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Installation of mains
 

Installation of mains

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    Installation of mains Installation of mains Presentation Transcript

    • Installation of Mains
      • Definition
      • Gas Main: pipes used to carry gas from one point
      • to another & generally carry gas in large
      • volume for general or collective use
    • Installation of Mains
      • Common Materials Used
      • Steel (ST)
      • Plastic (PE)
      • *Older materials include: PVC plastic, fiberglass and cast iron (CI). The first mains were constructed with wood.
    • Installation of Mains
      • Common Sizes & Pressure Ratings
      • Sizes range from 11/4” to 24” depending on intended use and desired load.
      • *Pressure limits on plastic(PE) pipe are commonly
      • 60 PSIG or less.
      • *Pressure limits on steel(ST) pipe are commonly between 60 and 1,000 PSIG.
    • Installation of Mains
      • Common Joining Methods
      • Steel – welded joints preferred
      • Plastic – heat fusion preferred (includes butt,
      • socket, saddle and electrofusion)
      • Threaded – above ground and inside buildings
      • only
      • Mechanical – includes bolt on, compression and stab
      • fittings
    • Installation of Mains
      • Steel Pipe Coatings
      • Pipe coatings are used to protect the underground pipes from corrosion. Common coatings include: epoxy, mastic, X-trucoat(yellow wrap) and coal tar wrap.
    • Installation of Mains
      • Material Handling
      • The storing, handling, loading, hauling, unloading,
      • stringing, and placing of pipe and piping materials
      • shall be done in a manner which will avoid damage
      • to the pipe.
    • Installation of Mains
      • Construction
      • Handling and Storage of Pipe
      • Stringing – pipe is strung (laid) along the route
      • as close as possible to the trench so
      • that it can be readily installed.
    • Installation of Mains
      • Planning
      • Route
      • Environmental Assessment
      • Locates: Where are other utilities located?
      • Specifications: Company codes and standards
    • Installation of Mains
      • Planning
      • Multiple Utility Trench Occupancy (Joint Trench )
      • Materials: Plastic (PE) or Steel (ST)
      • Common Installation Methods: Direct Burial,
      • Plowing, Insertion, and Boring
      • Quality Control/Inspection
    • Installation of Mains
      • System Pressure Design
      • One Way Feed – distribution system has gas
      • pressure supplied from only one direction
      • Two Way Feed – distribution system has gas
      • pressure supplied from both directions,
      • also called ‘loop feed’
    • Installation of Mains
      • Construction
      • Breaking and Removal of Pavement
      • Construction/Installation Methods
      • Direct Burial
      • Plowing
      • Insertion
      • Boring
    • Installation of Mains
      • Construction
      • Depth of Main
      • Measured from surface to the top of pipe.
      • DOT requires a minimum of 30” of cover.
      • Common depth used by most utilities is 36”
    • Installation of Mains
      • Construction
      • Clearances for Paralleling or Crossing other
      • underground facilities or structures.
      • Should be a minimum of 1 foot from other
      • facilities or structures.
    • Installation of Mains
      • Direct Burial
      • Backhoe/Loader
      • Can dig in all types of soils
      • Effective for larger diameter gas mains
      • Dig out obstacles if needed
      • Due to size limited access to some area’s
      • Time consuming and costly to backfill and restore
    • Installation of Mains
      • Direct Burial
      • Trenching
      • Can dig in most types of soil
      • Effective for smaller size gas mains (2″ or smaller)
      • Obstacles must be dug out with backhoe
      • Greater accessibility to more area’s
      • Less time consuming and costly to backfill and restore
    • Installation of Mains
      • Plowing
      • Vibratory Plow
      • >Pipe is fed through plow chute and is laid
      • into the ground as plow moves forward.
      • >Limited to certain soil conditions.
      • >Limited to smaller size mains
      • >Minimal backfill and restoration needed
    • Installation of Mains
      • Plowing
      • Plug Plowing
      • >As plow moves forward the pipe is pulled
      • into the earth behind the blade.
      • >Limited to certain type soils
      • >Weak link must be used with plastic pipe.
    • Installation of Mains
      • Insertion
      • Insert new plastic mains inside older
      • abandoned steel or cast iron mains.
      • >Requires less excavation and restoration
      • >Usually includes replacement of gas services at the same time.
      • >Annular space must be sealed to prevent freezing around plastic gas pipe.
    • Installation of Mains
      • Boring
      • Various Methods:
      • Pneumatic Torpedo (Hole Hog/Gopher)
      • PTO (Mechanically) Driven Augers
      • Horizontal Directional Drilling (HDD)
      • >All require potholing to locate and avoid other
      • utilities in path of bore.
    • Installation of Mains
      • MAOP
      • M aximum
      • A llowable
      • O perating
      • P ressure
      • Note: Plastic (PE) pipelines may not be installed in
      • systems with MAOP of more than 60 PSIG
    • Installation of Mains
      • Construction
      • Pigging – forcing a mechanical device through with air
      • pressure to clean the interior of the pipe.
      • A pig catcher must always be installed and no one is
      • allowed in the vicinity of the pig catcher during the
      • pigging operation.
    • Installation of Mains
      • Construction
      • Pressure Testing – all newly installed mains must be
      • tested for strength and leakage.
      • Test pressure commonly is 150% of the MAOP of the
      • installed pipeline. PE pipe test pressure would be a
      • minimum of 90 PSIG.
    • Installation of Mains
      • Construction
      • Pressure Testing – Test Mediums
      • Air: most common but limited to about 100 PSIG
      • Nitrogen: used in steel pipelines up to 1,000 PSIG but
      • limited to smaller volumes due to cylinder size
      • Water: hydrostatic test commonly used on large diameter
      • cross country pipelines which required pigging to
      • remove excess water
    • Installation of Mains
      • Construction
      • Pressure Testing – Test Duration
      • Determined by type ,size and length of installed main.
      • Minimum commonly is one hour and maximum is 24
      • hours. Always refer to the company standards for the
      • specific requirements.
    • Installation of Mains
      • Construction
      • Pressure Testing – Test Measuring Equipment
      • Manometer/ U-tube - “W.C. only < 1 PSIG
      • Pressure Gauges – select proper pressure: “W.C. or PSI
      • Recording Chart – provides a permanent record of your pressure test, also select proper pressure level
    • Installation of Mains
      • Construction
      • Transition Fittings
      • Manufactured fitting that allows you to make the
      • transition from steel to plastic for under ground
      • pipelines. Sizes vary depending on existing pipe and the
      • specific need required in your distribution system.
      • Usually the steel is welded and the plastic is fused for
      • installation.
    • Installation of Mains
      • Construction
      • Tie-ins – making physical connection in
      • excavation
      • Three basic steps:
      • 1. Controlling the gas pressure at the source main
      • 2. Making the physical connection (called a ‘hot tap’)
      • 3. Purging gas out of the new main connection, along
      • with a test of the final piping connection
    • Installation of Mains
      • Construction
      • Bell Hole – an enlarged hole dug in a trench to allow
      • adequate work room for workers to conduct a
      • required operation – i.e. install service, make
      • hot tap, make tie-in, perform maintenance and
      • repair work, etc.
    • Installation of Mains
      • Construction
      • Hot Tap – the process to drill into a ‘live’ gas main to
      • make a connection for a main extension,
      • service line connection, line stopper usage, etc.
    • Installation of Mains
      • Construction
      • Controlling Gas Pressure and/or Flow
      • 1. Valves: steel or plastic
      • 2. Line Stopper (low or high pressure equipment &
      • fittings) steel or cast iron only
      • 3. Squeeze-off (most common is plastic but steel can be
      • squeezed off with special equipment)
    • Installation of Mains
      • Construction
      • Tie-ins – making physical connection in
      • excavation
      • Pressure Testing – all newly installed mains must be
      • tested for strength and leakage.
      • Pigging – forcing a mechanical device through with air
      • pressure to clean the interior of the pipe.
    • Installation of Mains
      • Construction
      • Purging – removal of all air and air/gas mixtures from
      • pipe prior to customer usage
      • Safety Alert: Use of an approved grounding method for
      • removing static charge is critical at the purge outlet.
      • Sources of ignition shall be eliminated from the
      • proximity of all purging operations.
    • Installation of Mains
      • Construction
      • Purging – removal of all air and air/gas mixtures from
      • pipe prior to customer usage
      • Safety Alert: Use combustible gas indicator (CGI) for continuous testing of atmosphere of the pipeline and work area. Never leave the purge discharge point unattended. Fire extinguisher shall be readily available during entire purging process.
    • Installation of Mains
      • Construction
      • Purging – can also be used for taking a pipeline out of
      • service to insure all gas is released to the atmosphere.
      • Use your CGI to verify 0 % gas in air to insure that
      • no combustible gas mixture remains in your pipeline.
    • Installation of Mains
      • Construction
      • Backfilling and Pavement Restoration – important for
      • maintaining good customer relations
    • Installation of Mains
      • Construction
      • As built measurements for company mapping/records system – critical for future system protection
    • Installation of Mains
      • Construction
      • Purging – removal of all air and air/gas mixtures from
      • pipe prior to customer usage
      • Backfilling and Pavement Restoration – important for
      • maintaining good customer relations
      • As built measurements for company mapping/records system – critical for future system protection