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

API STANDARD 677

FOURTH EDITION, SEPTEMBER 2021

Special Notes

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Copyright © 2021 American Petroleum Institute

Foreword

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Contents

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 5

   1. Terms and Definitions 5

   2. Acronyms and Abbreviations 15

4. General 15

   1. Unit Responsibility 15

   2. Unit Conversion 15

   3. Standards and Codes 15

5. Requirements 15

   1. Units of Measure 15

   2. Statutory Requirements 16

   3. Hierarchy of Requirements 16

6. Basic Design 16

   1. General 16

   2. Shaft Assembly Designation 18

   3. Shaft Rotation 20

   4. Rating 21

   5. Casings 29

   6. Casing Connections 32

   7. Gear Elements 35

   8. Dynamics 40

   9. Bearings and Bearing Housings 51

   10. Lubrication 56

   11. Materials 58

   12. Nameplates and Rotation Arrows 62

7. Accessories 63

1. Couplings and Guards 63

2. Belt Drives 64

3. Mounting Plates, Soleplates, Subsoleplates, and Baseplates 64

4. Controls and Instrumentation 67

5. Piping and Appurtenances 68

6. Special Tools 70

1. Inspection, Testing, and Preparation for Shipment 70

   1. General 70

   2. Inspection 71

   3. Testing 76

   4. Preparation for Shipment 79

2. Low-speed/High-torque Applications, Extruder Gears 82

   1. General 82

   2. Basic Design 83

   3. Materials 84

   4. Controls and Instrumentation 84

   5. Inspection 85

   6. Testing 87

   7. Preparation for Shipment 89

3. Epicyclic Gear Units 89

   1. Scope 89

   2. General 89

   3. Definition of Terms 90

   4. Configurations and Shaft Arrangements 91

   5. Rating 93

   6. Casings 102

   7. Casing Connections 103

   8. Gear Elements 103

   9. Balancing 105

   10. Bearings 106

   11. Lubrication 106

   12. Materials 107

   13. Nameplates and Rotation Arrows 107

   14. Controls and Instrumentation 107

   15. Testing 108

4. Vendor’s Data 108

Annex A (informative) Data Sheets 109

Annex B (normative) Lubrication Systems 124

Annex C (normative) Material Specifications for General-purpose, Extruder, and Epicyclic Gear Units 129

Annex D (informative) Proposal and Contract Documents and Engineering Design Data 134

Annex E (normative) Vendor Drawing and Data Requirements 140

Annex F (normative) Procedure for the Verification of Residual Unbalance 147

Annex G (informative) Inspector’s Checklist 153

Annex H (informative) Nomenclature for General-purpose, Extruder, and Epicyclic Gears 157

Annex I (informative) Toothing Configuration—Applicable to Epicyclic Gear Applications 161

Annex J (informative) Installation and Commissioning 163

Bibliography 176

Figures

1. Apex 6

2. Lead 9

3. Shaft Assembly Designations 19

4. Shaft Rotation Designations 20

5. Gear Mesh 20

6. Material Index Number, Through Hardened 25

7. Material Index Number, Carburized 25

8. Allowable Bending Stress Number, Through Hardened 27

9. Allowable Bending Stress Number, Carburized Steel 28

10. Undamped Lateral Critical Speed Map 41

11. Unbalance Placement 44

12. Rotor Response Plot 46

13. Plot of Applicable Speed Range of Vibration Limit 47

14. Star Gearing Configuration 91

15. Planetary Gearing Configurations 91

16. Compound Gearing Configuration 92

17. Solar Gearing Configurations 92

18. Single Stage Epicyclic Rotor Pitch Diameters 94

19. Compound Epicyclic Rotor Pitch Diameters 95

20. Face Width-to-Diameter Ratio (b/dws) Limits 99

1. Typical Circulating Lube Oil System for Gear Units 125

2. Schematic Symbols for a Pressurized Lube Oil System 126

3. Typical Pressurized Lube Oil System for Hydrodynamic Bearings in Gear Units 127

1. Residual Unbalance Worksheet 150

2. Sample Residual Unbalance Worksheet for Left Plane (Metric) 151

3. Sample Residual Unbalance Worksheet for Right Plane (USC) 152

1. Parallel Shaft Gearbox 157

2. Co-rotating Twin Screw Extruder 158

3. Epicyclic Gearbox—Planetary Configuration 159

4. Epicyclic Gearbox—Star Configuration 160

Tables

1. Corresponding DN and NPS Pipe Sizes 8

2. Pipe Sizes and Number of Threads per Inch (ASME B.1.20.1 Table 2) 11

3. Driver Trip Speeds 18

4. Shaft Assembly Combinations 19

5. Minimum Gear Tooth Service Factors 22

6. Allowable Material Index Numbers, Im 24

7. Allowable Bending Stress Number, Sall 27

8. Overhung Load Factors Applied to Parallel Shaft Gears 29

9. Minimum Tubing Wall Thickness 31

10. Drain Pipe Sizes 33

11. Bearing Cap Vibration Limits 50

12. Maximum dmN Numbers for Rolling Element Bearings 51

13. Cage Types 52

14. Minimum Requirements for Piping System Components 69

15. ASME Materials Inspection Standards 72

16. Maximum Severity of Defects in Castings 73

17. Mesh Load Factor, Ky 96

18. Material Index Number, Im 97

19. Allowable Bending Stress Number, Sa 100

20. Guideline for Maximum Ratio for Simple Star and Planetary Epicyclics with Different Numbers of Planets 105

B.1 Lube Oil System Schematic 128

1. Gear Unit Housings 130

2. Shafts, Pinions, and Gear Wheels 131

3. Fabricated Gears 133

F.1 Trial Weight Multiplier vs Nmc 148

I.1 Differentiating Characteristics of Spur, Single Helical, and Double Helical Gearing 162

J.1 Storage Preservative Types 166

Introduction

Users of this standard should be aware that further or differing requirements may be needed for individual applications. This standard is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative equipment or engineering solutions for the individual application. This may be particularly applicable where there is innovative or developing technology. Where an alternative is offered, the vendor should identify any variations from this standard and provide details.

A bullet () at the beginning of a section or subsection indicates that either a decision is required or the purchaser is required to provide further information. It is necessary that this information be indicated on data sheets or stated in the enquiry or purchase order (see examples in Annex A).

This standard requires the purchaser to specify certain details and features. Although it is recognized that the purchaser may desire to modify, delete, or amplify sections of this standard, it is strongly recommended that such modifications, deletions, and amplifications be made by supplementing this standard, rather than by rewriting or incorporating sections thereof into another standard.

For effective use of this standard and ease of reference to the text, the use of the data sheets in Annex A is recommended.

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

1. Scope

   
   

   This standard covers the minimum requirements for general-purpose, enclosed single and multistage gear units incorporating parallel shaft spur, and helical gears for use in the petroleum, chemical, and gas industry services. General-purpose and extruder gears manufactured according to this standard are limited to pitch line velocities that do not exceed 60 m/s (12,000 ft/min).

   
   

   The requirements for parallel shaft helical gears applied to extruder services are included in Section 9 of this standard.

   
   

   The requirements for epicyclic gears driving equipment, such as electrical generators, centrifugal compressors, and pumps, are included in Section 10 of this standard.

   
   

   This standard does not apply to gears in special-purpose service, which are covered in API 613, to gears integral with other equipment, or gears with noninvolute tooth forms.

   NOTE 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 systems, and other general-purpose equipment trains.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Specification 5L, Line Pipe

API Standard 670, Machinery Protection Systems

API Standard 671, Special-purpose Couplings for Petroleum, Chemical, and Gas Industry Services

API Recommended Practice 686, Recommended Practice for Machinery Installation and Installation Design

API Recommended Practice 691, Risk-based Machinery Management

API Manual of Petroleum Measurement Standards (MPMS) Chapter 15, Guidelines for the Use of Petroleum Industry-specific International System (SI) Units

AGMA 925-A03 1, Effect of Lubrication on Gear Surface Distress

ANSI 2/API Standard 614, Lubrication, Shaft-sealing and Oil-control Systems and Auxiliaries, Fifth Edition, April 2008

ANSI/ABMA Standard 7 3, Shaft and Housing Fits for Metric Radial Ball and Roller Bearings (Except Tapered Roller Bearings) Conforming to Basic Boundary Plan

1 American Gear Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, Virginia 22314, www.agma.org.

2 American National Standards Institute, 1899 L. Street, NW, 11th Floor, Washington, DC 20036, www.ansi.org.

3 American Bearing Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, Virginia 22314, www.americanbearings.org.