1、GEOP Gas Engineering and Operating Practices A Series by the Operating Section The American Gas Association Volume III DISTRIBUTION Book D-1 SYSTEM DESIGN REVISED The American Gas Association Washington, DC ii SYSTEM DESIGN Notices, Disclaimers and Copyright The Gas Engineering and Operating Practic
2、es Series (GEOP Series or materials) was prepared by the American Gas Association (AGA), its member companies and other individuals and groups with an interest in the natural gas industry. The AGA disclaims liability for any personal injury, property or other damages of any nature whatsoever, whethe
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11、he materials shall not be attributable to the AGA and is solely the responsibility of the certifier or maker of the statement. It may become necessary to make revisions to this document in the future. Whenever any revisions are advisable, recommendations should be forwarded to the American Gas Assoc
12、iation, 400 N. Capitol Street, NW, 4thFloor, Washington, DC 20001, USA. Copyrights 1990 and 2004 by the American Gas Association, (AGA) All rights reserved Library of Congress Catalog Card Number: 85-70460 ISBN 0-87257-011-8 AGA Catalog Number XY0403 Printed in the United States of American iii CONT
13、ENTS LIST OF TABLES AND FIGURES xvii List of Tables . xvii List of Figures xx PREFACE xxv ACKNOWLEDGMENTS . xxvii ENGLISH/METRIC CONVERSION FACTORS xxix INTRODUCTION . 1 The Typical System . 1 The Gas Supply 1 Pipe Networks 2 Classification by Pressure Level. 2 Pressure Regulation 3 PART I. CAPACITY
14、 DESIGN. 5 CHAPTER 1. SYSTEM LOADS AND DESIGN LOAD ESTIMATION 7 Load Behavior 7 Demand Profile. 7 Residential, Commercial, and Industrial-Firm; Excluding Space Heating 7 Space Heating . 9 Off-peak or Seasonal. 9 Interruptible. 9 Seasonal Load Variations . 9 Load Curves 10 Factors That Determine Dema
15、nd . 12 Weather Factors 12 Customer Factors 12 Timing Factors 13 Weather-Load Relationships 13 Degree Days . 14 Applications of Degree Day Index 16 Wind Effects. 18 General Equations. 19 Numerical Description of Load Behavior 20 Nomenclature . 20 Load Curve . 20 Load Factors . 21 Coincidence and Div
16、ersity Factors. 22 Demand Factor . 24 Ideal Load Characteristics 25 Methods of Obtaining Data on Load Characteristics 26 iv SYSTEM DESIGN Selection of Customers for Testing27 Group Load Characteristics Studies.27 Need for Continuing Studies27 Analysis of Results of Demand Meter Studies28 Distributio
17、n System Demands 28 Customer Demands .28 Effects of Conservation.28 Estimation of Design Loads29 The Need for Design Load Estimates29 Design Load Estimation Procedures General.30 Estimating Design Loads for Services 31 Estimating Design Loads for Mains32 Method Based on Connected Load34 Method Based
18、 on Consumption Data 35 Method Based on Average Design Load per Customer38 Design Load Parameters41 Timing of Peak Demand41 Design Weather Conditions.41 Design Load/Weather Relationship .42 Design Load Characteristics 43 Demand Interval 44 Leakage Allowance .45 Statistical Approach to Design Load Es
19、timation.45 Geographical Distribution of Loads48 Load Gathering by Nodal Areas49 Load Gathering by Land Area.49 Computerized Load Gathering 50 Finder Systems 51 Errors, Pitfalls, and Sources of Inaccuracy53 Other Load-Gathering Methods 55 Validation of Design Load Estimates55 Future Loads .55 Land G
20、rowth Patterns56 Forecasting 57 Load Records61 CHAPTER 2. GAS FLOW CALCULATIONS63 Fundamentals of Fluid Flow.63 Frictional Effects.64 Types of Flow Behavior65 Evaluation of Frictional Energy Loss67 The General Flow Equations 68 Evaluation of Friction/Transmission Factor69 Moody Diagram.70 Transmissi
21、on Factor for Laminar Flow .73 Transmission Factor for Turbulent Flow .73 Field Measurement 74 CONTENTS v Practical Flow Equations 75 Low Pressure Equations . 75 Selection of a Flow Equation 77 Equations for Fully Turbulent Flow 77 Equations for Partially Turbulent Flow. 78 Determination of Type of
22、Turbulent Flow Behavior 81 The Colebrook-White Equation 86 Examples of Flow Calculations 87 Manual Flow Calculations 88 Resistance Factors. 88 Equivalent Length. 91 Equivalent Resistance Factor 94 Partial Looping 96 Capacity Data 98 Modification and Efficiency Factors 98 Modifications for Dirty and
23、Rough Pipe 102 Flow Calculation Applications . 103 Flow Calculation Aids 104 Flow Computer Programs. 104 Elevation Corrections . 105 High Pressure Systems . 105 Low Pressure Systems 105 Pressure Setting Caution . 107 Sizing of Individual Mains. 108 Stub or Dead End Mains. 108 Undersized Mains in a N
24、etwork . 109 Rule-of-Thumb Test of Adequacy 111 CHAPTER 3. CAPACITY DESIGN OF SERVICES AND FUEL RUNS . 113 Services 113 Design Load 113 Newly Installed Equipment-Single Residential Unit 113 Newly Installed Equipment-Multiple Dwelling Units 114 Equipment Converted to Gas 115 Configuration of the Serv
25、ice. 116 Route Layout. 116 Materials . 116 Fittings and Valves 117 Allowable Pressure Drop 118 Flow Calculations. 119 Calculation Aids 120 Fuel Runs . 123 Sizing and Capacity 124 Allowable Loss in Pressure. 124 Demand Factor and Maximum Gas Demand 125 Length of Pipe and Number of Fittings. 126 Opera
26、ting Pressure Limitations. 127 vi SYSTEM DESIGN Basis of Design128 Flow Equations128 Design of Vertical Risers 128 CHAPTER 4. DISTRIBUTION CAPACITY DESIGN PRINCIPLES.135 Structure of the System Design Problem135 Constraints.136 Operating Limitations136 Delivery Pressure Commitments .136 Source Press
27、ure Available .137 Pipeline Right-of-Way.138 Physical Barriers138 Safety Considerations 138 Reliability of Supply139 Standardization of Pipe Sizes 140 Design Policy.140 Capacity Design Variables 140 Operating Pressure Level.140 Minimum Allowable Pressure .146 Source Pressure Control.147 Spacing Betw
28、een Sources149 Gradient Pattern.152 Gas Velocity 154 Reliability and Safety Factors .154 Looped or Radial System.154 System Layout and Valve Placement 157 Service Layout.158 Regulator Station Design.159 Development of the Layout for New Systems 159 Layout Guidelines .159 Constraints.159 Location of
29、Mains160 Principles of Design Logic 160 Layout Procedure 163 Performance Criteria .164 Reinforcement/Redesign of Existing Systems 165 Causes of Need for Redesign/Reinforcement166 Changes in Distribution System Load .166 Deterioration of Existing Pipe Systems .167 Public Works .168 Methods of Reinfor
30、cement168 Redesign Considerations .171 Low Pressure Systems .171 High Pressure Systems 172 General Considerations172 Large Loads .172 Urban Development.173 CONTENTS vii Implementation Planning 173 CHAPTER 5. NETWORK SIMULATION. 175 The Importance of Modeling . 175 Modeling Design 176 Modeling in Ope
31、rations 176 Company-Wide Benefits of Modeling 176 Engineering Department . 176 Operations Department . 178 Marketing and Sales Department 178 Rate Department . 178 Customer Service Department 179 Gas Supply Planning. 179 Types of Network Simulation Models . 179 Direct Measurement Model 179 Scale Phy
32、sical Model 181 Electrical Equivalence 181 Mathematical Models Solved on Digital Computers 182 The Network Modeling Structure 182 States of Information 182 Transition From State to State 185 The Process: Steady-State Model Formulation and Solution . 186 The Schematic 186 System Components . 187 The
33、System Model 188 The Nodal Approach. 189 The Loop Approach 191 Modeling Networks With Gas of Various Heating Values . 195 Modeling Networks With Significant Elevation Changes 198 The Input: Developing the Database for Network Monitoring . 198 Describing the Facilities . 199 Preparing Customer Load I
34、nformation. 199 Assigning Customer Load to the Model. 200 Derivation of Customer Loads for the Model. 201 Supplemental Information Needed for Network Modeling. 201 The Output: Interpretation of Model Results . 202 Typical Result Presentation for Decision-Making 202 Printed Tabular Results. 202 Graph
35、ical Results 203 Model Checking . 205 Managing the Modeling Function 207 Departments Involved in the Modeling Process . 207 Modeling as a Continuous Process . 208 viii SYSTEM DESIGNRelationship of the Modeling Function to the Automated Facilities Information System.208 Key Ingredients for Successful
36、 Network Modeling 209 Continual Updating, Checking, and Reporting209 Commitment to Network Modeling.209 Sufficient Staffing209 Effective Communication of Results.210 Modeling Unsteady Flow in Distribution Systems .210 Unsteady Flow as Related to Design.210 Unsteady Flow in Operations Analysis .212 C
37、HAPTER 6. ECONOMICS OF CAPACITY DESIGN .217 I. Review of Fundamental Concepts.217 Costs .217 Depreciation 218 Straight Line Depreciation.218 Declining Balance Depreciation 219 Return on Capital 220 Taxes .223 Income Taxes.223 Ad Valorem Taxes.225 Gross Receipt Tax226 Summary of Fixed Costs.226 Incre
38、mental Costs226 Time Value of Money.227 Time-Line Diagram.228 Compound Interest Factors .229 Net Present Worth229 Applications.231 Classical Methods of Project Economic Analysis.235 Net Present Worth .236 Uniform-Annual-Equivalent-Cost Method236 Rate-of-Return Method .237 Revenue Requirements Approa
39、ch to Economic Analysis.238 Evaluation of the Revenue Requirement for Fixed Costs238 The Income Tax Factor239 Example: Automobile Purchase.240 Alternative Formula for Evaluating Capital Costs.241 The Fixed-Cost-Per-Dollar Factor.242 Decision Criteria for Revenue Requirements244 Feasibility Studies24
40、4 Comparison of Alternatives.246 Sensitivity and Breakeven Analysis 247 II. Applications of Economic Analysis.249 Economics of Facility Sizing249 Sizing of a Feeder Main 249 CONTENTS ix Break-Even Analysis. 252 Pipe Sizing Nomograph 254 Sizing of New Distribution System 257 Effectiveness Index. 257
41、Other Indices. 259 Comparison of Alternatives by Economic Analysis . 259 Irreducibles. 259 Reinforcement of Existing Systems 260 The Benefit Index . 261 Regulator Station Economics 263 Long-Term Reinforcement Plans 264 Feasibility Studies for Service to New Areas. 264 Example of Economic Analysis fo
42、r Proposed New Business Extension 266 Year-by-Year Analysis. 268 Perspective on Extensions of Service . 273 PART II. MATERIALS 275 CHAPTER 7. HISTORICAL BACKGROUND 277 CHAPTER 8. LOAD, STRESS, AND STRAIN . 281 Stress and Strain-General Theory 281 Modulus of Elasticity, E . 281 Shearing Modulus of El
43、asticity, G (Modulus of Rigidity) 281 Poissons Ratio . 282 Yield Point 282 Proportional Limit 283 Elastic Limit . 283 Offset Yield Strength 283 Ultimate Tensile Strength. 283 Types of Strain . 283 Linear Elastic Strain (Hooks Law) 284 Non-linear Elastic Strain. 284 Viscoelastic Strain. 284 Plastic S
44、train . 284 Stress-Strain Curves . 284 Behavior of Material Under Constant Load 285 Tension and Compression Stress and Strain . 285 Shear Stress and Strain 286 Torsional Stress and Strain . 286 Thermal Stress and Strain . 287 Stress in Steel Pipelines . 287 Equations for Calculating Hoop Stress. 288
45、 Procedure for Calculating Stress Due to Internal Pressure (SI) 288 Procedure for Calculating Stress Due to External Loading (SE) 289 External Forces (Loads) Acting on Pipelines . 290 x SYSTEM DESIGNGeneral Types of External Forces (Loads) 291 External Loading on Buried Pipelines .292 Effects of Ear
46、th Loads and Super Loads293 Interaction of Internal Pressure and External Loading.294 Calculation of External Loads Acting on Buried Pipelines 294 The General Theory.294 Methods for Calculating Dead Loads Distributed to the Top of the Pipeline.296 Standard Vertical Ditch Conditions .297 Negative Pro
47、jection Embankment Conditions .298 Methods for Calculating Live Traffic Loads Distributed to the Top of the Pipeline302 Live Loads Under Rigid Pavement The Portland cement Association Method .303 Live Loads Under Flexible Pavement The Spangler Iowa Formula Method307 Stress Research on a Buried Stree
48、t Pipeline .310 Soil Dead-Load Stresses310 Highway and Railroad Crossings 311 Stresses in Steel Gas pipelines Installed on Bridges.311 Thermal Stresses .312 Effect of Temperature on Pipe Length and Strength .313 Maximum Permissible Thermal Stress 314 Design Methods for Thermal Stress 314 Absorption
49、of Stresses315 Pipe Loops315 Expansion Joints.315 Support Systems315 CHAPTER 9. METAL MATERIALS IN SYSTEM DESIGN 317 Steel Systems317 Specifications 317 Specifications for Steel Pipe-ASTM API-5L.317 Specifications for Steel Tubing-ASTM-539318 Specifications for Steel Fittings.318 ANSI-B16.9 .318 ANSI-B16.11 .318 ANSI-B16.5 .318 Fabrication Methods and Characteristics 318 Electrical Fusion Welding .322 Electric Resistance Welding 322 Submerged Arc Electric Welding 322 Seamless Pipe 322 Selecting Suitable Pipe322 Ductility.323 Heat treating 324 CONTENTS xi Impact Resistance . 324 Welda
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