the proper type of lubricant oil in the compressor contributes greatly to its good performance and longer lifetime. The lubricating oil has the following functions: In order to be used in refrigeration compressors, a lubricant must have the following characteristics: Reduce friction in the bearings; Seal the refrigerant in the cylinder during the suction and compression cycles; Cool the motor and pump (transport of heat). Miscibility with the refrigerant; No chemical reaction with the refrigerant; Fluidity at low temperatures; Thermal and electrical stability; Thermal conductor; Electrical insulation. 9

10 The following table shows the compatibility of lubricating oils with refrigerants: Refrigerant Mineral Oil Alkylate Oil Polyol Ester R12 Compatible Compatible Incompatible R134a Incompatible Incompatible Compatible R600a Compatible Compatible Compatible R22 Compatible Compatible Compatible R290 Compatible Compatible Compatible Lubricants containing silicone or silicate are not compatible with hydrocarbons and should not be used. III. SYSTEM DESIGN Compressors designed for application of hydrocarbon refrigerants have some peculiarities that differ from those used with other refrigerants. The characteristics of Tecumseh compressors for these refrigerants are presented below. Displacement COOLING CAPACITY (Btu/h) Min. Displacement R290 Max. Displacement R134a R600a R DISPLACEMENT (cm 3 /s) Test made at LBP ASHRAE 32 The graph beside, built for LBP application, presents the relation between compressor displacement and cooling capacity for different refrigerants. The dashed lines establish the displacement range of the compressors produced by Tecumseh for this application. Considering the same displacement, the R290 performs a cooling capacity approximately 70% higher than the obtained with R134a. On the other hand the R600a demands a displacement approximately 55% higher than R134a, to perform the same cooling capacity. Thus, the choice of R290 and R600a determines a new project with a new compressor displacement and does not allow the activity of retrofitting with R134a compressors 10

11 originally installed on the application. This can be seen in the example below: Characteristic / Refrigerant R134a R600a R290 Model TP1390YS TPJ1350MJS TPA2414UKS Cooling Capacity at 50 Hz Displacement (cc/rev) 7,28 7,28 7,28 Lubricant POE Mineral POE Comparing the R290 with a R22 compressor in the same displacement, we have: Characteristic / Refrigerant R22 R290 Model AE9415ES AE9415US Cooling Capacity at 50 Hz Displacement (cc/rev) 5,67 5,67 Lubricant AB1 Mineral Lubricants Electrical components Hydrocarbons are compatible with both mineral oils used in refrigeration systems for R12 and R22 and with the polyol ester oil used in R134a systems, as mentioned in Chapter II. As mentioned in chapter I of this bulletin, the hydrocarbon is a flammable refrigerant, thus, Tecumseh compressors for R290 and R600a are designed with electrical components that ensure its safe operation and maintenance, since they are free of electric event. Compressor designator Tecumseh offers selected compressors for use with R600a and R290. These compressors have the letter M as the designator for R600a and the letter U as the designator for R290, e.g., TSA1370MGS and THA2395UDS. It will be necessary to test each compressor selection in the applications to determine its suitability, since system operating conditions vary greatly from one application to another. 11

12 Besides the previous label, all Tecumseh compressors for R290 and R600a are identified according to their flammability, as shown at picture 4 below: When modifying or designing a product for the use of hydrocarbons, certain aspects should be carefully studied to obtain a good system performance and maximum reliability. In a product design, the best practice is to follow the specifications of the system manufacturer when modifying one of its components. In the following there are some recommendations for the refrigeration system with hydrocarbons. Evaporators and condensers There is no need to modify the evaporator or condenser when converting a system for the use of hydrocarbons, thus, it is possible to use the same components designed for R12, R22 and R134a that operate at similar pressures, without efficiency loss. Filter-driers Hydrocarbons allow the use of different types of filters when compared with R12, R22 or R134a. The Molecular Sieve desiccant type used with R600a (XH5, XH7, XH9 and MS594) may be fully applied to systems with R290. The table below shows the compatibility of filter driers in refrigeration systems loaded with the following refrigerants. Refrigerants Screen Silica XH5 XH6 XH7 XH9 Universal (MS 594) R22 R134a R600a R290 12

13 Capillary tubes In general, capillary tubes selected for R22 applications should be suitable for systems with the R290, and, likely, capillary tubes selected for R134a applications should be adequate as a preliminary selection for R600a. The use of mineral oil in systems for R600a implies in a lower risk of capillary blockage, when compared to R134a and POE oil. Thus, Tecumseh recommends using capillary tubes similar to those designed for R12, which have similar values of volume flows as to R600a. It is important to emphasize the need to conduct system tests to determine the final selection in a proper way. Refrigerant charge It is possible to establish a correlation of the refrigerant charge between hydrocarbons and CFC s and HCFC s through an analysis between their densities, as shown at picture 5 below. However, Tecumseh recommends performing an empirical analysis when modifying a system originally designed for a specific refrigerant. Reduction R22 R134a 40% R290 Reduction R12 60% R600a Reduction R134a 45% R600a 13

14 Working temperatures and pressures The recommended working temperatures and pressures for systems with hydrocarbons are shown below: Working Temperatures Condensing temperature Suction temperature Compressor discharge temperature Compressor dome temperature Compressor winding temperature C (50-55 F) over the environment temperature 3-5 C (37-41 F) below the environment temperature Lower than or equal to 120 C (248 F) Lower than or equal to 110 C (230 F) Lower than 130 C (266 F) Working Pressures (Application: LBP) Maximum pressures (psig) R134a R22* R600a R290 Equilizing pressure 85 / / /58 128/128 Peak pressure (discharge) Stabilized discharge pressure *Application: HBP Evacuation The evacuation levels for R600a or R290 systems should be the same as for HCFC systems (minimum of 200 microns at the system and pulled from both low and high pressure sides of the system). If care is not taken to prevent moisture from entering the system components prior to assembly, evacuation could be expected to take longer to achieve acceptable limits of system moisture and non-condensables. IV. SAFETY ASPECTS General aspects The main disadvantage in the use of hydrocarbons (R290 and R600a) is the flammability. Due to this characteristic, some safety measures are necessary, both in the refrigerator, as well as the environment of the factory that produces it. Thus, it is important to have knowledge of 14

15 the conditions for the occurrence of an accident, which are: Flammable mixture between air and flammable refrigerant; Source of heat that causes the ignition. The occurrence of the two conditions above must be prevented, so that no accidents occur. According to the TS standard for household refrigerators, all elements of the refrigerator that can emit or generate electric events are considered sources of heat or ignition, since there is no guarantee that the environment around the compressor or the refrigeration system is kept below the lower limit of explosion. Safety aspects of the product System components that are considered sources of leakage: evaporators, condensers, connectors, and the compressor. Products with flammable refrigerants shall be identified with the symbol below. All Tecumseh compressors have a label with this identification: The risk of explosion of a system equipped a flammable refrigerant depends on certain factors that should be analyzed according to the situation and location. Inside a cabinet, the risk depends on the evaporator and is much higher, because it is where the confinement of the refrigerant occurs. Outside the cabinet, the risk is lower because the combined conditions do not imply a saturation of the refrigerant in the environment. All electric switches installed in the product must be insulated. Thermostat, door contacts, internal lights contacts, defrost relay contacts, and others must be considered. Certain methods can be applied to assure the safety of the electrical components: Insulate terminals Locate within IP65 enclosure Replace with solid state type component Replace with Ex type component Locate externally Fans that can be installed inside or outside the refrigerator also must be included in the complement of these safety guidelines. They should not produce arcs, even when short circuit or blocked. Tecumseh compressors are equipped with sealed starting relays and thermal overload protectors, preventing the production of electric events that can cause the ignition of the flammable mixture. 15

16 The dimensional design of the product must take into consideration the separation of the environment of a possible ignition source (switches) and where the refrigerant leakage may occur. For instance, the evaporator must not be placed in the same environment that a electric event may occur. The replacement of any such equipment must be done by others with the same characteristics, assuring the safety and preventing the risk of explosion. Any device with flammable gases must be tested and approved in accordance with the procedures of the TS / IEC / EN by an independent body. Consult standards for details. Safety aspects in the manufacturing process In the manufacturing process, a safety system regarding the storage and handling of flammable refrigerants, containing authorities approval and compliance with legislation, must be adopted. This system must include: Adequate and secure facilities for storage of cylinders; Special fans (no arcs in the engines) to prevent the storage of gases; Control of areas with risk of leakages in pipes through detectors or sensors; Chargers designed for flammable refrigerants. Suppliers of chargers, detectors and the refrigerant itself can offer security systems projects In addition, controls and procedures must be followed as below: Leakage testing with equipment able to detect refrigerants R290 and/or R600a. If not available, Helium or Nitrogen can be used; Proper sealing of the system by cold welding or ultrasound, which does not require brazing with torch; Electronic leakage detectors must be calibrated (greater sensitivity = less than 0.5 g / year) for use with flammable gases and certificates; Trained team to handle the flammable gases. Maximum refrigerant charge According to international safety standards, the maximum refrigerant charge must be less than or equal to 150 g. This can be complied by keeping a maximum of 25% of the minimum explosion (LEL), which is approximately 8 g/m³ for the dimensions of a standard kitchen. To ensure the maximum efficiency in the leakage controls, it is recommended to use a detector specifically designed for use with the R290, or alternatively, a detector designed for use with Helium. 16

17 Accident situations Eye injuries At burns use cold water immediately. At frostbite use warm water. Lift the eyelid careful and rinse for at least 20 min. with copious amounts of water. Do not rub the eyes. Remove contact lenses, if present. Loose fitting, amicrobic dressing. Then take the injured person immediately to an eye specialist or accident hospital. Skin contact At frostbite warm up person by body heat. Do not rub. Do not open blisters from burns. Cover wounds aseptic. Take the injured person to a doctor or accident hospital as quickly as possible. Injuries from swallowing liquid refrigerant Give the injured person, as long as he or she is conscious, as much water or other warm drink as possible. V. RETROFITTING Since special safety considerations must be applied in the design of equipment using hydrocarbon refrigerants, such as R600a and R290, Tecumseh does not approve of, endorse, nor recommend retrofitting existing systems with R600a and R290. VI. FAQs (FREQUENTLY ASKED QUESTIONS) Can R134a systems be adapted to hydrocarbons such as R600a and R290 without any modification? No, Tecumseh does not recommend this practice. What should I do to detect leakages in the system? Tecumseh recommends the use of appropriate equipment able to detect refrigerants R290 and/or R600a or electronic leakage detectors. Are hydrocarbons flammable? Yes, hydrocarbons are flammable refrigerants. Can I use the torch to make repairs on the system that uses hydrocarbon refrigerant? Yes, repairs can be performed like for any conventional cooling system, but it is needed to ensure that the vacuum system is free of refrigerant. 17

18 If a leakage occurs inside a residence, is there a risk of explosion? The risk is almost zero due to the small quantity of hydrocarbon refrigerant used in domestic refrigerators (40 to 120g). How do I perform a refrigerant charge? After performing the evacuation in the system, charge the refrigerator according to the specified by the manufacturer, respecting the safety procedures. Tecumseh recommends the use of a precise balance to perform the charging, since small variations in the quantity can affect the performance of the system. Can I charge any quantity of hydrocarbons in the system? No, the maximum refrigerant charge for hydrocarbons is 150g. VII. REFERENCES ACRIB -. Guidelines for the use of Hydrocarbon Refrigerants in Static Refrigeration and Air Conditioning Systems Air Conditioning and Refrigeration Industry Board First Published February ANSI/ASHRAE Standard Designation and Safety Classification of Refrigerants - American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. BS EN :2001. Title Identifier Specification for safety of household and similar electrical appliances. Particular requirements for refrigerating appliances, ice-cream appliances and ice-makers. DIN 8960:1998: Requirements and coding system for refrigerants. Little Inc., A.D. Global comparative analysis of HFC and alternative technologies for refrigeration, air conditioning, foam, solvent, aerosol propellant, and fire protection applications, report for The Alliance for Responsible Atmospheric Policy, Cambridge, MA, Reference 75966, Handbook for the Montreal Protocol on Substances that Depletethe Ozone Layer - Eighth edition (2009). Ozone Secretariat United Nations Environment Programme (UNEP). IEC/TRF ( ), Ed. 2.0, English. This Test Report Form applies to IEC :2002 (Sixth edition) used in conjunction with IEC :2001 (Fourth edition). IPCC Fourth Assessment Report: Climate Change 2007 (AR4). Working Group I Report. The Physical Science Basis, chapter II. Jazwin, Richard. Alternative refrigerants, Business News Publishing Company, USA, Wikipedia the free encyclopedia. 18

19 VIII. GLOSSARY Boiling Point: the temperature and pressure at which a liquid changes states to a gas. CFC: chlorofluorocarbon. Condenser: the component in the refrigeration system where the refrigerant releases heat and changes from vapor to a liquid. Critical Temperature: The highest temperature a gas can reach and still be able to be condensed by applying pressure. Evaporator: The component in the refrigeration system that absorbs heat, thereby allowing liquid refrigerant to change to vapor. Flammability: defined as how easily something will burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Global Warming Potential (GWP): measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. HC: hydrocarbon; a compound containing only the elements hydrogen and carbon. HCFC: hydrochlorofluorocarbons. HFC: hydrofluorocarbons. Lower flammability limit (LFL): the minimum concentration of a substance, a refrigerant in this standard, that is capable of propagating a flame through a homogeneous mixture of the substance and air under specified test conditions. Montreal Protocol: an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. Ozone depletion potential (ODP): the relative amount of degradation to the ozone layer a chemical compound can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0. Chlorodifluoromethane (R-22), for example, has an ODP of CFC or R11 has the maximum potential amongst chlorocarbons because of the presence of three chlorine atoms in the molecule. Refrigerant: the fluid used for heat transfer in a refrigerating system; the refrigerant absorbs heat and transfers it at a higher temperature and a higher pressure, usually with a phase change. Retrofitting: procedure of converting a system originally design and built to operate with a certain refrigerant to operate with another refrigerant.

20 Informações sujeitas a alterações sem prévio aviso. Nos reservamos el derecho de introducir cambio en las informaciones sin-aviso previo. All information is subject to change without previous notice. Consulte para atualizações on-line. / Consulte para actualizaciones on-line. / Visit for online updates. TECUMSEH DO BRASIL LTDA. Rua Ray Wesley Herrick 700 Jd. Jockey Club São Carlos - SP, Brasil PHONE: FAX: marketing@tecumseh.com.br BIT /10