Specialist lining equipment is inserted into pipe opening. Photo by WRc
Click here to enlarge imageThe company sought the advice of the WRc, an international water and environmental consultancy from the United Kingdom, which carried out a condition survey. This investigation revealed severe internal corrosion and only six years of useful life remaining. An early solution was needed to avoid pipeline failure and power loss.
The two options were replacement or refurbishment but the location made replacement difficult and costly. The feed water pound is located in the mountains some 285m higher than the turbines, and the pipes run down the side of the mountain at a gradient of up to 1 in 1.4. The only access is by a cable railway, which runs to the mountaintop and is suitable for the light loads of a rehabilitation project.
Experts from WRc Rehabilitation Division examined the pipes and concluded it was possible to fully renovate them, despite the high operating pressure of over 30 bar and surface temperatures in excess of 40°C. The method chosen was to clean the pipelines internally and then apply a resin lining.
WRc designed and supervised the operation, which was carried out by a South African specialist company, John Davies Pipeline Services CC. One of the main technical difficulties was preparing the corroded pipe internally to obtain a satisfactorily clean surface on which the resin would bond. The large pipe diameter and high operating pressures require a good bond.
The technicians cut openings in the pipes to insert the specialist lining equipment. The internal surfaces were first cleaned using automated grit-blasting equipment to obtain the high quality finish needed for successful reinstatement, and then the pipelines were given a final wash to remove debris.