Gas Pipe Line design
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(2) PLEASE NOTE Operations personnel use a combination of skill, knowledge, and technology to accomplish specific goals. A key objective of the Gas Controller Training Program is to promote an understanding of theoretical basis for operational decisions used on the job every day. This training program enhances job-related skills by providing relevant and current information with immediate application for employees. Information contained in the modules is theoretical. A foundation of basic information facilitates an understanding of technology and its application. Every effort has been made to reflect pure scientific principles in the training program. Nevertheless, in some cases, pure theory conflicts with the practical realities of daily operations. Usefulness to the employee is our most important priority during the development of the materials in the Gas Controller Training Program.. INTRODUCTION TO PIPELINE DESIGN GAS CONTROLLER TRAINING PROGRAM © 2002 ENBRIDGE TECHNOLOGY INC.. Reproduction Prohibited. ENBRIDGE TECHNOLOGY INC. Suite 60, PO Box 398 10201 Jasper Avenue Edmonton, Alberta Canada T5J 2J9 Telephone Fax. +1 - 780-412-6469 +1 - 780-412-6460. Reference: G0.6 Introduction to Pipeline Design – APRIL 2003.
(3) STUDY SKILLS Each of the modules in the Gas Controller Training Program is designed in a performance based self-instructional format. This means that you are responsible for your own learning and for ensuring that you are ready to demonstrate your knowledge and skills. Our focus is on the performance of the necessary skills and demonstration of the knowledge needed to perform your job. 1. The modules are designed for short but concentrated periods of study from ten to forty-five minutes each. Remember that generally one week of self-study replaces 10 hours of in-class attendance. For example, if you have a three week self-study block, then you have to account for 30 hours of study time if you want to keep pace with most learning programs. 2. When you are studying the module, look for connections between the information presented and your responsibilities on the job. The more connections you can make, the better you will be able to recall. 3. There are self-tests at the end of each section in the module. Habitually completing these tests will ensure your knowledge of the information. Use the test to measure your understanding. If you have an incorrect answer, check the information in the section of the module to find out why the error was made. Remember, you are responsible for your own performance. 4. Start studying each section of the module by reading the objectives and the introduction. This provides both the focus for your learning and a preview of the test items. 5. Each module is prepared to adapt to a number of different learning styles. Some learners will proceed directly from the introduction and objectives to the review questions. Then they will study any topic that is missed. Most learners, however, work from the introduction through to the end of the text in a systematic way. Whichever way you choose to learn, you are free to use the materials as you see fit..
(4) 6. Every module has a performance based test. Each item in the test is related to an objective for each section. To prepare for the test, you should ensure that all section reviews are completed and understood. Many learners review the material in the module before taking the test. 7. To aid your understanding and enhance your time in the learning activities, new terms, concepts and principles are printed in bold face along with their definition highlighted in italics. These are also listed in the Glossary supplied at the end of the module. 8. Many learners have had success by reading the module Summary and Glossary. Items in the Glossary are cross-referenced to the place in the module where they were first introduced. This way, if there is a topic or a definition that you do not recognize, you can easily find it in the module..
(5) INTRODUCTION TO PIPELINE DESIGN. INTRODUCTION Introduction to Pipeline Design is an overview of the modules GAS PIPELINE DESIGN FUNDAMENTALS, HYDRAULICS LEVEL I, and other modules dealing with gas pipeline design. The detailed modules are theoretical in nature and provide Controllers with comprehensive and detailed knowledge of the design issues that affect their ability to maintain a safe and efficient pipeline operation. Many modules provide concrete examples of calculations and formulas commonly used in advanced pipeline design. Because this module is intended as a general overview, these formulas and calculations are not provided here. Rather, readers should refer to the specific module in question for more information.. This module provides information on the following goals. • It provides a general overview of pipeline design. • It explains the relationship between volume and pressure in a pipeline. • It describes how pipeline size and wall thickness are selected. • It explains the key factors that influence pipeline costs.. MODULE GOALS. None PREREQUISITES. 1.
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(7) INTRODUCTION TO PIPELINE DESIGN. SECTION 1. PIPELINE DESIGN FUNDAMENTALS. This section of the module provides a general description of how friction caused by gas flowing in a pipe affects pipeline pressures. This section also describes how the pressure loss can be determined.. INTRODUCTION. Readers should note that the module PIPELINE DESIGN FUNDAMENTALS contains an extensive appendix that provides numerous examples which use the following equations and numbers to solve pipeline design problems: • the Reynolds Number • the Moody Diagram • the Steady State Equation • the Total Energy Equation. For more information, readers should refer to the module – PIPELINE DESIGN FUNDAMENTALS.. After this section, you will be able to complete the following OBJECTIVES objectives. • Describe the three major gas pipeline design parameters. • Explain which pipe characteristics and gas properties are important in pipeline design. • Understand how to determine pressure loss due to friction in a gas pipeline.. 3.
(8) GAS CONTROLLER TRAINING PROGRAM. KEY PIPELINE DESIGN PARAMETERS. PIPELINE CHARACTERISTICS. Pipeline design involves a number of progressive steps using basic scientific laws and equations for calculations to determine optimum size and operating characteristics of a pipeline system. It is necessary to understand the conditions that affect the gas in the pipeline in order to design it properly. In addition, the following parameters must be considered in pipeline design: pipeline characteristics, physical properties of the gas, and the relationship between the pipe and the gas. The physical characteristics of the pipe affect how a gas will behave in a pipeline. Specifically, three pipe parameters must be considered in design: • pipe inside diameter (ID) • pipe length (L) and • relative roughness of internal pipe wall surface.. Wall Roughness. Length Inside Diameter. Figure 1 Pipe Characteristics Pipe inside diameter, pipe wall roughness and pipe length affect how a gas will behave in a pipeline.. PHYSICAL PROPERTIES Along with the characteristics of the pipe, the physical properties of the gas affect the design of the pipeline. There are four properties of OF THE GAS gas that must be considered: • natural gas liquids (NGL) or liquefied propane gas (LPG) and moisture content • density or specific gravity • compressibility, and • temperature.. 4.
(9) INTRODUCTION TO PIPELINE DESIGN. Pipe diameter, gas viscosity, and velocity combine to affect flow. The interdependence between the pipe diameter, liquid viscosity, and flow viscosity is defined by a mathematical relationship called the Reynolds number, Re. The Reynolds number is used to describe the type of flow exhibited by a particular gas flowing through a pipe of a specific dimension (see Figure 2).. THE RELATIONSHIP BETWEEN THE PIPE & THE GAS. Velocity, v. Diameter. Re =. D ×v n. Friction, n. Figure 2 The Reynolds Number The Reynolds Number is used to describe the type of flow in a pipe.. The first step in determining pressure loss due to friction is to calculate the Reynolds Number. After the Reynolds number is calculated, there are two additional steps required to calculate the pressure loss: a Moody Diagram is used to determine a friction factor; then a Steady State Flow Equation is used to calculate the pressure loss.. DETERMINING LOSS OF PRESSURE DUE TO FRICTION. The value of the Reynolds Number determines if the type of flow in a pipe is laminar, critical, or turbulent. Refer to the module PIPELINE DESIGN FUNDAMENTALS for detailed instructions on calculating the Reynolds number.. STEP 1 – CALCULATE THE REYNOLDS NUMBER, (RE). The friction factor can be read from a Moody Diagram. The Moody Diagram is a graphical representation of friction factors for a series of related flow conditions. These curves relate two dimensionless parameters (the Reynolds number and the relative roughness of the inside pipe wall) to the friction factor (see Figure 4).. STEP 2 – DETERMINE THE FRICTION FACTOR, (F). Turbulent. Figure 3 Turbulent Flow The relative roughness and Reynolds Number are used to find the friction factor.. 5.
(10) GAS CONTROLLER TRAINING PROGRAM. Flow in vhich the gas in the center of the pipe moves faster than the gas near the pipe walls is called laminar flow. If there is laminar flow, minimal mixing of gas occurs and the friction factor can be read from the Moody Diagram. For laminar flow there is a linear relationship between the Reynolds Number and the friction factor. If flow is turbulent, the friction factor is also found using the Moody Diagram. However, with turbulent flow, the relative roughness must also be taken into account so that the correct curve is used (see Figure 4). Under normal pipeline operating conditions, the flow is turbulent.. Figure 4 Moody Diagram. STEP 3 – CALCULATE THE PRESSURE LOSS USING FLOW EQUATIONS. A general steady-state flow equation has been developed from an energy balance over a pipeline. Steady State is a state or condition of a system, such as a pipeline, that stays constant or does not change over time. This equation and its derivation is defined in most texts on fluid mechanics and thermodynamics. Several pipeline flow equations have been developed for different flow conditions and pipeline diameters. Some examples are Weymouth, Panhandle A & B, and AGA flow formulas. These formulas contain adjustment factors that are found in practice and are specific to local field conditions. These flow formulas are used to predict pressure drops at differing flow rates with various sizes of pipe.. 6.
(11) INTRODUCTION TO PIPELINE DESIGN. 1. What are the three pipe characteristics that must be considered in pipeline design? a) Inside diameter, wall thickness, and relative roughness of internal wall surface b) Outside diameter, wall thickness, and relative roughness of internal wall surface c) Inside diameter, length, relative roughness of internal wall surface d) Outside diameter, length, relative roughness of internal wall surface. REVIEW 1. 2. The Reynolds number describes which of the following? a) It relates the characteristics of the pipe and the fluid flowing through it b) It is dimensionless (i.e., has no units of measurement) c) It describes the type of flow for a gas flowing through a specific pipe d) All of the above 3. For laminar flow, there is a linear relationship between the Reynolds Number and the friction factor. a) True b) False 4. What is the flow under normal gas transmission pipeline operating conditions called? a) It is laminar b) It is turbulent c) It is critical d) All of the above. Answers are at the end of this module.. SECTION 2. 7.
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(13) INTRODUCTION TO PIPELINE DESIGN. SECTION 2. PIPE SIZE OPTIMIZATION. Most pipelines are designed using computer programs to process the basic pipeline flow equations. Computers allow us to look quickly at many different alternatives with respect to pipeline size, temperature, pressure, and volumes. However, in order to understand computer calculations, a basic understanding of universal gas laws is required.. INTRODUCTION. This section of the module provides an overview of the concepts of energy conservation in relation to the practice of pipeline design. This section also discusses the importance of determining optimum pipe size, volume capacity, line pressure, and other related criteria for pipeline design. The module PIPELINE DESIGN FUNDAMENTALS provides numerous practical examples of typical problems related to the application of universal gas theory as well as pipe design pressure calculations. To see these examples and calculations, readers should refer to those modules and also to the WORKBOOK, which is a collection of problems designed to show the application of universal gas laws to pipeline design.. After this section, you will be able to complete the following objectives. • Identify the main factors affecting pipeline design. • Describe different methods of capacity expansion. • Recognize the relationship between present and future capacity requirements.. OBJECTIVES. 9.
(14) GAS CONTROLLER TRAINING PROGRAM. PIPE SIZING & SELECTION. PHYSICAL PROPERTIES OF THE GAS. Pipelines are designed not only to meet present needs, but also to accommodate future demands. In addition, economic factors such as the high cost of equipment and component parts also affect pipeline design. The design engineer is faced with the dilemma of satisfying the capacity requirements for all foreseeable demands while at the same time minimizing the economic burden of building and operating the pipeline. Selection of the most desirable combination of design factors to maximize capacity and minimize cost is called optimization. The selection of the size of the pipe is a crucial factor in designing a pipeline (see Figure 5). The pipe size, wall thickness, and strength determine the operating conditions of the pipeline. The diameter determines the compression requirement for a given volume.. $ $. OVER CAPACITY. ELAPSED TIME. LIMITED CAPACITY. VOLUME. Volume Capacity = Elapsed Time. Figure 5 Pipe Sizing Optimum pipe size satisfies capacity requirements at a reasonable cost. An oversized pipeline results in overspent funds, while an undersized pipeline restricts capacity.. The pipe size selection process is not complete without considering the cost of all the factors. Smaller pipe limits the volume and flow but costs less. Larger pipe has lower pressure loss and operating pressures, but costs more. All factors (cost of materials, cost of operation) must be determined to identify the most effective pipeline design.. 10.
(15) INTRODUCTION TO PIPELINE DESIGN. The selection of pipeline size involves calculating the annual costs, which are the costs incurred every year in the operation of a pipeline system. These annual costs are divided into two categories: • fixed (capital) costs, and • variable (operating) costs.. ECONOMIC FACTORS. Fixed costs are costs which do not depend on the capacity of the pipeline. An example of a fixed cost is property tax. Variable costs, unlike fixed costs, are dependent on the capacity of the pipeline. An example of a variable cost is the cost of compressor fuel. Total annual costs are approximately 20% of the capital costs for a typical pipeline. A pipeline has reached its capacity when there is no more physical room to increase the throughput under any conditions. Consequently, the discharge pressures of the existing compressor stations cannot be increased nor can suction pressures be decreased. Capacity expansion is the process of safely increasing the volume capacity of an existing pipeline. Methods of achieving increased capacity include adding: • parallel line (“looping”) • adding more compression at existing stations. The decisions on what measures to take for increasing pipeline capacity depend upon the increased volume requirements. If the pipeline capacity needs to be doubled, normally the solution would be to loop the pipeline completely. For increases between 10% and 50%, the pipeline company has the choice of installing a combination of loops and additional compression, depending on design requirements.. PIPELINE CAPACITY EXPANSION. 11.
(16) GAS CONTROLLER TRAINING PROGRAM. Pipeline loops are similar to parallel electric circuits as described in. PIPELINE LOOPS Figure 6. In Figure 6, the flow in both the main and looped lines. between Points A and B depends on the relative size of each line’s inside diameter. However, the pressure drop in each line is identical, since the two lines are connected to the same two end points. Looping is the installation of sections of pipe of different sizes that run parallel to the existing pipeline to change the capacity of the pipeline. Looping is usually added to the downstream segment of a section between two compressor stations to reduce the pressure loss between stations. A. A. B. B. Figure 6 Looped Pipeline A pipeline loop is similar to an electrical circuit. As the gas flow (current) reaches Point A, it separates into two streams. The sum of the flows (currents) in each stream is equal to the flow (current) before and after Points A and B.. The capacity of a pipeline can be increased by installing more. ADDITIONAL compression at stations along the pipeline. The additional COMPRESSOR compression is required to compensate for pressure loss at the higher STATIONS flow rates.. CAPACITY REQUIREMENTS. 12. The pipeline designer must know the expected capacity of the proposed pipeline. However, it is often difficult to forecast future capacity requirements. For example, future capacity requirements may increase with the addition of more production from newly drilled wells or newly discovered fields. New customers may be added to the system, such as gas fired power plants. In contrast, future capacity may decrease as gas field productivity decreases due to reservoir depletion..
(17) INTRODUCTION TO PIPELINE DESIGN. Nevertheless, estimates of pipeline input and delivery volumes are required. Often, compromises are made between building a pipeline capable of handling future requirements and one capable of handling only current requirements. Economics is the key consideration. If excessive capacity exists for an extended period of time, the system’s profitability is reduced. Conversely, if the pipeline’s capacity is smaller than the volume demand requirements, profits are not being maximized and the system must be expanded. Generally, pipelines are either designed with some excess capacity or so that capacity can be increased with the addition of compression limited by the Maximum Operating Pressure (MOP) of the system. MOP is the highest pressure at which a given segment of a pipeline can be safely operated. MOP is determined by regulations governing pipe size, weight, material composition, and geographic area in which the pipeline is located.. 13.
(18) GAS CONTROLLER TRAINING PROGRAM. REVIEW 2. 1. What does pipeline design consider? a) Future capacity demand only b) Right of way as highest priority c) Present and future capacity requirements d) All of these 2. How is the annual cost of operating a pipeline divided ? a) Into short term and long term costs b) Into fixed and variable costs c) Into gross and capital costs d) Into gross and net costs 3. Which of the following is NOT an option for increasing the capacity of a pipeline? a) Looping portions of the pipeline b) Adding compressor stations c) Adding compression at existing stations d) Operating above the MOP 4. What are the key considerations in sizing a pipeline? a) Economics b) Gas supply c) Customer demand d) All of these Answers are at the end of this module.. 14.
(19) INTRODUCTION TO PIPELINE DESIGN. SECTION 3. PIPE WALL THICKNESS CALCULATIONS. Pipeline regulations set out the standards that must be followed in designing a pipeline. In the United States, all gas pipelines must be designed according to the Department of Transportation Regulation, DOT 49 CFR Part 192 – Transportation of Natural and other Gas by Pipeline. The international standard for pipeline design is ANSI/ASME B31.8 – Standard for Gas Transmission Piping Systems.. INTRODUCTION. This section of the module describes how the nominal wall thickness is determined for a design pressure. This calculation is done after the pipe size has been determined through an optimization process. The module PIPELINE DESIGN FUNDAMENTALS gives numerical examples of pipe stress and wall thickness calculations.. After this section, you will be able to complete the following objectives. • Identify the factors involved in selecting the pipe wall thickness. • Recognize the causes of pipe stress. • Understand the application of wall thickness/design pressure formulas.. OBJECTIVES. 15.
(20) GAS CONTROLLER TRAINING PROGRAM. PIPE WALL THICKNESS CALCULATIONS. Once the optimum pipe size (diameter) is determined, the wall thickness and design pressure must be calculated in order to establish the pipe specifications. These calculations are set out in detail in ANSI/ASME B31.8 – Standard for Gas Transmission Piping Systems. Some jurisdictions have special or supplementary requirements that go beyond B31.8. SELECTING PIPE WALL The initial selection of a pipe wall thickness for a specific application is based on the following factors: THICKNESS • design pressure • • • • •. pipe diameter pipe material grade class location pipeline operating temperature longitudinal pipe joint factor.. Figure 7 Gas pipeline in Northern Canada. CAUSES OF PIPE Additional factors may influence the final selection of pipe wall thickness. Factors that may require consideration include: STRESS • foreign crossing requirements • • • •. external forces corrosion allowance transportation and handling during construction other non-typical loadings.. Figure 8 Pipes being transported during construciton. 16.
(21) INTRODUCTION TO PIPELINE DESIGN. The design pressure for gas pipeline steel piping or the nominal wall thickness for a given design pressure is determined by using the following ASME B31.8 formula: P=. where: t OD P S F E T. 2×S×F×t×E×T OD. DESIGN PRESSURE FORMULA. = nominal wall thickness (in.) = nominal outside diameter of pipe (in.) = design pressure (psig) = specified minimum yield strength (psi) = design factor = longitudinal joint factor = temperature derating factor. The outside diameter of the pipe (OD) and the design pressure are determined by the design optimization process. The pipe minimum yield strength (S) and the longitudinal joint factor (E) are established from the pipe manufacturer design specifications . The design factor (F) changes, depending on the final location of the pipe within the pipeline system. The ANSI/ASME B31.8 code sets out a procedure for dividing the pipeline into class locations (1, 2, 3 or 4) based on the number of buildings or population in proximity to the pipeline. There is a different design factor for each class location and within each class location there may be additional increases in design safety factors to account for added stress on the pipeline, e.g. road crossing or compressor station piping. A temperature derating factor is applied if the pipeline will operate above 150 °F (65 °C). Natural gas transmission pipelines are normally limited to a maximum operating temperature of 120 °F (49 °C). Above this temperature, the external coating will have the potential to disbond, exposing the pipe and creating the possibility of corrosion. The final pipe wall thickness can be determined once all pipeline design factors are known. Typically, a gas transmission pipeline will have a thin wall pipe in remote, sparsely populated areas. Heavy wall pipe is installed at road, river and rail crossings, throughout populated areas, in cities and towns, and at compressor stations.. 17.
(22) GAS CONTROLLER TRAINING PROGRAM. REVIEW 3. 1. What is the international standard for pipeline design? a) API 6D b) ANSI/ASME B31.8 c) ASME Section VIII d) All of these 2. Which of the following factors is not used to select pipe wall thickness? a) Pipe diameter b) Class location c) Gas quality d) Design pressure 3. What are determined by the design optimization process? a) Outside diameter (OD) and design pressure (P) b) Longitudinal joint factor (E) and specified minimum yield strength (S) c) Class location and design factor d) All of these 4. Where is heavier wall pipe usually installed? a) At road crossings b) At river crossings c) At compressor stations d) All of these Answers are at the end of this module. 18.
(23) INTRODUCTION TO PIPELINE DESIGN. SECTION 4. PIPELINE COSTS. This section describes the main components that make up the cost of a gas pipeline. These costs can be grouped as follows: • Right-of-way costs • Material costs • Construction costs • Engineering and contingency costs.. INTRODUCTION. For information on compressor station costs, readers should refer to the module – COMPRESSOR STATIONS.. After this section, you will be able to complete the following objective. • Identify the major components of transmission pipeline costs.. OBJECTIVES. 19.
(24) GAS CONTROLLER TRAINING PROGRAM. COST OF GAS TRANSMISSION PIPELINES. The cost of a gas transmission pipeline is made up of the following components: • Right-of-way (ROW) cost • Material cost • Construction cost • Engineering and contingency. Material and construction costs are the major cost components. Together, they make up 60% to 70% of the total project cost. A discussion of each component follows.. RIGHT-OF-WAY (ROW) Right-of-way costs consist of payment for land rights as well as compensation for work related damages. These include damages to COSTS crops, trees, and fences. The key factors affecting ROW costs are: • Population density – Higher density means higher costs. Figure 9 ROW through high density area. • Environmental sensitivity – Environmentally sensitive areas can be bypassed but this results in increased pipe and pipeline costs. Figure 10 ROW through environmentally sensitive terrain.. 20.
(25) INTRODUCTION TO PIPELINE DESIGN. • Time urgency – If negotiation time is short, ROW costs may increase • Surveying requirements – Surveys for easements across federal and state lands can be more expensive than private property Material costs include the pipe, coating, valves, and fittings. These costs increase significantly as the pipe diameter increases.. MATERIAL COSTS. The pipe is the most costly item. The wall thickness establishes the weight of the pipe, which determines the cost. Factors that affect the cost of materials are: • Design flow rate and MOP of pipe – These establish the size of pipe, valves, and fittings • Population density along ROW – This establishes the wall thickness of pipe • Availability of material – Some sizes and specifications of pipe material may be in short supply, driving up costs. This will depend on the number of similar pipeline projects happening concurrently. In addition to material costs, construction costs are a major component CONSTRUCTION of total pipeline costs. The key factors that influence construction COSTS costs are: • Population density – Urban areas present more obstacles to pipeline construction than rural areas • Environmental constraints – Construction costs will increase with directional drilling, terrain restoration, and archaeological sites. 21.
(26) GAS CONTROLLER TRAINING PROGRAM. • Rough terrain – Rocky areas, wetlands, and mountainous terrain can increase construction costs greatly. Figure 11 Pipeline construction through mountains. • Weather factors – Winter construction in cold climates, summer construction in hot climates, or rainy season construction can increase labour costs considerably • Availability of contractors – If contractors are busy, bid prices will increase. Engineering costs are dependent on the complexity of the project.. ENGINEERING & They could be significant if there are several complicated engineering CONTINGENCY COSTS designs such as water crossings, unstable slope areas, and mountainous terrain. Contingency costs are included to cover unknown project costs. These include material price escalation, unexpected construction difficulties, ROW acquisition problems, or unusually bad weather. The more the estimators know about a project, the lower the contingency cost should be.. 22.
(27) INTRODUCTION TO PIPELINE DESIGN. 1. What are the major cost components of a gas pipeline? a) Engineering and contingency b) Material and construction c) Right-of-Way and engineering d) Construction and engineering. REVIEW 4. 2. Population density is a key factor in the cost of a pipeline. a) True b) False 3. What are the main factors that affect the cost of pipeline materials? a) Design flowrate b) Population density along ROW c) Availability of materials d) All of these 4. Which is not a key factor in the construction costs of a pipeline? a) Population density along ROW b) Environmental constraints c) Survey requirements d) Rough terrain 5. What is the result when the estimators know more about a pipeline project ? a) It should lower engineering cost b) It should lower contingency cost c) It should lower ROW cost d) It should lower population density. Answers are at the end of this module. 23.
(28) GAS CONTROLLER TRAINING PROGRAM. SUMMARY. SECTION 1 – PIPELINE DESIGN FUNDAMENTALS • To design a pipeline, it is necessary to understand the pipe characteristics, physical properties of the gas, and the relationship between the pipe and the gas. • The main pipe characteristics in pipeline design are inside diameter, length, and relative roughness. • The physical properties of the gas that are considered in pipe design are viscosity, specific gravity, compressibility, and temperature. • The three steps to determining pressure loss due to friction in a pipeline are: – Calculate the Reynolds Number (Re). – Determine the Friction Factor (f) from the Moody diagram. – Calculate the pressure loss using an industry flow formula. SECTION 2 – PIPE SIZE OPTIMIZATION • Optimization is the selection of the most desirable pipeline design that maximizes throughput capacity at a minimum cost. • The annual costs of a pipeline are made up of fixed costs (which do not depend on capacity) and variable costs (which are capacity dependent). • The methods for increasing capacity of a pipeline are looping and adding more compression at existing stations. Optimization is used to select the best expansion method. • Pipeline capacity design is often a compromise between meeting projected future requirements and meeting current demands. Generally, pipelines are designed with expansion capability at reasonably low cost. SECTION 3 – PIPE WALL THICKNESS CALCULATIONS • The pipe wall thickness is calculated once the optimum pipe diameter and design pressure (MOP) are determined. These calculations are done according to formulas set out in government regulations, such as DOT 49 CFR Part 192 in the U.S.. 24.
(29) INTRODUCTION TO PIPELINE DESIGN. • The factors that determine pipe wall thickness are: – design pressure – pipe diameter – pipe material grade – class location – pipeline operating temperature – longitudinal pipe joint factor. • Each pipeline is divided into class location, depending on the proximity to buildings and population. A design factor is assigned to each class with increases to account for added stress on the pipeline due to unusual loads (e.g. road crossings) or external forces (e.g. unstable slopes). • The final pipe wall thickness is calculated for the different locations once all the factors are known. Typically, gas pipelines have thin-walled pipe in remote areas and heavy-walled pipe at river, road and rail crossings and through populated areas. SECTION 4 – PIPELINE COSTS • The total cost of a gas pipeline can be broken up into the following four components: Right-of-way, Material, Construction, and engineering and contingency. The largest cost areas are material and construction. • Right-of-way costs increase with population density, environmental sensitivity, short negotiation timeframes and increased survey requirements. • Material costs are a function of the pipe diameter, pipe wall thickness, and current availability of pipe. • Construction costs are driven by ROW population density, environmental obstacles, rough terrain, weather, and contractor availability. • Engineering costs increase with the number of specific unusual pipeline designs required. Contingency costs decrease as more detailed information is known about the project.. 25.
(30) GAS CONTROLLER TRAINING PROGRAM. GLOSSARY. annual costs the costs incurred every year in the operation of a pipeline system. (p. 11) fixed costs operational costs that do not depend on the capacity of the pipeline. (p. 11) laminar flow a flow in which the gas in the center of the pipe moves faster than the gas near the pipe walls. (p.6) looping the installation of additional sections of different sizes of pipe that run in parallel and are connected to the original pipeline to change the capacity of the pipeline. (p.12) Maximum Operating Pressure (MOP) the highest pressure at which a given segment of a pipeline can be safely operated. (p.13) Moody Diagram a graphical representation of friction factors for a series of related flow conditions, whose curves relate two dimensionless parameters (the Reynolds Number and the relative roughness of the inside pipe wall) to the friction factor. (p. 5) optimization selection of the most desirable combination of pipeline design factors to maximize capacity and minimize cost. (p.10) Reynolds Number mathematical relationship that defines the interdependence between the pipe diameter, liquid viscosity, and flow viscosity. (p.5) steady state operating condition of a system, such as a pipeline, that stays constant or does not change over time. (p. 6) variable costs costs of pipeline operation that change with increases or decreases in pipeline operational capacity. (p.11). 26.
(31) INTRODUCTION TO PIPELINE DESIGN. REVIEW 1 1. a. REVIEW 2 1. c. REVIEW 3 1. b. REVIEW 4 1. b. 2. d. 2. b. 2. c. 2. a. 3. a. 3. d. 3. a. 3. d. 4. b. 4. d. 4. d. 4. c 5. b. ANSWERS.
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