Procedure for changing the refrigerant oil in ammonia refrigeration systems, as well as lubricants specifically designed for compressors using special gases such as propylene and propane

CP-4700 Series Fully Synthetic Alkylbenzene Refrigerant Oils Product Features: The CP-4700 series are alkylbenzene-based synthetic refrigerant oils. This product features excellent stability, a low flocculation point, and good compatibility with structural materials. This product is widely designed, specified, initially installed, branded, or recommended by manufacturers of R12, R22, R407C, and R502 refrigeration compressors. This synthetic alkylbenzene material is fully compatible with mineral oil, and therefore can be added to mineral oil-based systems. This product brings significant improvements in the following aspects: energy savings, lubrication performance, cooling efficiency, reduction of filter clogging, decrease in compressor vibration, extension of equipment lifespan, reduced dosage requirements, improved cleanliness of the system, and extended service life of the lubricating oil. The CP-4700 series is suitable for the design of iso-viscosity alkylbenzene oils for the following compressor manufacturers: Hanbell, Fusheng, Thermo King, Dunham-Bush, Carrier (Carlyle), Bitzer, Grasso GEA, Century, Copeland, Embraco, BOCK, Maneurop, Danfoss, Mcquay, CIAT, J&E Hall (APV Baker), Trane, Refcomp, Frascold, GRAM, Sabroe (York Group), Frick, Daikin (Namirei), Rorocold, Bristol, Hitachi. Typical technical specifications: * Viscosity at 40°C, cSt, ASTM D445: 32, 68, 100; Viscosity at 100°C, cSt: 4.46, 5.9, 7.98; Viscosity at 100°F: 34.07, 63.70, 109.6; Viscosity at 210°F: 4.56, 6.06, 8.22. Viscosity index, ASTM D2270: 10, 1, 11. Density at 1 lb/gal at 60°F: 7.17, 7.20, 7.17. Pour point, °F (°C), ASTM D97: -49 (-45), -31 (-35), -22 (-30). Flash point, °C, ASTM D92: 360 (182), 355 (179), 430 (221). Ignition point, °C, ASTM D92: 375 (190), 380 (193), 460 (237). Specific gravity, ASTM D1298: 0.86, 0.864, 0.86. Maximum solidification point, °C, ASTM ASH86: -65, -55, -55. Heat capacity, BTU/lb·°F: at 100°F: 0.445; at 200°F: 0.474. The above data are not intended for use in preparing product specifications.

CP-4624-68-F (Compressor oil specifically for carbon dioxide) – a fully synthetic, food-grade lubricant for gas processing compressors. Product description: The CP-4624 F series is composed of synthetically derived hydrocarbon lubricants that improve lubrication performance in high or low temperature conditions and reduce volatility; it is also compatible with mineral oils or equipment designed to use mineral oils. It also contains additives for corrosion and oxidation resistance. The CP-4624F series of products is a long-lasting food-grade lubricant. Specialized in handling sealants used for pumping in chemical processes, compressor lubricants/coolants, and other applications that require improved chemical stability. Complies with FDA 21 CFR 178.3570 and the regulations regarding lubricants that have occasional contact with food. Typical technical parameters: ** 5-F 15-F 32-F 46-F 68-F Viscosity at 40°C, cSt, ASTM D445: 5.1 16.8 31.4 46.9 68.5 Viscosity at 100°C, cSt: 1.7 3.8 6.0 7.9 10.4 Viscosity at 100°F: 5.4 18.2 34.3 51.5 75.7 Viscosity at 210°F: 1.7 3.9 6.1 8.1 10.7 Viscosity index, ASTM D2270: 122 120 140 139 140 Density, 1 lb/gal, at 60°F: 6.65 6.82 6.88 6.91 6.96 Pour point, °F (°C), ASTM D92: -92 (-69), -98 (-72), -87 (-66), -76 (-60), -60 (-51) Flash point, C.O.C., °F (°C), ASTM D92: 320 (160), 432 (222), 464 (240), 514 (268), 519 (268) Ignition point, C.O.C., °F (°C), ASTM D92: 345 (174), 478 (248), 514 (268), 554 (290), 568 (298) Specific gravity, ASTM D1298: 0.798 0.818 0.826 0.829 0.835 Note: The data above are not intended for use in preparing product specifications.

CP-1542-32/46 series – high-quality polyether/ester-based air compressor oils: service life of 8,000 hours. Product details: This product is currently used by many air compressor manufacturers; it offers equivalent performance to products from brands such as Sullube and Ingersoll-Rand. It meets or exceeds the general 8,000-hour PAG/POE air compressor oil specifications. The CP-1542 series are custom-blended polyether/ester spiral air compressor oils. This formula provides superior lubrication performance at both high and low temperatures, reduces volatility, has a high viscosity index, and offers excellent corrosion protection. The CP-1542 series (with typical characteristics as follows) are lubricants with a long service life, formulated with rust inhibitors and antioxidants. There are various viscosity levels available depending on the specific application. Compared to mineral oil-based products, the CP-1542 series has the advantage of not producing carbon deposits or varnish-like substances. Typical characteristics: * Viscosity: 32–46; Viscosity at 40°C (ASTM D445): 39.34–48.25; Viscosity at 100°C: 7.89–9.38; Viscosity at 100°F, SUS: 199.3–244; Viscosity at 210°F, SUS: 52.6–57.8. Viscosity Index (ASTM D2270): 177–182. Density, g/ml, at 20°C: 0.974–0.974. Flash point, °C/°F (ASTM D92): 510°F/525°F. Fire point, °C/°F (ASTM D92): 575°F/540°F. Color: Green; Water content: White. Pour point: -51°C/-48°C. Copper content: La la. Note: 1. Lubricants based on fatty acid esters are not recommended for use in ammonia systems. 2. The above data are not intended for preparing product specifications.

CP-1009 –68 (OEM) synthetic refrigerant oil (compressor oil specific for R717), with a service life of two years. CP-1009-68 is a professionally formulated semi-synthetic refrigerant oil that possesses high chemical stability. It contains additives for antioxidant properties, corrosion resistance, a low pour point, and antifoaming effects. Such lubricants are widely used in harsh chemical environments ； Such as the requirements in the application of ammonia (R717) refrigeration compressors. This product is widely used for OEM original installation, designation, recommendation, and equivalent use by major ammonia compressor (R717) manufacturers around the world. Such as: Grasso, Mcquay, BOC (British Oxygen), Praxair, Sabroe, Linde, MESSER, Air Liquide, Mycom, Frick, York, APV, Vilter, FES, Toromont – and so on. Product applications and relative advantages • It has significant advantages in terms of cooling and lubrication functions in ammonia (R717) compressors. In compressor applications involving ammonia, it is particularly effective in combating corrosion and extending service life; especially when compared to designs using 68cSt mineral oil and alkylbenzene (AB) oil, its consumption is only about 20% to 25% of that of mineral oil and alkylbenzene oil. • In ammonia (R717) screw compression, the service life is approximately 6 times that of mineral oil. For example, under continuous operation conditions, CP-1009-68 can last up to 12,500 hours, while a typical naphthenic refrigeration oil (mineral oil) with a viscosity of 68 cSt has a continuous service life of around 2,000 hours. • Significantly reduces the cost of replacing filters and freezing components: since mineral oil is a product of the distillation process in petroleum refining, it contains a large amount of impurities. It is prone to undergoing a chemical reaction with the ammonia (R717) refrigerant, resulting in the formation of black particles that can clog the filter and cause a pressure drop. • CP-1009-68 has an extremely low vapor pressure and very low solubility in ammonia, which helps to reduce the carryaway, evaporation, and consumption of lubricating oil. • With over 30 years of experience and close collaboration with global ammonia (R717) compressor manufacturers, these specialized additive formulas offer distinct advantages such as reduced bearing wear, improved efficiency in ammonia refrigeration systems, excellent oxidation resistance, and a higher flash point. • It can extend the lifespan of the equipment, enable safer operation of the same, and provide better protection against rusting and chemical reactions in freezing components. • This product is widely used as compressors for cooling food, meat, vegetables, seafood, and everyday foods around the world. • A higher viscosity index ensures minimal changes in viscosity across extremely high and low temperature ranges, as well as provides better lubrication, thereby improving the efficiency of the compressor. • It is basically compatible with mineral oil or alkylbenzene oil, and can be directly added to compressor systems using mineral oil or alkylbenzene oil. • With all these advantages, it can significantly reduce the costs associated with the maintenance of mechanical equipment, as well as the amount of machinery that needs to be repaired or recycled. Therefore, it is widely installed and used by OEM manufacturers around the world. Product Introduction: The CP-1009 series consists of professionally formulated, highly refined, chemically inert semi-synthetic lubricants. It contains additives for antioxidant properties, corrosion resistance, a low pour point, and antifoaming effects. Such lubricants are widely used in harsh chemical environments ； As required in ammonia cryogenic applications. Typical technical parameters: 32 68 100 – Viscosity at 40°C, cSt per ASTM D445: 34.4; 69 108 – Viscosity at 100°C, cSt: 5.8, 9.1, 12.0; Viscosity at 100°F, SUS: 176.7, 357, 560; Viscosity at 210°F, SUS: 45.6, 56.8, 68.3. Viscosity index per ASTM D2270: 110, 100, 100. Density, 1 lb/gal at 60°F: 7.3, 7.4, 7.3. Pour point, °F (°C) per ASTM D97: -35 (-37), -38.2 (-39), 10 (-12). Flash point, C.O.C., °F (°C) per ASTM D92: 420 (216), 440 (226), 510 (266). Ignition point, C.O.C., °F (°C) per ASTM D92: 460 (238), 475 (246), 550 (288). Specific gravity per ASTM D1298: 0.87, 0.867, 0.87. ** The data above are not intended for use in formulating product specifications.

CPI Solest-220 (OEM) is used for R-134a, R404, R407, R410, and R507 refrigerant systems. Currently used by the following companies, or products equivalent to them. Hanbell, Fusheng, GEA (Grasso), Thermo King, Blissfield, Sabroe, Bitzer, Bock, Carrier (Carlyle), Dunham-Bush, J&E Hall (APV Baker), Frick, Statoil. This product is also suitable for the design of POE oils with a viscosity of 220 cSt. Physical properties as determined through performance tests: THE SOLEST lubricant is specifically designed for use in the air conditioning industry and for standard factory installations of refrigeration equipment. To provide maintenance and after-sales market services for original equipment manufacturers (OEMs), CPI’s laboratory conducts tests on air compressors from various OEMs, and then offers a range of specially designed products. And these products fully meet the system’s requirements, are non-toxic, and comply with the standards of 29CFR 1910.1200 in the United States. CPI offers improved performance, far exceeding that of conventional mineral oils in terms of viscosity index, flash point, ignition point, and pour point. Typical technical parameters of SOLEST:
Properties: 31-HE LT-32 46 68 70 120 170 220 370
Viscosity at 40°C: 32.7 33.1 49.5 66.3 65.5 127.7 175.2 233.3 393.1
Viscosity at 0°C: 5.7 5.7 6.9 8.9 9.0 12.7 16.5 18.4 26.1
Viscosity at 100°F: 35.9 36.4 55.1 73.9 72.9 144.8 198.8 267.9 455.3
Viscosity at 210°C: 5.8 5.8 7.1 9.1 9.2 13.1 17.0 19.0 27.0
Viscosity index: 115 112 93 108 113 90 93 86 89
Density at 1 lb/gal: 7.81 8.03 7.80 7.96 7.85 7.91 7.93 7.94 8.00
Pour point/°C(°F)

CP-9345-46 8000-hour synthetic air compressor oil Product description: CP-9345-46 is a professionally formulated triple-hydrogenated synthetic air compressor oil. This lubricant possesses excellent lubricating properties; it maintains good chemical and hydrolytic stability as well as low volatility, regardless of whether it is in high or low temperature conditions. It can be equal to or exceed that of conventional 8000-hour polyalphaolefin (PAO) synthetic air compressor oils; this product is compatible with mineral oils and polyalphaolefins. In experiments with screw-type air compressors, CP-9345-46 can operate continuously for 8,000 hours at a higher discharge temperature of 85°C, or it has a service life four times that of conventional mineral-based air compressor oils. Compatibility: This product is compatible with and can be used in conjunction with the following brands: Quincy QUIN-SYN, Atlas Copco (ROTO FLUID), Gardener Denver (AEON 9000 SP), Le Roi SSL-46, Ingersoll-Rand XHP-505 or PERFORMANCE 500, KAESER (SIGMA 8000 S-460), GRIMMER SCHMIDT (SUPER 46), PALATEK-SULLIVAN (PALASYN45), Sullair LLL-4-46, SYN-FLO (SYN-FLO 80-XP)……and so on. Typical properties: Viscosity at 40°C (cSt) – ASTM D445: 42; Viscosity at 100°C (cSt) – ASTM D445: 7.2; Viscosity at 100°F: 46; Viscosity at 210°F: 7.4. Viscosity coefficient – ASTM D2270: 133. Density, lb/gal at 60°F: 7. Flash point, C.O.C., °F(°C) – ASTM D92: 475 (246). Ignition point, C.O.C., °F(°C) – ASTM D92: 500 (260). Pour point, °F(°C) – ASTM D92: -4 (-20). Acid value: 0.1. *The above data are not intended for use in formulating product specifications. **The product is packaged in 55 gallons (208 liters)

CP-1400-130 Stationary Gas Engine Oil – Product Description: The technical requirements for stationary gas engine oil have been continuously evolving in recent years. Fixed gas engines play a crucial role in many areas, such as pipeline natural gas compression, power generation, and waste heat recovery. These engines operate for extended periods at various speeds, loads, and temperatures. Many others also work in harsh environments such as those in the oil and gas sector. The composition of a high-quality fixed-gas engine oil varies depending on the different types of gases. For example, natural gas mainly contains methane, high-sulfur liquefied petroleum gas contains large amounts of sulfur, biogas contains hydrogen sulfide, and waste gases from landfills contain corrosive gases. A successful design for a gas engine requires not only consideration of the use of different gases, but also a thorough understanding of engine design and operation. A major example is the dual use of engine oil in compressors. CP-1400-130 is a high-performance lubricant used to lubricate natural gas compressors and motors. It uses highly refined base oil, which is stable and has low volatility. The latest technologies are applied in the additives to meet the requirements of natural gas compressors and motors. The lubricant provides excellent performance for compressors/motors under various operating conditions and with different natural gas compositions, offering clean operation of the motor, low wear, and low costs. Features and advantages (CPI, exclusive for Mr. Wang in Shenzhen: 13926549484) The viscosity grade of CP-1400-130 is SAE 40 ； It performs well in two-stroke and four-stroke stationary gas engines that require low or zero ash content, offering advantages such as easy cleaning of the engine, a long oil change interval, and low fuel consumption. The composition must also take into account the minimization of impurities/sludge generation, as well as low wear of the pistons/cylinders and rods/bushings in reciprocating gas compressors. Since certain impurities in the gas can cause corrosion to the machinery, special additives have been included in CP-1400-130 to protect the engine and compressor. The advantages of CP-1400-130 include: a. Its optimized composition makes it suitable for use with both natural gas compressors and motors: 1. It effectively controls the formation of impurities, wear, oil oxidation, and nitration in natural gas motors, thereby reducing downtime and maintenance costs. 2. It effectively controls the formation of impurities and wear in reciprocating gas compressors, thereby reducing downtime and maintenance costs. 3. Additives control the occurrence of corrosion in the motor and compressor (caused by H2S and other impurities). b. The motors and compressors remain clean due to the oxidative stability of the oil and the low formation of impurities. c. The additives provide good protection for the motor and compressor, thereby preventing clogging of the spark plugs and the combustion ports. d. The high stability of the lubricant and its low tendency to form impurities result in a longer service life for it and the filtration device. e. Low freezing point, suitable for various extreme weather conditions. Technical parameters: SAE grade 40. Viscosity at 40°C: 130.9 cSt; at 100°C: 14.6 cSt; at 100°F: 147.3 cSt; at 210°F: 15.0 cSt. VI: 112; TAN: 0.625. Density at 20°C: 0.875 g/mL. Flash point: 520°F/271°C; Ignition point: 550°F/288°C. Pour point: -26°F/-32°C. Foam production: 0 mL. Sulfate ash, wt%: 0.09. (http://cpihualai.178b2b.com/ Contact Mr. Wang at 13926549484)

CP-4600 series (OEM) Fully synthetic PAO refrigeration compressor oil specifically designed for ammonia (R-717) propylene refrigerators. 13926549484, Youwang. Product description: The CP-4600 series is a professionally formulated poly-alpha olefin (PAO) synthetic refrigeration oil. It can improve lubrication under high and low temperatures, reduce volatility, and possesses good chemical inertness and hydrolytic stability. And it has good compatibility with mineral oil. The CP-4600 series (with typical properties as follows) is a long-life lubricant, especially for oil-immersed screw compressors. CP-4600-68 is often recommended for use in refrigerators due to its excellent performance characteristics at low temperatures. This product contains no wax, and it has a low pour point and flocculation point on the freezing production line. Even with the dilution of the refrigerant, CP-4600-68 possesses high oil film strength, enabling good lubrication. Typical technical parameters: 32, 46, 68, 100, 150. Viscosity at 40°C, cSt – ASTM D445: 31.4, 46.9, 68.5, 100.3, 147.7. Viscosity at 100°C, cSt: 6.0, 7.9, 10.4, 13.7, 18.2. Viscosity at 100°F, SUS: 34.3, 51.5, 75.7, 111.4, 164.8. Viscosity at 210°F, SUS: 6.1, 8.13, 10.7, 14.1, 18.7. Viscosity index – ASTM D2270: 140, 139, 140, 138, 138. Density, 1 lb/gal, at 60°F: 6.88, 6.91, 6.96, 6.99, 7.04. Pour point, °F (°C) – ASTM D97: -87 (-66), -76 (-60), -60 (-51), -55 (-52), -49 (-45). Flash point, C.O.C., °F (°C) – ASTM D92: 464 (240), 475 (246), 480 (248), 510 (265), 530 (277). Ignition point, C.O.C., °F (°C) – ASTM D92: 514 (268), 525 (273), 530 (276), 560 (293), 580 (304). Specific gravity – ASTM D1298: 0.826, 0.829, 0.835, 0.839, 0.845. ** The data above are not intended for use in formulating product specifications. .

Introduction to the Selection of Refrigerant Oil for Compressor Maintenance: As the core component in the HVAC&R industry and one with the highest cost, the performance and maintenance of compressors are issues that receive significant attention from professionals and users in this sector. The author has been engaged in the research and development of compressors, and would like to share personal views on the use of refrigeration oil in the operation and maintenance of compressors, in the hope that it will be helpful to my colleagues. 　　I. Matching of Compressors and Refrigerant Oils 　　1. Select the refrigerant oil based on the requirements of the refrigerant used in the compressor. Environmentally friendly refrigerants, including R134a, are paired with ester-based synthetic refrigeration oils ； Non-environmentally friendly refrigerants such as R22 are paired with mineral refrigeration oils. 　　2. Select the refrigeration oil based on the requirements imposed by the operating conditions of the compressor. The air-conditioning compressor is equipped with a refrigerant oil whose dynamic viscosity ranges from 30 to 50 at 40°C ； Refrigeration and cold storage compressors are equipped with refrigerant oils whose dynamic viscosity at 40°C ranges from 20 to 40 ； High-temperature screw compressors are equipped with refrigeration oils whose dynamic viscosity is above 100 at 40°C ； The refrigerator compressor is equipped with a refrigerant oil whose dynamic viscosity ranges from 20 to 40 at 40°C ； 　　3. For the compatibility table of refrigerant oils for various types of compressors, please check the album on QQ: 1163727045. II. Tips for using refrigerant oils in compressors 1. The amount of refrigerant oil to be used. The amount of refrigerant oil should be adjusted such that, after the entire refrigeration system has been installed and tested, the level of the oil returning to the compressor, as seen through the sight glass, is at the middle line of the sight glass. Excess return oil can cause the refrigerant to be overly diluted, resulting in very low cooling efficiency ； Too low a return oil level can lead to a decline in the lubrication, heat dissipation, sealing, and insulation properties of the refrigerant oil. Therefore, when the piping of the installed unit is long, an appropriate amount of compatible refrigerant oil should be added. 　　2. Replacement of refrigeration oil. The compressor should be kept in clean and orderly working conditions. To ensure optimal performance, safety, and the compressor’s service life, maintenance work and regular inspections are necessary, including the replacement of refrigerant oil. The replacement of the refrigeration oil involves cleaning the filter; the first replacement is carried out after the new compressor has been running for 100–200 hours, and subsequent replacements are needed once a year. Of course, the used refrigerant oil must be disposed of in accordance with **requirements; otherwise, it can lead to safety hazards and pollution. 　　3. Use of ester-based synthetic refrigeration oils. When using environmentally friendly refrigerants, ester-based synthetic refrigeration oils should be selected for compressors, as only such oils can ensure good miscibility with the refrigerant. It is important to note that ester-based synthetic refrigeration oils have a high degree of hygroscopicity. This imposes much higher requirements on the engineers and operators who install refrigeration systems with regard to maintaining the cleanliness and dryness of the equipment. The safe operating condition for a refrigeration system is such that a residual humidity of 100 ppm can already cause damage to the entire system. 　　4. Mixed use of various mineral refrigerant oils. Different brands of refrigeration oil can be mixed together when they have the same viscosity. The manufacturer has conducted tests in this regard. According to tests conducted by a compressor manufacturer in Germany with over 70 years of experience, it has been found that FUCHS DEA, MO-BIL, American CPI, ICI (acquired by CPI in 2007), and LUBIL refrigeration oils can be mixed together when they have the same viscosity, or actually very similar viscosities. As standard refrigeration oil, FUCHS DEA Reniso SP 46 is pre-charged in Bock compressors. It can be mixed with refrigeration oils such as LUBIL 4GS. III. Examples of problems with compressor oils 1. High paraffin content. When the operating temperature of the compressor drops to a certain level, paraffin begins to precipitate out of the refrigeration oil, causing it to become cloudy. When the refrigeration oil releases paraffin, excess amounts of it can accumulate at the throttle valve, causing it to become clogged, or it may accumulate on the heat transfer surfaces of the evaporator, thereby affecting its heat transfer efficiency. 2. The pour point is too high. The temperature at which the refrigeration oil cools to a point where it stops flowing under experimental conditions is called the pour point. In refrigeration systems, heat exchange equipment and pipes typically operate at low temperatures, and an oil film more or less forms on their walls. If the pour point of this oil is too high, it will affect the flow of the refrigerant, increase flow resistance, and impair heat transfer efficiency. Generally speaking, for refrigeration equipment, the lower the pour point, the better. When designing a refrigeration system, the pour point of the refrigerant oil must be 5°C lower than the lowest evaporation temperature of the system. 3. It has low chemical stability. Pure refrigerant oils have stable chemical compositions, do not oxidize, and do not corrode metals. However, corrosion occurs when the refrigeration oil contains refrigerants or moisture; oxidation of the lubricating oil produces acidic substances that corrode metals. When the refrigeration oil is at high temperatures, coke is formed. If this substance adheres to the valve elements, it will affect their proper functioning and also cause blockages in the filters and throttle valves. Therefore, it is necessary to choose a refrigeration oil with good chemical stability and antioxidant properties. Figures 5 and 6 show the carbon deposition problem caused by the low chemical stability of the refrigeration oil. 　　4. The levels of mechanical impurities and moisture are above the specified limits. If the refrigeration oil contains moisture, it will accelerate the chemical changes in the oil, causing it to deteriorate and leading to corrosion of metals. It can also cause \"ice blockages\" at the throttle valve or expansion valve. Mechanical impurities present in lubricating oil can exacerbate wear on the friction surfaces of moving parts, and they can quickly clog filters as well as throttle or expansion valves; therefore, refrigeration machine lubricating oil should not contain mechanical impurities. 　　IV. Selection of refrigeration oil 1. Consider the brand. The refrigerant oil is pre-prepared in the compressor factory before the products leave there; therefore, for future maintenance, using the oil that was pre-prepared from the start is a foolproof solution. However, in practice, the compressor factories charge very high prices for this pre-prepared oil. To reduce costs, our maintenance staff opt for alternative refrigeration oils. Among the products available on the market that offer guaranteed quality at affordable prices are brands such as American CPI (CPI’s sales representative in China: 13926549484, http://cpicpi.b2b.youboy.com), ICI, SUNISO, and LUBIL. 　　2. Check the color. The simplest way to determine the quality of refrigerant oil is by checking its color. The normal color of mineral refrigerant oil is transparent with a slight yellow tint; if it is cloudy or has a dark color, it indicates a high level of impurities and paraffin in the oil. The normal color of ester-based synthetic refrigeration oils is a transparent yellowish hue, slightly darker than that of mineral oils. The color becomes darker as the dynamic viscosity increases; at a viscosity of 220, it takes on a yellowish-red appearance.

Analysis of common compressor failures -- Motor burnout. Failures in motor-compressors (hereinafter referred to as compressors) can be divided into motor-related failures and mechanical failures (including the crankshaft, connecting rods, pistons, valve plates, cylinder head gaskets, etc.). Mechanical failures often cause the motor to operate under overload or even to stall, which is one of the main reasons for motor damage. Damage to motors is mainly manifested as damage to the insulation layer of the stator windings (short circuits) and open circuits. Damage to the stator windings is difficult to detect in a timely manner, which can ultimately lead to the windings burning out. After the winding burns out, it masks some of the phenomena or direct causes that led to the burnout, making post-event analysis and root-cause investigation more difficult. However, the operation of a motor relies on a proper power supply, a reasonable motor load, good heat dissipation, and protection for the insulation layer of the winding enameled wire. By examining these aspects, it is not difficult to see that the reasons for winding burnout are essentially one of the following six: (1) abnormal load and stall ； (2) Winding short circuit caused by metal shavings ； (3) Contactor issues ； (4) Power supply phase loss and voltage abnormalities ； (5) Insufficient cooling ； (6) Evacuate using a compressor. In fact, motor damage caused by a combination of various factors is more common. 1. Abnormal load and stall: The motor load includes the load required to compress gas as well as the load needed to overcome mechanical friction. An excessively high pressure ratio, or an excessive pressure difference, will make the compression process more difficult ； The increased frictional resistance caused by lubrication failure, along with motor stalling under extreme conditions, will **increase the motor load**. Lubrication failure and increased frictional resistance are the primary causes of abnormal loads. The return of liquid dilutes the lubricating oil; overheating of the lubricating oil, its coking and deterioration, as well as a lack of oil can all disrupt proper lubrication and lead to lubrication failure. The returning liquid dilutes the lubricating oil, interfering with the formation of a proper oil film on the friction surfaces; it may even wash away the existing oil film, thereby increasing friction and wear. Compressor overheating can cause the lubricating oil to become thin or even coker at high temperatures, affecting the formation of a proper oil film. The system’s oil return is poor, resulting in a lack of oil in the compressor, which naturally prevents proper lubrication. As the crankshaft rotates at high speeds and components such as connecting rods and pistons move rapidly, the friction surfaces that lack oil film protection heat up quickly. The high local temperatures cause the lubricating oil to evaporate or carbonize rapidly, making it even more difficult to lubricate those areas; severe local wear can occur within just a few seconds. Lubrication failure and localized wear require more torque to rotate the crankshaft. Low-power compressors (such as those in refrigerators and household air conditioners), due to their low motor torque, often experience stall conditions when lubrication fails; this leads to a vicious cycle of stall – thermal protection – stall, and motor burnout is only a matter of time. High-power semi-hermetic compressor motors have high torque, and local wear does not cause stalling. The motor power increases with the load within a certain range, which leads to more severe wear, and may even result in serious damages such as piston seizure (the piston getting stuck inside the cylinder) or broken connecting rods. The current during stall (stall current) is approximately 4–8 times the current under normal operation. At the moment the motor starts, the peak value of the current can approach or reach the stall current. Since the heat generated by resistance is proportional to the square of the current, the currents during startup and stall cause the windings to heat up rapidly. Thermal protection can safeguard the electrodes during stall, but it generally does not respond quickly and cannot prevent changes in winding temperature caused by frequent startups. Frequent starting and abnormal loads subject the windings to high temperatures, which reduces the insulation performance of the enameled wire. Furthermore, the load required to compress gas also increases as the compression ratio and pressure difference increase. Therefore, using a high-temperature compressor in a low-temperature application, or a low-temperature compressor in a high-temperature application, affects the motor load and heat dissipation; it is inappropriate and will shorten the service life of the electrodes. Once the insulation performance of the windings deteriorates, other factors (such as metal shavings forming conductive paths or acidic lubricants) can easily lead to short circuits and damage. 2. Short circuits caused by metal shavings: Metal shavings mixed within the windings are the main cause of short circuits and low insulation resistance. The normal vibration of the compressor during operation, as well as the twisting of the windings due to electromagnetic forces each time it starts up, both cause relative movement and friction between the metal shavings trapped among the windings and the enameled wires of those windings. Sharp metal shavings can scratch the insulation layer of enameled wire, causing a short circuit. Sources of metal shavings include copper pipe shavings left over from construction, welding slag, and metal shavings that result from wear inside compressors and damage to components (such as broken valve plates). For hermetically sealed compressors (including hermetically sealed scroll compressors), these metal shavings or particles will fall on the windings. In semi-hermetically sealed compressors, some particles flow through the system along with the gas and lubricating oil, and eventually accumulate in the windings due to their magnetic properties ； And some metal shavings (such as those generated by bearing wear and wear of the motor rotor and stator, known as slot cleaning) fall directly onto the windings. Once metal shavings accumulate in the windings, a short circuit is only a matter of time. Special attention should be paid to the two-stage compressor. In a two-stage compressor, the return gas and normal oil return flow directly into the cylinders of the first stage (low-pressure stage). After compression, they pass through medium-pressure pipes to reach the motor chamber where they cool the windings; thereafter, just like in a conventional single-stage compressor, they proceed to the second stage (high-pressure stage cylinders). The return gas contains lubricating oil, which already makes the compression process extremely risky; if liquid also returns, the valve plates in the first-stage cylinder can easily be damaged. The broken valve pieces can enter the winding through the medium-pressure pipe. Therefore, two-stage compressors are more prone to motor short circuits caused by metal shavings than single-stage compressors. Bad things tend to happen together; when analyzing a compressor that is having problems, one often detects a burnt smell of lubricant. The temperature is very high when the metal surface is severely worn, and lubricating oil begins to coker at temperatures above 175ºC. If there is excessive moisture in the system (due to inadequate vacuum extraction, high water content in the lubricating oil and refrigerant, or air entering after a rupture in the negative pressure return pipe), the lubricating oil may become acidic. Acidic lubricants can corrode copper pipes and the insulation layers of windings; on one hand, it causes copper plating ； On the other hand, this acidic lubricant containing copper atoms has poor insulating properties, which creates conditions for winding short circuits. 3. Contactor issues: The contactor is one of the important components in a motor control circuit; an inappropriate selection can damage even the best compressors. It is extremely important to select the contactor appropriately based on the load. Contactors must be able to meet harsh conditions such as rapid cycling, continuous overload, and low voltage. They must have a large enough area to dissipate the heat generated by the load current, and the contact material chosen must prevent welding under conditions of high current such as startup or stall. For safety and reliability, the compressor contactor must disconnect all three phases of the circuit at the same time. Takumi Corporation does not recommend the method of disconnecting two-phase circuits. In the United States, contactors approved by Takumi Corporation must meet the following four requirements: • The contactors must comply with the operating and testing criteria specified in ARI Standard 780-78, \"Standard for Special Purpose Contactors\". • The manufacturer must ensure that the contactor can close at room temperature at 80% of the minimum voltage specified on the nameplate. • When using a single contactor, its rated current must be greater than the motor’s nameplate current rating (RLA). Additionally, the contactor must be able to handle the motor’s stall current. • If there are other loads downstream of the contactor, such as motor fans, they must also be taken into consideration. • When two contactors are used, the stall rating of the separate windings of each contactor must be equal to or greater than the stall rating of the compressor’s half-winding. The rated current of the contactor must not be lower than the rated current specified on the compressor’s nameplate. Contactors of small size or poor quality cannot withstand the high current surges that occur during compressor startup, stall conditions, and low voltage; as a result, they are prone to single-phase or multi-phase contact oscillation, welding, or even detachment, which can lead to motor damage. Contactors with vibrating contacts frequently start and stop the motor. Frequent starting of the motor, along with the high starting current and resulting heat generation, accelerates the aging of the winding insulation layer. Every time it is started, the magnetic torque causes slight movement of the motor windings and friction between them. If other factors are present (such as metal shavings, lubricants with poor insulating properties, etc.), it is easy to cause short circuits between the windings. The thermal protection system is not designed to prevent such damage. Furthermore, the vibrating contactor coil is prone to failure. If the contact coil is damaged, a single-phase condition is likely to occur. If the contactor is selected to be too small, its contacts cannot withstand the arc and the high temperatures generated by frequent switching cycles or unstable control circuit voltages, which may cause them to weld together or fall off the contact holder. The welded contacts will create a permanent single-phase condition, causing the overload protector to continuously cycle on and off. It should be particularly emphasized that once the contacts of the contactor are welded together, all controls that rely on the contactor to disconnect the compressor’s power supply circuit – such as high/low pressure control, oil pressure control, defrost control, etc. – will cease to function, leaving the compressor without any protection. Therefore, checking the contactor is an essential step after the motor burns out. Contactors are an often-overlooked but important cause of motor damage. 4. Power supply phase loss and voltage abnormalities. Abnormal voltages and phase loss can easily destroy any motor. The range of variation in the supply voltage must not exceed ±10% of the rated voltage. The voltage imbalance between the three phases must not exceed 5%. High-power motors must be powered independently to prevent low voltage caused by the startup and operation of other high-power devices on the same circuit. The motor power cable must be able to carry the motor’s rated current. If a phase loss occurs while the compressor is running, it will continue to operate but with a high load current. The motor windings will overheat quickly, and under normal conditions the compressor will be protected by a thermal switch. When the motor windings cool down to the set temperature, the contactor closes, but the compressor fails to start and experiences stall, entering a dead loop of \"stall – thermal protection – stall\". The differences in modern motor windings are very small; when the power supply is three-phase balanced, the differences in phase currents can be ignored. Under ideal conditions, the phase voltages remain equal at all times; installing a protector on any one of the phases is sufficient to prevent damage caused by overcurrent. In fact, it is difficult to ensure the balance of phase voltages. The percentage of voltage imbalance is calculated as the ratio of the maximum deviation of the phase voltages from the average value of the three-phase voltages to that average value. For example, in a three-phase power supply with a nominal voltage of 380V, the voltages measured at the compressor terminals are 380V, 366V, and 400V respectively. The average value of the three-phase voltages is 382V, and the maximum deviation is 20V; therefore, the percentage of voltage imbalance is 5.2%. As a result of voltage imbalance, the imbalance in load current under normal operation is 4 to 10 times the percentage of voltage imbalance. In previous cases, a 5.2% unbalanced voltage can cause a 50% current imbalance. The motor and generator standards publication issued by the National Electrical Manufacturers Association (NEMA) in the United States states that the percentage increase in temperature of the phase windings caused by unbalanced voltage is approximately twice the square of the percentage of voltage imbalance. In the previous case, the number of voltage imbalance points was 5.2, and the percentage increase in winding temperature was 54%. As a result, one winding overheated while the temperatures of the other two windings remained normal. A survey conducted by U.L. (Underwriters Laboratories, USA) showed that 43% of power companies allow a voltage imbalance of 3%, while another 30% of power companies permit a voltage imbalance of 5%. 5. Insufficient cooling: Compressors with high power are generally of the return-air cooling type. The lower the evaporation temperature, the smaller the system mass flow tends to be. When the evaporation temperature is very low (above the manufacturer’s specifications), the flow rate is insufficient to cool the motor, causing it to operate at a higher temperature. Air-cooled compressors (usually not exceeding 10 HP) rely less on return air, but they have specific requirements regarding the compressor’s operating temperature and the volume of cooling air. A large leak of refrigerant can also lead to a decrease in the system’s mass flow, which in turn affects the cooling of the motor. In some unmonitored cold storage facilities, it is often only when the cooling performance becomes very poor that a large leak of refrigerant is discovered. When the motor overheats, it will trigger frequent protection mechanisms. Some users do not investigate the reasons behind this in detail; they even short-circuit the thermal protector, which is a very bad thing to do. It won’t be long before the motor burns out. Compressors all have a safe operating range. The main considerations for safe operation are the load and cooling of the compressor and motor. Due to the different prices of compressors in various temperature ranges, it was common in China’s refrigeration industry in the past for compressors to be used beyond their designated scope. With the increase in professional knowledge and improved economic conditions, the situation has improved significantly. 6. Evacuation using a compressor Open-type refrigeration compressors have been forgotten by most people, but some field technicians in the refrigeration industry still retain the old practice of using compressors for evacuation. This is very dangerous. Air acts as an insulating medium. After evacuating a sealed container, discharge phenomena between the electrodes inside it occur easily. Therefore, as the vacuum level inside the compressor housing increases, the insulating material is lost between the exposed terminals inside the housing or between windings that have minor insulation defects; once electricity is applied, the motor may short-circuit and burn out in an instant. If the housing leaks electricity, it can also cause electric shock to people. Therefore, vacuuming using a compressor is prohibited, and it is strictly forbidden to power on the compressor when the system and the compressor are in a vacuum state (after vacuuming but before refrigerant has been added). 7. Conclusion: After the motor burned out, the damage to the windings was concealed, posing certain difficulties for fault analysis. However, the root cause of damage to the compressor motor does not disappear. Abnormal loads or even stall caused by poor or failed lubrication, as well as insufficient heat dissipation, can all shorten the lifespan of the windings ； The presence of metal shavings in the windings further facilitates short circuits ； Contactor welding will prevent the compressor from being protected ； An abnormality in the power supply on which the motor relies for operation will completely destroy any motor ； Creating a vacuum with a compressor may cause discharge at the internal terminals. Unfortunately, the aforementioned adverse factors can also trigger each other: the high currents during abnormal loads and stall conditions may cause the contactors to weld together ； Arcing or even welding at a single contact can cause phase imbalance or single-phase operation ； Phase imbalance can cause heat dissipation problems ； Insufficient heat dissipation can cause wear ； Wear and tear generates metal shavings… Therefore, proper installation and use of the compressor, along with adequate routine maintenance, can prevent such adverse effects; this is the fundamental way to avoid damage to the compressor motor.