Cleaning Sydney Harbour Bridge with robotic lasers

The Canberra Times

Canberra engineers devise amazing new way to preserve Sydney Harbour Bridge. Footage Physics ANU

Transcript

00:00So the purpose of this project is to use lasers for cleaning dirt and rust from the surfaces

00:08of Sydney Harbour Bridge.

00:13That's like the most iconic building in Australia.

00:16It's amazing.

00:17So when you're like an international student and you come here and it's just like the fireworks

00:20at night you see, so it's amazing to be actually part of restoring this bridge.

00:27The surfaces which you see outside, they are reasonably in good shape and in good condition.

00:34The problem is with the internal surfaces of the channels the bridge is built of.

00:40The length of the channels is about 7.2 kilometres.

00:44The bridge has about 6 million rivets and rivets are made of different kinds of steel

00:50so there could be some corrosion between the rivets and the main construction of the bridge.

00:57So it's a huge job.

00:58The problem with the channels is that they are relatively small and non-human passable.

01:04The standard method for cleaning paint is to use sandblasting and in such an enclosed

01:10space it's basically impossible to know what's happening.

01:14So we need to build a robot which will have the laser head on top of it so it can crawl

01:20on the bridge and clean every part of the bridge and even the difficult area.

01:36This new generation of laser uses femtosecond laser pulses.

01:40This means that they are ultra-short, they are just a millionth of a billionth of a second

01:43long.

01:44These ultra-short pulses, they let us ablate the material with no heat introduced into

01:49the steel for example.

01:50That means we are in a cold ablation machine and this means there's less energy wasted

01:55and we can have a very effective process.

01:57So this is the original bridge with the paint on it and when we laser clean it, this is

02:02how the result looks like.

02:10I'm working on cleaning the granite cladding of the pylons of the Sydney Harbour Bridge.

02:15So we are looking at the highest energy that we can apply without removing material from

02:23the surface.

02:24It's a difficult aspect because our granite is a complex material so what we have been

02:32doing is focusing on the black minerals because they are the most sensitive ones.

02:43So during this project we put a lot of effort into the testing of the materials after they

02:48have been exposed to the laser using pretty much every technique we could think of and

02:52lay our hands on.

02:53And we have developed a process that doesn't seem to damage either the bridge steel or

02:57the granite itself and that's a really important outcome.

03:01We are looking to move towards deployment, the world's first portable femtosecond laser

03:08cleaning system.

03:09This is quite a large engineering challenge.

03:12The top of the bridge could be 40 degrees air temperature, high humidity, solar radiation

03:17coming down as well.

03:19The laser was never designed to operate in that environment.

03:22The laser itself is not actually on the robotic device itself so we have to find a means to

03:29deliver the laser beam from the gantry where the laser is mounted and we then have to feed

03:34it down to the cleaning head on the front of the robot.

03:38At some points on the bridge you may have to drop 50 metres from the gantry down to

03:43the lower arch and then go into the arch and this is not a solved technology today.

03:49I think that there should be several robots.

03:51One robot is cleaning, another robot is sucking all the stuff which was cleaned and the third

03:57one is putting some layers of paint so they could go one after another.

04:0410 kilowatt level lasers would do the job in 3-5 years, but they have to work 24 hours a day.

04:18I really enjoy the fact that we are applying the lasers on heritage materials.

04:23I think that's pretty cool.

04:27The strange thing is you go up there and you stop looking at the view and you really start

04:32to appreciate the engineering in the bridge.

04:34The historical connection with the engineers of the past who spent so much time trying

04:39to work out how to make this thing work and we're now like the caretakers who've got to

04:44carry it forward for the next set of generations to marvel at.

04:49It's a really satisfying and pleasurable thing to do.

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