HVC snail crane

Sturdy and prominent in the Alkmaar landscape is our waste-to-energy plant. Here we have been processing residual waste from our municipalities since 1995. But this does not happen by itself. To keep the plant running, proper maintenance and replacement of parts are necessary. Invisible to many colleagues, behind the striking red walls of the building, a true feat is accomplished. Project leader Nico Groen tells how the great efforts of the team, made up of specialists from the supplier EPMC and technicians from the in-house maintenance department, helped to replace the slag tap last week.

Automatic faucet

What is a slag tap and what does it do? When you burn waste, you are left with slag (bottom ash). This still contains parts of iron, for example. The ash goes from the combustion grid into a container with water to cool. All bottom ashes then end up in a bunker. An automatic crane with a grab (snail crane) then transports the ash to a screen to screen out the coarse parts. This crane did its work from 1995 and was at the end of its life.

Deployment of shovel

'All together it takes 8 weeks to dismantle the crane and replace it with a new one,' Nico explains. 'You can't schedule that in a maintenance stop, but it has to happen during the running operation. From the start of the disassembly, the day shift crew had to haul away all the bottom ash 24/7 with a shovel. Because the shovel was driving back and forth, a moving work platform had to be made to replace the rails, on which the crane hangs. The platform was made specifically for this job.'

New techniques

The new crane with cab is equipped with the latest technology. When we purchased it, we took the experiences of our colleagues into account. 90% of the time the crane does the work automatically, the other 10% an operator operates the crane, for example, to remove large pieces of iron separately from the bunker. A lot of attention has been paid to the quality of the crane and cabin. Nice is the coating that protects the crane and cabin from corrosion. The technology has also been greatly improved. Instead of thick cables, we now have a thin package of cables, because we use fiberglass,' Nico says.

Proud

Nico is proud of the team who completed the job with great precision. He cites an example. 'It involved 2 x 85 meters of rails that we had to replace. With the driving platform you could do 6 meters at a time, before it drove on to replace the next section. When the rails were finished, the platform was removed and the new crane cab was put up. There was very little room to work in. It was fitting and measuring to mount the crane in it, a clever piece of work we can be proud of.' In the coming weeks we will test and adjust the crane so that it is ready for the coming years.