New for old strainer wheel refurbishment
Methods
New for old strainer wheel refurbishment
Keywords Coatings,Corrocoat, Marine corrosion, Power plants, Sea water
Corrocoat have completed a major refurbishment project on two ten foot diameter cast iron strainer wheels in use at BNFL Magnox Generation's Bradwell Power Station in Essex (Plate 8). The total cost of the project was just £50,000 a fraction of the proposed replacement cost for the two units.
Plate 8 Work in progress on the refurbishment of one of the ten foot diameter
cast iron strainer wheels, including repairs to damaged shafts and reprofiling of filter locations</FONT
The strainers are used to filter incoming cooling water from the seawater estuary, of the River Blackware. Each has a rotor weight of eight tonnes and a shaft length of nine feet.
The contract called for removal of the filter plates and all associated fixings. The exposed cast iron wheel framework was then gritblasted, pressure washed and inspected to ascertain the extent of the corrosion damage.
The prepared areas were then coated using Corroglass 200 series materials, Corrocoat's own flake glass filled polyester coating, developed for applications where good corrosion,abrasion and mechanical resistance is required. Areas of deep pitting were filled and reprofiled using Corroglass 202, and the surface was then coated to a minimum dry film thickness of 1.5mm.
Following this work, the filter locations were repaired, rebuilt and reprofiled using similar techniques and materials. The filter plates were cleaned using high pressure washing, and then replaced. Missing and badly damaged places were substituted with replacement units.
The Corrocoat team then removed the gear teeth on the outside circumference of the strainer wheels and refitted these so that the unworn face presented for operation.
Repairs were also carried out to damaged shafts, including machining new lands and manufacturing new sleeves and nuts.
The strainer wheels are now back in operation at Bradwell Power Station.
Corrocoat are also enjoying a very visible position on England's south coast, with stretches of the company's Polyglass 100 material giving added protection to a section of the sea defence wall (Plate 9).
Polyglass 100 was first used on Dover's sea wall, on the Marine Parade, back in 1996. Here, evidence had shown that the concrete thickness over the re-bars in the sea wall was insufficient for the 120 year design life of the structure.
Plate 9 A section of the Marine Parade at Dover, where sea wall has been treated using Corrocoat's Polyglass 100 coating system
A number of companies were requested to apply their coatings to a test area of the wall, and these were then evaluated over a period of time. Polyglass 100 was selected as the most suitable material in terms of performance potential, including abrasion resistance.
Dover's recurve sea wall is a wave deflector design. The scope of work involved grit blasting some 600ft2of the face of the wall, removing surface laitence and producing a lightly abraded finish.
All pitting was then repaired using Corrocoat's own Corrofill filler materials, and the area was coated using the company's PPA primer, a moisture tolerant flake glass filled acrylic/polyester system.
Multiple spray applied coats of Polyglass 100, Corrocoat's own isophthalic polyester flake glass system, were then layered to achieve a minimum dry film thickness of 3mm.
Following the success of this project, when Kent County Council acting as agents for the Highways Agency recognised the need to apply a protective coating to the retaining wall on Sandgate Esplanade, Folkestone, the Corrocoat team was again commissioned. Here, the task involved a similar project, to coat the seaward side of the road retaining wall face and top.
Details from: Corrocoat Services Ltd. Tel: +44 (0)113 276 0760; Fax: +44 (0)113 276 0700; E-mail: enquiries@corrocoat.com Website: www.corrocoat.com
