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Case Studies

CASE STUDY 1 - South West Reinforcement Project

The Project was constructed by Laing O'Rourke Infrastructure for their Client, National Grid, in three spreads:

Mobilization commenced 25th June 2007. Swabbing, gauging and testing operations on spread 1 Ottery AGI to Aylesbeare AGI began one week later. Water for filling was pumped from the River Otter, transferring from spread 1 into spread 2. The sections were filled three test sections east to Ottery AGI and five test sections west to the River Exe crossing. Equipment was then transferred positive of the River Exe and a 150NB x 2.5km water supply line installed between the Exeter Canal and Powderham site to complete the remaining two test sections west to Kenn AGI. The sections were tested-out and de-watered out by the end of August 2007.

Equipment was transferred to the River Dart to commence filling and testing spread 3 Fishacre to Choakford. Eight sections were filled and tested from the River Dart, three test sections east to Fishacre and five test sections west to Avonwick. The eight sections were completed mid October and the equipment transferred to the River Erme. Testing and de-watering of the final nine sections, four sections east to Avonwick and five sections west to Choakford AGI was completed by the end of November 2007.

Whilst testing spread 3, tie-ins and drying of hydrotested sections was undertaken. Spread three completed tie-ins and drying of 17 test sections on the 8th December 2007.

"HTC were involved in the Project planning from a very early stage. They brought a wealth of experience to the initial discussions and helped develop the hydrostatic testing programme to overcome difficult site conditions and a tight schedule. I found the site team, led by Mark Lacey, to be extremely professional and knowledgeable. They successfully completed the swabbing, gauging, hydrostatic testing and drying of 27 No. test sections within the required timescale, often having to re-schedule the works at very short notice. I would definitely call on the services of HTC in the future."

Dave Morgan - Project Manager - Laing O'Rourke

CASE STUDY 2 - Chalgrove to East Iisley 900mm pipeline project for National Grid

At the start of 2003 Laing O'Rourke Ltd awarded HTC a major pre-commissioning sub-contract for the pressure testing and drying of a 900mm diameter, 24.95km gas pipeline for National Grid. The pipeline was constructed to connect an existing AGI at Chalgrove, in Oxfordshire, to a newly constructed AGI at East Ilsley, Berkshire . The project, which was carried out in June 2003, involved the swabbing, gauging, filling and testing of a 24.95km of 900mm diameter Natural Gas pipeline in three test sections. Approximately 3.4 million gallons of water were extracted from the River Thames to use in the testing. Afterwards, the water was returned to the river in a carefully controlled operation that fully satisfied strict monitoring by the Environment Agency. After the testing was completed, the three sections were welded together to enable final swab, gauge, Kaliper™ survey and drying of the entire pipeline. Drying of the pipeline, using desiccant dry air, was achieved in seven days.

Martin Sperrink, of Laing O'Rourke, was impressed with HTC's performance. He said:

"HTC executed the work in a professional, diligent manner and made a vital contribution to the success of the project, which was worth about £10 million overall. The site management team, headed up by Mark Lacey , were helpful and responsive."

CASE STUDY 3 - Burlington project at Barrow-in-Furness

Environmental considerations were part of the challenge successfully met by HTC in a major pipeline-testing project for Burlington in Cumbria . HTC was sub-contracted by VanOord ACZ JV to pressure test the onshore terminal pipeline section from the COGAP (Costain Oil Gas and Process Ltd) terminal site at Barrow-in-Furness to a landfill tie-in on the Isle of Walney, across a tidal stretch of water. Testing was to be carried out on approximately 6.8km of 24” diameter steel gas pipeline, together with a 3” condensate return line. The pipelines were tested in two phases: terminal to boundary fence in May 2003, and from the beach at Walney to the boundary fence tie-in in August 2003. The beach section was filled with seawater which had been dosed with a cocktail of biocide, corrosion inhibitor and oxygen scavenger. Due to the shallow beach and tidal range, the HTC team installed extraction pumps, each with 700m of suction. The quantity of sand in the available water was found to be a problem.

Nigel Kirk , the construction manager employed by Van Oord during the project, was impressed with the way this was solved by HTC. He said:

"HTC responded quickly to this challenge and sourced a specialist mud-shaker to remove sand and seaweed before pumping it into the pipeline. Within 48 hours the shaker was with us, set up and doing the job."

On completion of testing, the pipelines were left full of treated seawater prior to the final tie-ins to the offshore and terminal sections.

"The HTC team was fully committed to getting the job done and the project was completed successfully" said Nigel Kirk.
"They're a really good company to work with. They've never let me down and I would most definitely use them again."


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