The Van Don district in the north-east of Vietnam belongs to the province Quang Ninh, located approximately 150 km east of Hanoi. The province is home to Hạ Long Bay, a World Heritage site with 1,969 islands.
In this sensitive landscape, network operator Quang Ninh Water Company (QUAWACO) operates a DN 300 steel water main located underneath and inside a bridge construction to supply Van Don Island with drinking water. The three bridges have individual lengths of 410 m, 170 m and 270 m.
The steel pipes were originally installed in 2002 with the construction of the bridges, while corrosion and water quality security induced the water network operator to undertake preventative maintenance.
The goal of the renovation works was to elongate the life span of the pipes and secure the water supply. Due to its difficult access and a desire to quickly upgrade the existing pipe, the Primus Line® system was the preferred method.
As the first deployment of the Primus Line system in Vietnam, the liner’s use was the idea of QUAWACO’s Chairman Nguyen Van Thanh, who was first introduced to the trenchless rehabilitation technology at Vietwater 2018 where he met Primus Line’s Australian representative.
At the time, the Australian and Vietnam Water Association had begun a twinning program and Vietwater was a central platform for knowledge sharing. In order to install the Primus Line system, only a small investment in the necessary tools was required.
Additionally, a Primus Line instructor performed a local training for the contractor in two working days and, during the same week, the contractor renovated the first bridge under this instructor’s supervision.
QUAWACO proactively manage the water supply in its region and has reduced the non-revenue water rate below 18 per cent over the past couple of years.
The process
To begin, the host pipe was CCTV inspected to assess its condition,, and this inspection revealed several areas where incorrect welding seams were protruding into the cross-section of the pipe. The individual pipe shots were butt-welded and, due to the complex accessibility of the steel pipe underneath the bridges and inside a box girder, the contractor’s team removed the welding seams manually.
The contractor performed mechanical cleaning of the host pipe using scrappers and rubber pigs as the 840 m of liner was delivered pre-folded into U-shape on timber transport reels directly to the site.
The contractor mounted a pulling wire to the start of the liner and connected it to a rotation joint and subsequently to the cable of a pulling winch, allowing the liner installation to take less than one hour for each section.
Afterwards, it was re-rounded with compressed air before the contractor’s installation team finally mounted the end fittings equipped with DIN flanges PN 10. The renovated section was successfully pressure-tested using potable water with 9 bar and the pipe was reintegrated into the network using HDPE pipe shots.
The whole renovation was completed after three weeks and extended the asset’s life by 50 years, therefore securing both the water quality and supply.
This article was featured in the June 2020 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.
For more information visit the Primus Line website.
If you have news you would like featured in Trenchless Australasia contact Journalist Sophie Venz at svenz@gs-press.com.au