COATINGS
of colour to the network
“Whilst we have internal Network Rail standards, we tend to work to British standards when removing or applying paint”
In the majority of cases structures are blasted back to a standard called SA2.5, which is a clean, bright and almost mirrored steel with either very limited or no pitting in the steel.
“This means you don’t get any black spots or pitting corrosion.
“This also gives us a good level of substrate preparation prior to the application of a new paint system, whilst also giving a good profile for adherence for the new system.
“We mandate with our Network Rail specification that we apply, at the very least, a holding primer to the structure within four hours after cleaning the structure to SA2.5. This ensures we have the right preparation of substrate, which means we are going to get at least a 25 year lifespan from the paint system.”
When the teams come up against either a very large or complicated steel structure - which means they would not be able to apply holding primer within four hours - they will blast the steel down to SA2.5 and then carry out a flash blast.
do is scaffold and then environmentally wrap the structure, which provides a sealed environment in which you can contain lead contaminates. We can also introduce forced ventilation into that environment, which then goes through dust extractors and then skips in order to remove any harmful substances from the air.”
This also collects the blast media which engineers use to remove the paint and then the skips are taken away to be disposed of.
“We tend to use dry blasting for all of our structures, because
“ We tend to use dry blasting for all of our structures, because not only is it easy to manage the waste afterwards, but it also provides us with a good blast profile on the asset afterwards”
not only is it easy to manage the waste afterwards, but it also provides us with a good blast profile on the asset, which is crucial for adherence of the new paint system when we come to apply it.”
The teams who are carrying out this work will also be issued with the appropriate breathing apparatus.
“They are also subject to health monitoring, noise control and controlled trigger time on the blast pots. They are also subject to decontamination when they leave that environment.”
“This is where the team just would not be able to get the primer on in time, so we allow the clean steel to go ginger again and then we flash blast it, going over the top where you previously worked to take off any corrosive material and then to apply the initial holding primer.”
The team will have chosen to use either a three, four or five coat system. Once this system has been specified, the contractor will apply that paint system in accordance with the manufacturer’s recommendations.
rail technology magazine Dec/Jan 11 | 27
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