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Copyright © 2001, MCB UP Limited
Protection for Suffolk silos
Protection for Suffolk silos
Keywords Winn & Coales (Denso), Corrosion prevention, Coatings
Ardex UK Ltd is carrying out a refurbishment exterior coating programme on eight industrial silos at its Haverhill, Suffolk, premises. Looking for a long-life system, they have chosen Winn & Coales' Denso ST Epoxy followed by a topcoat of Denso Weathershield gloss which they specified to RAL 7000 colour.
The silos, which contain materials used in Ardex's exclusive range of tiling and flooring products, have an average height of 25 metres. This called for application of the Denso coatings by specialist contractors, Altico Services Ltd, using rope access techniques recognised by the Industrial Rope Access Trade Association (IRATA). After removal of all loose coating and surface preparation, Altico applied two coats of Denso ST Epoxy followed by the Denso Weathershield gloss coat, including on surrounding structures, such as roofing, flooring, pipework etc.
Denso ST Epoxy is described as a mastic coating with exceptional adhesion properties. It can be spray or brush applied to deliver long-term protection in a wide range of corrosive environments.
Weathershield is a urethane based material to give extra protection, particularly to prevent chalking after exposure to sunlight.
In another project reported on by Winn & Coales oily water drainage from the tank farm area at BP Amoco's Sullom Voe Terminal in the Shetland Isles, plus on occasion ballast water from shipping, is separated, chemically treated and filtered before passing through an effluent pumping system for discharge into the sea via an 890mm diamter outfall pipe system. At this stage there is a very low oil content and the discharge and oil in water levels are monitored in accordance with SEPA (Scottish Environmental Protection Agency) discharge regulations – typically below 5 ppm.
A few years ago a number of Viking Johnson Couplings on the buried GRP section of the effluent discharge pipeline had suffered from corrosion due to acidic ground water attack. The couplings failed at the centering guide plugs. To ease installation, a different coupling was chosen for repair, but these too failed due to hydrogen induced stress corrosion cracking of carbon steel tensioning bolts.
BP Amoco's maintenance engineers decided to revert to the original specification for the VJ couplings when the terminal was first completed in the late 1970s.
This specification recommended a number of proprietary anti-corrosive pastes and tape wrapping systems, including Winn & Coales' Denso materials.
According to Winn & Coales, because of the Denso track record in such locations, BP chose Denso Paste, followed by Denso Profiling Mastic, to smooth all contours before applying Denso Tape.
The Denso materials are being applied to the couplings and adjacent pipe areas by local Civil Engineering Contractors, Nicolson Plant. Denso Tape is a woven synthetic fibre fabric impregnated and coated with an adhesive compound based on petrolatum.
Details are available from: Winn & Coales (Denso) Ltd. Tel: +44 (0) 20 8670 7511; Fax: +44 (0) 20 8761 2456.