Petroleum, Petrochemical, and Natural Gas Industries—Air-cooled Heat Exchangers

ANSI/API STANDARD 661-2015 SEVENTH EDITION, JULY 2013

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Copyright © 2013 American Petroleum Institute

Foreword

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms and Definitions 2

4. General 5

5. Proposals 7

6. Documentation 7

   1. Approval Information 7

   2. Final Records 9

7. Design 9

   1. Tube Bundle Design 9

   2. Air-side Design 23

   3. Structural Design 35

8. Materials 39

   1. General 39

   2. Requirements for Carbon Steel in Sour or Wet Hydrogen Sulfide Service 40

   3. Headers 40

   4. Louvers 40

   5. Other Components 41

9. Fabrication of Tube Bundle 41

   1. Welding 41

   2. Postweld Heat Treatment 42

   3. Tube-to-Tubesheet Joints 42

   4. Gasket Contact Surfaces 43

   5. Thread Lubrication 44

   6. Alignment and Tolerances 44

   7. Assembly 44

10. Inspection, Examination, and Testing 44

    1. Quality Control 44

    2. Pressure Test 47

    3. Shop Run-in 47

    4. Equipment Performance Testing 47

    5. Nameplates 47

11. Preparation for Shipment 48

    1. General 48

    2. Surfaces and Finishes 48

    3. Identification and Notification 48

12. Supplemental Requirements 48

    1. General 48

    2. Design 49

    3. Examination 49

    4. Testing 50

Contents

Page

Annex A (informative) Recommended Practices 51

Annex B (informative) Checklist and Data Sheets 58

Annex C (informative) Winterization of Air-cooled Heat Exchangers 69

Annex D (informative) Recommended Procedure for Airflow Measurement of

Air-cooled Heat Exchangers 120

Annex E (informative) Measurement of Noise from Air-cooled Heat Exchangers 128

Bibliography 146

Figures

1. Typical Bay Arrangements 3

2. Typical Components of an Air-cooled Heat Exchanger 6

3. Typical Construction of Tube Bundles with Removable Cover Plate and

   Removable Bonnet Headers 14

4. Typical Confined and Full-faced Gasket Joint Details 15

5. Typical Construction of a Tube Bundle with Plug Headers 16

6. Nozzle Loads 20

7. Fan Dispersion Angle 25

8. Typical Drive Arrangements 31

9. Typical Plenum Arrangements 38

10. Standard Tolerances 45

1. System A — Airflow Control with Variable Speed Drives or Automatically

   Controlled Variable-pitch Fans 76

2. System A — Airflow Control with Automatically Controlled Outlet Louvers and Fixed-pitch Fans 77

3. System B — Induced Draught with Non-contained Internal Air Recirculation 77

4. System B — Forced Draught with Non-contained Internal Air Recirculation 78

5. System C — Typical Forced-draught Air-cooled Heat Exchanger with

   Contained Internal Air Recirculation 78

6. System D — Typical Forced-draught Air-cooled Heat Exchanger with External Air Recirculation 79

7. Freezing Points of Phenol-water Solutions 84

8. Freezing Points of Ethanolamine-water Solutions 84

9. Freezing Points of Glycerol-water Solutions 85

10. Dissociation Constant of Ammonium Bisulfide (NH4HS) 86

11. Hydrate Pressure-temperature Equilibria 87

12. Tempered-water System 98

1. Static Pressure Probe Locations 122

2. Location of Measurement Points 123

1. Isolated Single Bay Noise Measurement Points 131

2. Lp Measurement Locations Forced — Draught Unit (2-fan Bay) 139

3. Lp Measurement Locations Induced — Draught Unit (2-fan Bay) 140

Tables

1. Minimum Nominal Thickness of Header Components 12

2. Minimum Flange Bolt Spacing 15

3. Minimum Nozzle Neck Nominal Thickness 18

   Contents

   Page

4. Maximum Allowable Nozzle Loads 20

5. Minimum Required Wall Thickness of Tubes 21

6. Radial Clearances 26

7. Dry-air Standard Conditions 27

8. Minimum Thickness of Expanded Metal Fan Guard Mesh 28

9. Maximum Allowable Louver Deflection 33

10. Live Loads on Platforms, Columns and Walkways 36

11. Nominal Tube Hole Diameters and Tolerances 43

12. Maximum Weld Hardness 46

1. Maximum Fin Selection Temperature for Fin Bonding Types 52

2. Header Selection 53

3. Gasket Types 55

4. Gasket Contact-surface Finish 55

5. Service Conditions 56

6. Gasket Selection 56

1. Safety Margins for Different Process Categories 73

2. Freezing Points of Frequently Encountered Liquid Pure Components 83

3. Description of Indirect and Direct Air Cooling Systems (SI Units) 99

4. Description of Indirect and Direct Air Cooling Systems (US Customary Units) 99

5. Comparison of Costs of Indirect and Direct Air Cooling Systems 100

6. Values for rm Referred to the Total Outside Area for a Tube with an Outside Diameter

   of 25.4 mm and Aluminum Fins 15.9 mm High and 0.4 mm Thick. 102

7. Values for rm Referred to the Total Outside Area for a Tube with an Outside Diameter

of 1 in. and Aluminum Fins 5/8 in. High and 0.016 in. Thick 106

1. Instruments 120

2. Location of Measurement Points 123

1. Required Instrumentation and Applicable Specifications 128

2. Symbols and Abbreviations 129

3. Isolated Single Bay Noise Measurement Points 132

4. Background Correction Values 133

5. Background Correction Values — Example for One Measurement Point “X” 133

6. Background Noise Correction Values 141

7. Background Noise Correction Values — Example Using One Measurement Point “X” 141

8. Background Noise Correction Values — Example Using Measurement Point “n” 141

9. Background Noise Correction Values 143

10. Background Noise Correction Values — Example Using One Measurement Point “X” 143

11. Background Noise Correction Values — Example Using Measurement Point “n” 143

Introduction

It is necessary that users of this standard be aware that further or differing requirements can 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 can be particularly applicable where there is innovative or developing technology. Where an alternative is offered, it is the responsibility of the Vendor to identify any variations from this standard and provide details.

Petroleum, Petrochemical, and Natural Gas Industries—Air-cooled Heat Exchangers

1. Scope

   
   

   This standard gives requirements and recommendations for the design, materials, fabrication, inspection, testing, and preparation for shipment of air-cooled heat exchangers for use in the petroleum, petrochemical, and natural gas industries.

   
   

   This standard is applicable to air-cooled heat exchangers with horizontal bundles, but the basic concepts can also be applied to other configurations.

   
   

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.

AGMA 6001 1, Design and Selection of Components for Enclosed Gear Drives ANSI/AGMA 6010, Spur, Helical, Herringbone and Bevel Enclosed Drives ASME PTC 30 2, Air-Cooled Heat Exchangers

ICC 3, International Building Code

ISO 76 4, Rolling bearings — Static load ratings

ISO 281, Rolling bearings — Dynamic load ratings and rating life

ISO 286 (all parts), Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes

ISO 1081, Belt drive — V-belts and V-ribbed belts, and corresponding grooved pulleys — Vocabulary

ISO 1461, Hot-dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods

ISO 2491, Thin parallel keys and their corresponding keyways (dimensions in millimeters)

ISO 4183, Belt drives — Classical and narrow V-belts — Grooved pulleys (system based on datum width)

ISO 4184, Belt drives — Classical and narrow V-belts — Lengths in datum system

ISO 5287, Belt drives — Narrow V-belts for the automotive industry — Fatigue test

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

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

3 International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, DC 20001, www.iccsafe.org.

4 International Organization for Standardization, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, www.iso.org.