Coupling Selection Contents Essential Information Required Service Factors Coupling Ratings Choosing a coupling arrangenment Question Examples Additional Checks Special requirements Selection Tools Coupling Selection Essential Information for selection Driver Machine Driven Machine Power (HP or kW ) Normal • Max. Transient or Torque (Nm or lbs.ft) if available Speed (rpm) Normal • Maximum if available Distance between shaft ends (DBSE) (mm or inches) Driving and Driven shaft types and diameters Select a suitable SERVICE FACTOR In coupling design the basic stress analysis considers the Steady- torque condition. Time Select a suitable SERVICE FACTOR Knowing the DRIVEN & DRIVING machinery What is a service factor ? • A multiplication factor applied to the nominal rating which allows for CYCLIC TORQUE applied by certain machinery. SF=1 1. Steady Torque (eg. Centrifugal compressor) Time 2. Cyclic Torque (eg. Reciprocating comp.) SF=3 Time Service Factors LOAD CLASSIFICATIONS: Continuous & uniform operation (Infrequent starts/ Low starting torques) Continuous operation with minor torque fluctuations or frequent start/stop cycles Torque loading varies during operation in conjunction with some shock loading Substantial torque fluctuations & heavy shock loads SERV. FAC. 1.0 1.5 2.0 2.5 Allowable alternating Torque S-N Curve Stress Tension (+) 800 Stress range 0 Compression (-) Stress range (Mpa) 700 Time 600 500 Fatigue limit 450 400 103 104 105 106 107 Number of Cycles 108 109 Modified Goodman Diagram Alternating stress 1200 1000 800 600 400 200 0 0 500 1000 Steady stress 1500 Modified Goodman Diagram Alternating stress 1200 1000 800 600 400 200 0 0 500 1000 Steady stress 1500 Alternating stress Modified Goodman Diagram FRETTING LIMIT MEAN TORQUE (MAX) SPEED (MAX) (MAX) AXIAL DEFLECTION Steady stress RATED OPERATING POINT Determine Coupling RATING Determine the coupling Rating in kW/1000 rpm from the following formula: Given: Power (kW) and Speed (rpm) Rating = kW x 1000 x SF N where SF is service factor kW is power rating N is shaft speed Choose Coupling Arrangement The coupling arrangement will depend upon: • • • • • available DBSE (distance between shaft ends) bearing arrangement of the coupled machines allowable overhung moment mating interfaces with the shafts special features required Choose the coupling arrangement required to suit the application SINGLE BANK NON-SPACER COUPLINGS • LDE0, LSE0, MHSO CLOSE COUPLED ARRANGEMENTS • MODO, LDEC, LSEC • TSKC, TSNC, TSRC, TSE1 Choose the coupling arrangement required to suit the application STANDARD SPACER COUPLINGS • MHSS, • LSES, TSKS, TLKS, TSCS, TLCS • TSJE; TLJE; TTJE MINIMUM OVERHUNG MASS • TSGE, TLGE, TTGE • TSDE, TLDE, TTDE Bearing arrangements Equipment design X X X 3 Bearing X X X X 4 Bearing X Bearing Misalignment and 3 Bearing System X X X Parallel offset X X X Converted to angular X Bearing 4 bearing systems and misalignment X X X X X X Parallel offset X X Converted to angular at each end X Bearing 3 and 4 Bearing Systems – The difference 3 bearing systems • Angular and axial misalignment only • Requires one flexing plane (1 membrane pack) 4 bearing systems • Angular, axial and parallel misalignment • Requires two flexing planes (2 membrane packs) • Increase in flexing plane separation (distance between membrane packs) increases parallel misalignment capability Misalignment Capability Axial and Angular Misalignment Only Non Spacer Axial, Angular and Lateral Misalignment Spacer Question 1 Steam Turbine to Centrifugal Compressor 6MW @ 10000 RPM What is the required rating? Answer to Question 1 Required Rating = kW x 1000 x SF N Rating kW/1000 rpm = 6000 x 1000 x 1.0 10,000 = 600 kW/1000 rpm Choose Coupling Arrangement The coupling arrangement will depend upon: • available DBSE (distance between shaft ends) • bearing arrangement of the coupled machines • allowable overhung moment • mating interfaces with the shafts • special features required Decide on the type of disc design ‘T’ series is the prime selection unless otherwise specified. ‘T’ series maintains the drive on disc failure through emergency drive collars. ‘M’ series disconnects the drive on disc failure. For API 671 requirements generally use ‘T’ series. Choose the coupling arrangement required to suit the application SINGLE BANK NON-SPACER COUPLINGS • LO, MHSO CLOSE COUPLED ARRANGEMENTS • MODO • TSRC, L***-*C, TSKC, TSKD Choose the coupling arrangement required to suit the application STANDARD SPACER COUPLINGS • MHSS, MODS • L Series, TSKS, TLKS, • TSJE; TLJE; TTJE MINIMUM OVERHUNG MASS • TSGE, TLGE, TTGE • TSDE, TLDE, TTDE Coupling size From the appropriate catalogue select the coupling for the calculated rating. Always select a coupling with a higher rating: eg. Calculated rating: 211kW/1000rpm Select: TSKS 0230 Question 2 Electric Motor to Screw Compressor 1500KW @ 3000 RPM What is the rating? Select a coupling Answer to Question 2 Required Rating = kW x 1000 x SF N Rating kW/1000 rpm = 1500 x 1000 x 1.5 3,000 = 750 kW/1000 rpm Select a TLKS-0750 or L081 SERVICE FACTOR for TRANSIENT TORQUE Standard couplings are suitable for transient torques as follows: • • • • M-series up to 3 times continuous rating. TSK up to 2.5 times continuous rating. TLK up to 2 times continuous rating. High Performance up to 2 times continuous rating. To calculate the required coupling rating for Transient torque Required Rating = Transient torque/f where f is the factor given above Example: Generator drive has a transient torque of 7 x nominal rating. For TLKS selection the minimum service factor is 7 / 2 = 3.5 Question 3 Steam Turbine to Generation set through a 3:1 ratio Steam Turbine 5MW @ 5400rpm Generator set 5 x Continuous torque Select gearbox to generator coupling Answer to Question 3 Steam turbine 5MW @ 5400rpm = 5000kW @ 5400rpm Generator 5000kW @ 5400/3 = 1800rpm Steady duty SF generator = 1.5 Prime Mover, steam turbine = no change BUT Gearbox present so minimum SF = 1.25 Required Steady service factor = 1.5 Answer to Question 3 Generator Transient torque = 5 x steady torque TLKS coupling transient capacity = 2 x rating Required Transient service factor = 5 / 2 which gives worst case is TF = 2.5 Required Rating Rating kW/1000 rpm = kW x 1000 x SF N = 5,000 x 1000 x 2.5 1,800 = 6944 kW/1000rpm (for transients) Need TLKS- 8500 Additional checks Speed • Check that the application maximum speed is within the permitted range for the coupling. Dimension • Check that the hub maximum bore is adequate for each shaft. Use a large hub or use a larger coupling if necessary. • Check that the shaft end separation [DBSE] is acceptable for the design chosen. Coupling Selection Shaft end types Cylindrical (Straight) with key W Key height Keyway height (shaft) Keyway height (hub) Coupling Selection Shaft end type Conical (Tapered) with key Key details Size Parallel to taper or centerline Taper Required counter bore or across corners of shaft nut (Ratio, in/ft or degree) Question 4 Electric Motor to Centrifugal Pump Motor shaft - Parallel B + K Pump shaft - Taper B + K Dia 36 @ large end Shaft end separation 100mm Power absorbed by pump 17KW Motor Speed 2980 Selection + Assumptions made + Limitations Answer to Question 4 Duty Conditions 17kW @ 2980rpm; DBSE =100: Is pump centrifugal? If so assume SF = 1 Rating kW/1000 rpm = 17 x 1000 x 1.0 = 5.7 kW/1000 rpm 2,980 Select either >> MHSS-0006 or L001 or TSKS-0013 Pump shaft diameter = 36 mm taper OK for TSK and MHS, but L series Re-select L003 Motor shaft diameter = ?? Clarify requirement. STATE maximum for selection Question 5 Motor 1500KW @1500 rpm 220 shaft Gearbox 2.6 : 1 increasing, motor side 200 mm diameter 145mm pump side. DBSE 200mm motor side, 140mm DBSE pump side AP1 610 Select High speed coupling Answer to Question 5 Motor 1500kW at 1500rpm Gearbox increasing pump speed to 1500 x 2.6 = 3900rpm Shaft diameter GearBox(driver) = 145 mm Pump shaft diameter = 140 mm DBSE = 200mm 1500 x 1000 x 1.25 3900 TLKS-0750-0078-2000 Coupling Selection Special requirements Required Misalignment • • • Axial Misalignment (in / mm) Angular deflection deg Parallel Offset (in / mm) Industrial or Customer specifications apply? • (API 610, API 671, etc.) Is this a new or retrofit application? • If retrofit, obtain mass elastic data of original coupling Enquiry form PLEASE SUPPLY DIMENSIONS USING CORRECT SKETCH: Shaft Length John Crane UK Ltd Sales and Service Division Nash Road, Trafford Park, Manchester. M17 1SS. Tel: 0161 872 2484 Fax: 0161 886 6335 or 5910 Shaft Length METASTREAM COUPLING ENQUIRY B&K (driver) TAPER KEY DETAILS Parallel To Axis Parallel To Bore D.B.S.E DRIVER END DRIVEN END Shaft Length PLANT / CONTRACT REF: B&K (driven) TAPER KEY DETAILS Parallel To Axis Parallel To Bore Tol B&K (driver / driven) Shaft Length DRIVER / DRIVEN END Recess Diameter E.MAIL DRIVEN MACHINE: kW / HP SHAFT END SEPARATION (DBSE) mm / in AMBIENT -15oC to + 150oC TEMPERATURE IF NO - PLEASE SPECIFY Recess Depth DRIVER / DRIVEN END DATE: PHONE: DRIVER RATING: Recess Diameter B&K (driver / driven) TAPER BORE DETAILS End: Large / Small Shaft: Tol Taper Angle: CONTACT: FAX: SELECTION DATA DRIVING MACHINE: Shaft Length D.B.S.E ENQUIRY REF: Tol Tol CUSTOMER: Shaft Length TAPER KEY DETAILS Parallel To Axis Parallel To Bore Recess Diameter DUTY SPEED: rpm SERVICE: (e.g. cooling water pump) YES / oF NO oC APPLICABLE SPECIFICATION API 610 API 671 NONE IF API 610 OR 671 PLEASE SPECIFY EDITION: OTHERS (PLEASE SPECIFY) PREFERRED COUPLING TYPE OPTIONAL FEATURES (PLEASE TICK). PLEASE SPECIFY BALANCE GRADE IN BOX GIVEN TAPPED PULLER HOLES PROFILED HUBS AXIAL ADJUSTMENT INSULATED SPARK RESISTANT LIMITED END FLOAT TRIM BALANCE HOLES BALANCED BALANCE GRADE G TRANSMISSION BALANCE HUB BALANCE ASSEMBLY BALANCE TORSIONAL TUNING SHEAR PIN FEATURE VERTICAL REMARKS D.B.S.E B&K (driver) TAPER BORE DETAILS End: Large / Small Shaft: Tol Taper Angle: Recess Depth DRIVER END Recess Depth DRIVEN END B&K (driven) TAPER BORE DETAILS End: Large / Small Shaft: T ol Taper Angle: COUPLING SELECTION ORIGINATOR: TYPE SIZE FEATURES DATE: D.B.S.E. Selection Software Selection Software