30,000 nozzles at the ready!

Published:  04 March, 2016

The world’s largest water-mist system is being installed in a new hospital in Denmark – and the solution is expected to save the hospital millions. Jose Sanchez de Muniain reports.

The existing hospital in Aarhus, central Denmark is Skejby Hospital, a large university hospital which has for the last eight years running been voted Denmark’s best university hospital. When it first opened in 1988 it was considered one of the most modern and well equipped in Europe.

A significant extension to the hospital is currently under construction by MT Højgaard which will add 220,00m2 to the current 160,000m2 of floor area. Once complete, the new hospital will be the biggest workplace in Aarhus municipality with more than 9,500 staff and around one million patient treated annually.

The vision for the new hospital, which is scheduled for completion in 2019, is to become a leading university hospital with a balance between efficiency, sustainability and an attractive working environment.

When planning the new project, rather than installing a traditional sprinkler system, Skejby Hospital decided to install a 20 million-euro high-pressure water mist system supplied by Danish company Danfoss Semco.

Interestingly, according to Danfoss Semco country manager Lasse Sørensen Laustsen (pictured above), even though the cost of the sprinkler system is comparable to the cost of the water mist solution, the use of water mist will translate to significant savings for the project. In fact, he believes that the contractor could be saving as much as €11.4 million in related construction activities and materials, which include less insulation in ventilation shafts, less fire glass and fewer chimney dampers and fire doors.

To understand these savings it is first necessary to look at how Danfoss Semco high-pressure water mist works, explains Laustsen: ‘We all recognize the little nozzles which hang down from the ceiling in offices, cinemas, hospitals, and elsewhere. If fire breaks out, water is sprayed over the fire, and everything is covered in water. This is a conventional sprinkler solution.

‘But Danfoss Semco offers a gentler way: to the untrained eye the nozzles look the same but they cover a larger area, so there are fewer of them. And they are connected to a high-pressure system that - in response to a fire - vaporises the water which then covers the flames like a fog. This means that far less water is needed; from a third to a tenth the quantity depending on the system. And secondly, the Sem-Safe high-pressure water mist causes the heat generated by the fire to drop dramatically – which is precisely why major savings are obtained with the high-pressure water-mist solution.’

Because water mist is so much more successful at cooling the fire than sprinklers, the resulting temperatures are much lower so less insulation is required around ventilation pipes. In addition, less costly types of fire glass are needed to prevent fire spread into surrounding areas.

‘In the construction of hospitals with limited space for technical installations, the high-pressure water mist installation is the optimal choice. It means major savings on building components, increased flexibility, and greater architectural freedom of scope,’ confirms fire advisor to the Skejby Hospital project, Kenneth Jaquet from Rådgivergruppen DNU.

In fact, as many of the steps of the construction process can be executed differently through the use of water mist, Danfoss Semco and DNU Rådgivergruppen started working together from the very beginning, with the intention of getting the best results possible for Skejby Hospital.

The result includes, for example, installing circles of nozzles in the walls and in the ceiling at strategic areas in the hospital’s long connecting corridors rather than fitting fire doors. When activated, these nozzles are designed to create a curtain of water mist that isolates  heat and smoke in the restricted area.

So far, around 15,000 water mist nozzles have been delivered to the site for installation by Danfoss Semco’s partner - and Denmark’s largest installation company - Kemp & Lauritzen, and another 15,000 are on their way.

Managing the plumbing, heating and sanitation contractors installing the system is Preben Christensen, project leader for Kemp & Lauritzen, who outlines some of the benefits of the high-pressure system for this type of project: ‘The pipe diameter is much smaller, and this means that the installation time is much shorter. With a sprinkler system, it takes two to three people to lift a pipe. Here, only one person is needed. Bends are easier to do and it is also easier to make the pipes fit under the ceiling.’

Ease of installation and cost savings aside, there are other benefits for the new university hospital. Should a fire occur, the first arriving firefighters – or other trained personnel – will be able to make use of special hose cabinets connected to the high-pressure system. Firefighters will thus be able to quickly tackle the fire even before laying out their own hose, which could take several minutes.

Hospitals such as Skejby make up one of the markets which Danfoss Semco has identified as being of particular interest, says Laustsen. The company has already installed Sem-Safe high-pressure water-mist systems in several other hospitals in Europe and expects the new extension for Skejby Hospital will open up the door to further projects. ‘This places heavy demands on visionary consultants to obtain correspondingly large savings as in this case. For us, it is about getting in contact early with the consulting engineers and the architects,’ concludes Laustsen.

  • Operation Florian

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