Wessex Water Codford: Pressure Filter Coating Removal and Relining
Specialist Painting Group carried out a critical project at the Wessex Water Codford site, removing and replacing the coating system inside the site’s pressure filters. The original coating had failed completely, so SPG removed it, prepared the steel to Sa 2½ and applied new internal potable water lining and external protective coating systems to all seven pressure filter vessels.
Table of Contents
Why the Original Coating Failed
The original coating had experienced 100% failure, mainly because of poor inter-coat adhesion, which led to delamination and localised corrosion. Stress cracking made the problem worse, most notably on the plenum floor within each pressure filter, and was likely caused by over-application of the coating.
The existing coating was found to be 5mm thick and applied in multiple layers, with poor adhesion between them. This pointed to inadequate surface preparation before the original coating was applied, a reminder that even a thick coating will fail if it is not properly bonded to the steel and to each previous layer.
Removing the Defective Coating at Wessex Water
SPG operatives used a combination of mechanical tools and dry abrasive blast cleaning to remove the defective coating system completely. The plenum floor was prepared mechanically first, which reduced the quantity of blast media needed and allowed the required standard to be reached more efficiently.
All surface preparation met the specified BS EN ISO 8501-1 Sa 2½ standard. Learn more about our abrasive blast cleaning service.
Measuring Surface Cleanliness and Profile
Precision was maintained throughout. An Elcometer grit comparator was used for visual surface assessment, and an Elcometer surface profile needle gauge measured the surface profile. Checking both cleanliness and profile before coating gives confidence that the new system will bond properly and avoid the adhesion failures seen in the original coating.
New Linings for Seven Pressure Filter Vessels
An internal potable water lining system and an external protective coating system were applied across all seven pressure filter vessels, which have since gone into full commissioning. The work supports the longevity and reliability of the water filtration system at the Codford facility. Find out more about our tank linings service.
Coating Work in Potable Water Assets
Linings in contact with drinking water must be suitable for that use, and the Drinking Water Inspectorate oversees materials used in public water supply in England and Wales. Careful specification, preparation and inspection are essential to protect both the asset and water quality.
Choosing the Right Surface Preparation Method
No single surface preparation method suits every job. Abrasive blasting, UHP water jetting, mechanical preparation, CO2 blasting and RPR heat induction each have strengths depending on the substrate, the coating being removed and the environment around the work. On the Wessex Water pressure filters, the method was chosen to suit the structure and its setting. Assessing these factors early helps avoid delays and reduces risk once work begins. Our coating inspection team can help assess existing linings before work is planned.
Planning a Coating Project
Every successful coating project starts with understanding the condition of the existing coating and the steel beneath it. A survey identifies where the coating has failed, how far corrosion has progressed and whether the old system can be overcoated or needs to be removed completely. That information shapes the choice of surface preparation method and the new coating specification.
SPG supports asset owners through each of these stages, from coating inspection and specification advice through to preparation and application. Projects such as the Wessex Water pressure filters show how the right plan, agreed at the outset, keeps work safe, efficient and on programme.
Why Choose SPG
Specialist Painting Group has delivered industrial coating projects since 1997. Our operatives are ICATS certified, and we hold RISQS, SafeContractor, ISO 9001, ISO 45001 and ISO 14001 accreditations, giving clients the competence, safety management and quality systems they expect from a specialist contractor.
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