Selecting the Right Gear Coupling for your Application
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This webinar discusses selecting the appropriate gear coupling for various applications, detailing key terminology and functions of couplings, including torque transmission and misalignment accommodation. It highlights the characteristics and benefits of different coupling types, with a focus on gear couplings' advantages such as high torque capacity and reliability. The presentation also covers coupling installation, maintenance, and standards to ensure optimal performance.
Selecting the Right Gear Coupling for your Application
- 1. Selecting the Right Gear Coupling for Your Application
- 2. q This webinar will be available afterwards at www.designworldonline.com & email q Q&A at the end of the presentation q Hashtag for this webinar: #DWwebinar Before We Start
- 3. Moderator Presenter Miles Budimir Design World Paul Konkol Altra Ameridrives Gear Couplings
- 4. Design World Webinar Selecting the right gear coupling for your application April 29, 2015
- 5. What is a Coupling ? A Flexible Coupling is a machine part that transmits rotating power from one shaft to another while accommodating misalignment and axial displacement between the two shafts.
- 6. The basic functions of a flexible coupling: • Transmit power • Accommodate misalignment • Compensate for shaft end movement Basic Coupling Functions
- 7. Transmit Torque While allowing for: Misalignment Axial Movement DRIVERDRIVEN
- 8. • Torque: The tendency of a force to cause or change rotational motion of a body, calculated by multiplying Force and distance. Defined more fully in the Torque section below. • Misalignment: The state of being not in alignment. Alignment is generally defined as the state where opposing equipment shaft centerlines are coaxial. For machinery and couplings, it is the proper orientation of mechanical parts to obtain minimal wear and/or dynamic forces. • Hub: The coupling component which is machined for mounting on a shaft. • Spacer: A removable center member that provides a specified axial shaft separation. • Distance Between Shaft Ends (DBSE): The distance from the face of one shaft to the face of the next shaft. • Shaft: The revolving cylindrical bar, the centerline of which is also the center of rotation for the components to which it is attached, through which torsional power is transmitted or delivered. • Bore: Cylindrical or conical holes in hubs of couplings with axes coincident with the rotational axis of the coupling. • Flexible Element: The part of a coupling which provides flexibility. There are 3 main categories: Mechanical, Metallic, and Elastomeric. • Sleeve: A gear coupling component with internal teeth. • Hardware: The nuts, bolts, washers, etc., which are used to attach the various coupling components together. • Clearance Fit: A condition where the hub bore diameter is equal to or larger than the shaft diameter. • Interference Fit: A condition where the hub bore diameter is equal to or smaller than the shaft diameter. • Pilots: A surface that positions a coupling component, subassembly or assembly. • Key: A mating torsional load transmitting member placed in a groove in both shaft and hub. • Keyway: The axial groove in the hub that holds the key in the proper location. Coupling Terminology
- 9. Basic Torque Calculation Torque = Power x Unit Constant Speed • in-lb. = HP x 63025 / RPM • Nm = kW x 9554 / RPM • HP/100 RPM = HP x 100 / RPM
- 10. Torque = HP transmitted x 63,025 x Service Factor RPM
- 11. Service Factors are a multiplier to the calculated torque when selecting a coupling. • Selection Torque = Calculated TQ x SF • Note: Different coupling types and/or manufacturers recommend different service factors for similar operating conditions. Always check your catalog CLASS SMOOTH STEADY MODERATE MEDIUM HEAVY EXTRA HEAVY EXTREMELY HEAVY DRIVER TYPE MOTOR OR TURBINE MOTOR OR TURBINE MOTOR OR TURBINE MOTOR OR TURBINE HIGH STARTING TORQUE MOTOR OR ENGINE ENGINE ENGINE LOAD TYPE - SOFT START WITH STEADY LOAD - CENTRIFUGAL EQUIPMENT - NORMAL STARTING LOADS - SLIGHT TORQUE VARIATIONS - ABOVE AVERAGE STARTING LOADS - MODERATE LOAD VARIATIONS - HIGH STARTING TORQUE - MEDIUM TO HEAVY LOAD VARIATIONS - MILD SHOCK LOADING ENGINES WITH SMOOTH LOADING - EXTREME RELIABILITY - HEAVY SHOCK LOADING - LIGHT TO MODERATE REVERSING - EXTREME SHOCK LOADING - HEAVY REVERSING WIDE TORQUE VARIATION SERVICE FACTOR 1.0 1.5 2.0 2.5 3.0 3.25 4.0 Service Factors
- 12. Angular Misalignment Parallel Offset Misalignment Types of Misalignment
- 13. Misalignment Parallel offset Combination of both Angular misalignment
- 14. Types of Misalignment • Axial Misalignment or End Float o Some couplings will limit shaft movement, others will not o Sometimes limited end float (LEF) devices may be added to a coupling
- 15. A. Small amount • Thermal growth • Bearing float B. Large amount • Axial adjustment • Operational shifting Axial Movement
- 16. Coupling Categories and Types Gear Chain Grid UJoint Mechanical Disc Diaphragm Metallic Shear Compression Elastomeric Pin & Bushing Spring Slider Block Miscellaneous
- 20. Performance L-jaw Sure-Flex® Dura-Flex® Gear Form-Flex® Grid Make to Stock Modify/MTO Price Couplings Cover a Wide Range
- 21. So, which is the right coupling for my application?
- 27. Types of Couplings & Application Requirements Coupling Characteristics Gear Spindle Grid U Joint Elastomeric Shear Elastomeric Compression Disc Diaphragm Lubrication Yes Yes Yes Yes No No No No Backlash Med High Med None None Low None None Overhung Moment Med High Med High High High Low Low Unbalance Med High High High High High Med Low Bending Moment High High Med High Low Med Med Med Axial Force High High Med High Low Med Med Med Torsional Stiffness High High Med High Low Med High High Damping Low Low Med Low High Med Low Low Coupling selection based on application needs
- 28. Costs and BenefitsCriteria Coupling Types Elastomeric -‐‑ Shear Elastomeric -‐‑ Compress Tire Block Sleeve Jaw Curved-‐‑Jaw Block Gear Disc Grid Lubrication N N N N N N Y N Y Ease of Installation ++ +++ +++ +++ +++ +++ + + + Fail Safe N N N Y Y Y N N N Misalignment Rating +++ + ++ + + + ++ + + Purchase Cost $$ $ $ $ $ $ $$$ $$$ $$ Maintenance Cost N N N N N N Y N Y Replacement Cost $$ $ $ $ $ $ $$$ $$$ $$ Installation Cost/Time ++ +++ +++ +++ +++ ++ + + + Life ++ + ++ + + + +++ +++ ++ Torsional Stiffness Low High Low High High High Highest Highest Low +++ = BEST ++ = BETTER + = GOOD $$$ = HIGHEST $$ = LOWER $ = LOWEST
- 29. Why Select a Gear Coupling? Coupling Characteristics Gear Spindle Grid U Joint Elastomeric Shear Elastomeric Compression Disc Diaphragm Lubrication Yes Yes Yes Yes No No No No Backlash Med High Med None None Low None None Overhung Moment Med High Med High High High Low Low Unbalance Med High High High High High Med Low Bending Moment High High Med High Low Med Med Med Axial Force High High Med High Low Med Med Med Torsional Stiffness High High Med High Low Med High High Damping Low Low Med Low High Med Low Low Gear Coupling is selected because it is torque dense, has axial capacity independent of angular misalignment, large bore capacity, and long life.
- 30. Why a Gear Coupling? • High torque • High misalignment • Axial capacity
- 31. Basic Gear Coupling Parts Lube Plugs Flange Nuts & Bolts Sleeve O-ring Seal Hub
- 32. How a Gear Coupling Transmits Torque Torque is transmitted on the flank or face of the gear tooth Major Diameter Sleeve Piloting
- 33. • Gear teeth are either straight or crowned • Clearance in gear mesh allows for misalignment • Crowned tooth allows for greater misalignment, higher torque capacity, less backlash Gear Tooth Design
- 34. Crowned or Fully Crowned Gearing A) Flank (Face) B) Tip (and Root) C) Chamfer
- 35. When everything is “perfectly” aligned all teeth share the load equally How a Gear Coupling Works
- 36. As you misalign, fewer and fewer teeth are in contact Ratings are based on the torque that can be transmitted at a given misalignment Reduce your misalignment, increase your ratings How a Gear Coupling Works
- 37. Fully Crowned Gearing Allows for Max Misalignment
- 38. Fully Crowned Gear Reduces Backlash and Vibration
- 39. Gear Couplings Require Lubrication Original gear couplings 75+ years ago were filled with oil for lubrication A metal labyrinth seal and centrifugal force kept the gear mesh lubricated
- 40. O-ring Seal Buna-N O-ring seals keep contamination out, and lubricant in. Designed to accommodate temperatures up to 250°F. Viton seals are available for temperatures up to 550°F. O-ring Seal Clean grease of the proper amount and type will give longest life
- 41. Recommended Grease Suggested grease by manufacturer and operating conditions
- 42. Gear Coupling Standards • Flange Diameter is standard for manufactures • Shrouded or Exposed bolt pattern is standard • Allows for Identification & Half-to-Half Interchangeability
- 43. Standard AGMA Nomenclature Size 1 ½ to 7 Size Mfg. K Mfg. F Mfg. A O.D. # SB Bolts # EB Bolts 1-‐‑1/2 1-‐‑1/2H 1015 201.5 6.00” 8 8 2 2H 1020 202 7.00” 10 6 2-‐‑1/2 2-‐‑1/2H 1025 202.5 8.38” 10 6 3 3H 1030 203 9.44” 12 8 7 7H 1070 207 20.75” n/a 16 O.D. • Measure flange O.D. • Count the bolts • Step in ½ sizes
- 44. Special Coupling Functions Many couplings today are special made to order and incorporate other special features. § Allow for axial travel § Maintain sleeve bearing motor rotor position (Limited End Float or LEF) § Allow for extended DBSE § Protect Equipment from overload § Dampen vibration and reduce peak or shock loads § Electrically insulate the driver from the driven equipment § Incorporate a brake disc or drum § Tune a system out of a torsional critical § Support the rotor of a generator or other radial load (single flex) § Electrically insulate the driver from the driven equipment § Measure output torque of driven equipment § Support axial loads on vertical installation § Support other PT Components § V-Belt Drive, Fluid Drive, Clutch, etc.
- 45. Special Coupling Functions Application Data Form to gather all information important to the installation § HP, speed, DBSE, shaft sizes, SF, temperature, etc. § What is currently being used? § Drawings of existing application § What changes have been made since original installation? § What operational problems are there? § Special documentation
- 46. BORES, FITS AND HUB MOUNTING
- 47. Hub to Shaft Fits • Slip or Clearance Fits o Hub bore is always larger than shaft OD • Press or Interference Fits o Hub bore is always smaller than shaft OD
- 48. Clearance Fits • Use for Low Speeds o 1800 to 3600 RPM max • Requires set screws and keyway o Worse for balance • Low HP ranges o Generally 250 HP and under • Smaller Shaft Diameters o Generally 3 3/8” or less • Risk of Fretting
- 49. Interference Fits • Light: under .0005 in/in o Must use a key – minimal interference will slip under heavy load o AGMA Standard A86 o Hub mounting: Heating necessary o Stresses are usually not an issue • Medium: ~.0005 - .0015 in/in o Usually tapered shaft and some keyless fits o AGMA standards A86 & A91 o Hub mounting: Must be heated or hydraulically mounted o Stresses may need to be checked • Heavy: ~over .0015 in/in o Keyless fits o AGMA Standard A91 o Hub mounting: Heating necessary o Stresses need to be checked
- 50. AGMA Fit Tables
- 51. Interference Fit Calculations • Steel expands .0006”/inch of diameter per 100°F temp rise • Heat the hub to expand bore by 150%+ of the interference • Example: 5” dia. shaft with .004” interference • 5” dia. x .0006” = .003” expansion per 100°F temp rise • .004” x 150% = minimum .006” growth • .003”/100°F x 2 = .006” bore growth = min 200°F temp rise • At 70°F temp, need to heat hub to at least 270°F Ø 350°F is recommended, even heat distribution, less that 600°F
- 52. Interference Fit Hub Installation • Calculate the correct temperature rise • Make sure bore and shaft are clean and free of burrs • Plan how you will handle the heated hub • Heat hub thoroughly – if not heated through, hub may cool, shrink and bind before completely on the shaft • Shield shaft and seals from over-heating when you install the hub • Quickly and safely position the hub on the shaft and allow it to cool
- 53. Metric vs. English Shaft Specification Inch Shafts • Standard AGMA tolerances • Square keys • Half in hub / half in shaft Metric Shafts • Various Metric standards DIN Standards • Rectangular keys • Keyway depth per metric standards • Overkey dimension for keyway depth Inch Keyways Metric Keyways
- 54. Fitting of Keys 1. Tight Fit in Shaft Keyway 2. Sliding Fit in Hub Keyway 3. Clearance over Top of Key 4. Chamfered Key Corners
- 55. Interference Fit with Key
- 56. The proper gear coupling selection and design will give you the maximum misalignment capacity & maximum torque capacity for the longest life in your application.
- 57. Questions? Miles Budimir Design World mbudimir@wtwhmedia.com Twitter: @DW_Motion Paul Konkol Altra Ameridrives Gear Couplings Paul.konkol@ameridrives.com
- 58. Thank You q This webinar will be available at designworldonline.com & email q Tweet with hashtag #DWwebinar q Connect with Design World q Discuss this on EngineeringExchange.com