The Van Don district in the north-east of Vietnam belongs to the province Quang Ninh, about 150 km east of Hanoi. The province is home to Hạ Long Bay, a World Heritage with 1,969 islands. Three quarters of the province are mountainous and they have abundant land, forest, water and mineral resources.
In this beautiful scenery, network operator Quang Ninh Water Company (QUAWACO) is operating a DN 300 steel water main located underneath and inside a bridge construction to supply Van Don Island with drinking water. The three single bridges have individual lengths of 410 m, 170 m and 270 m. The pipes were originally installed in 2002 with construction of the bridge. Corrosion and securing the water quality induced the water network operator to a preventative maintenance of these steel pipes.
The goal of the renovation works was to elongate the life span of the pipes and secure the water supply. Because of difficult access and in order to quickly upgrade the existing pipe, the Primus Line® system was the preferred method. It was the first deployment of the Primus Line® system in Vietnam.
In order to install the Primus Line® system, only a small investment in necessary tools was required. In addition, the training for the contractor was performed locally in two working days by a Primus Line instructor. During the same week, the contractor renovated the first bridge under supervision of this instructor. QUAWACO proactively manage the water supply in their region and have reduced the non-revenue water rate below 18% over the past couple of years.
In a first step, the pipe was CCTV inspected to assess the condition of the host pipe. 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. Due to the complex accessibility of the steel pipe underneath the bridges and inside a box girder, the welding seams were removed manually.
The contractor performed mechanical cleaning of the host pipe using scrappers and rubber pigs. The 840 m of liner were delivered pre-folded into U-shape on timber transport reels directly to the site. A pulling wire was mounted to the start of the liner and connected to a rotation joint and subsequently to the cable of a pulling winch. The liner could be installed in less than one hour for each section and was re-rounded using compressed air. The end fittings equipped with DIN flanges PN 10 were mounted. The renovated section was successfully pressure-tested using potable water with 9 bar. 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. Thus, the water quality and supply are secured.
