mycom V-Series Handling Manual
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mycom V-Series Handling Manual

Screw refrigeration compressor
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V SERIES
REFRIGERATION DIVISION
SCREW COMPRESSOR HANDLING MANUAL
New V-Series
Screw Refrigeration Compressor
Handling Manual
Supersedes all previous version. This information is for reference use only and subject to change without notice
Revision 2 (June 05,2000)
Page 1 of 61

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  • Page 1 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL New V-Series Screw Refrigeration Compressor Handling Manual Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 1 of 61...
  • Page 2 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL General Description of Mycom V-Series Compressor Introduction Refrigerant Compression Mechanism Explanation of Vi (Internal Volumetric Ration) Reasons for Adjusting Vi Variable Vi Mechanism External Adjustment of Vi Other Component Mechanisms Exploded View of V-Series Screw Compressor...
  • Page 3 (0 profile) has been introduced to further improve performance. The basic construction of the V Series is the same as standard MYCOM compressors except for the addition of the variable Vi mechanism.
  • Page 4 A two-pole motor connected directly to the M rotor drives the compressor at speeds of 2,950 rpm or 3,550 rpm (50 Hz or 60 Hz) Compressor efficiency is directly related to the shape of the rotor lobes. In the case of the V-Series, the rotors have unsymmetrical profiles in contrast to conventional screw compressor rotor lobes. This unsymmetrical design reduces the triangular blow off hole between the casing and the rotors to 60%, minimizing leakage due to the pressure difference.
  • Page 5 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL 1.1.1 Suction Phase (refer to Figs. 4 and 5) As shown in Fig. 4, the rotors of different lobe shape mate and the clearance between the M and F rotors and the casing expands gradually from the suction side as the rotors rotate. When the clearance reaches maximum as the rotors rotate further, it is sealed by the walls at both ends of the rotor and becomes independent.
  • Page 6 The V-Series, which incorporates a variable Vi, has consequently been developed for these general applications. The Vi of the V-Series can be readily changed between L, M and H at the installation plant according to operating conditions. Supersedes all previous version. This information is for reference use only and subject to change without notice...
  • Page 7 In the case of a conventional model, the axial and radial elements are combined to exhibit particular characteristics at partial load. In the case of V-Series compressors, the Vi can be changed by altering the size of the radial port while maintaining the axial port at Vi 5.10.
  • Page 8 As shown in Fig. 10A, the radial port of a conventional model becomes larger as Vi becomes smaller. In the case of V-Series compressors, the stop position of the variable Vi unloader slide valve moves to the discharge side and changes Vi by reducing the size of the radial port at full load operation.
  • Page 9 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL External Adjustment of Vi Determine P during operation based on the anticipated operating conditions of the system. = Absolute value of discharge pressure = Discharge gauge pressure + 1.033 kgf/cm Absolute value of suction pressure Suction gauge pressure + 1.033 kgf/cm Find V from the compression ratio...
  • Page 10 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Next, record the position of operation start (confirm the position of the stamp on the screw head). Turn the Vi changing rod counterclockwise the number of rotations indicated for the particular compressor as given in Fig. 13. After adjusting, secure the lock nut (approx.
  • Page 11 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL H port M port H port L port 160VS* 160VM* 160VL* 160VS* 160VM* 160VL* Distance 18mm 23mm 27mm Distance 37mm 45mm 55mm No. of Turns 10.8 No. of Turns 14.0 18.0 22.0 200VS* 200VM* 200VL*...
  • Page 12 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 12 of 61...
  • Page 13 The balance piston of the V-Series compressor M rotor is somewhat larger in diameter than that of a conventional screw compressor in order to allow for a decrease in the oil pressure load which is used for pressure difference lubrication.
  • Page 14 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Oil Flow Fig. 15 Schematic Diagram of Lubrication System Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 14 of 61...
  • Page 15 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Exploded View of V-Series Screw Compressor Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 15 of 61...
  • Page 16 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Parts List No. Parts Name 43 Thrust Bearing Gland 1 Main Rotor Casing 45 Hexagon Head Bolt 2 Hexagon Socket Head Cap Screw 46 Lock Washer 3 Alignment Pin 48 Retainer, Oil Seal 4 Hanger Bolt 49 "O"Ring 5 Suction Cover...
  • Page 17 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL 433 "O"Ring 456 Hexagon Socket Head Cap Screw 444 Vi Adjusting Rod 457 Spring Washer 445 Washer 458 Plug 446 Vi Square Washer 459 Plug 447 Name Plate 522 Domed Cap Nut 448 Bushing 523 "O"Ring 449 Thrust Washer...
  • Page 18 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 18 of 61...
  • Page 19 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 19 of 61...
  • Page 20 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 20 of 61...
  • Page 21 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Disassembly of V-Series Preparations for Disassembly Disassembly work on a base-mounted compressor unit is limited to the shaft seal; thrust bearing, unloader cylinder and balance piston section. Disassembly and inspection work on other parts of the compressor should be done with the unit removed from the base and positioned for maximum access and ease of disassembly.
  • Page 22 (100 mm x 100 mm). Disassembly Sequence Disassembly and inspection of V-Series compressors should be carried out according to the following work sequence. For model D, the discharge flange portion extends from the leg of the compressor. Place a square timber or piece of lumber under the compressor or position so that the flange extends beyond the surface plate (see Fig.
  • Page 23 Mechanical Seal (100) 3.4.1.1 Disassembly A new balance type single seal (100) is incorporated into V-Series compressors. A combination hard metal and carbon alloy is used for the frictional surface of the seal and an O-ring is provided for packing.
  • Page 24 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Remove four of the six hex-head socket cap screws (53) securing the seal cover (51), leaving two screws symmetrically positioned. Now loosen the remaining two screws alternately, allowing the shaft seal spring (110) to push off the cover slightly. If the cover adheres to the gasket, free it manually after the screws have been loosened.
  • Page 25 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 27A Oil Seal Sleeve Fig. 27B Shaft Seal Assembly 3.4.1.2 Inspection Inspect the frictional surfaces of the carbon and seal ring (104). A carbon with a smooth, unblemished face can be reused but if there are any signs of damage or peeling, replace the carbon, otherwise oil leakage may result.
  • Page 26 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 28 Removing Indicator Cover Fig. 29 Micro-switch Cam (127) and Coupling fixing screws (128) Remove all of the hex socket head cap screws (122) securing the micro-switch base plate (121) to the unloader cover. Fig.
  • Page 27 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL 3.4.3.2 Inspection If the indicator is not actuating normally, check the cylinder cam groove, bearing and slotted pin (unloader push set side) for abnormality. If there is refrigerant or oil leakage, replace the Teflon V-ring (82). In such a case, the shaft seal portion of the cylinder cam (77) should be disassembled according to the following procedures.
  • Page 28 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Loosen the lock nut (69) using the lock nut wrench provided in the tool kit. If the wrench does not reach the nut, turn the Vi changing rod counterclockwise to shift the variable Vi slide valve (289) to the L port position and then pull the piston out further.
  • Page 29 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL 3.4.6 Balance Piston (30) and Balance Piston Sleeve (33) With screw compressors the male rotor is subjected to strong thrust load from the discharge side and rotates considerably faster than the female rotor. If the same type of thrust bearing were used for both the male and female rotors, the male side bearing life would be much shorter.
  • Page 30 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 43 Loosening Balance Piston Sleeve Detent Fig. 44 Balance Piston Sleeve Set Screw Portion Screws (74) Fig. 45 Screwing in Position Detent Pin (34) Fig. 46 After Screwing in Positioning Detent Pin (34) Pull out the balance piston sleeve.
  • Page 31 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL the peripheral clearance and elasticity of the O-ring but sleeve wear is not unusual. Inspect the O-ring (35) and replace if any deformation is found. 3.4.7 Bearing Cover (16) The structure of this portion of the compressor differs between Model D and Model G units. Model D is provided with a discharge flange (95).
  • Page 32 For this reason, maximum care should be taken when disassembling and reassembling the bearing. The thrust bearing used on V-Series compressors is an angular type face-to-face duplex bearing with special retainer of high accuracy. This bearing receives thrust load only as the outer race is clearance fitted.
  • Page 33 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 53 Drawing out Thrust Bearing Fig. 54 Set of Thrust Bearing (L side lies on R side) Fig. 55 Stamps on Thrust Bearing Gland Fig. 56 Thrust Bearing Portion of models 160V**~200V** (step) (41) and Thrust Adjusting Washer (42) The thrust adjusting washer (42) and thrust bearing step (41) are provided behind the thrust bearing (some models do not have this arrangement for structural reasons).
  • Page 34 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL 3.4.8.2 Inspection Clean the thrust bearing thoroughly and blow dry. Inspect the ball bearings and races. The ball bearings should be shiny bright and the ball cages free of burrs. Also, check the clearance between the balls and cages for the bearing step (41).
  • Page 35 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 58 O-Ring Gland (326) Remove the O-ring gland fixing screw (456) and remove the O-ring gland (326). To remove the side bearing (28), first remove the stop ring (29), and then push the side bearing out from the rotor side.
  • Page 36 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 61 Pulling out M rotor (25) Fig. 62 Removing Lock Washer Bolt Remove the remaining rotor in the same manner, taking care not to damage the main bearing in the bearing head as you pull the rotor free. Do not lay the rotors directly on the floor or the edges of the lobes may be damaged.
  • Page 37 With some special applications, the bearing journal and the shaft seal portions are finished with chrome plating. If any damage is found, contact the nearest MYCOM subsidiary for repair or replacement. 3.4.11 Bearing Head (11) and Main Bearing (27) Normally, further disassembly of this portion of the compressor is not required as there is nothing to be gained from separation of the bearing head and rotor casing.
  • Page 38 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Apply oil to both sides of the gasket before fitting it between the bearing head and rotor casing. Since the positions of the holes in the gasket are unsymmetrical, care should be taken to position the gasket correctly.
  • Page 39 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 69 View of Unloader Slide Valve (54), Fig. 70 Unloader Slide Valve (54) and portion Variable Vi Slide Valve (289) and Vi changing Rod (444) Removed from Rotor Casing (1) Mount the Vi changing rod (444) from the bearing head side. Be careful not to forget to install the thrust washer (449).
  • Page 40 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 75 Overall View of Unloader Slide Valve (54) Fig. 76 Fitting Vi Slide Valve Lock washer (round) (445) And Variable Vi Slide Valve Rotor Casing (1) and Rotors (25,26) Coat the main bearing and the shaft portion of the male rotor with compressor oil and install first.
  • Page 41 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 79 Positioning Side Bearing (28) Fig. 80 Mounting Secure the stop ring. Mount the O-ring retainer (326) for the unloader push rod. The suction cover side also requires an O-ring so do not forget to mount during the assembly work. Mount the balance piston sleeve in the order of stop ring (32), O-ring retainer (36), O-ring (35), balance piston sleeve (33) and stop ring (32).
  • Page 42 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Slide the suction cover across the surface plate and align the suction cover O-ring retainer with the push rod (67) Mate the side bearing (28) and rotor shafts and push the cover and casing together parallel with the shaft.
  • Page 43 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL If the thrust bearing is being replaced with a new one, confirm that the end clearance of the bearing is secured while loosening the bolt little by little. Since the difference in the side faces of the inner and outer bearing races vary even if the bearing is within specifications, no clearance is secured in some cases.
  • Page 44 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 90B Adjusting End Clearance First method: Since the dimension at “A” shown in Fig. 90B is too large because the thrust adjusting washer is too thick, the face of the washer must be ground down by the amount of the difference between the measured value and the specified value.
  • Page 45 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 91 Determining Axial Deflection Next, check the axial deflection of shaft rotation with the dial indicator positioned on the oil seal fitting portion. Maximum deflection of the 0.015 mm is acceptable. Deflection may be cause by no uniformity of the thrust adjusting washer or mismatching of the stamped bearing parts.
  • Page 46 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Screw a long stud bolt into the bearing head and fit the gasket and the bearing cover, taking care not to damage the shaft seal portion. First mount the Vi changing rod (444), then align the parallel pin (3) and push the bearing cover onto the bearing head, being careful to maintain even alignment.
  • Page 47 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 97A Unloader Cylinder and Blind Cover Fig. 97B Tighten the bolts securing the blind cover and unloader cylinder to the suction cover (5). Fig. 98 Unloader Cylinder (60) Screw and eye bolt into the unloader piston (64) and manipulate to confirm smooth movement of the slide valve (54).
  • Page 48 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 99 Mounting Unloader Cover Fig. 100 Exploded View of Unloader Cover (74) Rotate the cylinder cam (77) manually to confirm smooth rotation. Fit the O-ring (75) on the unloader cover (74). Position the unloader slide valve (54) in the no-load position (piston at the innermost point) and push in the cover while mating the groove on the cylinder cam with the pin on the push rod (67).
  • Page 49 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fit the oil seal sleeve (528) and secure the two set screws (529). Mount the shaft seal assembly (100). Push the O-ring (49) in carefully so that it is not damaged. Two screws are provided for the seal collar (109).
  • Page 50 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Disassembly and Adjustment of Unloader Indicator The potentiometer (129), micro-switch (125) and micro-switch cam (127) are mounted in the automatic control indicator portion of the compressor. Fig. 107 106V**~250V** Standard Indicator Disassembly and Adjustment of Unloader Indicator (120) Remove the machine screw (140) securing the indicator pointer (139).
  • Page 51 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL The potentiometer is secured to the mounting plate with three machine screws (131). The micro-switch (125) is secured with two long machine screws (126). Loosen these screws to remove the micro-switch. The micro-switch component on the right side is for the no-load position signal and the one on the left side is for the full-load position signal.
  • Page 52 Check the actuation of the contact points of the micro-switch components using a tester (for details contact the Electric Department of Mycom). Supersedes all previous version. This information is for reference use only and subject to change without notice...
  • Page 53 (146). Be careful not to pinch the wires with the cover. Disassembly, inspection and reassembly of the V-Series compressor unit are now completed. Supersedes all previous version. This information is for reference use only and subject to change without notice...
  • Page 54 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Fig. 112 Adjustment of Potentiometer at Fig. 113 Groove in Micro-Switch Cam No-Load Position Fig. 114 Potentiometer Shaft Fig. 115 Potentiometer Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 54 of 61...
  • Page 55 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Standards of Components Single-stage Booster (Low-stage) Model High-stage 160V** 0.04~0.06 0.20~0.22 0.22~0.24 0.24~0.26 200V** 0.05~0.07 0.26~0.30 0.28~0.32 0.31~0.35 250V** 0.06~0.08 0.40~0.44 0.45~0.49 0.50~0.54 320V** 0.23~0.27 0.70~0.76 0.73~0.79 0.77~0.83 Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 55 of 61...
  • Page 56 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 56 of 61...
  • Page 57 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 57 of 61...
  • Page 58 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Compressor Oil The quality of lubricating oil significantly affects the performance and life of the compressor. Important requirements of refrigeration system lubricating oil include suitable viscosity over a wide temperature range, low fluidity and high flash point. Taking the above-mentioned characteristics of lubricating oil into consideration, oil used should satisfy the following requirements: Proper viscosity should be maintained within the potential working temperature range.
  • Page 59 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 59 of 61...
  • Page 60 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 60 of 61...
  • Page 61 V SERIES REFRIGERATION DIVISION SCREW COMPRESSOR HANDLING MANUAL Supersedes all previous version. This information is for reference use only and subject to change without notice Revision 2 (June 05,2000) Page 61 of 61...

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