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Dyno Nobel's Record Breaking blast


DYNO Nobel Americas (DNA) and Cliffs Natural Resources, a major customer, have detonated the largest explosive volume blast in Minnesota state history at Northshore Mine.

Located in Babbitt, Northshore Mine is one of five taconite mines that Cliffs Natural Resources operates in the United States.

DNA services four large open-pit taconite mines in Minnesota, including Northshore Mine, located atthe eastern end of the Mesabi Iron Range. Dyno Nobel's blasting crew loaded the Aprilll, 2012 blast.

Biwabik is 52 kilometres (32 miles) from Babbitt and operates an emulsion plant. It also delivers down-the-hole bulk product, provides blasting service and sells package and initiation products.

Dyno Nobel Iron Range General Manager Joseph Hejny said the record blast was a great success. '1he fragmentation was excellent, no post-blast fumes, very little fly rock, low noise output and limited vibration made it seem like a routine day of blasting on Minnesota's Iron Range," he said.

The explosion was a taconite (low-grade iron ore) blast to provide production for the mine.

"The big blast was originally designed to be two large blast events, but the drills finished early and the mine decided to fire them as one;• Joseph said. "The loading and blasting all went according to plan."

The success is even more important given the mine is located near small communities and surrounded by lake cabins. All the mine's blasts are designed to be 'non-events' for local residents, which means they are unaware of them due to successful noise, vibration and air-blast prevention measures.

Northshore Mine's Drill and Blast Engineer, Chris Lassi, planned the blast day around wind direction and the weather to control dust and keep noise to a minimum.

He worked with Biwabik blasters Ron Stanaway and Randy Armstrong to plan, prepare and schedule the blasting program.

Northshore Mine engineers, designs and drills the blast patterns while Dyno Nobel tapes, primes, loads, stems and initiates the blasts. Northshore Mine selected Titan LD bulk explosive for the 1.45 million kilogram (3.2 million pound) blast. An average Northshore blast is 363,000-544,000 kilograms (800,000-1.2 million pounds).

It used three of five electric drills to bore 1,036 blastholes an average of 109 centimetres (43 inches) deep. The 41-centimetre (16-inch) blastholes were loaded with 1,441,000 (3, 176,690 pounds) of Titan LD at a density of 1.28. The record blast fragmented 2,594,266 tonnes (2,859,689 tons) of taconite ore at 503 grams (1.11 pounds) of powder per US short ton.

Safety was paramount in the preparation. From March 26, the Biwabik crew loaded an average of 120,200 kilograms (26S,OOO pounds) of Titan LD per day for 12 days. Northshore Mine knew the blast area was drilled over a well defined fault zone and expected the blast pattern to contain slumping powder columns and powder loss due to cracked ground.

It therefore selected Titan LD bulk explosive due to its thickened viscosity, extended sleep time, water resistance and clean post-blast fumes.

The April ll blast was a success and a cause for celebration for the DNA and Cliffs Natural Resources team.