1. TORQUE
The vendor shall furnish couplings with the maximum practical service factor, considering torque transmitted by the coupling, overhung movement, speed, and lubrication. Unless otherwise specified, the coupling, coupling-to-shaft junctures, and machinery shafting shall be capable of continuos operation at a torque determined by equation given in Chapter 3 using an experience factor of 1.75. the purchaser will specify the expected magnitude, nature and number of occurrences of transients to which the coupling will be subjected in service. The coupling, coupling-to-shaft juncture and shafting shall be capable of transmitting 115 percent of the purchaser-specified maximum transient torque without damage. The vendor shall state the coupling design without damage. The vendor shall state the coupling design rating (in horsepower per 100 revolutions per minute). The coupling size selection shall be submitted to the purchase of approval.
Note: Should reasonable attempts to achieve the specified experience factor fail to result in a coupling weight and subsequent overhung moment commensurate with the requirement for rotor dynamics of the connected machines, a lower factor may be selected by mutual agreement of the purchaser and the vendor. The selected value shall not be less than 1.25.
2. CRITERIA FOR CONTINOUS OPEATION
The coupling design shall permit continuos operation at the maximum continuos torque level with at least 125 percent of the purchaser-specified maximum steady-state for transient axial displacement (whichever is larger) occurring simultaneously with 125 percent of the purchaser specified maximum angular misalignment and 125 percent of the purchase-specified maximum parallel offset. (the maximum changes in misalignment and parallel offset are normally experienced during start-p of a machinery train).
3. SPACER
All couplings shall be if the spacer type. The spacer shall be of sufficient length to allow removal of coupling hubs and to allow for maintenance of adjacent bearings and seals without removal of the shaft or disturbance of the equipment alignment. The minimum spacer length shall therefore correspond to a between-shaft-ends dimension of 18 inches (457 millimeters), unless otherwise specified by the purchaser.
4. HUBTYPE
The purchaser will specify whether integral or removable hubs are to be used.
5. DRILL JIG
Unless otherwise specified, when the coupling is to be used with integrally flanged shaft ends, a drill jig (or template) shall be used to locate the flange holes. The purchaser will specify whether he or the coupling vendor is to furnish the jig (or template).
6. CORROSIVE ENVIRONMENT
When the purchaser specifies that the coupling is to operate in a corrosive environment, either oil mist or an inert-gas purge may be necessary. The vendor shall advise the purchaser when material limitations demand such protection for the coupling.
7. MOMENT SIMULATOR/ADAPTER PLATE
7.1 When specified, a moment simulator shall be supplied. The purchaser will supply the vendor with the measurement of the distance from the end of the shaft to the first bearing. The simulator shall also serve as an adapter plate.
7.2 The vendor shall supply an adapter plate for the price end of the coupling to allow uncoupled operation of the driver. The adapter plate shall be designed so that the late can rigidly bolted to the sleeve and centered on the hub by a pilot fit.
8. Removable Hubs
8.1. Removable coupling hubs shall be secured to the shaft by means of interference fit. The degree of interference will be specified by the purchaser and is subject to approval by the vendor. The choice of non-keyed (tapered-bore, hydraulically fitted) or keyed (tapered-or-straight-bore) hubs will be specified by the purchaser.
8.2. The surface finish of the hub bore shall be 125 micro-inches (3.2 micrometers)
arithmetic roughness (R ) or better.
8.3. The eccentricity of the hub bore, whether straight or tapered, shall not exceed 0.0002 inch (5.1 micrometers) TIR for bores less than or equal to 4 inches (102 millimeters) in diameter and shall not exceed 0.0005 inch (12.7 micrometers) TIR for hub bores greater than 4 inches in diameter, Eccentricity measurements shall be made before any keyways are cut.
8.4. The following guidelines are recommended for hub-to-shaft fits:
a) The interference fit for straight-bore keyed hubs shall be from 0.0005 or 0.00075 inch per inch of bore diameter. Shaft sizes and coupling bores shall conform to AGMA 9002.
b) The interference fit for tapered-bore keyed hubs shall be at least 0.001 inch per inch of bore diameter. The inspection procedure shall be in accordance with AGMA 9002.
c) The interference fit for tapered-bore hydraulically fitted hubs shall be at least 0.0015 inch per inch of bore diameter. The inspection procedure shall be in accordance with AGMA 9002.
For tapered-bore hubs and keyed hubs, please refer the API standard 671.
9. COMPONENET FIT TOLERANCES
9.1 Components of intermediate and high-speed couplings shall be centered by means of piloted fits. The eccentricity of these fits shall not exceed 0.001 inch TIR per foot of diameter or 0.0005 inch TIR, whichever is greater. Fits that tighten under centrifugal loading are preferred. The fit clearance shall range from a loose fit of 0.001 inch to an interference fit, with actual fit determined by balancing equipment.
9.2 The face run-out of mating faces (except for flexible elements) shall not exceed 0.001 inch TIR, whichever is greater.
9.3 Radial indicator surfaces used to align equipment shall be concentric to the hub bore within 0.001 inch TIR per foot of diameter or 0.001 inch TIR whichever is greater.
9.4 For hubs, pilot fits at fear coupling teeth shall be concentric to the bore within 0.001 inch TIR per foot of diameter or 0.0005 inch TIR, whichever is greater.
9.5 For sleeves, pilot fits at gear coupling teeth shall be concentric within 0.001 inch TIR per foot of diameter or 0.001 inch TIR, whichever is greater. Pilot fits shall be round within 0.002 inch TIR per foot of diameter or 0.0015 inch TIR, whichever is greater.
10. BOLTING CONSIDERATIONS
10.1 Bolting between coupling components shall be designed to transmit the required torque without dependence on flange-face friction.
10.2 Bolts for piloted flanges shall have a diametrical clearance of from 0 to 0.0005 inch (127 micrometers) in the bolt holes.
10.3 Bolts for low-speed couplings with nonpiloted flanges shall be of the body-bound style and shall be through-fitted into line-reamed holes, with the assembly’s diametrical clearance ranging from 0 to 0.0015 inch (38 micrometers).
10.4 Self-locking nuts shall be used. Lock washers shall not be used.
Note: The self-locking feature of nust may lose effectiveness with each removal of the nut. The coupling vendor shall recommended the interval at which nuts should be replaced.
10.5 the coupling vendor shall specify the required bolts torque, and shall state whether this value is for dry or lubrictaed applications.
10.6 the bolt shall be held within dimensional tolerances sufficient to permit both interchange within the same sset of bolts and substitution of spare bolts withut affecting coupling integrity and balance by more than 1 percent.
11. ELECTRICAL INSULATION
When specified, the coupling shall be electrically insulated.
12. MACHINGING
All coupling parts, except for flexible disks, shall be machined all over to minimise inherent unbalance.
The vendor shall furnish couplings with the maximum practical service factor, considering torque transmitted by the coupling, overhung movement, speed, and lubrication. Unless otherwise specified, the coupling, coupling-to-shaft junctures, and machinery shafting shall be capable of continuos operation at a torque determined by equation given in Chapter 3 using an experience factor of 1.75. the purchaser will specify the expected magnitude, nature and number of occurrences of transients to which the coupling will be subjected in service. The coupling, coupling-to-shaft juncture and shafting shall be capable of transmitting 115 percent of the purchaser-specified maximum transient torque without damage. The vendor shall state the coupling design without damage. The vendor shall state the coupling design rating (in horsepower per 100 revolutions per minute). The coupling size selection shall be submitted to the purchase of approval.
Note: Should reasonable attempts to achieve the specified experience factor fail to result in a coupling weight and subsequent overhung moment commensurate with the requirement for rotor dynamics of the connected machines, a lower factor may be selected by mutual agreement of the purchaser and the vendor. The selected value shall not be less than 1.25.
2. CRITERIA FOR CONTINOUS OPEATION
The coupling design shall permit continuos operation at the maximum continuos torque level with at least 125 percent of the purchaser-specified maximum steady-state for transient axial displacement (whichever is larger) occurring simultaneously with 125 percent of the purchaser specified maximum angular misalignment and 125 percent of the purchase-specified maximum parallel offset. (the maximum changes in misalignment and parallel offset are normally experienced during start-p of a machinery train).
3. SPACER
All couplings shall be if the spacer type. The spacer shall be of sufficient length to allow removal of coupling hubs and to allow for maintenance of adjacent bearings and seals without removal of the shaft or disturbance of the equipment alignment. The minimum spacer length shall therefore correspond to a between-shaft-ends dimension of 18 inches (457 millimeters), unless otherwise specified by the purchaser.
4. HUBTYPE
The purchaser will specify whether integral or removable hubs are to be used.
5. DRILL JIG
Unless otherwise specified, when the coupling is to be used with integrally flanged shaft ends, a drill jig (or template) shall be used to locate the flange holes. The purchaser will specify whether he or the coupling vendor is to furnish the jig (or template).
6. CORROSIVE ENVIRONMENT
When the purchaser specifies that the coupling is to operate in a corrosive environment, either oil mist or an inert-gas purge may be necessary. The vendor shall advise the purchaser when material limitations demand such protection for the coupling.
7. MOMENT SIMULATOR/ADAPTER PLATE
7.1 When specified, a moment simulator shall be supplied. The purchaser will supply the vendor with the measurement of the distance from the end of the shaft to the first bearing. The simulator shall also serve as an adapter plate.
7.2 The vendor shall supply an adapter plate for the price end of the coupling to allow uncoupled operation of the driver. The adapter plate shall be designed so that the late can rigidly bolted to the sleeve and centered on the hub by a pilot fit.
8. Removable Hubs
8.1. Removable coupling hubs shall be secured to the shaft by means of interference fit. The degree of interference will be specified by the purchaser and is subject to approval by the vendor. The choice of non-keyed (tapered-bore, hydraulically fitted) or keyed (tapered-or-straight-bore) hubs will be specified by the purchaser.
8.2. The surface finish of the hub bore shall be 125 micro-inches (3.2 micrometers)
arithmetic roughness (R ) or better.
8.3. The eccentricity of the hub bore, whether straight or tapered, shall not exceed 0.0002 inch (5.1 micrometers) TIR for bores less than or equal to 4 inches (102 millimeters) in diameter and shall not exceed 0.0005 inch (12.7 micrometers) TIR for hub bores greater than 4 inches in diameter, Eccentricity measurements shall be made before any keyways are cut.
8.4. The following guidelines are recommended for hub-to-shaft fits:
a) The interference fit for straight-bore keyed hubs shall be from 0.0005 or 0.00075 inch per inch of bore diameter. Shaft sizes and coupling bores shall conform to AGMA 9002.
b) The interference fit for tapered-bore keyed hubs shall be at least 0.001 inch per inch of bore diameter. The inspection procedure shall be in accordance with AGMA 9002.
c) The interference fit for tapered-bore hydraulically fitted hubs shall be at least 0.0015 inch per inch of bore diameter. The inspection procedure shall be in accordance with AGMA 9002.
For tapered-bore hubs and keyed hubs, please refer the API standard 671.
9. COMPONENET FIT TOLERANCES
9.1 Components of intermediate and high-speed couplings shall be centered by means of piloted fits. The eccentricity of these fits shall not exceed 0.001 inch TIR per foot of diameter or 0.0005 inch TIR, whichever is greater. Fits that tighten under centrifugal loading are preferred. The fit clearance shall range from a loose fit of 0.001 inch to an interference fit, with actual fit determined by balancing equipment.
9.2 The face run-out of mating faces (except for flexible elements) shall not exceed 0.001 inch TIR, whichever is greater.
9.3 Radial indicator surfaces used to align equipment shall be concentric to the hub bore within 0.001 inch TIR per foot of diameter or 0.001 inch TIR whichever is greater.
9.4 For hubs, pilot fits at fear coupling teeth shall be concentric to the bore within 0.001 inch TIR per foot of diameter or 0.0005 inch TIR, whichever is greater.
9.5 For sleeves, pilot fits at gear coupling teeth shall be concentric within 0.001 inch TIR per foot of diameter or 0.001 inch TIR, whichever is greater. Pilot fits shall be round within 0.002 inch TIR per foot of diameter or 0.0015 inch TIR, whichever is greater.
10. BOLTING CONSIDERATIONS
10.1 Bolting between coupling components shall be designed to transmit the required torque without dependence on flange-face friction.
10.2 Bolts for piloted flanges shall have a diametrical clearance of from 0 to 0.0005 inch (127 micrometers) in the bolt holes.
10.3 Bolts for low-speed couplings with nonpiloted flanges shall be of the body-bound style and shall be through-fitted into line-reamed holes, with the assembly’s diametrical clearance ranging from 0 to 0.0015 inch (38 micrometers).
10.4 Self-locking nuts shall be used. Lock washers shall not be used.
Note: The self-locking feature of nust may lose effectiveness with each removal of the nut. The coupling vendor shall recommended the interval at which nuts should be replaced.
10.5 the coupling vendor shall specify the required bolts torque, and shall state whether this value is for dry or lubrictaed applications.
10.6 the bolt shall be held within dimensional tolerances sufficient to permit both interchange within the same sset of bolts and substitution of spare bolts withut affecting coupling integrity and balance by more than 1 percent.
11. ELECTRICAL INSULATION
When specified, the coupling shall be electrically insulated.
12. MACHINGING
All coupling parts, except for flexible disks, shall be machined all over to minimise inherent unbalance.
1 comment:
i want to know the design formulae
Post a Comment