Gade Valley Viaduct

Specific risks associated with this project include working at heights, working in confined spaces, abrasive grit blasting, ultra high pressure jet washing and paint application by spray methods. All of our site personnel were selected to take account of these particular skill set requirements. Access to the work areas is via fully fixed scaffold supplied by Geoffrey Osborne Ltd who have also supplied a blast booth integral to the scaffold. New plates required for the strengthening process are lifted up to the blast booth by means of a mobile scissor lift trolley and positioned using a lifting magnet. The plates are then grit blasted, removed from the blast booth and placed where needed in the structure, ready for painting.

The specifications are as follows:

Stiffener Plate Installation – Designated External Areas

• Debris netting and hessian matting erected for containment purposes
• All surfaces cleaned to remove any traces of grease and contamination
• Burrs ground down to be suitable for primer application
• Areas of existing coatings fully removed where required by UHP water jetting to expose original SA3 standard with a medium profile
• All prepared areas visually examined with an illuminated magnifier to ensure no traces of thermal metal spray remain in profile troughs
• Salt levels checked using Elcometer 130 salt contamination meter
• New plates checked to ensure they have a radius on all edges and are blast cleaned to SA2.5
• Existing surfaces flash blast cleaned
• During plate installation a heavy brush coat of Jotamastic 90 Aluminium is applied around the mating face of the new plate immediately prior to installation
• Once plates are fitted, apply full coat of Jotamastic 90 Aluminium and check dft readings for QA conformity
• Apply Jotamastic 90 stripe coat to all edges, welds, fixings, etc and take wft readings
• Apply Jotamastic 90 intermediate/build coat to all surfaces and check dft readings
• Apply Hardtop XP finish coat to all surfaces and take dft readings

Stiffener Plate Installation – Designated Internal Areas

• All surfaces cleaned to remove any traces of grease and contamination
• Preparation by rotary wire brush to provide a key for subsequent coats
• Apply 2 coats of Jotamastic SF intermediate/build coat to all surfaces, taking dft readings between coats

Full Bottom Flange, Webs & External Portion of Top Flange – Designated External Areas

• Debris netting and hessian matting erected for containment purposes
• All surfaces cleaned to remove any traces of grease and contamination
• Areas of existing coatings fully removed where required by UHP water jetting to expose original SA3 standard with a medium profile
• All prepared areas visually examined with an illuminated magnifier to ensure no traces of thermal metal spray remain in profile troughs
• Salt levels checked using Elcometer 130 salt contamination meter
• Apply primer coat of Jotamastic 90 Aluminium and record dft readings
• Apply Jotamastic 90 stripe coat to all edges, welds, fixings, etc and take wft readings
• Apply Jotamastic 90 intermediate/build coat to all surfaces and check dft readings
• Apply Arbokol 1000 Polysulphide sealant to designated areas between the concrete and steel interfaces
• Apply Hardtop XP finish coat to all surfaces and take dft readings