Special Straub pipe couplings for the wastewater treatment facility in Singapore.
Since 2001, Singapore, a city spreading over 650 km2, has been planning and constructing a new centralised wastewater treatment facility. Connection problems arose when it came to joining the over 3-metre diameter sewerage tunnels into the distribution system.
Due to construction tolerances, the axes had been shifted by up to 45 mm, and the ends of the pipes had been deformed by initial efforts to connect them up. To ensure that the construction schedule was not put in jeopardy, it was necessary to quickly find a new connection solution.
Problems with construction tolerances during connection to the new installation The wastewater influent tunnel to the Changi Water Reclamation Plant is almost 4 metres across. This made it virtually impossible to avoid a certain construction tolerance, and at the point of link-up to the installation, there were axial deviations of up to 45 mm.
Following initial attempts at welding, the engineers from the company coordinating the project, CH2M HILL of Washington DC, quickly realised that it would not be possible to stay on schedule using conventional means to connect the sewer in-feed to the installation. There was also the risk that the heat generated by the welding process would destroy the internal cement coating.
Exacerbating the problem of bridging the axial offset was the fact that the extremely uneven pipe ends and tensions in the pipe system also had to be taken into account. Thus, a problem had developed that threatened progress on the construction of the entire facility.