PIPELINE EMERGENCIES. Chapter 5 Gas Pipeline Operations. Michael Callan

Transcription

1 PIPELINE EMERGENCIES Gas Pipeline Operations Michael Callan

2 Gas Pipeline Operations Objectives a) Describe The Following Physical Properties And Explain Their Significance In The Risk Assessment Process For An Incident Involving A Natural Gas Pipeline. i) Color And Odor ii) Vapor Density iii) Boiling Point iv) Vapor Pressure v) Solubility b) Describe The Following Chemical Properties And Explain Their Significance In The Risk Assessment Process For An Incident Involving A Natural Gas Pipeline. i) Flammable (Explosive) Range ii) Ignition Temperature c) List The Basic Byproducts Of Complete And Incomplete Combustion Of Natural Gas. d) Describe The Two Primary Reasons For Odorizing Natural Gas. e) Describe The Basic Principles Of Operation Of The Following: i) Natural Gas Gathering Systems ii) Natural Gas Processing And Treatment Facilities iii) Natural Gas Transmission Pipelines f) Given A Natural Gas Transmission Pipeline System, Describe The Purpose Of The Following: i) Compressor Stations ii) Gate Settings / Main Line Valves g) Describe The Following Underground And Aboveground Options For The Storage Of Natural Gas: Page 2 of 25

3 i) Underground ii) Depleted Natural Gas Reservoirs iii) Aquifers iv) Salt Caverns And Formations v) LNG Storage Tanks h) Given A Natural Gas Distribution Pipeline System, Describe The Purpose Of The Following: i) Gas Stations Or City Gates ii) Distribution Mains iii) Regulator Stations iv) Farm Taps v) Meters vi) Curb Valves vii) Main Valves i) List At Least Three Signs Or Indicators Of A Leaking Natural Gas Pipeline. CHAPTER 5 Instructor Overview 1. Describe the following physical properties and explain their significance in the risk assessment process for an incident involving a natural gas pipeline. Color and odor natural gas is colorless and odorless in its natural state. Risk assessment must consider this hazard and understand the explosive potential for a natural gas pipeline. Natural gas is odorized to indicate a leak and reduces gas losses through early detection. Vapor density the weight of a pure vapor of gas with air. Natural gas vapor density is less than 1 which is lighter than air. Risk assessment is gas will rise rapidly and dissipate. Boiling point low boiling point at -259 deg F. Risk assessment is that more Page 3 of 25

4 vapors that are produced at a given temperature. Vapor pressure vapor pressure for natural gas is 120 psi at 60 deg F. Assessment is that natural gas can be under extreme pressures when transported. Solubility slightly soluble in water. Assessment is that water spray can be used to move or redirect natural gas vapors. 2. Describe the following chemical properties and explain their significance in the risk assessment process for an incident involving a natural gas pipeline. Flammable (explosive) range for natural gas is 4% to 15%. Significant information for risk assessment in that the range of the gas igniting is easy. Therefore eliminating sources of ignition from the area and evacuation of people is top priority. Ignition temperature of natural gas is 1,200 deg F. In assessment it is a significant property in evaluating the ease with which it may ignite. 3. List the basic byproducts of complete and incomplete combustion of natural gas. Complete combustion water vapor and carbon dioxide Incomplete combustion carbon monoxide, excessive water vapor, aldehydes and soot 4. Describe the two primary reasons for odorizing natural gas. Natural gas is odorized to detect/indicate a leak and reduce gas losses by early detection. Page 4 of 25

5 5. Describe the basic principles of operation of the following: Natural gas gathering systems is a system of smaller-diameter, low-pressure pipelines that collect natural gas during exploration and transport the gas to gas processing plants. Natural gas processing and treatment facilities incorporates specific treatment processes to remove impurities fro the natural gas. This process includes compression, absorption and dehydration. Once impurities are removed the final natural gas product is considered pipeline quality. Natural gas transmission pipelines are the interstate highways of natural gas transportation system. These pipelines are high-strength welded steel pipelines with diameters of up to 48 inches and pressures ranges from 300 to 1500 psi. 6. Given a natural gas transmission pipeline system, describe the purpose of the following: Compressor stations are used to maintain pipeline flows and pressures. Compressor stations are generally build every 50 to 100 miles and monitored by SCADA. Gate settings/main line valves are installed along the transmission pipeline to help isolate or control the flow of the gas. Installed approximately 10 to 20 miles along pipeline. 7. Describe the following underground and aboveground options for the storage of natural gas: Page 5 of 25

6 Underground helps to maximize the use of pipeline system capacity year round and creates additional flexibility in operation of the pipeline system. Depleted gas reservoirs most common form of underground storage. Depleted reservoirs proven to be geologically capable of holding natural gas. Aquifers are underground porous, permeable rock formations that act as natural water reservoirs. Located in regions where there are no nearby depleted reservoirs and with a single winter withdrawal period. Salt caverns and formations are well suited to natural gas storage in that salt caverns, once formed, allow little injected natural gas to escape from the formation unless specifically extracted. LNG Storage tanks insulated cylindrical bulk storage tanks ranging from 50 to as large as 200 ft n diameter. 7. Given a natural gas distribution pipeline system, describe the purpose of the following: Gate stations or city gates are the point where natural gas from a transmission pipeline enters the distribution system. Gate stations metering and control pipeline flow, and regulating, monitoring and reducing pipeline pressure. Natural gas is odorized at this point. Distribution mains are the initial connection from the transmission pipeline system downstream of a gate station. Regulator stations sometimes referred to as limiting stations, control the gas pressure for major sections of the Page 6 of 25

7 distribution system. These stations have several valves and pressure regulators to protect against system overpressures. Main distribution valves normally located in the street and control large sections of the main gas grid. A farm tap is a single pressure reducing station connected to a pipeline with a pressure greater than 60 psi. Meters natural gas customers have a meter to measure the amount of gas being used for billing purposes. Every gas meter has a shut-off valve. Curb valves located in a circular or square box in the sidewalk, near the street or in a parking strip and is protected by a secured cover. The purpose of the curb valve is to isolate and control flow to a specific building or several related structures. Main valves are found in the street or major intersections and used to isolate and control larger areas of a natural area gas distribution system. 8. List at least three signs or indicators of a leaking natural gas pipeline. What you see, what you hear and what you smell. Discolored vegetation, vapor cloud or mist, dirt blown in the air, bubbles in a pond or river, fire coming out of the ground, ice ball around pipeline, dead insects. Hissing or roaring sound. Odor of sulfur or mercaptan. Page 7 of 25

8 Slide [1] Gas Pipeline Operations P-83 [2] Objectives a) Describe The Following Physical Properties And Explain Their Significance In The Risk Assessment Process For An Incident Involving A Natural Gas Pipeline. i) Color And Odor ii) Vapor Density iii) Boiling Point iv) Vapor Pressure P-84 v) Solubility [3] Objectives a) Describe The Following Chemical Properties And Explain Their Significance In The Risk Assessment Process For An Incident Involving A Natural Gas Pipeline. b) Flammable (Explosive) Range c) Ignition Temperature d) List The Basic Byproducts Of Complete P-84 And Incomplete Combustion Of Natural Gas. e) Describe The Two Primary Reasons For Odorizing Natural Gas. Page 8 of 25

9 [4] Objectives a) Describe The Basic Principles Of Operation Of The Following: b) Natural Gas Gathering Systems c) Natural Gas Processing And Treatment Facilities d) Natural Gas Transmission Pipelines P-84 e) Given A Natural Gas Transmission Pipeline System, Describe The Purpose Of The Following: f) Compressor Stations g) Gate Settings / Main Line Valves [5] Objectives a) Describe The Following Underground And Aboveground Options For The Storage Of Natural Gas: i) Underground ii) Depleted Natural Gas Reservoirs iii) Aquifers P-84 iv) Salt Caverns And Formations v) LNG Storage Tanks [6] Objectives a) Given A Natural Gas Distribution Pipeline System, Describe The Purpose Of The Following: i) Gas Stations Or City Gates ii) Distribution Mains iii) Regulator Stations iv) Farm Taps v) Meters P-84 vi) Curb Valves vii) Main Valves Page 9 of 25

10 b) List At Least Three Signs Or Indicators Of A Leaking Natural Gas Pipeline. [7] Introduction a) We Will Look At The Specifics Of Natural Gas Pipeline Operations And Their Facilities, With The Primary Emphasis Upon Natural Gas Transmission And Distribution Pipeline Systems b) Knowledge Of The Container, Its Contents, And The Behavior Of Both Are Critical Information In Sizing Up The Problem, Assessing The Behavior Of Each, Estimating Future Outcomes, And Developing A Sound Incident Action Plan. P-85 [8] Natural Gas: Physical And Chemical Properties a) To Mount A Safe And Effective Response At A Pipeline Emergency, Responders Must Understand i) How The Product Will Behave (I.E., Its Physical Properties) P-85 ii) How It Can Harm (I.E., Its Chemical Properties) b) Natural Gas (CH4) Is A Clean-burning Fuel That Consists Of Approximately 94% Methane, 4% Ethane, And The Remaining 2% Of Other Gases, Including Butane, Carbon Dioxide, Nitrogen And Iso-pentane. Page 10 of 25

11 [9] Primary Characteristics Of Natural Gas Are: a) Odorless, Colorless And Tasteless In Its Natural State b) When Mixed With The Proper Amount Of Air, Can Burn c) Capable Of Being Either A Liquid Or Gas. However, At Ambient Temperatures, Natural Gas Will Be In Its Gaseous Form P-85 d) With Few Exceptions, Is Transported Via Pipeline In Its Gaseous Form [10] Primary Characteristics Of Natural Gas Are: a) May Be Found As A Cryogenic Liquid (I.E., Liquefied Natural Gas Or LNG) In Some Storage And Transportation Containers. b) Is Non-toxic, But Can Present Inhalation Hazards. If Released Within An Enclosed Area, Natural Gas Can Displace Oxygen And Act As A Simple Asphyxiant. P-86 [11] Physical Properties a) Physical Properties Provide Information On The Behavior Of A Material b) Color And Odor - In Its Natural State, Natural Gas Is Colorless, Odorless And Tasteless c) When Considering Odor As A Method For Detecting Natural Gas Leaks, Responders Should Remember The Following: d) Natural Gas Transported Via Transmission Pipelines Is Usually Transported In An P-86 Unodorized State. Page 11 of 25

12 e) In Certain Underground Release Scenarios Involving Soil Conditions With A High Sand Or Moist Clay Content, The Concentration Of Odorant May Be Reduced Or Leached [12] Physical Properties a) The Human Sense Of Smell Can Be Desensitized To The Odorant When Individuals Are Exposed To Low Concentrations For An Extended Period Of Time. b) Vapor Density the Weight Of A Pure Vapor Or Gas Compared With The Weight Of An Equal Volume Of Dry Air At The Same Temperature And Pressure. P-86 c) Natural Gas Is The Most Common Gas That Emergency Responders Will Encounter That Is Lighter Than Air. [13] 4H MEDIC ANNA: 4H H = Hydrogen (VD = 0.069) H = Helium (VD = 0.14) H = Hydrogen Cyanide (VD = 1.0) H = Hydrogen Fluoride (VD = 0.34) P-87 [14] 4H MEDIC ANNA: Medic M = Methane (VD = 0.6) E = Ethylene (VD = 0.97) D = Diborane (VD = 0.96) I = Illuminating Gas (10% Ethane And 90% Methane Mixture -VD = 0.6) C = Carbon Monoxide (VD = 0.97) P-87 Page 12 of 25

13 [15] 4H MEDIC ANNA: Anna A = Anhydrous Ammonia (VD = 0.588) N = Neon (VD = 0.7) N = Nitrogen (VD = 0.96) A = Acetylene (VD = 0.90) P-87 [16] Physical Properties a) Boiling Point the Temperature At Which A Liquid Changes Its Phase To A Vapor Or Gas. Natural Gas Has An Extremely Low Boiling Point Of -259 F (-161 C). In Comparison, Propane Has A Boiling Point Of-44 F (-42 C). b) Vapor Pressure The Vapor Pressure Of Natural Gas At 60 F (15.5 C) Is Approximately 120 Psi. c) Solubility Natural Gas Is Slightly Soluble In Water. P-87 d) Simple Asphyxiant Natural Gas Is Generally Considered A Non-toxic Material. [17] Combustion Characteristics Of Natural Gas a) Chemical Properties Are The Intrinsic Characteristics Or Properties Of A Substance Described By Its Tendency To Undergo Chemical Change. Chemical Properties Typically Provide Responders With An Understanding Of How A Material May Harm. i) Requirements For Combustion ii) Combustion Is A Chemical Reaction. P-88 iii) The Combustible Ingredients In Natural Gas Are Hydrocarbons Consisting Of One Part Carbon And Four Parts Of Hydrogen (CH 4 ). Page 13 of 25

14 [18] Flammable (Explosive) Range a) The Flammable Or Explosive Range Is Defined As The Range Of Gas Or Vapor Concentration (Percentage By Volume In Air) That Will Burn Or Explode If An Ignition Source Is Present. b) Limiting Concentrations Are Commonly Called The Lower Flammable (Explosive) Limit And The Upper Flammable (Explosive) Limit. P-89 [19] Flammable (Explosive) Range a) Most Combustible Gas Indicators (CGI) And Flammable Gas Detectors Are Set To Alarm At 10% Of The LEL Of The Gas Upon Which The Sensor Is Calibrated (Approximately 4,000 Ppm). [20] Combustion Characteristics Of Natural Gas a) Ignition Temperature P-89 i) Even With An Ideal Natural Gas And Air Mixture, There Must Still Be An Ignition Source Present For Combustion To Occur. The Ignition Temperature Of Natural Gas Is 1,200 F (649 C) P-89 [21] Combustion Characteristics Of Natural Gas a) Heat Value i) The Purpose In Using Any Fuel Is To Develop As Much Heat As Possible Per Cubic Foot Of Fuel Gas. The Heat Produced By Burning Natural Gas Is Expressed In British Thermal Units (Or Btu s) Per Cubic Foot Of Gas. The Heating Value For Natural Gas Is 1,012 BTU/Ft3. In Comparison, The Heating P-89 Page 14 of 25

15 Value Of Propane Vapor Is 2,488 BTU/Ft 3. [22] Natural Gas And Its Combustion Products a) When The Combustion Process Is Incomplete, Harmful Products Of Combustion Are Generated. b) Carbon Monoxide c) Exposure Values For Carbon Monoxide Include The Following: P-90 i) American Society Of Heating, Refrigeration And Air Conditioning Engineers (ASHRAE) Ventilation Standard Specifies A Maximum Permissible Concentration Of 9 Ppm Of CO In Residential Living Areas. ii) The Occupational Safety And Health Administration (OSHA) Has Established An 8- hour Time Weighted Average / Threshold Limit Value (TLV/TWA) Of 35 Ppm. [23] Other Gas Products a) There Are Other Gases And Special Products That Are Transported Through Gas Pipelines. b) Ethane Is A Simple Hydrocarbon (C 2 H 6 ). c) Ethylene (C 2 H 4 ) Is A Colorless Flammable Gas With A Faint Odor That Is Sweet And Musty. d) Methane Gas Is A Flammable Gas Often Generated By The Anaerobic Bacterial P-91 Decomposition Of Organic Material In Landfills And Swamp Areas. e) Chlorine Is A Greenish-yellow, Non-flammable Gas With A Distinctive, Pungent Odor. Page 15 of 25

16 [24] Natural Gas Gathering And Transmission Pipeline Operations a) Natural Gas Gathering Systems b) The Natural Gas Is Collected Through A Series Of Smaller Diameter, Low Pressure Pipelines Normally Referred To As Gathering Lines c) From The Gathering System, Natural Gas P-92 May Be Injected Into A Transmission Pipeline System Or Transported Directly To A Storage Facility Or A Gas Processing Plant. [25] Gas Processing And Treatment Facilities a) Natural Gas Liquids b) Water c) Liquefied Petroleum Gas (LPG) d) Ethane P-94 e) Hydrogen Sulfide (H2S) f) Carbon Dioxide (CO2). [26] Natural Gas Transmission Pipelines a) Large Transmission Pipelines Are The Interstate Highways Of The Natural Gas Transportation System. They Are Generally The Link Between Gathering Systems And Distribution Systems. b) These Are High-strength Welded Steel Pipelines With Diameters Of Up To 48-inches. P-94 Page 16 of 25

17 [27] Natural Gas Transmission Pipelines a) Operating Pressures Can Range From 300 To 1,500 Psi, And Compressor Stations Are Used To Maintain Pipeline Operating Pressures. b) Most Natural Gas Transmission Pipelines Cover Large Geographical Areas And May Be Several Hundred Miles Long. P-94 [28] Compressor Stations a) The Movement Of Natural Gas Through A Pipeline System Is No Different Than Moving Water In A Fire Department Relay Operation. b) Similarly, As Natural Gas Flows Through A Pipeline, The Pipeline Pressure Will Decrease Due To Friction Loss And Elevation Differences. [29] Compressor Stations a) Pipeline Pressure Cannot Be Allowed To Drop Below The Required Delivery Pressure At The Delivery Points Or The Flow Will Cease. b) Compressor Stations May Be Either Attended Or Unattended P-95 Page 17 of 25

18 [30] Compressor Stations a) Equipment At A Compressor Station Will Vary Depending Upon A Number Of Factors. b) Engine And Compressor Units (A) c) Positive-displacement Compressors d) Continuous-flow Compressors e) Piping And Piping Manifolds (B) P-96 f) Filter Separators (C) g) Cooling Units (D) h) Pig Manifolds i) Generators (E) j) Gas And Fire Detection And Suppression Systems. [31] Gate Settings / Main Line Valves a) In Addition To Compressor Stations, Gate Settings Or Main Line Valves (MLV) Are Installed Along The Natural Gas Transmission Pipeline System To Help Isolate Or Control The Flow Of The Gas. b) Emergency Response Personnel Should Never Attempt To Isolate Any Pipeline Valves On Transmission Or Distribution Lines P-97 [32] Gate Settings / Main Line Valves i) Operation Of Pipeline Valves And Systems Must Be Under The Full Control And Direction Of The Pipeline Operator. Failure To Do So May Create Additional Problems That Are Worse Than The Original Event. P-97 Page 18 of 25

19 [33] Transmission Pipeline Customers a) The Purpose Of A Natural Gas Transmission Pipeline Is To Transport Natural Gas From Production Locations To Customers Who Will Be Using It. b) Large Industrial Customers And Manufacturers May Contract Directly With The Natural Gas Transmission Pipeline Operator For Gas P-97 Delivery To Their Facilities. c) The Largest Customer Base For Natural Gas Transmission Pipeline Companies Is Comprised Primarily Of Local Distribution Companies. [34] Natural Gas Storage a) Storage Serves Two Major Purposes: b) It Helps To Maximize The Use Of Pipeline System Capacity Year-around c) Creates Additional Flexibility In Operation Of The Pipeline System. d) Natural Gas May Be Stored In Either Underground Or Aboveground Storage Facilities. e) Depleted Gas Reservoirs P-98 f) Aquifers [35] Natural Gas Storage a) Underground Salt Caverns And Formations i) Salt Domes ii) Salt Beds b) Aboveground Storage. Natural Gas May Also Be Converted To Liquefied Natural Gas (LNG), And Then Stored As A Cryogenic Liquid In Aboveground Storage Tanks. P-100 Page 19 of 25

20 [36] Natural Gas Distribution Pipeline Operations a) Gate Stations Or City Gates b) Distribution Mains c) Regulator Stations d) Main Distribution Valves e) A Farm Tap P-100 [37] Natural Gas Distribution Pipeline Operations P-101 [38] Natural Gas Distribution Pipeline Operations a) Distribution Systems b) Bare Steel Ranges From.75 To 8-inches In Diameter, And Is Used For Pressures Up To 60 Psi. c) Wrapped Or Coated Steel Piping Ranges From.5 To 30-inches In Diameter, And Is Used For Pressures Up To Several Hundred Psi. P-102 The Coating Is Usually Yellow Plastic Or Brown Paper. d) Cast Iron Ranges From 4 To 20-inches In Diameter, And Is Usually Used For Low Pressure Gas (.25 Psi). Page 20 of 25

21 [39] Natural Gas Distribution Pipeline Operations i) Wrought Iron Ranges From 2 To 8-inches In Diameter, And Is Used For Pressures Up To 60 Psi. ii) Polyethylene (PE) Plastic Piping Ranges From.5 To 8-inches In Diameter, And May Be Used For Pressures Up To 100 Psi. PE Piping Is Also Susceptible To The Buildup Of P-102 Static Electricity And May Possibly Cause The Ignition. [40] Natural Gas Distribution Pipeline Operations a) A Pressure Relief Valve (PRV) Venting To The Atmosphere Is Normally Performing Properly. i) A PRV Should Never Be Shut-off, Isolated Or Restricted By Emergency Response Personnel. P-102 [41] Natural Gas Service Meters a) Natural Gas Customers Have A Meter To Measure The Amount Of Gas Being Used For Billing Purposes. b) Every Gas Meter Will Have A Shut-off Valve Located On The Supply Side (I.E., Upstream) Of The Meter. c) Meters May Be Classified By Pressure Or Use d) Intermediate Pressure (2 60 Psi) And P-103 High Pressure ( Psi) Meters Will Have A Regulator Between The Supply Side And The Meter To Reduce The Pressure. Page 21 of 25

22 [42] Natural Gas Service Meters P-104 [43] Natural Gas Service Meters P-103 [44] Natural Gas Service Meters a) Multiple Meters b) Industrial Meters c) Earthquake Shut-off Valves d) Curb Valves e) Main Valves P-105 Page 22 of 25

23 [45] Clues Of A Natural Gas Pipeline Incident a) What You See b) Browning Or Discolored Vegetation That Is Otherwise Green Along A Pipeline Right-of-way. c) Presence Of A Vapor Cloud Or Mist Around The Pipeline Right-of-way. d) Dirt Being Blown Into The Air. P-105 e) Bubbles Coming From A Pond Or River. [46] Clues Of A Natural Gas Pipeline Incident a) Fire Coming Out Of The Ground. b) Presence Of Construction Or Excavation Equipment In The Area, Such As Backhoes, Drilling Rigs, Telecommunications Vehicles, Etc. c) Ice Ball Around The Pipeline. d) Collection Of Dead Insects. P-105 e) Odor Of Mercaptan Or Sulfur. Remember That Transmission Pipeline Systems Typically Handle Unodorized Natural Gas. f) What You Hear i) Unusual Hissing Or Roaring Sound Along A Pipeline Right-of-way. Page 23 of 25

24 [47] Street Smart Tips a) Natural Gas Is Lighter Than Air And Will Rise. b) Natural Gas Can Be Trapped Under Asphalt, Concrete Or Frozen Ground, And Move Laterally From Its Source In Underground Conduit, Casings And Right-of-ways. c) Underground Leaks Of Natural Gas Will P-106 Follow The Path Of Least Resistance. Soil That Has Been Disturbed By Excavation Will Allow For The Easier Passage Of Natural Gas. In Addition, Certain Soils May Cause The Mercaptan Odorants To Be Scrubbed From The Natural Gas. [48] Street Smart Tips a) A Combustible Gas Indicator (CGI) Or Flammable Gas Detector Will Be Required To Determine The Concentration Of Natural Gas Vapors Present. If Your Detector Is Not Calibrated On Methane, A Calibration Curve Or Factor Will Be Required To Determine The Actual Reading Of Natural Gas Present. P-106 b) Eliminate All Ignition Sources. Do Not Operate Vehicles Or Equipment That Can Produce A Spark, Including Door Bells, Telephones And Light Switches When A Natural Gas Leak Is Suspected. [49] Street Smart Tips a) If Ventilating An Enclosed Space, Remember The Explosive Limits Are 4-15% Gas In Air. Ventilation May Momentarily Increase The Hazard As You Pass Though This Range. b) Natural Gas That Is Trapped In Enclosed Areas Or Confined Spaces Will Cause A Significant Explosion If Ignited. P-106 c) Natural Gas Vapors Will Quickly Flash Back To Their Source When Ignited. Page 24 of 25

25 d) Natural Gas Fires Will Give Off Tremendous Amounts Of Radiant Heat And Provide Significant Exposure Concerns. [50] Summary a) Natural Gas (CH 4 ) Is The Predominant Product Transported In Gas Pipelines. b) Natural Gas (CH 4 ) Is A Clean-burning Fuel That Consists Of Approximately 94% Methane, 4% Ethane, And The Remaining 2% Of Other Gases, Including Butane, Carbon Dioxide, Nitrogen And Iso-pentane. P-106 c) An Odorant That Smells Like Sulfur Or Rotten Eggs is Added To Natural Gas So That It Can Be Detected By Human Smell At Concentrations [51] Summary a) Natural Gas Will Burn In The Presence Of An Ignition Source When It Is Within Its Flammable Range Of Approximately 4 To 15%. b) Natural Gas Is Initially Collected From Underground Wells Into A Series Of Small, Low Pressure Pipelines Normally Referred To As Gathering Lines. P-106 Page 25 of 25