Out of the tunnel of the dust

Supplied by idrotech the dust prevention system that has allowed to dig safely and cleanly the exploratory tunnel of the brenner base gallery.

There is Idrotech hand with its twenty-year experience pertaining to the design and construction of fogging systems in the important yard of the Brenner base gallery in "Alto Adige" (Tyrol), and in particular in the excavations of the exploratory tunnel. With its 55 kms, the Brenner tunnel will be the longest railway tunnel in the world, it will start from Innsbruck in Austria to arrive in Italy at Fortezza, in the self-governing province of Bolzano, allowing to halve travelling time of goods and passengers trains between Munich and Verona (from six to three hours). Works began in April 2011 and should be completed by 2020. This work is part of the so-called "Corridor 1" that in the "TEN" plan (Trans European Network) will connect Berlin to Palermo becoming an important link for transporting of goods on long distances.

In this context the excavation of an exploratory tunnel was necessary beneath the future track of the two railway tunnels to collect information about the hydrogeological characteristics of the soil. Excavation works, located approximately 1500 meters deeper than the Alca-Mules exploratory tunnel (that during the construction of the base tunnel, 10.450 meters long, will be used for the transport of muck and for drainage), have produced since the very beginning so much dust to make professionals’works extremely difficult and dangerous. Hence the need of the manufacturing company to get in a supply of a fogging system capable of removing dust in order to have the possibility to work more efficiently, thus safeguarding the health of workers too.

The system supplied by Idrotech, a company of Idrobase Group in Borgoricco (Padua) was designed by dividing the areas to be treated by the fogging system in several sectors, grouped into two macro-areas and served by two distinct fogging lines. And according to Seli, the company that dug the tunnel, it really worked.

Fog in the yard

A double fogging line, we said: the first line has been used for dust suppression during the excavation works and transport of materials, while the second line has had the dual task of stiffling dust sources under the conveyor belt as well as those still suspended in the air. The first line went into service contemporaneously with the conveyor belt, or with the release of the excavatedmaterials 154 is the number of nozzles used for the high line. In this way the plant has led into the surrounding area very thin micronized particles of water at 100-bar pressure and 21-liter/minute flow rate. The second line has worked according to the adjustable pause / work device by using 216 fogging nozzles at 100-bar pressure and 25-liter/minute flow rate.

Both plants, which have worked with drinkable water, have been equipped with a filtering system capable of stopping any bacteria with a nal absolute ltering power of 0.2 microns. These lines can be easily installed also on mobile equipment such as machines for the digging sector or even the "moles" (as happened in this yard), the huge milling cutters used to open underground galleries.

Seli: contractor and manufacturer

Founded in 1950, Seli is a company specialized in underground excavations, whose growth during the last years allowed it to be placed among the first companies in the world in its sector. Today the company boasts an unusual position: contractor and manufacturer of equipment at the same time. In Seli workshops all TBM "moles" are indeed designed and built together with excavation equipment and back up systems used to dig galleries.

Idrotech

It was founded in 1995 as the natural development of the Idrobase industrial division to better supplying appropriate answers for the specific needs of well-definite clients. The company manufactures fogging systems, set in action by one or more pumps, which convey inside polyamide or stainless steel lines (pipes), pressurized water (60/120 bar) that emerges as a mist composed of very thin water drops from nozzles that are placed on the same lines. Idrotech also produces the classic dust suppression fog makers, with a range up to 60 meters.

Fogging lines

The peculiarity of these systems is the ability to "operate" on the dust source, their very low water consumption, the great capacity of the fog produced (thick) to make dust fall down, they do not produce any rivulet on the ground (water droplets are so fine as to create humidity only). Dust sources can be conveyor belts in mining facilities, hoppers, conveyors, grinding machines and mills. The lines can even be put on buckets of rubber mechanical diggers or digging machines, exploiting the hydraulic system of the same vehicle.

Interview Aristodemo Busillo Seli Technical director

"Which is the need you asked Idrotech to satisfy?

The rock mass with which we had to deal, consisting of granite from "Bressanone" (Brixen), typical of the area, that proved to be very hard and compact, as well as tending to be dry for long stretches, therefore not very suitable to be milled. The TMB has thus started to produce a huge quantity of rock since the action of demolition of the cutting head required a lot of energetic work in terms both of turns and pushing. Then, if we add that the entire system of extraction is done via belts, with continuous pouring in subsequent hoppers, we can realize that the dust problem was almost everywhere in the tunnel. The requirement then arose from the need to reduce the ying dust in the tunnel, from the excavation space to the tunnel itself, since the turbofilter tearing machine was not able to perform the task. Our on-site safety of- cer has so ordered us to verify a solution to improve the quality of the air in the tunnel.

How was the project of the plan developed and which was the balance of the provision?

We usually use after the units some portals to nebulize, which work more or less as antismoking walls. Here the need was certainly different. Along with Idrotech we did a search to locate specific fogging equipment that could be distributed on the TMB, all along the belts, and on pouring hoppers. I have to say that in a month and a half we have moved from the conception to installation and that the equipment supplied by Idrotech has de- nitely been for the yard an important technical contribution, due to the fact that the fogging effect worked and dust was drastically suppressed. Now that the excavation is completed, among other things, Idrotech system is part of the TMB outfit… "

Fogging systems in a Brennero tunnel

Nebulization system

Giraffa - Industrial fogging system
for dust suppression

Auger in action at the Seli site

Fogging lines

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Article extracted by Costruzioni magazine

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