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EPC Projects: Flowline & Pipeline Construction/Maintenance

Pipelines, facilities & platforms. EPC projects on flowlines and pipelines, the facilities they feed, and the wellhead platforms at the end of them: built, maintained and kept in service.

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The service

Flowlines and pipelines, built and kept in service.

Winsko takes flowline and pipeline work as an EPC contractor: the same team plans, procures, builds, tests and hooks up, and then keeps the line in service. Most of this work is on flowlines: the lines that carry well fluids and gas-lift gas between wellheads, manifolds and flow stations. Since 2013 that has meant new flowlines and gas-lift lines, sectional replacement of corroded lines, leak repairs on live lines, and hook-ups to wellheads and flow stations for operators in the Niger Delta.

The sites are mostly swamp and creek locations in Rivers and Bayelsa, at fields such as Cawthorne Channel, Alakiri, Akaso and Krakama. Crews, pipe and plant go out from the company's own jetty at Trans-Woji, Port Harcourt, on its own barges, tug boats and swamp buggies, with a house boat for the crew, so a job does not wait on a hired marine spread.

Each job runs to an approved welding procedure, a coating specification and an inspection and test plan, and closes with a record of every weld, repair and pressure test.

Crew member in a life jacket and white hard hat at the wellhead on a new wellhead platform over the creek
Flowline hook-up at a wellheadPhotograph

Where it sits in the project lifecycle

  1. 01Engineering / Design
  2. 02Procurement & Logistics
  3. 03Fabrication
  4. 04Construction / Roads / Erection / Installation
  5. 05Testing / Pre-Commissioning
  6. 06Commissioning
  7. 07Operation, Maintenance & Handover

By the numbers

1.6 km
Flowline replaced
Cawthorne Channel 1 Well 16, with hook-up and a new wellhead platform (2024)
6.5 km
Longest gas-lift line
Akaso 011, built at Akaso in 2019
8
Swamp buggies owned
Wilco 3200 amphibious excavators for swamp right-of-way
27
Welding machines
Lincoln, Miller and Daewoo, 220 to 600 A, diesel and electric

Scope of work · 06 work packages

What the work covers.

  • 01

    Flowline construction

    New flowlines and gas-lift lines, including runs of several kilometres.

  • 02

    Sectional replacement

    Cutting out corroded or failed sections of existing flowlines, replacing them and returning the line to service.

  • 03

    Leak repair and clamping

    Planned and emergency leak repairs on live flowlines, by clamp or by section.

  • 04

    Hook-up

    Tie-ins to wellheads, manifolds and flow stations, with the isolation and permits agreed with the operator.

  • 05

    Maintenance and integrity

    Planned and emergency maintenance on flowlines and pipelines, with integrity checks to decide what to clamp, what to replace and when.

  • 06

    Marine and swamp spread

    Barges, tug boats, swamp buggies, cranes and house boats from the company's own fleet.

Method · 10 stages

From load-out to hook-up.

The stages of a flowline replacement or new line in swamp and on land, in the order the work is carried out, with the checks that close each one.

  1. 01

    Survey and right-of-way

    The route is set out from the approved drawing, existing lines and crossings are located, and the right-of-way is cleared. Where the ground will not carry ordinary plant, swamp buggies clear and open the corridor.

    • Centreline and working width pegged
    • Existing pipelines located and marked
    • Access by land or water agreed before clearing
    Two surveyors in orange coveralls on a cleared right-of-way, one holding a GNSS pole over a peg while the other drives in a second peg
    Setting out the right-of-wayIllustration
  2. 02

    Load-out and mobilisation

    Pipe, fittings and plant are loaded at the company's jetty at Trans-Woji onto its own barges, then towed to site with the tug boats. A crane barge, swamp buggies and a house boat for the crew go out with the spread.

    • Pipe and fittings checked against their certificates before load-out
    • Lift plan for every crane lift onto the barge
    • Marine crew, life jackets and transfer plan in place
    Two cranes lifting a bundle of line pipe onto a flat-top barge at the jetty, crew in orange coveralls on the quay
    Load-out at the jetty, Cawthorne Channel 1 W16Photograph
  3. 03

    Excavation

    On land, excavators open the trench to the depth of cover on the drawing. In swamp, swamp buggies dig and keep the ditch open, and water is pumped out before pipe goes in.

    • Depth of cover and width checked against the drawing
    • Trench walls battered or supported in soft ground
    • Spoil kept clear of the working side
    Yellow Wilco swamp buggy, an excavator on pontoon tracks, working in cleared mangrove swamp
    Swamp buggy on the right-of-way, Cawthorne Channel 1 W16Photograph
  4. 04

    Isolation and cut-out

    On a sectional replacement the failed section is isolated and depressurised with the operator, the area is gas-tested, and the old pipe is cut out at the agreed points.

    • Permit to work and isolation agreed with the operator
    • Gas test before and during every cut
    • Line ends prepared for the new section
    Sparks fly as a crew member cuts a pipe on a grassy land location while two colleagues stand by
    Cutting out a section on landPhotograph
  5. 05

    Welding

    New pipe is lined up and welded to a qualified procedure, root pass first, then hot pass, fill and cap. Each weld is numbered on the weld map and logged against the welder who made it.

    • Welding procedure and welders qualified before production
    • Preheat, interpass temperature and electrodes controlled
    • Every weld numbered and logged
    Pipeline worker in a face shield crouching to grind a girth weld on a coated pipeline while two crew look on
    Girth weldIllustration
  6. 06

    Weld inspection

    Welds are inspected visually and by the non-destructive testing the client specifies, radiography or ultrasonic testing. Rejected welds are repaired or cut out and inspected again.

    • Method and acceptance criteria set in the inspection and test plan
    • Every repair re-inspected
    • Reports tied to weld numbers
    Technician kneeling on a mat beside a girth weld, pressing an ultrasonic probe to the weld with a flaw detector in his other hand
    Ultrasonic weld inspectionIllustration
  7. 07

    Field joint coating

    The bare steel at each weld is blast-cleaned and coated, with a heat-shrink sleeve or liquid coating, to close the gap in the factory coating. A holiday detector is run over it to find pinholes.

    • Surface preparation and steel temperature checked first
    • Holiday test over the full joint
    • Damage repaired and tested again
    Worker shrinking a coating sleeve over a girth weld with a propane torch while a second worker runs a holiday detector along the coated pipe
    Field joint coatingIllustration
  8. 08

    Laying and backfill

    The coated line is laid into the ditch from the bank, the barge or the swamp buggies, and supported so the pipe and coating are not overstressed. The ditch is backfilled and the right-of-way reinstated.

    • Coating holiday-tested just before laying
    • Pipe resting on an even bed
    • Backfill placed and the ground reinstated
    Black coated line pipe with red end caps on the deck of a barge in a creek, mangrove and crew in the background
    Coated line pipe on the barge, Cawthorne Channel 1 W16Photograph
  9. 09

    Flushing and hydrostatic test

    The line is flushed with the flush pumps, filled with water and held above its design pressure for the period the design code sets, with pressure and temperature recorded throughout, then dewatered.

    • Test pressure and hold time taken from the design code
    • Calibrated gauges and chart recorder
    • Test pack signed by the client's representative
    Hydrotest set-up inside a taped exclusion zone: test head with two pressure gauges, a chart recorder on a stand and a test pump, technician writing on a clipboard
    Hydrostatic testIllustration
  10. 10

    Hook-up

    The tested line is connected to the wellhead, manifold or flow station at the agreed points. Where a wellhead platform is part of the scope it is installed first, then the line is hooked up and returned to the operator.

    • Isolation and permit to work agreed with the operator
    • Closing welds fully inspected
    • Leak test on start-up and as-built records handed over
    Crew member in a life jacket and white hard hat at the wellhead on a new wellhead platform over the creek
    Wellhead hook-up, Cawthorne Channel 1 W16Photograph

Plant and equipment

Our own spread, from the jetty to the joint.

Flowline jobs in the swamp stand or fall on marine and swamp plant. Winsko owns the spread it uses, so the plan is not built around what can be hired that week.

Swamp buggies
8 × Wilco 3200 C and D
Lay barges
600 t and 500 t
Ramp and dump barges
400 t to 1,200 t
Track crane
80 t, crawler
Welding machines
27 units, 220 to 600 A
Flush pumps
4 units, 4" suction, 2" discharge
Compressors
Ingersoll-Rand, 600 and 450 CFM
House boat
80-man accommodation
Swamp buggy working in cleared mangrove swamp
Swamp buggyPhotograph
Tug boats and barges moored at the Winsko jetty
Tugs and barges at the jettyPhotograph
Two-storey house boat moored at the jetty
House boatPhotograph

From the record

Cawthorne Channel 1, Well 16

Sectional replacement of a 1.6 km flowline at a swamp location on the Cawthorne Channel, with hook-up to the well and installation of a new wellhead platform. Pipe and plant went out from the Trans-Woji jetty by barge.

Line
4-inch Schedule 40 flowline
Length
1.6 km sectional replacement
Scope
Replacement, hook-up, wellhead platform installation
Setting
Swamp and creek, Cawthorne Channel, Rivers State
Worker on the steel frame of a wellhead platform being installed over the creek, its reflection in the waterPhotograph
Platform installation
Coated line pipe with red end caps on the barge deckPhotograph
Pipe on the barge
Swamp buggy working in cleared mangrove swampPhotograph
Swamp buggy
Two cranes lifting a bundle of line pipe onto a barge at the jettyPhotograph
Load-out at the jetty
Crew member at the wellhead on the new platformPhotograph
Wellhead hook-up
Four crew in life jackets and hard hats working at the wellhead on the platform over the creekPhotograph
Crew at the wellhead

Track record

Twelve years of flowlines in the Delta.

A selection from the list of jobs in the company profile.

  1. 20244" × 1.6 km flowline sectional replacement and hook-up, Well 16Cawthorne Channel 1
  2. 2022Sectional replacement, Alakiri Well 37TAlakiri
  3. 2019Four gas-lift lines, 4.3 to 6.5 kmAkaso
  4. 2019Flowline construction and wellhead platform works, PMMO-1Akaso
  5. 2018Gas-lift bulkline construction for Wells 5, 13 and 17 and the gas-lift manifoldCawthorne Channel
  6. 2018Akaso Well 13L: seven leaks repaired, by clamp and sectional replacementAkaso
  7. 2017Flowline construction, Wells 8S, 14L and 16SKrakama
  8. 2016Flowline construction, Wells 9T and 27L, with a 4" and 6" gas lineAlakiri
  9. 2015–16Oil flowline sectional replacement, Wells 3S and 29SAkaso
  10. 2014–16Leak repairs by clamping on live flowlines, well by wellAlakiri, Cawthorne Channel and Krakama
  11. 2014Oil flowline replacement, Well 4TCawthorne Channel

Inspection and testing

Every weld has a record.

Quality on a flowline is proven, not assumed. Each check below produces a record that goes into the job's test pack, and the pack is what the operator accepts before the line goes back into service.

01Material receiptPipe, fittings and consumables match the specification and their mill certificatesWhenOn delivery, before load-outRecordReceiving report, heat numbers
02Procedure qualificationThe welding procedure produces sound, tough weldsWhenBefore production weldingRecordPQR and WPS
03Welder qualificationEach welder can make that weld in that positionWhenBefore a welder startsRecordWelder qualification records
04Weld inspectionNo rejectable defects in the weldsWhenEvery weldRecordWeld map, visual and NDT reports
05Holiday testNo pinholes or damage in the coatingWhenEvery joint, before layingRecordHoliday test record
06FlushingThe line is clean of debris and water-filled for testingWhenBefore the pressure testRecordFlushing record
07Hydrostatic testThe line holds pressure without leakingWhenEach test sectionRecordPressure and temperature charts, test certificate
08As-built recordWhere the new line runs and how it is connectedWhenAt hand-overRecordAs-built drawings

Codes commonly specified for this work

  • API 5LLine pipe
  • API 1104Pipeline welding and inspection
  • ASME B31.4Liquid pipelines
  • ASME B31.8Gas pipelines
  • ISO 21809External coatings
  • ISO 15589-1Cathodic protection

Health, safety and environment

The hazards are known. So are the controls.

Flowline work puts people beside live hydrocarbon lines, open ditches and suspended loads, near flames and stored pressure, and most days on water. Each hazard has a control planned before the work starts.

  • 01

    Live lines

    Permit to work, isolation and depressurisation agreed with the operator, and gas testing before and during every cut.

  • 02

    Swamp and water

    Life jackets on the water and the barge, planned boat transfers, and a rescue plan for every location.

  • 03

    Lifting

    Lift plans for crane and barge work, certified slings, one banksman in charge and nobody under a suspended load.

  • 04

    Hot work

    Hot work permits, gas testing, a fire watch and extinguishers at the joint.

  • 05

    Pressure testing

    A marked exclusion zone, pressure raised in stages and only the test crew inside the barrier.

  • 06

    Open excavations

    Walls battered or supported in soft ground, spoil set back from the edge, and no entry without a permit.

Our HSE approach

FAQ · 05 questions

Questions, answered.

Short answers about epc projects: flowline & pipeline construction/maintenance at Winsko, from the company profile.

01

What flowline and pipeline work does Winsko carry out?

EPC projects on flowlines and pipelines, built and kept in service: new flowlines and gas-lift lines, sectional replacement of corroded lines, leak repairs on live lines, hook-ups to wellheads and flow stations, and planned and emergency maintenance, in swamp, creek and land locations in the Niger Delta.

02

Can Winsko build flowlines in swamp locations?

Yes. Most of its flowline work is at swamp and creek sites in Rivers and Bayelsa. Swamp buggies clear the right-of-way and dig the ditch, and pipe, plant and crew are carried on Winsko's own barges and tug boats, with a house boat for accommodation.

03

What is a flowline sectional replacement?

The corroded or failed section of an existing flowline is isolated with the operator, cut out, and replaced with new welded, inspected and coated pipe. The line is then pressure tested, hooked up and returned to service. In 2024 Winsko replaced 1.6 km of 4-inch flowline at Cawthorne Channel 1 Well 16, with hook-up and a new wellhead platform.

04

Does Winsko repair pipeline leaks by clamping?

Yes. Leaks are clamped where a clamp will hold, and the pipe is cut out and replaced by section where it has thinned too far. On Akaso Well 13L in 2018, seven leaks on one line were repaired by clamp and sectional replacement.

05

How is the quality of a new flowline checked?

Each job runs to an approved welding procedure, a coating specification and an inspection and test plan. Welds are numbered and inspected, field joints are coated and holiday tested, and the line is hydrostatically tested before hook-up, with a record of every weld, repair and test handed over.

Also in the scope

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Operational base / jettyElshcon Close, Trans-Woji (Slaughter), Port Harcourt, Rivers State

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