Minskade ljudnivåer kritiskt för Hagfors stålverksinvesteringar

– Correct measurements clear the way for the right environmental investments.

Uddeholm’s steel works in Hagfors, Sweden is the main source of income locally, but it is also a source of noise. Since January 1, 2011 the Environmental Protection Agency has laid down the law telling the company to reduce noise or shut down! Now it is imperative that costly environmental investments are placed in exactly the right places, or be avoided if possible using other measures. Achieving this requires accurate measurement and monitoring of noise levels.

The steel mill in Hagfors produces special steel for tool manufacturing. The main raw material is sorted scrap metal that is loaded into “baskets” weighing about thirty tons each before entering the plant. The loading process continues day and night in the scrap yard where a large overhead crane lifts scrap with a large magnet and drops it into the baskets. Noise levels are primarily determined by the height of the drop, but the quantity and the type of scrap is also a factor. The loads vary depending on the type of steel to be produced from each basket. The mill is surrounded by residential areas on three of four sides.

From measurement to solution
Unit manager for raw materials, Börje Gustafsson says: “There are five to twenty-drops per hour, and every drop requires precision and patience from the crane operator. The operator can drop more quietly, but that takes a lot of extra time for each loaded basket. We are currently coming down from 48 decibels on average to the required peak of 45 decibels at night, which is actually a drastic reduction. This is taking place without any investment at all in the way of noise walls or similar measures.”

Each time the limit is exceeded, the sound is recorded into the INFRA system’s microphone and a bright light shines from the two alarm lights within the scrap yard. This gives the crane operator prompt notice that the noise levels are too high. Every day Börje, or one of his collegues, can listen to the previous night’s recordings. Crane operators can also listen to the offending sounds as a type of direct feedback. Noise problems from scrap metal loading are now being solved only through a change in working methods.

Positive experience breeds confidence
“The INFRA system gives us more chances to alert and report than we had before,” continues Börje. “We have trucks that produce a lot of noise, particularly from the warning signals when they back up, and we also have fans that need to be attended to. The measurement system is a very useful tool for managing the environmental investments at just the right place and with the right action. It is more difficult to demonstrate the profitability of environmental actions than it is for productive investments, which have a clear revenue side. We need to show policy makers that we focus on environmental issues as well.”

“We received presentations from several vendors when we were selecting a measuring system, but with Sigicom, all the pieces fell into place right away. The price seemed right and we got concise answers to our questions. That gave us a lot of confidence in the system. The installation also went well, so everything felt good right from the start,” says Börje. “The system has now been fine-tuned so that the scrap yard automatically transitions between the different noise levels of night and day activities.”