Application Engineering

Transcription

1 Application Engineering Application Guidelines for Copeland Scroll Horizontal Cryogenic Compressors ZCH22/48/68/72 AE R2 March 2013 TABLE OF CONTENTS Section Page Section Page Safety Instructions... 2 Safety Icon Explanation... 2 Instructions Pertaining to Risk of Electrical Shock, Fire, or Injury to Persons... 3 Safety Statements... 3 Introduction... 4 Nomenclature... 4 Oil Management... 4 Oil Separation... 4 Oil Flow Rate... 4 Reverse Oil Flow... 4 Oil Type and Removal... 4 Oil Charge... 4 Compressor Operating Temperature... 4 Shell Temperature... 5 Discharge Line Thermostat... 5 Motor Protection... 5 Mounting... 5 Compressor Orientation... 5 High Pressure Control... 5 Low Pressure Control Valve... 5 Discharge Check Valve... 5 Internal Pressure Relief... 6 Cycle Times... 6 Shutoff Sound... 6 Rotation Direction... 6 Brief Power Interruptions... 6 Electrical Connections... 6 Deep Vacuum Operation... 6 Suction and Discharge Fittings... 7 Brazing Procedure... 7 Removing System Components... 7 Screens... 7 Scroll Functional Check... 7 System Clean Up... 8 Figures & Tables Port Locations... 9 Oil Management Diagram... 9 Horizontal CryoScroll Operating Map Scroll Suction Tube Brazing Bracket Compressor Mounting ZCH Bracket Compressor Mounting ZCH Minimum Oil Flow Mounting Specifi cations Valve Requirements Cryogenic Scroll Specifi cations

2 Safety Instructions Copeland Scroll compressors are manufactured according to the latest U.S. and European Safety Standards. Particular emphasis has been placed on the user's safety. Safey icons are explained below and safety instructions applicable to the products in this bulletin are grouped on Page 3. These instructions should be retained throughout the lifetime of the compressor. You are strongly advised to follow these safety instructions. Safety Icon Explanation DANGER WARNING CAUTION NOTICE CAUTION DANGER indicates a hazardous situation which, if not avoided, will result in death or serious injury. WARNING indicates a hazardous situation which, if not avoided, could result in death or serious injury. CAUTION, used with the safety alert symbol, indicates a hazardous situation which, if not avoided, could result in minor or moderate injury. NOTICE is used to address practices not related to personal injury. CAUTION, without the safety alert symbol, is used to address practices not related to personal injury. 2

3 Instructions Pertaining to Risk of Electrical Shock, Fire, or Injury to Persons WARNING ELECTRICAL SHOCK HAZARD Disconnect and lock out power before servicing. Discharge all capacitors before servicing. Use compressor with grounded system only. Molded electrical plug must be used when required. Refer to original equipment wiring diagrams. Failure to follow these warnings could result in serious personal injury. WARNING PRESSURIZED SYSTEM HAZARD System contains refrigerant and oil under pressure. Remove refrigerant from both the high and low compressor side before removing compressor. Never install a system and leave it unattended when it has no charge, a holding charge, or with the service valves closed without electrically locking out the system. Use only approved refrigerants and refrigeration oils. Personal safety equipment must be used. Failure to follow these warnings could result in serious personal injury. WARNING BURN HAZARD Do not touch the compressor until it has cooled down. Ensure that materials and wiring do not touch high temperature areas of the compressor. Use caution when brazing system commponents. Personal safety equipment must be used. Failure to follow these warnings could result in serious personal injury or property damage. CAUTION COMPRESSOR HANDLING Use the appropriate lifting devices to move compressors. Personal safety equipment must be used. Failure to follow these warnings could result in personal injury or property damage. Safety Statements Refrigerant compressors must be employed only for their intended use. install, commission and maintain this equipment. All valid standards and codes for installing, servicing, and maintaining electrical and refrigeration equipment must be observed. 3

4 Introduction The information given below is intended to provide guidance to those intending to use the Copeland Scroll Cryogenic compressors in their cryogenic systems. These guidelines provide necessary requirements for a successful application of the compressor and components but do not guarantee satisfactory results for user performance or regulatory agency approval. Nomenclature The Copeland Scroll Cryogenic compressor model number includes the mass fl ow (SCFM) pumping rate of the compressor. SCFM is Standard Cubic Feet/ Min calculated based upon helium properties at 1 Atm pressure and 70 F (21 C). The SCFM is indicated by the fourth and fi fth digits, (e.g. ZCH22C1G moves 23.5 SCFM (34.5Nm³/hr)). The mass fl ow in the model number is taken at the Copeland Cryo rating point (CCRP) of 85psig (5.9 bar) suction pressure and 285psig (19.7 bar) discharge pressure. For actual compressor performance information, please visit Online Product Information at Please refer to the product literature for model number details. Oil Management Oil Separation A primary oil separator is necessary to separate and return oil to the compressor for proper cooling and lubrication of compressor running hardware. A secondary oil separator, located downstream of the primary oil separator, is required to limit oil circulation through the system to <5 ppm. This oil must be returned to the compressor (not applicable to absorbers) by teeing into the oil return line running from the primary oil separator to the compressor or into the low pressure side of the compressor. Both the primary and secondary separators need to incorporate an internal fl oat. This is necessary to keep helium vapor from returning to the compressor through the oil return line. A high capacity oil fi lter should be incorporated into the system to reduce the possibility of contaminates restricting the oil feed orifi ce. Refer to Figure 2 at the end of this bulletin. A properly sized orifi ce should be used in the oil return line from the oil separators to regulate the fl ow of oil and prevent a high to low helium leak within the system. Too large an orifi ce will result in a high to low leak, while too small an orifi ce will result in oil carryover. Oil Flow Rate Rate of oil fl ow returning to the compressor for all operating conditions is essential to ensure proper lubrication and cooling of the compressor running hardware. For example, Table 1 (at the end of this bulletin) indicates for ZCH22 models the rate of oil fl ow returning to the compressor shall be no less than 0.8 GPM (3 Liters/Min.) and for the ZCH72 models returning oil fl ow rate shall be no less than 1.8 GPM (6.8 Liters/Min.) The original equipment manufacturer (OEM) is to specify the orifi ce size and design to maintain a discharge line temperature below 200 F (93 C) 6 (150mm) from the outlet of the compressor. Reverse Oil Flow Oil inside the compressor must be prevented from fl owing backward from the compressor to the low side of the system during shutdown and during the off cycle. This can be accomplished by using the auxiliary suction port of the compressor and by installing a lowleak check valve in the suction line of the compressor. With the compressor discharge port pointing straight down, the auxiliary suction port will be located at the upper portion of the compressor, see Figure 1. Oil Type and Removal Copeland Scroll Cryogenic compressors are designed to operate with PAG oil, UCON LB300X or equivalent, with a kinematic viscosity between 30 and F (40 C). Any other oil must be approved by Emerson Climate Technologies, Inc. When a compressor is exchanged in the fi eld it is possible that a major portion of the oil from the replaced compressor may still be in the system. While this may not affect the reliability of the replacement compressor, the extra oil will add to rotor drag and increase power usage. Excess oil may need to be removed from the system. Oil Charge Cryogenic compressors are shipped with a complete charge of oil from the factory. Note that additional oil may be required to compensate for pre-charging of the oil separators and initial wetting of the system. Compressor Operating Temperature Compressor operating temperature, as measured by the compressor gas outlet temperature, shall be 200 F 4

5 (93 C) or less for all operating conditions, maximum ambient and maximum inlet gas temperature for the purposed application. The operating temperature can be controlled with the appropriate selection of an oil cooler (heat exchanger), and varying the return oil fl ow rate. Note that excess oil fl ow (above that needed for temperature control) may reduce compressor operating effi ciency. Proper oil fl ow is required to not only lubricate the load bearing and thrust surfaces, but also is used to cool the scroll sets during operation. Operating pressures must be kept within the envelope in Figure 3. Shell Temperature CAUTION Certain types of system failures such as loss of charge or loss of oil may cause the compressor shell and discharge line to briefl y, but repeatedly, reach temperatures above 350 F (177 C) as the compressor cycles on its protection devices. Care must be taken to ensure that wiring or other materials which could be damaged by these temperatures do not come in contact with these potentially hot areas. Discharge Line Thermostat A discharge line thermostat located within 6 inches (150mm) of the discharge fi tting is required. See Compressor Operating Temperatures section for allowable limits. The discharge line thermostat should have a manual reset feature for the highest level of system protection. Motor Protection For three phase compressors, an internal line break motor protector, located in the center of the Y of the motor windings, disconnects all three phases in case of an overload condition. The internal protector protects against single phasing. If current monitoring to the compressor is available, the system controller can take advantage of the compressor internal protector operation. The controller can lock out the compressor if current draw is not coincident with contactor energizing, implying that the compressor has shut off on its internal protector. This will prevent unnecessary compressor cycling on a fault condition until corrective action can be taken. For single phase compressors, an internal line break protector opens the common connection of the motor. By opening the common, both the start and run windings are taken out of the circuit. These internal protectors react to a combination of motor current and motor winding temperature. Time must be allowed for the motor to cool down before the protector will reset. Mounting Compressor and other component installation should be accomplished with minimal motion allowed during both shipment and normal operation. See Table 2 for mechanical specifi cations for compressor mounting cradles. These cradles are not available through Emerson Climate Technologies. These or similar designs are recommended. Mechanical vibration and unbalanced shaking forces for the cryogenic compressors are minimal, but neoprene rubber grommets and sheeting are recommended as a minimal procedure for vibration isolation of the compressor from the mounting cradle. Materials used for these vibration isolation components should be rated for temperatures of 248 F (120 C) and above to avoid material degradation with time. All system tubing must be designed and stress tested for both stop-start and excessive resonance vibration over the operating frequency of the product. Compressor Orientation Cryogenic compressors should be oriented radially so the high pressure discharge fi tting is pointed straight down. This will insure that the internal compressor components are at a proper orientation to allow effi cient passage of oil through the scroll components. See Figure 1. High Pressure Control The system is required to have a high pressure switch which will prevent the compressor from operating at discharge pressures above 450 psig (31 bar). The high pressure control should have a manual reset feature for the highest level of system protection. Low Pressure Control A low pressure control is required for the cryogenic compressor. Minimum setting should be at 15 psig (1.0 bar). Discharge Check Valve Only Copeland Scroll Cryogenic compressors with a model variation of 2 (refer to Table 3) contain a discharge check valve. Therefore, since the model variation of 1 does not have a check valve, the system pressures will balance during the off cycle. 5

6 Internal Pressure Relief Valve (IPR) Cryogenic compressors contain an internal pressure relief valve. The internal pressure relief valve will open at a discharge to suction differential pressure of 375 to 450 psi (26 to 31 bar). This action will result in a trip of the motor protector. A high pressure control must be used with this compressor. Cycle Times There is no set answer to how often the cryogenic compressor can be started and stopped in an hour. Emerson Climate Technologies, Inc. recommends a maximum of twelve cycles per hour. One critical consideration is a minimum run time required to return oil to the compressor after start up. To assure proper oil return, one minute is the minimum run time for all cryogenic compressors. A second consideration is a four minute minimum off cycle time once the compressor cycles off. Shutdown Sound Cryogenic compressors without a discharge line check valve will reverse rotate during shutdown as the pressures equalize through the scroll members. This reversal of direction has no effect on compressor durability and is entirely normal. Development testing should include a review of the shutdown sound for acceptability in a particular system. The use of an external check valve in the discharge line will reduce reverse rotation and therefore reduce shutdown sound if so desired. Rotation Direction Scroll compressors will only compress in one rotational direction. Direction of rotation is not an issue with single phase compressors since they will always start and run in the proper direction. Three phase compressors will rotate in either direction depending upon phasing of the power. Since there is a chance of connecting power in such a way as to cause rotation in the reverse direction, it is important to include notices and instructions in appropriate locations on the equipment to ensure proper rotation direction when the system is installed and operated. Verifi cation of proper rotation direction is made by observing that suction pressure drops and discharge pressure rises when the compressor is energized. Reverse rotation also results in substantially reduced current draw as compared to specifi cation sheet values. There is no negative impact on durability caused by operating three phase scroll compressors in the reversed direction for a short period of time (under one hour) but oil may be lost. Oil loss can be prevented during reverse rotation if the tubing is routed at least six inches (150 mm) above the compressor. After several minutes of operation in reverse, the compressor s internal protector will trip. If allowed to repeatedly restart and run in reverse without correcting the situation, the compressor will be permanently damaged. All three phase scroll compressors are identically wired internally. As a result, once the correct phasing is determined for a specifi c system or installation, connecting properly phased power leads to the same Fusite terminals will maintain proper rotation direction. Brief Power Interruptions Brief power interruptions (less than ½ second) may result in powered reverse rotation of single phase Scroll compressors. High pressure discharge gas expands backwards through the scrolls at power interruption, causing the scroll to orbit in the reverse direction. If single phase power is re-applied while this reversal is occurring, the compressor may continue to run in the reverse direction for several minutes until the compressor s internal protector trips. This has no negative impact on durability. When the protector resets the compressor will start and run normally. Emerson strongly encourages use of a timer which can sense brief power interruptions and lock the compressor out of operation for two minutes. No time delay is required on three phase models to prevent reverse rotation due to brief power interruptions. The torque of the motor is strong enough to assure proper rotation under all starting circumstances. Electrical Connections The orientation of the electrical connections of the compressors can be found on the wiring diagram inside the terminal box cover. The screw terminals used on this compressor should be fastened with a torque of 21 to 23 in-lb (2.4 to 2.6 N-m). Deep Vacuum Operation WARNING Scroll compressors (as with any refrigerant compressor) should never be used to evacuate a system. Low suction pressures will result in overheating of the scrolls and galling of the scroll tips and bases leading to performance losses and eventual compressor failure. Operation of scrolls in a vacuum for as little as 30 seconds can cause permanent damage. 6

7 Suction and Discharge Fittings The Copeland Scroll Cryogenic compressor is available with stub tube connections. The stub tube version has copper plated steel suction and discharge fi ttings. These fi ttings are far more rugged than copper fi ttings used on other compressors. Due to the different thermal properties of steel and copper, brazing procedures may have to be changed from those commonly used. See Figure 4 for assembly line and fi eld brazing procedures. Brazing Procedure NOTICE Figure 3 discusses the proper procedures for brazing the suction and discharge lines to a scroll compressor. Good brazing practices require the fl ow of nitrogen through the system while making all joints during the system assembly process. Nitrogen displaces the air and prevents the formation of copper oxides in the system. If allowed to form, the copper oxide fl akes can later be swept through the system and block screens such as those protecting capillary tubes and thermal expansion valves. The blockage whether it is of oil or refrigerant is capable of doing damage resulting in compressor failure. Removing System Components WARNING Remove all system components by cutting into the system rather then unbrazing. This is due to the amount of oil which will be circulated throughout the cryogenic compressor system. Some refrigerant lines will contain high quantities of oil. Oil fl ow rate on this type of system is measured in gallons/liters per minute instead of 10ths of a percent of mass fl ow. Before opening a system it is important to remove all refrigerant from both the high and low side. If the refrigerant charge is removed from a scroll-equipped unit by bleeding the high side only, it is possible for the scrolls to seal, preventing pressure equalization through the compressor. This may leave the low side shell and suction line tubing pressurized. If a brazing torch is then applied to the low side while the low side shell and suction line contain pressure, the pressurized refrigerant and oil mixture could ignite when it escapes and contacts the brazing fl ame. To prevent this occurrence, it is important to check both the high and low side with manifold gauges before unbrazing. Instructions should be provided in appropriate product literature and assembly (line repair) areas. If compressor removal is required, the compressor should be cut out of system rather than unbrazed. See Figure 4 for proper compressor removal procedure. Screens The use of screens fi ner than 30 x 30 mesh (0.6 mm openings) anywhere in the system is not recommended. Field experience has shown that fi ner mesh screens used to protect thermal expansion valves, capillary tubes, or accumulators can become temporarily or permanently plugged with normal system debris and block the fl ow of either oil or refrigerant to the compressor. Such blockage can result in compressor failure. Scroll Functional Check CAUTION A functional compressor test with the suction service valve closed to check how low the compressor will pull suction pressure is not a good indication of how well a compressor is performing. Such a test will almost certainly damage a cryogenic compressor. The following diagnostic procedure should be used to evaluate whether a cryogenic compressor is working properly. 1. Proper voltage to the unit should be verifi ed. 2. The normal checks of motor winding continuity and short to ground should be made to determine if the inherent overload motor protector has opened or if an internal motor short or ground fault has developed. If the protector has opened, the compressor must be allowed to cool suffi ciently to allow it to reset. 3. With service gauges connected to suction and discharge pressure fi ttings, turn on the compressor. If suction pressure falls below normal levels, the system is either low on charge or there is a fl ow blockage in the system. 4. If suction pressure does not drop and discharge pressure does not rise to normal levels, reverse any two of the compressor power leads and reapply power to make sure compressor was not wired to run in reverse direction. (This is for three phase compressors only, see Rotation Direction section). If pressures still do not move to normal values the compressor may be faulty. 5. To test if the compressor is pumping properly, the compressor current draw must be compared to 7

8 published compressor performance curvesusing the operating pressures and voltage of the system. If the measured average current deviates more than ±15% from published values, a faulty compressor may be indicated. 6. Before replacing or returning a compressor: Be certain that the compressor is actually defective. As a minimum, recheck a compressor returned from the fi eld in the shop or depot for Hipot, winding resistance, and ability to start before returning. More than one-third of compressors returned to Emerson Climate Technologies, Inc. for warranty analysis are determined to have nothing found wrong. They were misdiagnosed in the fi eld as being defective. Replacing working compressors unnecessarily costs everyone. Start-up of a New or Replacement Compressor Do not start the compressor while the system is in a deep vacuum. Internal arcing may occur when a compressor is started in a vacuum. Do not operate compressor without enough system charge to maintain at least 7 psig (0.5 bar) suction pressure. Do not operate with a restricted suction. Do not operate with the low pressure cut-out jumpered. Allowing pressure to drop below 7 psig (0.5 bar) for more than a few seconds may overheat scrolls. Never install a system in the fi eld and leave it unattended with no charge, a holding charge, or with the service valves closed without securely locking out the system. This will prevent unauthorized personnel from accidentally operating the system and potentially ruining the compressor by operating with no refrigerant fl ow. System Clean Up After a Motor Burn In the case of a motor burn, contact the original equipment manufacturer for proper system clean up procedures. 8

9 Auxiliary Suction Suction / Braze Shut Discharge Figure 1 Port Locations Figure 2 Oil Management Diagram 9

10 /355 55/ /335 Discharge Pressure (PSIG) /245 85/285 CCRP 115/ /135 49/ Suction Pressure (PSIG) Figure 3 Horizontal CryoScroll Operating Map (PSIG) 10

11 3 2 1 { { { Figure 4 Scroll Suction Tube Brazing New Installations The copper-coated steel suction tube on CP compressors can be brazed in approximately the same manner as any copper tube. Recommended brazing materials: Any silfos material is recommended, preferable with a minimum of 5% silver. However, 0% silver is acceptable. Be sure suction tube fi tting I.D. and suction tube O.D. are clean prior to assembly. If oil fi lm is present wipe with denatured alcohol, Dichloro-Trifl uoroethane or other suitable solvent. Using a double-tipped torch apply heat in Area 1. As tube approaches brazing temperature, move torch fl ame to Area 2. Heat Area 2 until braze temperature is attained, moving torch up and down and rotating around tube as necessary to heat tube evenly. Add braze material to the joint while moving torch around joint to fl ow braze material around circumference. After braze material fl ows around joint, move torch to heat Area 3. This will draw the braze material down into the joint. The time spent heating Area 3 should be minimal. As with any brazed joint, overheating may be detrimental to the fi nal result. Field Service To disconnect: Reclaim refrigerant from both the high and low side of the system. Cut tubing near compressor. To reconnect: Recommended brazing materials: Silfos with minimum 5% silver or silver braze material with fl ux. Insert tubing stubs into fi tting and connect to the system with tubing connectors. Follow New Installation brazing instructions. 11

12 Figure 5 Bracket Compressor Mounting ZCH22 12

13 Figure 6 Bracket Compressor Mounting ZCH72 13

14 Table 1 Minimum Oil Flow Model # ZCH22 ZCH48 ZCH68 ZCH72 Minimum Oil Flow Requirements.8 gal/min (3 L/min) 1.5 gal/min (5.7 L/min) 1.8 gal/min (6.8 L/min) 1.8 gal/min (6.8 L/min) Compressor Model # Table 2 Mounting Specifi cations Mounting Print Package # Figure # ZCH22 S A Fig. 5 ZCH48 S A Fig. 5 ZCH68 S A Fig. 6 ZCH72 S A Fig. 6 Model Variation Table 3 Valve Requirements IPR Valve Discharge check valve ZCH22C*G Yes No ZCH48C*G Yes Yes ZCH68C*G Yes Yes ZCH72C*G Yes Yes 14

15 Table 4 Cryogenic Scroll Specifi cations Specifi cation ZCH22C#G-PFV/PFJ ZCH48C#G-TF5/TFD ZCH68C#G-TF5/TFD ZCH72C#G-TF5/TFD Compressor Type Refrigerant Hermetic Helium (R-704) Oil Type PAG (UCON LB 300X) Oil Charge (L / oz) 1.1 / / / / 57 Motor Speed 50 & 60 Hz Mass (kg / lb) 25 / / / / 85 Length (mm / in) 377 / / / / Width (mm / in) 243 / / / / 9.71 Power Supply (volts) Max Allowable Tilt Angle (Degrees) Operating Pressure (bar / psia) TF5 TFD PFJ PFV Max. Discharge Line Temp. (ºC / ºF) 50Hz 60Hz 50Hz 60Hz +/ Hz 60Hz 50Hz 60Hz Discharge: / ; Suction: / ºC / 200 ºF Displacement (cc/rev / CIR) 30.7 / / / / Max Sound Power Level (dba) 50 Hz : 60 Hz CCRP (100 Suction and 300 Discharge) - 50Hz/60Hz Helium Flow (Nm3/hr) / (lb/hr) / SCFM Effi ciency (Nm3/kW-hr) / (lb/kwhr) / (SCFM / kw) Oil Injection Flow (L/min / gal/min) Power Consumption (kw) Return Gas Temperature (ºC / ºF) Ambient Air Temperature (ºC / ºF) S = Standard (70ºF; 1 atm) N = Normal (0ºC; 1 atm) 70 : : : : Hz 28.3 / 12.0 / / 25 / / 37 / / 38.9 / Hz 34.5 / 14.6 / / 30.5 / / 45 / / 46.9 / Hz 13.5/ 5.7 / / 6.1 / / 6.1 / / 6.2 / Hz 13.8/ 5.8 / / 6.2 / / 6.0 / / 6.1 / / / / / Hz Hz ºC / 70 ºF 35 ºC / 95 ºF The contents of this publication are presented for informational purposes only and are not to be construed as warranties or guarantees, express or implied, regarding the products or services described herein or their use or applicability. Emerson Climate Technologies, Inc. and/or its affi liates (collectively "Emerson"), as applicable, reserve the right to modify the design or specifi cations of such products at any time without notice. Emerson does not assume responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use and maintenance of any Emerson product remains solely with the purchaser or end user. 15