A key component of the pump, the impeller uses centrifugal force to distribute the cooling water, with the eye at the centre of the impeller sucking the water up into the structure. It is a vulnerable transition piece due to the high volume of abrasive seawater travelling through at force, as well as its external location underground. Damage had occurred to the surrounding concrete and leaks had formed, compromising the efficiency of the pump.
The work had to be completed during regulatory mandatory maintenance periods planned with the National Grid to ensure minimal disruption to the supply of more than two million homes a year that depend on the station for electricity.
Our experienced concrete repair team has worked with EDF for over 20 years and we carefully planned our programme of concrete repair, concrete coatings and leak sealing to co-ordinate with the other works taking place during the nine-week shutdown. It was essential that the timescales and budgets were met and the project delivered to a high standard.
The first task was to assess the structure for concrete damage. The magnesium sulphate naturally found in seawater attacks concrete by reacting with the hydrated compounds found within the hardened cement. These chemical reactions cause pressure within the concrete that disrupts it enough to reduce cohesion, strength and ultimately, erosion. Concrete is naturally absorptive and so the constant conditions of wetting and drying mean the sulphates are continuously pulled through the mortar.
Our team assessed the concrete seal and concrete components along the pipe for damage and repaired with Intercrete concrete repair products from our partner supplier Flexcrete. With outstanding high-strength and waterproofing qualities this mortar repair solution provided excellent abrasion resistance for this structure.
Leaks were sealed using Tampur 100, a hydrophobic resin injection that produces a rigid polyurethane foam when coming into contact with water. This product was chosen due to its excellent qualities in reacting with saline water, high expansion ratio and excellent chemical and biological resistance.
The work was overcoated with Irathane Aqualine 400 (polyurethane coating) which was hand-applied by our specialist team. This product is a two component polyurethane, specifically designed for use as an external water proofing membrane with good abrasion resistant properties for water containing structures. Its manual application allows it to be used in difficult-to-access sites and it has outstanding elongation properties, meaning future cracks stay well protected.
Where required, we used our specialist dustless abrasive blasting system to prepare and key the surface for correct adhesion of the coating.
As with all our large-scale projects, our directors Mark and Mick remained on site throughout to oversee the work and ensure delivery points were met.
All CSC operatives undergo regular training to ensure their knowledge and qualifications are up-to-date and are Confined Space and Water Jet Association qualified. The employees who worked on this project were also NVQ-level 2 qualified in concrete repair.
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