Power Transmission drives belt drive chain drive pulley

power plant power transmission

1. Power transmission drives

2. Couplings Coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power, accommodate misalignment and compensate for axial movement or end float . Motor Coupling Pump

3. Selecting the right coupling depends on four basic conditions of shaft misalignment or movement. Parallel misalignment occurs when the two shafts do not share the same rotation axis. Their end faces may be parallel, but their center axes are laterally displaced with respect to each other. Angular misalignment applies when shafts are neither coaxial nor parallel. The angle at which the shafts are misaligned may be symmetrical or asymmetrical. End float occurs when either or both shafts display axial movement, moving in and out. Torsional flexibility is the torsional movement in planes perpendicular to the shaft axis. Shock or vibration typically causes this. A torsionally flexible coupling absorbs and dampens these movements.

4. Types of shaft couplings 1. Rigid coupling It is used to connect two shafts which are perfectly aligned. The types are Sleeve (or) muff coupling Clamp (or) split muff (or) compression coupling Flange coupling 2. Flexible coupling It is used to connect two shafts having lateral and angular misalignments. The types are Bushed pin type coupling Universal coupling Oldham coupling

5. Rigid coupling Flange Driven Shaft Driving Shaft Key Hub Rigid couplings are used when precise shaft alignment is required Simple in design and are more rugged Generally able to transmit more power than flexible couplings Shaft misalignments cannot be compensated Flanged Coupling

6. Flexible Coupling Bush Flange Flange Driving Shaft Driven Shaft Pin A flexible coupling permits with in certain limits, relative rotation and variation in the alignment of shafts Pins (Bolts) covered by rubber washer or bush is used connect flanges with nuts The rubber washers or bushes act as a shock absorbers and insulators.

7. SLEEVE OR MUFF COUPLING

8. Sleeve coupling Sleeve couplings are nothing but just sort of thick hollow cylinder/pipe called as sleeve or muff. The sleeve is manufactured keeping the diameter of shaft in mind so that the shaft fits perfectly into the sleeve. The driver & driven, both the shafts are then inserted into each side of the sleeve. Also two or more threaded holes are provided into the sleeve as well as in both of the shaft’s end so that they don’t move in longitudnal direction when the bolts are inserted into them. Also the keyway and key ensures that the shaft and sleeve doesn’t slip. The sleeve coupling is easy to manufacture as there are neither more nor more number of parts. Application- They are used where the shafts don’t require any alignments and load capacity is light to medium duty.

9. The gear coupling is another modified version of the flange coupling. In gear coupling, the flange and hub are different parts assembled together instead of a single part as in flange coupling. The hubs are externally splined but they are so thick and deep that you can regard them as gear teeth. Also the flanges have internal teeth. The gear ratio is 1:1 and are meshed together. The single joint gear couplings are limited to lower angular misalignments. Application- Gear couplings are used for heavy-duty applications where requirement of torque transmission is higher.

10. Disc Type Metallic Couplings Torque is transmitted by driving bolts pulling driven bolts through the disc material, which is in tension . More bolts provide greater capacity but reduce the coupling flexibility. For special-purpose applications, the discs are provided as a pack. ..

11. Disc type metallic couplings Disc type metallic couplings, also known as disc couplings or disc pack couplings, are used in power transmission systems to connect two shafts while accommodating misalignment and providing high torsional stiffness. They are widely used in various industries and applications due to their ability to transmit high torque and handle misalignment effectively. The discs can flex slightly to accommodate misalignment. The flexibility in the disc pack allows it to handle angular, parallel, and axial misalignments without significant loss of torque transmission.

12. Disc Type Metallic Couplings

13. Jaw/spider couplings have their elastomers in compression. The flex element can be one piece or split to facilitate replacement. They also have a fail-safe feature. Flex elements are made of many types of elastomeric materials , such as rubber and urethane. These couplings are used primarily to accommodate misalignment and transmit power. Small and medium-size equipment employ these types of couplings . JAW/SPIDER TYPE COUPLING

14. Tire Type Elastomeric Couplings Tire Couplings These couplings have a rubber or polyurethane element connected to two hubs. The rubber element transmits torque in shear. Reduces transmission of shock loads or vibration. High misalignment capacity Easy assembly w/o moving hubs or connected equipment Moderate to high speed operation Wide range of torque capacity

15. Belt drive

16. Types of belts There are 4 types belts used in belt drives they are as follows : Flat belts shaft distance 5 to 10 meters, low power, high speed Round belts smaller initial tension, absence of vibration and noise, high power, shaft distance > 5 meters V belts shaft distance < 2 meters, high power, moderate speed Timing Belts positive drives, precise, reliable

17. FLAT BELT DRIVE A flat belt drive is one wherein the width of the belt is larger than the thickness. These are used where power has to be transmitted for large distances between pulleys . The efficiency of flat belt transmission or flat belt drives is approximately 99%

18. Power Transmitted (P) = (T1-T2)V

19. BELT DRIVES A belt drive is a method of transferring torque /rotary motion between two shafts. A belt drive includes one pulley on each shaft and one or more continuous belts over the two pulleys. The motion of the driving pulley is, generally, transferred to the driven pulley via the friction between the belt and the pulley. Generally belt drives are friction drives. A Belt is a looped strip of flexible material , mostly Rubber, Polyurethane, Kevlar fabric, Steel cords etc.. used to mechanically link two or more rotating shafts. A pulley is a wheel with a groove between two flanges around its circumference.

20. Timing belts Also known as Toothed , Notch or Cog belts are a positive transfer belt and can track relative movement. These belts have teeth that fit into a matching toothed pulley . They are often used to replace chains or gears, reducing noise and avoiding the lubrication bath or oiling system requirement. Requires the least tension of all belt drives and are among the most efficient.

21. Types of Belt drives based on the arrangement are as follows Open belt drives Crossed or twist belt drives Belt drive with idler pulleys Compound belt drive Types of belt drives based on arrangement

22. The Open belt drive is arranged with shafts arranged parallel and rotating in the same direction. The driver pulls the belt from one side and delivers it to the other side thus the tension in the one side belt will be more than that in the other side belt. Open belt drive

23. Crossed or twist belt drive The crossed or twist belt drive is used with shafts arranged parallel and rotating in the opposite directions. The tension in the tight side will be more than the slack side. The point where the belts rubs against each other and there will be excessive wear and tear. To avoid this the shafts should be placed at a maximum distance of 20b where b is the width of the belt and the speed should be less than 15 m/s.

24. Belt drive with idler pulleys The idler pulley is placed on the slack side of the belt. They improve the belt drive's performance as they reduce vibration by supporting the belt. Idler pulleys can increase the wrap angle for smaller pulleys, ultimately increasing the surface area between the drive belt and the pulley

25. Compound belt drive A compound belt drive is used when power is transmitted from one shaft to another through a number of pulleys. The belts are connected in such a way that the driver moving one system of drives is simultaneously moving the other connected system.

26. ‘ V belts In a multiple V belt drive, when a single belt is damaged , all together should be replaced. Replacement of a single belt will upset the load balance between the new and old belts.

27. Power transmission by V Belts The power which can be transmitted by a V‐belt drive depends on: 1. Cross section of the Belt 2. Speed of the Belt 3. Diameter of the Pulleys 4. Length of Belt 5. Number of Belts 6. Arc of Contact 7. Service Conditions

28. V‐Belt Drives Some Advantages 1. Belt tension is reduced hence the load on the shafts and bearings is reduced. 2. Close centre distances can be used so that the drive is compact. 3. Large speed ratios can be used even when the centre distance is comparatively short . 4. The slip between belt and pulley is negligible, resulting in longer life of the belt. 5. V‐belts cushion the motor and bearings against load fluctuations. This is an important advantage of any belt drive as compared with a positive drive e.g . gears . 6. They are quieter than gear or chain drives. 7. They do not need the extreme accuracy of alignment required for couplings and gears . For high speed shafts, the initial cost is lower than gears or chains. 8. The maintenance is usually much less than that for gears and chains, which require adequate lubrication.

29. 1 . Higher Power Transmission Efficiency Better Grip and Traction : The V-shape of the belt fits into the corresponding V-shaped grooves on the pulleys. This design increases the contact area and provides better grip, reducing slippage and improving power transmission efficiency. Increased Friction : The wedging action of the V-belt in the pulley groove increases the frictional force, enhancing the belt's ability to transmit power without slipping. 2. Compact Design Space Efficiency : V-belts can transmit more power in a smaller space compared to flat belts. This allows for more compact and efficient machinery designs. Multiple Belts : Multiple V-belts can be used side by side in a single pulley system to handle higher power loads, which is not as effective with flat belts. 3. Higher Load Capacity Higher Tension and Load : V-belts can operate under higher tension and can carry heavier loads compared to flat belts. suitable for high-power applications . Self- Centering : The V-shape helps keep the belt aligned within the pulley groove, reducing the likelihood of the belt slipping off. This self- centering action reduces the need for frequent adjustments and maintenance . ADVANTAGES OF V BELTS

30. 4. Better Alignment and Reduced Maintenance Self- Centering : The V-shape helps keep the belt aligned within the pulley groove, reducing the likelihood of the belt slipping off. This self- centering action reduces the need for frequent adjustments and maintenance. Longer Service Life : Because V-belts operate with less slippage and maintain better alignment, they tend to have a longer service life and require less frequent replacement compared to flat belts. 5 . Shock Absorption Better Damping : The V-belt's construction and material composition provide better shock absorption and damping characteristics. This helps to protect both the belt and the machinery from sudden load changes and vibrations. 6. Versatility and Range Wide Range of Sizes : V-belts come in a wide variety of sizes and profiles, making them versatile and adaptable to different applications. Standardization : V-belts are widely standardized, making it easier to find replacements and compatible components. 7. Lower Initial Tension Reduced Bearing Load : V-belts typically require lower initial tension compared to flat belts. This reduces the load on bearings and other components, potentially extending their service life .

31. Nomenclature of V-belt A typical V-belt section is shown in Fig. The geometrical features of the belt section are indicated in the figure. The pitch line, which is also marked as N-A, is the neutral axis of the belt section. The design calculations for V-belt drives are based on the pitch line or the neutral axis. These belts are available in various sections depending upon power rating

32. ‘ V belts The strength of these belts is obtained by reinforcements with fibers like steel, polyester. V-belts are far superior to flat belts at small center distances and high reduction ratios. Require larger pulleys than flat belts because of their greater thickness. The "V" shape of the belt tracks in a mating groove (or sheave) in the pulley, with the result that the belt cannot slip off.

33. * Excessive Exposure to Oil or Grease • Use of Belt Dressing Belt Soft, Swollen SYMPTOMS CAUSES * Worn or Damaged Sheaves * Insufficient Tension • Wrong Belt Cross-Section or Type • Excessive Oil or Grease • Excessive Moisture • Overload Drive- Underbelting • Insufficient Wrap on Small Sheave Belt Slips, Squeals (Spin Burn) V Belt trouble shooting

34. Belt Cover Split * Belts Pried On or Misplaced Slack • Foreign Objects In Grooves Underside Cracked * Excessive Heat * Sheaves Too Small * Undersized Backside Idler * Improperly Positioned Backside Idler • Sheaves Misaligned • Improper Or Prolonged Storage Excessive Tension • Worn or Damaged Sheaves • Prying open The Split With a Screwdriver SYMPTOMS CAUSES V Belt trouble shooting

35. Gear Drives A gear wheel is a toothed machine part that meshes with another toothed part to transmit motion or to change speed or direction. Gears can produce mechanical advantage through a gear ratio and can be viewed as a simple machine. Gear wheels are often used for conversion of torque and speed of a power source. These can transfer large torques to drive very large loads. These are often used when speed changes are required. A gear setup which increases speed is called a step up gear while a setup which decreases speed is called a step down gear box. Some gear boxes are capable of achieving large reductions even in a small physical package

36. Spur gear is the simplest type of gear. These are used to transmit power when the shafts are parallel with each other. These gears are very economical for many applications. These have a simple shape and a design. These also encounter no thrust loads from tooth engagement Helical gears are ideal for a system which switches gear ratios frequently. These ensure a gradual tooth engagement which results in lower noise during operation. These could be used when the shafts are at an angle. Resulting thrust loads from teeth reaction forces generated during engagement could cause problems. Helical Gears Spur Gears Type of gears

37. Bevel gears are often used when the two shafts are an angle of 90 degrees; however, these could also be used when the two shafts are at other angles. The teeth of the two gears are on a conically shaped surface. These could have either straight or helical teeth. In this type of gears a worm, which has the form of a screw, meshes with a worm gear wheel. They can be used to obtain higher speed reductions allowing higher torques to be transmitted. There is greater friction between the worm and worm-wheel introducing higher losses and thus reducing the efficiency Worm Gears Bevel Gears Type of gears

38. A rack is the toothed linear drive and pinion is the toothed wheel of the gear train. A rack and pinion converts rotational motion into linear motion thus they can also be considered as a type of a linear actuator. The rack and pinion is used in the steering mechanism of automobiles. It provides less backlash and greater feedback, or steering "feel" for the driver. Type of gears

39. Simple gear train

40. Gear trains are multiple sets of gears meshing together to deliver power and motion more effectively than can be accomplished by one set of gears. Figure shows a simple gear train. Speed Ratio of Gear Train is ratio of speed of driver gear to driven gear N equals the rpm and T equals the number of teeth in the respective gears. When cancelling out like quantities, the equation can be reduced to the following N2 T2 = N3T3, N3T3 = N4T4, N4T4 = N5T5 So N2/N5 = (T5/T2), Independent of size and number of teeth of intermediate gears. Speed ratio of Simple Gear trains

41. Advantage of compound gear train,1 ) More ratios can be obtained . 2 ) The design is more compact . 3 ) There is one less shaft.

42. A speed reducer is a gear set assembled with appropriate shafting, bearings, and lubrication in a sealed housing, generally an oil-tight case. Such units are also sometimes referred to as gear boxes, speed increasers, and gear reducers. Speed reducers are available in a broad range of power capacities and speed ratios depending on gear size and type, with most having a maximum speed limit of 3,600 rpm, and usually driven at a full-load speed of 1,750 rpm or less. Lubrication of speed reducers is accomplished either by a splash or circulating system. Bearings may be lubricated automatically with the same oil as the gear set, or they may have separate systems. The specific lubricant required for a speed reducer depends on a number of factors including operating speed, ambient temperature, loads, and method of lubricant application Speed reducer

43. Gearboxes contain one or more pair of gears inside a housing which has an input shaft and one or more output shafts. The output shafts may be located on the sides or at the back of the gearbox. Gearboxes contain a gear lubricant, are sealed, and usually operate maintenance free. Connected to the input shaft is a high speed power source such as a motor and connected to the output shafts are devices which generally use lower rpms and higher torques to perform a particular task. The device may include a machine tool, a conveyor, an elevator, or the wheels of an automobile Gearboxes

44. Figure has a worm gearbox at left and a bevel gearbox at the right. Worm gearboxes are generally high reduction devices with ratios ranging from 5/1 to 60/1 for single reduction units such as shown in Figure to 3600/1 for double reduction units. Because of the high amount of sliding that occurs at the mesh, worm gears operate at efficiencies below that of other types of gears. To minimize this effect, the gear is usually made of a material with a low coefficient of friction such as bronze. Worm gears can be made to be non reversing by keeping the lead angle of the worm thread low Gearboxes

45. Bevel gearboxes have input and output axes 90° apart like worm gearboxes; however, bevel gearbox axes intersect as opposed to worm gearbox axes being offset. Bevel gearboxes generally have lower ratios than worm gearboxes and can be used as speed increasers as well as speed reducers. Bevel gearboxes having all steel gears can deliver more horsepower than worm gearboxes with bronze gears. Spiral bevel gears are stronger and quieter than straight bevel gears but are less efficient. Worm gearbox of a crane drive

46. Figure has a double reduction gearbox at left and a gearbox-motor combination unit at right. The double reduction gearbox can give twice the ratio as a single reduction gearbox in a slightly larger package. It features helical gears for quieter, more powerful operation over spur gears. The motor gearbox unit is an integral package that features a double reduction helical gearbox directly attached to a drive motor. Integral motor mounting features excellent alignment with the gearbox input shaft for smooth, vibration-free operation. Gearboxes

47. Most speed reducers use one or more of the common gear types previously discussed. However, the use of helical, worm, and bevel gear sets is particularly prevalent, especially in small and medium sized speed reducers. Helical gears are often used in combination with spiral-bevel or worm gears. Selection of a particular style of speed reducer for an application depends primarily on shaft arrangement, type of gearing, ratio range, and horsepower range. Three broad categories of speed reducers, grouped according to mounting arrangements, are base-mounted, shaft-mounted, and gear motor,

48. Worm gearing has perpendicular, nonintersecting shafts in which the worm acts as a screw. Several revolutions of the worm pull the wheel through one revolution.

49. Based-mounted speed reducer with shafts mounted at right angles Shaft-mounted speed reducer with torque arm to prevent housing rotation.

50. Worm gearbox of a crane drive

51. SELECTING GEAR DRIVES Gears can be selected, rated, installed, and maintained by most users through common standards and practices developed by the American Gear Manufacturers Association. However, the services of a gear-engineering specialist are generally required to make more detailed, in-depth analysis in cases where severe duty, extreme reliability, unusually long service, or other extraordinary conditions exist. In either case, the major selection factors include: shaft orientation, speed ratio, design style, nature of load, service factor, environment, mounting position, ratio, lubrication, and installation practices. All these factors must be carefully considered in selecting gears for optimal operation in a particular application.

52. Gear failure mode

53. Trouble shooting Gear box problems

54. Trouble shooting Gear box problems