Stockholm’s metro line is expanding. Underground blasting operations are ongoing in several areas of the city. In central Stockholm, Chief Measurement Technician Michel Ehn from Bjerking is conducting environmental monitoring at the historic Nationalmuseum, making sure that art objects from the late Middle Ages aren’t impacted by the blasting.

The blue metro line is being extended south to Södermalm and Nacka with expected completion in 2030. Currently, in the fall of 2021, working tunnels are being blasted in several places along the future train line. The historic Grand Hotel and Nationalmuseum are located on Södra Blasieholmen in central Stockholm. Excavation is being conducted in this area to uncover an old, closed working tunnel. This working tunnel will allow for blasting to begin on the main tunnel approximately 30 meters below Grand Hotel.

The Nationalmuseum has an art collection containing paintings, sculptures, and other art objects from the late 16th century to the 20th century. Vibration monitoring is not only being conducted for the protection of the historic building, Sigicom sensors are also being used to measure the response of these sensitive objects. This data provides the construction manager with the information needed to conduct operations safely.

Michel Ehn

– During blasting, people often become anxious, as most people are not aware of how small the risk is that something in the museum would be affected. What people feel, and especially hear, from the blasting can create some anxiety since humans can feel very low vibration levels. And that’s what we’re supposed to do, it triggers our escape reflex. However, these vibrations and the movements at this distance are so small that they shouldn’t cause any damage, says Michel Ehn.

A vibration monitoring plan was developed, and reference measurements were conducted in the museum before the blasting work started. Project leaders wanted to understand the levels of naturally occurring vibrations during a normal day in the museum, with visitors and other influences.

– It happens that someone might bump into a stand, or that the staff moves the objects in the exhibition, and the instruments measure that as well. Based on the reference measurement, we gained an understanding of what vibration levels the object should be able to handle when the blasting under Blasieholmen started, says Michel.

The new generation of vibration monitors

The project uses a set of Sigicom’s latest products, a new generation of autonomous measuring instruments with guaranteed long battery life. In a large glass stand, an INFRA C22 vibration monitor has been placed next to sensitive art objects. The INFRA C22 is a compact triaxial vibration sensor and data logger with built-in wireless communication. Using a wireless system is beneficial for several reasons in this type of environment. When art is in focus, compact wireless vibration monitors blend in better than a bulky cabled system. In addition to the INFRA C22, INFRA Point vibration monitors are used to perform measurements on the historic building’s structural elements.

This project is heavily based on the new generation of instruments, i.e., the new system with INFRA Point and INFRA C22, with that battery solution and so on. The battery life is a big part of why we chose Sigicom’s instruments, to ensure operation in challenging environments and still maintain a very high level of service, says Michel Ehn.

Despite using a large number of monitors, Michel and his colleagues rarely need to visit the job site. Most of their work is done remotely via INFRA Net, Sigicom’s web-based project management program for handling instruments and measurement data. Using INFRA Net, the measurement consultants can configure the instruments, check interval and time history recordings, and keep track of instrument diagnostics. This project is solely managed on the new INFRA Net platform and has had a major role in piloting its development. The new INFRA Net offers a clear project-based overview for the different users, making their daily work of following up on compliance run a lot smoother.

– In my team, we are four, five people who use INFRA Net daily for the metro project. We don’t perform analyzes, only deliver data. Within the project there are about 100 people (blasters, construction managers, and acousticians) who evaluate the results in INFRA Net from vibration and noise monitoring, says Michel.

These measurements will continue at the Nationalmuseum during all tunnel construction and blasting activities. Michel Ehn expects a somewhat extended monitoring plan in the area given the high density of sensitive historical and cultural sites.

An INFRA C22 wireless vibration monitor next to colorful art objects

This website uses cookies

Cookies consist of small text files. They contain data that is stored on your device. To enable us to place certain types of cookies we need to obtain your consent. At Sigicom AB, corp. ID no. 556207-1547, we use the following kinds of cookies. To read more about which cookies we use and storage times, click here to access our cookies policy.

Manage your cookie-settings

Necessary cookies

Necessary cookies are cookies that must be placed for basic functions to work on the website. Basic functions are, for example, cookies which are needed so that you can use menus on the website and navigate on the site.

Functional cookies

Functional cookies need to be placed on the website in order for it to perform as you would expect. For example, so that it recognizes which language you prefer, whether or not you are logged in, to keep the website secure, remember login details or to be able to sort products on the website according to your preferences.

Cookies for statistics

For us to measure your interactions with the website, we place cookies in order to keep statistics. These cookies anonymize personal data.

Personalization cookies

In order to provide a better experiance we place cookies for your preferances

Cookies for ad-tracking

To enable us to offer better service and experience, we place cookies so that we can provide relevant advertising. Another aim of this processing is to enable us to promote products or services, provide customized offers or provide recommendations based on what you have purchased in the past.

Ad measurement user cookies

In order to show relevant ads we place cookies to tailor ads for you

Personalized ads cookies

To show relevant and personal ads we place cookies to provide unique offers that are tailored to your user data