Exp Pr Eq180 En R0_1 Reduction Units 242a6y
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EQUIPMENT REDUCTION UNITS
TRAINING MANUAL Course EXP-PR-EQ180 Revision 0.1
Exploration & Production Equipment Reduction units
EQUIPMENT REDUCTION UNITS CONTENTS 2. WHAT ARE REDUCTION UNITS USED FOR? ..............................................................4 3. THE DIFFERENT TYPES OF REDUCTION UNITS ........................................................5 3.1. WORM REDUCTION UNITS ....................................................................................5 3.2. HELICAL REDUCTION UNITS .................................................................................6 3.3. PARALLEL SHAFT REDUCTION UNITS .................................................................7 3.4. PLANETARY REDUCTION UNITS ...........................................................................8 3.5. INDUSTRIAL REDUCTION UNITS ...........................................................................9 4. REDUCTION UNIT APPLICATIONS .............................................................................10 5. OPERATING PRINCIPLE..............................................................................................11 5.1. COMPOSITION.......................................................................................................11 5.2. PRINCIPLE .............................................................................................................11 5.3. THE DIFFERENT TYPES OF TEETH.....................................................................14 5.3.1. Straight-cut gears ............................................................................................14 5.3.2. Helical-cut teeth...............................................................................................14 5.3.3. Bevel-cut teeth ................................................................................................15 5.3.4. Worm-cut teeth................................................................................................16 5.3.5. Hypoid-cut teeth ..............................................................................................17 5.4. DEFINITION OF A REDUCTION UNIT RATIO .......................................................19 6. SERVICING AND MAINTENANCE ...............................................................................20 7. GLOSSARY ...................................................................................................................22 8. LIST OF FIGURES ........................................................................................................23 9. LIST OF TABLES ..........................................................................................................24
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 2 / 24
Exploration & Production Equipment Reduction units
1. OBJECTIVES Aim of the present course is to allow the future operator to understand the basic mechanical principles of reduction units, (the gear reducers) At the end of this course, the attendee would be able to: Explain functions of reducers Enumerate the different types of reducers encountered on site List the different applications Expose the working principles of reducers Enumerate the different types of gear used within reducers Calculate the ratio of a reducer Follow up a maintenance program for reducers
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 3 / 24
Exploration & Production Equipment Reduction units
2. WHAT ARE REDUCTION UNITS USED FOR? A reduction unit is a mechanical component which reduces the rotational speed of a drive shaft. A reduction unit transmits a high torque to the driven machine (pump, compressor, alternator or generator). Figure 1: Example of a reduction unit (1)
Figure 2: Example of a reduction unit (2)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 4 / 24
Exploration & Production Equipment Reduction units
3. THE DIFFERENT TYPES OF REDUCTION UNITS 3.1. WORM REDUCTION UNITS
Figure 3: Worm reduction unit
Figure 4: Cutaway view of a worm reduction unit and helical type
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 5 / 24
Exploration & Production Equipment Reduction units
3.2. HELICAL REDUCTION UNITS Helical reduction units perfectly illustrate the compact design of the new series of drives. They are robust angle drives adapted to all mechanical applications where a compact assembly is required. They provide a very wide torque range: 200 to 50000 Nm. Helical reduction units are used when the power must be transmitted through 90°. They are very efficient, particularly for applications where precision, efficiency, high speeds (up to 6500 rpm – depending on the size and the range) and high loads are required. Figure 5: Cutaway view of a helical reduction unit
Figure 6: Helical reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 6 / 24
Exploration & Production Equipment Reduction units
3.3. PARALLEL SHAFT REDUCTION UNITS Parallel shaft reduction units can be used in a wide range of configurations, even in the most unfavourable conditions, thanks to their torque range (130 to 18000 Nm) and the large number of positions in which they can be installed and their wide range of applications. These gear motors are compact due to the layout of the reduction unit's casing. The numerous output shaft and hollow shaft variants, and the possibility of installing the hollow shaft reduction unit using a reaction arm, feet or flanges, allow the right solution to be chosen at a cost-effective price. This is why this reduction unit has established itself worldwide as a solution for applications involving translation movement. Figure 7: Cutaway view of a parallel shaft reduction unit
Figure 8: Parallel shaft reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
3.4. PLANETARY REDUCTION UNITS Planetary gear motors are compact, have a low backlash and have one or two trains for powers of up to 3000 Nm to handle the most advanced, high-precision positioning tasks. Due to their structure they are ideal for use in compact assemblies with little available space.
Figure 9: Planetary reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 8 / 24
Exploration & Production Equipment Reduction units
3.5. INDUSTRIAL REDUCTION UNITS Production versions of 2 or 3 train parallel shaft reduction units are highly robust thanks to their very compact one-piece casing. Whether foot mounted, flange mounted or with a hollow shaft, with a wide range of versions and options, allows them to be used for torque ranges of up to 65000 Nm, even in difficult conditions.
Figure 10: Industrial reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 9 / 24
Exploration & Production Equipment Reduction units
4. REDUCTION UNIT APPLICATIONS Reduction units can be found in many industrial sectors. They are used where the drive shaft rotational speed of an internal combustion engine, electric motor, turbine, etc., must be modified.
Figure 12: Gear motor Figure 11: Reduction unit for mixer
Figure 13: High load reduction unit Figure 14: Marine reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 10 / 24
Exploration & Production Equipment Reduction units
5. OPERATING PRINCIPLE 5.1. COMPOSITION
Figure 15: Composition of a reduction unit
5.2. PRINCIPLE For a reduction unit to have a correct efficiency there must be no tooth friction. This is obtained by the shape of the teeth; we talk about involute teeth which are such that they mesh with each other without slide. Figure 16: Example of teeth (1)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
The must also be very regular, i.e. a tooth must take the relay well before the previous tooth has finished meshing. For conventional teeth, there is a good regularity up to a reduction ratio which must not exceed a value of around 4 or 5 for normal tooth sizes (the term modulus is used for the tooth size). Figure 17: Example of teeth (2) If we increase this ratio the problems begin, i.e. begins to deteriorate (only one tooth in at a time), and it will no longer be possible to achieve the ideal involute shape. The only way to correct this problem is to reduce the tooth modulus or increase the diameter of the pinions. If the size of the gear wheels is increased, the sizes become unacceptably large… Hence reduction units are limited to a single stage do not exceed a ratio of around 4. Figure 18: Gears and pinions of a reduction unit There is, of course, the notable exception of ‘GWS reduction units for indoor’ or’ park-flyer’ which reaches ratios of up to 11, but the powers at stake are low, which means that very small teeth can be used. Figure 19: Example of a reduction unit For applications with a lower efficiency requirement, and small reduction ratios (maximum of 3…), there is also the solution of belt reduction units which can transmit considerable powers while remaining costeffective. Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
This is always at the expense of size and no doubt of higher weight.
Figure 20: Composition of a reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
5.3. THE DIFFERENT TYPES OF TEETH A gear pair is an elementary mechanism consisting of two gears mobile around axes of invariable relative position, and one of which turns the other by the action of teeth successively in : we say that the two gears are conjugated. The smaller gear is called: the pinion; and the larger: the gear (a rack is a gear of infinite radius). There are 4 different types of gears: Straight-cut gears Helical-cut gears Bevel-cut gears Worm-cut gears Hypoid cut gears
5.3.1. Straight-cut gears The pinion is the smaller of the two gears and is often the driving gear. The shape of the gear varies with the dimensions. Straight teeth are used for small equipment and internal teeth. Figure 21: Straight-cut teeth
5.3.2. Helical-cut teeth They transmit movement between two parallel shafts. The inclination of the teeth (helix angle) is the same for both gears, but in opposite directions. Helical gears provide a transmission which is more flexible, more progressive and less noisy than straight gears.
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
The forces transmitted are higher (more teeth in ), even at high speeds.
Figure 22: Helical-cut teeth
The axial thrust can be neutralised by using two gears on each shaft, each with reversed helical teeth or a single gear with two symmetrical rows of teeth (called chevron or herringbone gears). Figure 23: Helical gears with two symmetrical rows of teeth Inconvenient of this type is the important axial thrust which requires specific bearings
5.3.3. Bevel-cut teeth These are the simplest teeth and they have the same problems as the straight gears at high speeds (noise, high pressures on the teeth, etc.).
Figure 24: Bevel-cut teeth They are used to transmit movement between two nonparallel shafts whose axes are concurrent (the most frequent type have axes at 90°).
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
The primitive surfaces are no longer cylinders but cones. The cones are tangents on a line MM' and their common summit is the point S (intersection of the rotational axes).
Figure 25: Right-angle bevel gears They reduce noise at high speeds and the transmission is more progressive. The typical pressure for straight teeth is 20° or 14°30', it is 35° for helical teeth.
5.3.4. Worm-cut teeth The transmission is achieved by a screw with one or more threads meshing with a gear. The direction of the helix is the same for the screw and for the gear. These gear systems give high reduction ratios and can be non-reversible. They provide the "smoothest" meshing of all gear systems. Their operation is silent and impact-free. However, they have a high level of slide and friction; thus their efficiency is poor. Efficiency is affected by good lubrication and an adapted choice of materials (steel screw and bronze gear). Figure 26: Worm
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
5.3.5. Hypoid-cut teeth Hypoid gears are helical bevel gears employed when the axes of the two shafts are perpendicular but do not intersect. One of the most common uses of hypoid gearing is to connect the drive shaft and the rear axle in automobiles. Helical gearing used to transmit rotation between shafts that are not parallel is often incorrectly called spiral gearing.
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
Position of shafts
Teeth size
Types
Type of and friction
Straight
Linear Rotation and slight slide
Helical
Curve Continuous mesh Rotation and pivoting Axial thrust
Chevrons
Curve Continuous mesh Rotation and pivoting Thrust compensated
Straight
Linear Rotation and slight slide
Straight
Linear Rotation and slight slide
Cylindrical Parallel
Cylindrical rack
Inclined straight Concurrent rectangular
Bevel Spiral
Curve Continuous mesh Rotation and pivoting Axial thrust
Chevrons
Worm Nonconcurrent rectangular
Curve Slide, slight rotation and pivoting
Gear and globoidal worm
Wider than with a tangent wheel Mainly slide (stretching the oil film)
Helicoidal
Curve Rotation, pivoting and slide
Inclined spiral
Curve Particularly very high slide speed at high pressures Axial thrust
Helical gears Hypoid
Non concurrent oblique
Tangent wheel
Hyperboloid
Left
Table 1: Types of reduction units Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 18 / 24
Exploration & Production Equipment Reduction units
5.4. DEFINITION OF A REDUCTION UNIT RATIO A reduction unit transmits a high torque to the driven machine. The step-up ratio or the step-down ratio is the ratio of the product of the number of teeth on the driving gear and of the product of the number teeth on the driven gear. In the vast majority of cases, gear trains are used as gear reducers (reduced speed and increased torque). The direction of rotation of an external gear train can easily be determined by counting the number of gears in . If this number is even, the driven gear rotates in the same direction as the driving gear. If this number is odd, the driven gear rotates in the opposite direction to the driving gear. For internal gear trains, this method must be reversed i.e. if an even number of gears are in , the driven gear rotates in the opposite direction to the driving gear. A gear train's step-down ratio is the ratio of the product of the number of teeth on the driving gears and of the product of the number of teeth on the driven gears.
Train with 1 gear pair R2/1 = Z1 / Z2
Train with 2 gear pairs R4/1 = (Z3 . Z1) / (Z4 . Z2)
R = Ratio
Z = Teeth
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
6. SERVICING AND MAINTENANCE As with all moving mechanical parts, reduction units need to be lubricated, whether by oiling, by oil splash lubrication or by an oil distribution system. This lubrication gives long machine life and also reduces the noise and the vibrations which may be generated by the meshing teeth.
Application with a paintbrush
Gravity lubrication (drop lubrication)
Mechanical lubricator (drop tube)
Sprayed with a spray can
Manually sprayed with a gun
Automatic sprayer
Figure 27: Reduction unit lubrication (1) Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 20 / 24
Exploration & Production Equipment Reduction units
Figure 28: Reduction unit lubrication (2)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
7. GLOSSARY
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
8. LIST OF FIGURES Figure 1: Example of a reduction unit (1) .............................................................................4 Figure 2: Example of a reduction unit (2) .............................................................................4 Figure 3: Worm reduction unit..............................................................................................5 Figure 4: Cutaway view of a worm reduction unit and helical type.......................................5 Figure 5: Cutaway view of a helical reduction unit ...............................................................6 Figure 6: Helical reduction unit ............................................................................................6 Figure 7: Cutaway view of a parallel shaft reduction unit .....................................................7 Figure 8: Parallel shaft reduction unit ..................................................................................7 Figure 9: Planetary reduction unit ........................................................................................8 Figure 10: Industrial reduction unit.......................................................................................9 Figure 11: Reduction unit for mixer....................................................................................10 Figure 12: Gear motor........................................................................................................10 Figure 13: High load reduction unit ....................................................................................10 Figure 14: Marine reduction unit ........................................................................................10 Figure 15: Composition of a reduction unit ........................................................................11 Figure 16: Example of teeth (1) .........................................................................................11 Figure 17: Example of teeth (2) .........................................................................................12 Figure 18: Gears and pinions of a reduction unit ...............................................................12 Figure 19: Example of a reduction unit ..............................................................................12 Figure 20: Composition of a reduction unit ........................................................................13 Figure 21: Straight-cut teeth ..............................................................................................14 Figure 22: Helical-cut teeth ................................................................................................15 Figure 23: Helical gears with two symmetrical rows of teeth..............................................15 Figure 24: Bevel-cut teeth..................................................................................................15 Figure 25: Right-angle bevel gears....................................................................................16 Figure 26: Worm ................................................................................................................16 Figure 27: Reduction unit lubrication (1) ............................................................................20 Figure 28: Reduction unit lubrication (2) ............................................................................21
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
9. LIST OF TABLES Table 1: Types of reduction units.......................................................................................18
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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TRAINING MANUAL Course EXP-PR-EQ180 Revision 0.1
Exploration & Production Equipment Reduction units
EQUIPMENT REDUCTION UNITS CONTENTS 2. WHAT ARE REDUCTION UNITS USED FOR? ..............................................................4 3. THE DIFFERENT TYPES OF REDUCTION UNITS ........................................................5 3.1. WORM REDUCTION UNITS ....................................................................................5 3.2. HELICAL REDUCTION UNITS .................................................................................6 3.3. PARALLEL SHAFT REDUCTION UNITS .................................................................7 3.4. PLANETARY REDUCTION UNITS ...........................................................................8 3.5. INDUSTRIAL REDUCTION UNITS ...........................................................................9 4. REDUCTION UNIT APPLICATIONS .............................................................................10 5. OPERATING PRINCIPLE..............................................................................................11 5.1. COMPOSITION.......................................................................................................11 5.2. PRINCIPLE .............................................................................................................11 5.3. THE DIFFERENT TYPES OF TEETH.....................................................................14 5.3.1. Straight-cut gears ............................................................................................14 5.3.2. Helical-cut teeth...............................................................................................14 5.3.3. Bevel-cut teeth ................................................................................................15 5.3.4. Worm-cut teeth................................................................................................16 5.3.5. Hypoid-cut teeth ..............................................................................................17 5.4. DEFINITION OF A REDUCTION UNIT RATIO .......................................................19 6. SERVICING AND MAINTENANCE ...............................................................................20 7. GLOSSARY ...................................................................................................................22 8. LIST OF FIGURES ........................................................................................................23 9. LIST OF TABLES ..........................................................................................................24
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 2 / 24
Exploration & Production Equipment Reduction units
1. OBJECTIVES Aim of the present course is to allow the future operator to understand the basic mechanical principles of reduction units, (the gear reducers) At the end of this course, the attendee would be able to: Explain functions of reducers Enumerate the different types of reducers encountered on site List the different applications Expose the working principles of reducers Enumerate the different types of gear used within reducers Calculate the ratio of a reducer Follow up a maintenance program for reducers
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 3 / 24
Exploration & Production Equipment Reduction units
2. WHAT ARE REDUCTION UNITS USED FOR? A reduction unit is a mechanical component which reduces the rotational speed of a drive shaft. A reduction unit transmits a high torque to the driven machine (pump, compressor, alternator or generator). Figure 1: Example of a reduction unit (1)
Figure 2: Example of a reduction unit (2)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 4 / 24
Exploration & Production Equipment Reduction units
3. THE DIFFERENT TYPES OF REDUCTION UNITS 3.1. WORM REDUCTION UNITS
Figure 3: Worm reduction unit
Figure 4: Cutaway view of a worm reduction unit and helical type
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 5 / 24
Exploration & Production Equipment Reduction units
3.2. HELICAL REDUCTION UNITS Helical reduction units perfectly illustrate the compact design of the new series of drives. They are robust angle drives adapted to all mechanical applications where a compact assembly is required. They provide a very wide torque range: 200 to 50000 Nm. Helical reduction units are used when the power must be transmitted through 90°. They are very efficient, particularly for applications where precision, efficiency, high speeds (up to 6500 rpm – depending on the size and the range) and high loads are required. Figure 5: Cutaway view of a helical reduction unit
Figure 6: Helical reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 6 / 24
Exploration & Production Equipment Reduction units
3.3. PARALLEL SHAFT REDUCTION UNITS Parallel shaft reduction units can be used in a wide range of configurations, even in the most unfavourable conditions, thanks to their torque range (130 to 18000 Nm) and the large number of positions in which they can be installed and their wide range of applications. These gear motors are compact due to the layout of the reduction unit's casing. The numerous output shaft and hollow shaft variants, and the possibility of installing the hollow shaft reduction unit using a reaction arm, feet or flanges, allow the right solution to be chosen at a cost-effective price. This is why this reduction unit has established itself worldwide as a solution for applications involving translation movement. Figure 7: Cutaway view of a parallel shaft reduction unit
Figure 8: Parallel shaft reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 7 / 24
Exploration & Production Equipment Reduction units
3.4. PLANETARY REDUCTION UNITS Planetary gear motors are compact, have a low backlash and have one or two trains for powers of up to 3000 Nm to handle the most advanced, high-precision positioning tasks. Due to their structure they are ideal for use in compact assemblies with little available space.
Figure 9: Planetary reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 8 / 24
Exploration & Production Equipment Reduction units
3.5. INDUSTRIAL REDUCTION UNITS Production versions of 2 or 3 train parallel shaft reduction units are highly robust thanks to their very compact one-piece casing. Whether foot mounted, flange mounted or with a hollow shaft, with a wide range of versions and options, allows them to be used for torque ranges of up to 65000 Nm, even in difficult conditions.
Figure 10: Industrial reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 9 / 24
Exploration & Production Equipment Reduction units
4. REDUCTION UNIT APPLICATIONS Reduction units can be found in many industrial sectors. They are used where the drive shaft rotational speed of an internal combustion engine, electric motor, turbine, etc., must be modified.
Figure 12: Gear motor Figure 11: Reduction unit for mixer
Figure 13: High load reduction unit Figure 14: Marine reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 10 / 24
Exploration & Production Equipment Reduction units
5. OPERATING PRINCIPLE 5.1. COMPOSITION
Figure 15: Composition of a reduction unit
5.2. PRINCIPLE For a reduction unit to have a correct efficiency there must be no tooth friction. This is obtained by the shape of the teeth; we talk about involute teeth which are such that they mesh with each other without slide. Figure 16: Example of teeth (1)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 11 / 24
Exploration & Production Equipment Reduction units
The must also be very regular, i.e. a tooth must take the relay well before the previous tooth has finished meshing. For conventional teeth, there is a good regularity up to a reduction ratio which must not exceed a value of around 4 or 5 for normal tooth sizes (the term modulus is used for the tooth size). Figure 17: Example of teeth (2) If we increase this ratio the problems begin, i.e. begins to deteriorate (only one tooth in at a time), and it will no longer be possible to achieve the ideal involute shape. The only way to correct this problem is to reduce the tooth modulus or increase the diameter of the pinions. If the size of the gear wheels is increased, the sizes become unacceptably large… Hence reduction units are limited to a single stage do not exceed a ratio of around 4. Figure 18: Gears and pinions of a reduction unit There is, of course, the notable exception of ‘GWS reduction units for indoor’ or’ park-flyer’ which reaches ratios of up to 11, but the powers at stake are low, which means that very small teeth can be used. Figure 19: Example of a reduction unit For applications with a lower efficiency requirement, and small reduction ratios (maximum of 3…), there is also the solution of belt reduction units which can transmit considerable powers while remaining costeffective. Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 12 / 24
Exploration & Production Equipment Reduction units
This is always at the expense of size and no doubt of higher weight.
Figure 20: Composition of a reduction unit
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 13 / 24
Exploration & Production Equipment Reduction units
5.3. THE DIFFERENT TYPES OF TEETH A gear pair is an elementary mechanism consisting of two gears mobile around axes of invariable relative position, and one of which turns the other by the action of teeth successively in : we say that the two gears are conjugated. The smaller gear is called: the pinion; and the larger: the gear (a rack is a gear of infinite radius). There are 4 different types of gears: Straight-cut gears Helical-cut gears Bevel-cut gears Worm-cut gears Hypoid cut gears
5.3.1. Straight-cut gears The pinion is the smaller of the two gears and is often the driving gear. The shape of the gear varies with the dimensions. Straight teeth are used for small equipment and internal teeth. Figure 21: Straight-cut teeth
5.3.2. Helical-cut teeth They transmit movement between two parallel shafts. The inclination of the teeth (helix angle) is the same for both gears, but in opposite directions. Helical gears provide a transmission which is more flexible, more progressive and less noisy than straight gears.
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 14 / 24
Exploration & Production Equipment Reduction units
The forces transmitted are higher (more teeth in ), even at high speeds.
Figure 22: Helical-cut teeth
The axial thrust can be neutralised by using two gears on each shaft, each with reversed helical teeth or a single gear with two symmetrical rows of teeth (called chevron or herringbone gears). Figure 23: Helical gears with two symmetrical rows of teeth Inconvenient of this type is the important axial thrust which requires specific bearings
5.3.3. Bevel-cut teeth These are the simplest teeth and they have the same problems as the straight gears at high speeds (noise, high pressures on the teeth, etc.).
Figure 24: Bevel-cut teeth They are used to transmit movement between two nonparallel shafts whose axes are concurrent (the most frequent type have axes at 90°).
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 15 / 24
Exploration & Production Equipment Reduction units
The primitive surfaces are no longer cylinders but cones. The cones are tangents on a line MM' and their common summit is the point S (intersection of the rotational axes).
Figure 25: Right-angle bevel gears They reduce noise at high speeds and the transmission is more progressive. The typical pressure for straight teeth is 20° or 14°30', it is 35° for helical teeth.
5.3.4. Worm-cut teeth The transmission is achieved by a screw with one or more threads meshing with a gear. The direction of the helix is the same for the screw and for the gear. These gear systems give high reduction ratios and can be non-reversible. They provide the "smoothest" meshing of all gear systems. Their operation is silent and impact-free. However, they have a high level of slide and friction; thus their efficiency is poor. Efficiency is affected by good lubrication and an adapted choice of materials (steel screw and bronze gear). Figure 26: Worm
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 16 / 24
Exploration & Production Equipment Reduction units
5.3.5. Hypoid-cut teeth Hypoid gears are helical bevel gears employed when the axes of the two shafts are perpendicular but do not intersect. One of the most common uses of hypoid gearing is to connect the drive shaft and the rear axle in automobiles. Helical gearing used to transmit rotation between shafts that are not parallel is often incorrectly called spiral gearing.
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 17 / 24
Exploration & Production Equipment Reduction units
Position of shafts
Teeth size
Types
Type of and friction
Straight
Linear Rotation and slight slide
Helical
Curve Continuous mesh Rotation and pivoting Axial thrust
Chevrons
Curve Continuous mesh Rotation and pivoting Thrust compensated
Straight
Linear Rotation and slight slide
Straight
Linear Rotation and slight slide
Cylindrical Parallel
Cylindrical rack
Inclined straight Concurrent rectangular
Bevel Spiral
Curve Continuous mesh Rotation and pivoting Axial thrust
Chevrons
Worm Nonconcurrent rectangular
Curve Slide, slight rotation and pivoting
Gear and globoidal worm
Wider than with a tangent wheel Mainly slide (stretching the oil film)
Helicoidal
Curve Rotation, pivoting and slide
Inclined spiral
Curve Particularly very high slide speed at high pressures Axial thrust
Helical gears Hypoid
Non concurrent oblique
Tangent wheel
Hyperboloid
Left
Table 1: Types of reduction units Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 18 / 24
Exploration & Production Equipment Reduction units
5.4. DEFINITION OF A REDUCTION UNIT RATIO A reduction unit transmits a high torque to the driven machine. The step-up ratio or the step-down ratio is the ratio of the product of the number of teeth on the driving gear and of the product of the number teeth on the driven gear. In the vast majority of cases, gear trains are used as gear reducers (reduced speed and increased torque). The direction of rotation of an external gear train can easily be determined by counting the number of gears in . If this number is even, the driven gear rotates in the same direction as the driving gear. If this number is odd, the driven gear rotates in the opposite direction to the driving gear. For internal gear trains, this method must be reversed i.e. if an even number of gears are in , the driven gear rotates in the opposite direction to the driving gear. A gear train's step-down ratio is the ratio of the product of the number of teeth on the driving gears and of the product of the number of teeth on the driven gears.
Train with 1 gear pair R2/1 = Z1 / Z2
Train with 2 gear pairs R4/1 = (Z3 . Z1) / (Z4 . Z2)
R = Ratio
Z = Teeth
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 19 / 24
Exploration & Production Equipment Reduction units
6. SERVICING AND MAINTENANCE As with all moving mechanical parts, reduction units need to be lubricated, whether by oiling, by oil splash lubrication or by an oil distribution system. This lubrication gives long machine life and also reduces the noise and the vibrations which may be generated by the meshing teeth.
Application with a paintbrush
Gravity lubrication (drop lubrication)
Mechanical lubricator (drop tube)
Sprayed with a spray can
Manually sprayed with a gun
Automatic sprayer
Figure 27: Reduction unit lubrication (1) Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
Page 20 / 24
Exploration & Production Equipment Reduction units
Figure 28: Reduction unit lubrication (2)
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
7. GLOSSARY
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
8. LIST OF FIGURES Figure 1: Example of a reduction unit (1) .............................................................................4 Figure 2: Example of a reduction unit (2) .............................................................................4 Figure 3: Worm reduction unit..............................................................................................5 Figure 4: Cutaway view of a worm reduction unit and helical type.......................................5 Figure 5: Cutaway view of a helical reduction unit ...............................................................6 Figure 6: Helical reduction unit ............................................................................................6 Figure 7: Cutaway view of a parallel shaft reduction unit .....................................................7 Figure 8: Parallel shaft reduction unit ..................................................................................7 Figure 9: Planetary reduction unit ........................................................................................8 Figure 10: Industrial reduction unit.......................................................................................9 Figure 11: Reduction unit for mixer....................................................................................10 Figure 12: Gear motor........................................................................................................10 Figure 13: High load reduction unit ....................................................................................10 Figure 14: Marine reduction unit ........................................................................................10 Figure 15: Composition of a reduction unit ........................................................................11 Figure 16: Example of teeth (1) .........................................................................................11 Figure 17: Example of teeth (2) .........................................................................................12 Figure 18: Gears and pinions of a reduction unit ...............................................................12 Figure 19: Example of a reduction unit ..............................................................................12 Figure 20: Composition of a reduction unit ........................................................................13 Figure 21: Straight-cut teeth ..............................................................................................14 Figure 22: Helical-cut teeth ................................................................................................15 Figure 23: Helical gears with two symmetrical rows of teeth..............................................15 Figure 24: Bevel-cut teeth..................................................................................................15 Figure 25: Right-angle bevel gears....................................................................................16 Figure 26: Worm ................................................................................................................16 Figure 27: Reduction unit lubrication (1) ............................................................................20 Figure 28: Reduction unit lubrication (2) ............................................................................21
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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Exploration & Production Equipment Reduction units
9. LIST OF TABLES Table 1: Types of reduction units.......................................................................................18
Training course EXP-PR-EQ180-FR Last revised: 14/05/2007
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