Cast Iron Rene al Techniq esCast Iron Renewal Techniques...ti itwin main • The pipeline after...
Transcript of Cast Iron Rene al Techniq esCast Iron Renewal Techniques...ti itwin main • The pipeline after...
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Cast Iron Rene al Techniq esCast Iron Renewal Techniques
Katie Harkless
Project Manager-Replacement
Washington Gas
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Washington Gas Overview
• Serve D.C. and adjoining areas in MD and VA
• Approximately 1.2M customers
• 22 gate stations, 2 peak shaving plants, and 1 storage fieldand 1 storage field
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WG Cast Iron Piping
DC 428 il• DC – 428 miles• MD- 75 miles• VA – 17 MilesVA 17 Miles• Total cast iron = 520 miles• Replace 5-6 miles annually
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WG Cast Iron Renewal Techniques
Li• Liners– Cured-in-place liner– U-liner
• Joint sealants– Internal joint sealants
External joint sealants– External joint sealants• Insertion
– Plastic insertion
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WG Cast Iron Renewal Techniques – Cured-In-Place Liner
C d I Pl Li• Cured-In-Place Liners– WG primarily uses on 12” and larger diameters due to
thicker pipe wall– Example project – Anacostia river rehab project
• Used liner because wanted to directionally drill but couldn’t obtain permit from National Park Service.
• Remediated 1800’ (2-900’ lengths)
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Cured-In-Place Anacostia River Rehab Project
C d i l• Cured-in-place process– Disconnect pipe– Clean pipe– Pre-lining inspection (CCTV)– Lining process– Post-lining inspection– Post-lining inspection– Pressure test– Activate the line
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Anacostia River Rehab Project
B k d f th P j t• Background of the Project– 16-inch cast iron pipes leaking under river Winter 2009
• Replace Option p p– Drill new lines– Install new lines through Anacostia Park
Complete line replacement– Complete line replacement • Rehabilitation Options
– Insertion– Lining – selected as best option
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River Crossing Location
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Project Design Concerns
C l t d t d i i f th i d ibl t• Concerns related to depressurizing of the main and possible water infiltration
• Double lining considered, first lining to stop water infiltration & d f isecond for gas carrier
• Obtaining Permits from Parks Dept• Working from Vault Side without dismantling the vault• Environmental issues related to dewatering of park side pit
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Pipeline Inspection
D i i f th Fi t L f T i 16 I h iDepressurizing of the First Leg of Twin 16-Inch main –Phase I
• Consideration was given to live camera inspect while simultaneously l i th t it t i filt tilowering the gas pressure to witness any water infiltration
• WGL opted not to live camera inspect and depressurized first leg of t i itwin main
• The pipeline after depressurizing was almost completely dry with l th fi t t t i j i t i littl tonly the first two cast iron joints weeping a little water
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Cured-in-place Lining Technology
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Pipeline Before Cleaning to Final Product
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Camera Inspection
W ki f th k id f th j t th fi t i ti f th• Working from the park side of the project, the first camera inspection of the pipeline revealed a clean main, except for the last 100ft or so before the drip
• The debris found was “sand like”, the amount of debris became greater the closer it came to the drip p
valve
Debris
Drip
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Blast Hose from Vault Side
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Pipeline Cleaning
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Cleaning Process
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Filling the Drip
Valve
Drip filling Methodology
• Inserted 2-14-Inch pigs into the bottom of the drip Camera
• Inserted 90ft of 2-Inch PVC pipe
• Mixed and poured adhesive into 2-Inch pipe and fill drip (27 Cans used)
2-14” Pigs
• Observed process through camera
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Lining Process
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Lining Process
PressureDrum
Concrete Vault Sub Station Side
Drum
P k Sid With St l
Direction of Lining
Drip filled with2-Pigs & Adhesive
Park Side With SteelSheeting Box
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Lining Process
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Clearance Concerns
Important: For every two feet (2ft) of additional cover, top of main,The cut-out section of space between the mains MUST increaseBy one additional foot (1ft) for example, a pipe with 6 feet (6ft) of
Cover requires a 7 foot (7ft) cut-out
6ft SectionRemoved
2-Foot
Section to be Lined
Utility Requirement
Removed@ 4FT cover
1-Foot
be Lined
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Clearance Requirements
Side View
PressureDrum
Approx 40ft LongIncluding Trucks4ft
DirectionOf Lining
Approx 10-12ft Long
Including Trucks
1ft
Approx 10 12ft Long
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Consequences of Misalignment
• Misalignment at the inversion point creates unsupportedliner within the rehabilitated pipeline and a
“Spot Repair” is required after curing
Unsupported liner
liner
Not enoughSpace to properlyAlign hose fittingAlign hose fitting
Unsupported liner
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Loading the Lining
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Inversion Cone Being Connected to Liner
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Lining
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Line Complete
Valve
Half/Pig to support Liner
Cast iron Joint
Half/Pig to support Liner
• Liner was installed and held pressure • PPM maintained positive pressure all night and next day to allow
Lineradhesive proper time to fully cure• Re-pressurized and tested pipeline• Cut open fish mouth valve position
Adhesive filled DripStarline-1000
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Pipeline Lining Completed
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Other Challenges - Flooding
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Other Challenges – Freezing and Blizzard
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Area Restored – Liner Project Complete
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WG Cast Iron Renewal Technique- Other Liners
U li• U-liner– Internal sealing
technique used in the l t 1990’late 1990’s
– U shaper liner that expands in pipe
– Useful on straight pipe with no service connections
– Remediated about 1000’ of main
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WG Cast Iron Renewal Techniques –Internal Joint Sealant
I t l j i t l t• Internal joint sealants– Only plausible on 16” diameter and up– More cost effective than external joint sealant because
don’t have to excavate every joint– Projected savings of up to 60% over conventional repair
methods – Example project – Embassy Row internal sealing rehab
• Remediated about 3,300’ of 20” cast iron main
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WG Cast Iron Renewal Techniques –Embassy Row Internal Sealing Rehab
Hi t f b ll d i t j i t l k• History of bell and spigot joint leakage• Main in good condition
– Pipe wall thickness = .71” thicknessp• Less expensive than direct bury• 11 customer included
E b id– Embassy residences– Textile museum– Large homes
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WG Cast Iron Renewal Techniques –Embassy Row Internal Sealing Rehab
Sequence of WorkSequence of Work
• Temporarily transfer services to low pressure main
• Install new 2” main - transfer services• Excavations• Gas stop-offs• Disconnects• Disconnects• Internal sealing• Air test main • Reconnect pipe segments• Stop-off to reconnect last segments• Service transfers• Additional work
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WG Cast Iron Renewal Techniques –Embassy Row Internal Sealing Rehab
Pl
Ave
e24th
St
23rd
St
Phe
lps
P
X
Mas
s A
Fla
Ave2 2 P
S STX X X X X X X X
X – Stop-off – (7’ x 8’)
X - Disconnect – (7’ x 20’)
X – Entry/Exit – (7’x 10’)
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WG Cast Iron Renewal Techniques –Georgetown Internal Sealing Rehab
I t l S liInternal Sealing– Seals
Nitrile rubber• Nitrile rubber• Steel retaining bands
– Process• Internal inspection/count• Clean/grout joints• Put seals and bands in place• Expand steel bands• Air test each seal
Crews worked inside 20” main for 7 days– Crews worked inside 20 main for 7 days
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Construction
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WG Cast Iron Renewal Techniques –Embassy Row Internal Sealing Rehab
Return To ServiceReturn To Service
• Air test at 25 psig for 1 hour
• Return to pressure at 5-psig increments
• Leak survey between increments
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WG Cast Iron Renewal Techniques –External Joint Sealant
E t l j i t l t• External joint sealants– Same concept as
encapsulation kit – Considered a repair, not a
renewal– Not used for mass
replacement, but more for big diameter joint repairs
– Not as cost effective as internal joint sealants
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WG Cast Iron Renewal Techniques –Plastic Insertion
Pl ti I ti• Plastic Insertion– Used mostly for small, 8”
and below diameter• Have done some 16”
diameter– Convert LP to MP after
i tiinsertion– Practice is to purge before
insertion, so not done on lilive gas
– Complete about 5 miles of replacement annually using th i ti th dthe insertion method
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Questions?