Petroleum, Petrochemical, and Natural Gas Industries—Steam Turbines— Special-purpose Applications

API STANDARD 612

EIGHTH EDITION, NOVEMBER 2020

Foreword

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

The verbal forms used to express the provisions in this document are as follows.

• the term “shall” denotes a minimum requirement to conform to the standard;

  
  

• the term “should” denotes a recommendation or that which is advised but not required to conform to the standard;

  
  

• the term “may” is used to express permission or a provision that is optional;

  
  

• the term “can” is used to express possibility or capability.

ThisdocumentwasproducedunderAPIstandardizationproceduresthatensureappropriatenotificationandparticipation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 200 Massachusetts Avenue, Suite 1100, Washington, DC 20001. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A onetime extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually by API, 200 Massachusetts Avenue, Suite 1100, Washington, DC 20001.

Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue, Suite 1100, Washington, DC 20001, standards@api.org.

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 4

   1. Terms and Definitions 4

   2. Acronyms and Abbreviations 12

4. Unit Responsibility 13

5. Requirements 13

   1. Units of Measure 13

   2. Statutory Requirements 13

   3. Documentation Requirements 13

6. Basic Design 13

   1. General 13

   2. Turbine Casings 18

   3. Casing Appurtenances 21

   4. Pressure Casing Connections 21

   5. External Forces and Moments 25

   6. Rotating Elements 25

   7. Seals and Internal Stationary Components 29

   8. Dynamics 30

   9. Bearings and Bearing Housings 45

   10. Lubrication and Control-oil System 48

   11. Materials 49

   12. Nameplates and Rotation Arrows 52

7. Accessories 53

   1. Turning Gear 53

   2. Relief Valves 54

   3. Couplings 55

   4. Guards 55

   5. Gland Vacuum System 55

   6. Mounting Plates 55

   7. Controls and Instrumentation 60

   8. Piping 75

   9. Special Tools 77

   10. Insulation and Jacketing 78

   11. Enclosures 78

   12. Grounding 79

8. Inspection, Testing, and Preparation for Shipment 80

   1. General 80

   2. Inspection 80

   3. Testing 83

   4. Preparation for Shipment 89

9. Vendor’s Data 92

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Contents

Page

Annex A (informative) Typical Datasheets 93

Annex B (informative) Steam Turbine Nomenclature 116

Annex C (normative) Steam Purity and Variations in Steam Conditions 119

Annex D (normative) Allowable Forces and Moments 121

Annex E (normative) Calculation of the Maximum Rotor Speed During an Overspeed Trip 138

Annex F (informative) Gland Sealing and Leak-off System 145

Annex G (normative) Vendor Drawing and Data Requirements (VDDR) 147

Annex H (normative) Report Requirements for Lateral and Stability Analyses 158

Annex I (normative) Report Requirements for Torsional Analysis 163

Annex J (normative) Procedure for the Verification of Residual Unbalance 166

Annex K (informative) Typical Material Specifications 172

Annex L (informative) Mounting Plate Arrangements 175

Annex M (informative) Inspector’s Checklist 179

Annex N (informative) Typical Inspection of Components 182

Annex O (informative) Contract Documents and Engineering Design Data 183

Bibliography 189

Figures

1. Unbalance Placement 35

2. Rotor Response Plot 36

3. Plot of Applicable Speed Range of Vibration Limit 37

4. Mechanical Drive Turbine Ramp Speeds 62

5. Trip Solenoid Valves—One-out-of-Two Configuration (1-o-o-2) 68

6. Mechanical Running Test 86

1. Typical Impulse Steam Turbine Nomenclature 117

2. Typical Reaction Steam Turbine Nomenclature 118

D.1 Components of Forces and Moments on Turbine Construction 122

E.1 Peak Kinetic Energy of the Rotor 138

1. Typical Gland Sealing and Leak-off System for Condensing Turbines 145

2. Typical Gland Leak-off System for Back-pressure Turbines 146

1. Undamped Critical Speed Map 160

2. Stability Sensitivity Plot 160

3. Geometry Definitions for Tilt Pad Bearing 161

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   Contents

   Page

4. Preload on Tilt Pad 162

I.1 Typical Campbell Diagram 164

1. Residual Unbalance Worksheet 169

2. Sample Residual Unbalance Worksheet for Left Plane (SI) 170

3. Sample Residual Unbalance Worksheet for Right Plane (USC) 171

1. Typical Mounting Plate Arrangement—Soleplate with Subplate 175

2. Typical Mounting Plate Arrangement—Baseplate with Subplate 176

3. Typical Mounting Plate Arrangement—Baseplate without Subplates 177

4. Typical Mounting Plate Arrangement—Soleplate without Subplates 178

Tables

1. Material Casting Factors 18

2. ASME Material Inspection Standards for Pressure Casings 24

3. Maximum Severity of Defects in Castings 25

4. Material Thicknesses of 12-Gauge Steel 70

5. Maximum Allowable Free Air Gauss Levels 82

C.1 Steam Purity Limits 119

1. Allowable Forces and Moments (SI Units) 124

2. Allowable Forces and Moments (USC Units) 125

3. Extraction Openings for a Steam Turbine 131

4. Extraction Openings for a Steam Turbine 137

H.1 Tilt Pad Bearing Dimensions and Tolerances 161

mc

J.1 Trial Weight Multiplier vs Maximum Continuous Speed (N ) 167

K.1 Typical Material Specifications for Major Component Parts 172

M.1 Inspector’s Checklist 179

N.1 Component Inspection 182

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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 supplier from offering, or the purchaser from accepting alternative equipment or engineering solutions for the individual application. This may be particularly appropriate where there is innovative or developing technology. Where an alternative is offered, the supplier should identify any variations from this standard and provide details.

This standard requires the purchaser to specify certain details and features. A bullet (●) at the beginning of a subsection or paragraph indicates that either a decision by, or further information from, the purchaser is required. Further information should be shown on the datasheets (see example in Annex A) or stated in the quotation request and purchase order.

In this standard, U.S. customary (USC) units are included in parentheses for information.

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Petroleum, Petrochemical, and Natural Gas Industries—Steam Turbines— Special-purpose Applications

1. Scope

   
   

   This standard specifies the minimum requirements for steam turbines for special-purpose applications for use in the petroleum, petrochemical, and gas industry services. It is not applicable to general purpose steam turbines, which are covered in API 611.

   
   

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. Standards referenced in the text portion of the document are undated but refer to the specific editions referenced in this section.

API Standard 520 (all parts), Sizing, Selection, and Installation of Pressure-relieving Devices

API Standard 526, Flanged Steel Pressure-relief Valves

ANSI 1 /API Standard 614, Lubrication, Shaft-sealing and Oil-control Systems and Auxiliaries, Fifth Edition, April 2008 (Errata, May 2008)

ANSI/API Standard 670, Machine Protection Systems, Fourth Edition, December 2000

ANSI/API Standard 671, Special Purpose Couplings for Petroleum, Chemical and Gas Industry Services, Fourth Edition, August 2007

API Recommended Practice 551, Process Measurement

API Recommended Practice 686, Recommended Practice for Machinery Installation and Installation Design, Second Edition, December 2009

API Recommended Practice 691, Risk-based Machinery Management, First Edition, June 2017

ANSI /AWS D1.1/D1.1M 2 , Structural Welding Code—Steel

ASME B1.1-2003 3 , Unified Inch Screw Threads (UN and UNR Thread Form)

ASME B1.3M-1986, Screw Thread Gaging Systems for Dimensional Acceptability—Inch and Metric Screw Threads (UN, UNR, UNJ, M and MJ)

ASME B1.13M-2005, Metric Screw Threads: M Profile

ASME B16.5-2009, Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard ASME B16.47-2011, Large Diameter Steel Flanges: NPS 26 through NPS 60 Metric/Inch Standard ASME B17.1 (R2008), Keys and Keysets

ASME B31.3-2010, Process Piping

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

2 American Welding Society, 8669 NW 36 Street, #130, Miami, Florida 33166-6672, www.aws.org.

3 American Society of Mechanical Engineers, Two Park Avenue, New York, NY 10016-5990, www.asme.org.

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