General-Purpose Gear Units for Petroleum, Chemical and Gas Industry Services

API STANDARD 677

THIRD EDITION, APRIL 2006 REAFFIRMED, NOVEMBER 2016

General-Purpose Gear Units for Petroleum, Chemical and Gas Industry Services

Downstream Segment

API STANDARD 677

THIRD EDITION, APRIL 2006 REAFFIRMED, NOVEMBER 2016

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Copyright © 2006 American Petroleum Institute

FOREWORD

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CONTENTS

Page

1. GENERAL 1

   1. Scope 1

   2. Alternative Designs 1

   3. Conflicting Requirements 1

   4. Definition of Terms 1

   5. Referenced Publications 2

   6. Dimensions 3

2. BASIC DESIGN 3

   1. General 3

   2. Shaft Assembly Designation 5

   3. Shaft Rotation 6

   4. Rating 6

   5. Casings 14

   6. Casing Connections 16

   7. Gear Elements 17

   8. Dynamics 19

   9. Bearings and Bearing Housings 22

   10. Lubrication 24

   11. Materials 24

   12. Nameplates and Rotation Arrows 25

3. ACCESSORIES 26

   1. General 26

   2. Couplings and Guards 26

   3. Mounting Plates 26

   4. Controls and Instrumentation 28

   5. Piping and Appurtenances 28

   6. Special Tools 28

4. INSPECTION, TESTING, AND PREPARATION FOR SHIPMENT 28

   1. General 28

   2. Inspection 29

   3. Testing 31

   4. Preparation for Shipment 33

5. VENDOR’S DATA 34

   1. General 34

   2. Proposals 34

   3. Contract Data 35

APPENDIX A GENERAL-PURPOSE GEAR DATA SHEETS 37

APPENDIX B LATERAL CRITICAL SPEED MAP AND MODE SHAPES FOR

A TYPICAL ROTOR 53

APPENDIX C TYPICAL LUBE-OIL SYSTEMS. 57

APPENDIX D MATERIAL SPECIFICATIONS FOR GENERAL-PURPOSE

GEAR UNITS 61

APPENDIX E VENDOR DRAWING AND DATA REQUIREMENTS 65

APPENDIX F REFERENCED SPECIFICATIONS 73

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Page

APPENDIX G SPIRAL BEVEL GEAR-TOOTH CONTACT ARRANGEMENT REQUIREMENTS FOR INSPECTION 75

APPENDIX H RESIDUAL UNBALANCE WORKSHEETS 85

Figures

1. Shaft Assembly Designations 7

2. Shaft Rotation Designations 8

3. Material Index Number, Through Hardened 11

4. Allowable Bending Stress Number, Sa 12

1. Lateral Critical Speed Map for a Typical Rotor 54

2. Mode Shapes versus Support Stiffness for a Typical Rotor 55

1. Typical Circulating Lube-oil System for Gear Units 59

2. Typical Pressurized Lube-oil System for Hydrodynamic

Bearings in Gear Units 60

1. Gear-tooth Nomenclature 75

2. Determining Mounting Distances 76

3. Reference Points in Bevel Gear Drives 78

4. Backlash in the Plane of Rotation 79

5. Measurement of Normal Backlash 81

6. Axial Movement Necessary to Obtain a Change in Backlash 82

7. Typical No Load Tooth Contact Pattern 83

8. Preferred Contact Resulting from Correct Mounting Position 83

9. Common Types of Contact Error 84

1. Residual Unbalance Worksheet 87

2. Residual Unbalance Polar Plot Worksheet 88

3. Sample Residual Unbalance Worksheet for Left Plane 89

4. Sample Residual Unbalance Polar Plot Worksheet for Left Plane 90

5. Sample Residual Unbalance Worksheet for Right Plane 91

6. Sample Residual Unbalance Polar Plot Worksheet for Right Plane 92

Tables

1. Driver Trip Speeds 4

2. Shaft Assembly Combinations 5

3. Minimum Gear Service Factors 8

4. Material Index Number, Im and Maximum L/d Ratios 11

5. Allowable Bending Stress Number, Sa 12

6. Overhung Load Factors Applied to Parallel Shaft and Right Angle Gears 12

7. Drain Pipe Sizes 16

8. Casing Vibration Levels 21

9. Maximum dmN Numbers for Rolling Element Bearings 22

1. Gear Unit Housings 63

2. Shafts, Pinionsc, & Gear Wheelsc 63

3. Fabricated Gears 64

G-1 Recommended Values of Normal Backlash at Tight Points

of Mesh (All Values in Inches) 78

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General-purpose Gear Units for Petroleum, Chemical and Gas Industry Services

1. General

   1. SCOPE

      1. This standard covers the minimum requirements for general-purpose, enclosed single and multistage gear units incorporat- ing parallel shaft helical and right angle spiral bevel gears for the petroleum, chemical, and gas industries. Gears manufactured according to this standard shall be limited to the following pitchline velocities. Helical gears shall not exceed 60 m/s (12,000 ft/ min), and spiral bevels shall not exceed 40 m/s (8,000 ft/min). Spiral bevel gearsets shall be considered matched sets.

         Note 1: This standard is not intended to apply to gears in special-purpose service, which are covered in API Std 613; to gears integral with other equipment; to epicyclic gear assemblies; or gears with non-involute tooth forms.

         Note 2: This standard requires the purchaser to specify certain details and features. A bullet (•) at the beginning of a paragraph indicates that either a decision by, or further information from, the purchaser is required. Further information should be shown on the data sheets or stated in the quotation request and purchase order.

      2. General-purpose gears are applied in equipment trains that are usually spared, or are in noncritical service.

Typical applications for which this standard is intended are cooling tower water pump systems, forced and induced draft fan sys- tems, and other general-purpose equipment trains.

1. ALTERNATIVE DESIGNS

   The vendor may offer alternative designs. Equivalent metric dimensions, fasteners, and flanges may be substituted as mutually agreed upon by the purchaser and the vendor.

   
   

2. CONFLICTING REQUIREMENTS

   In case of conflict between this standard and the inquiry or order, the information included in the order shall govern.

   
   

3. DEFINITION OF TERMS

   Terms used in this standard are defined in 1.4.1 through 1.4.26.

   1. axially (horizontally) split: A joint that is parallel to the shaft centerline.

   2. bending stress number (S): Defined in 2.4.4.2.

   3. critical speed: A shaft rotational speed at which the rotor-bearing-support system is in a state of resonance.

   4. design: Requirements normally defined by the equipment designer and the manufacturer.

      Note: The use of the word design in any term (such as design power, design pressure, design temperature, or design speed) should be avoided in the purchaser’s specifications.

   5. DN: An alphanumeric designation of size for components of a pipework system, which is used for reference purposes. It comprises the letters DN followed by a dimensionless whole number which is indirectly related to the physical size, in millime- ters (mm), of the bore or outside diameter of the end connection.

      Note 1: The number following the letters DN does not represent a measurable value (ISO 6708: 1995).

   6. gear: Refers to either the pinion or gear wheel.

   7. gear-rated power: The maximum power specified by the purchaser on the data sheets and stamped on the nameplate (see 2.4.1).

   8. gear service factor (SF): The factor that is applied to the tooth pitting index and bending stress number, depending on the characteristics of the driver and the driven equipment, to account for differences in potential overload, shock load, and/or contin- uous oscillatory torque characteristics.

   9. hunting tooth combination: Exists for mating gears when a tooth on the pinion does not repeat contact with a tooth on the gear until it has contacted all the other gear teeth.

1