At Irish Salt Mining and Exploration’s Carrickfergus mine, surefooted articulated dump trucks are hauling extracted salt to keep roads safe in winter – whatever the weather
Salt has been among the earth’s most abundant and essential minerals since the dawn of time. Composed primarily of sodium chloride (NaCl), it is known as rock salt, or halite in its natural, crystalline form.
In 2015, total world production of salt reached 273 million tonnes, according to market research company Statista, with the top five producers being Canada, China, Germany, India and the USA.
Situated to the north of Belfast, Northern Ireland, Irish Salt Mining and Exploration’s (ISME) Carrickfergus mine was developed specifically to mine de-icing rock salt for winter road maintenance. Founded in 1965, ISME is positioned in a prime location, thanks to its proximity to the coast, as well as the construction of a ship-loading terminal, which enables the company to develop a successful export market.
The company’s 55-strong workforce currently produces between 300,000 to 500,000 tonnes of road salt per year, and provides local authorities across the UK with rock salt to help keep the road network open during the icy winter months. Scottish local authorities are its biggest customer, followed by Ireland and then the rest of the UK. “Our job is simple,” says Derek Moore, mine manager at ISME. “We make the roads safer!”
Rock solid progress
Mining at Carrickfergus uses the ‘room and pillar’ dry mining method. There are five seams of salt, but ISME only mines one extensively, due to the thickness of the seams. This is because 3.5m (12ft) of salt must be left above the excavated rooms as a support.
At its deepest point, the mine reaches 305m (1,000ft) below ground. “The deeper you get, the larger the pillars,” explains Moore. “But on average the room sizes are 15.3m (50ft) wide and 9m (30ft) high. In the older part of the mine, they are just 6.7m (22ft) high, while the pillars are 39.6m (130ft) square in the newest part of the mine, and 27.4m (90ft) square in the older parts.”
The geology of the area is fairly simple too. There are no gases or moisture to contend with, which makes mining a simpler process too. Moore explains: “We drill; we cut; we blast; we muck out.”
During mining, the salt bed is undercut then drilled and blasted. Blasting happens at the end of each 10-hour shift, usually around 17.30, and sees three faces advance 3m (10ft) each time. The next morning’s first job is roof scaling, using a rotary cutting head designed specifically for the purpose.
The broken salt is then loaded into one of ISME’s seven Terex Trucks haulers, including two new TA400s, and hauled to the crushing plant. Crushing and screening are completed underground before the finished product is transported, via a 2km-long network of conveyors, to the surface.
The salt, ready for use, is then treated with an anti-caking additive and stored undercover for dispatch by sea from the company’s own quay, or by road.
ISME’s newest machine, a 38-tonne capacity TA400 with a six cylinder Scania DC13 Tier 4 Final engine, arrived on site in February 2016. It was supplied by local dealer Sleator Plant, based in Newtownabbey, County Antrim. Moore says he is extremely pleased with the machines and after sales support.
Moore says the company looked at other options before purchasing its newest hauler, but it was the ‘simple’ nature of Terex Trucks’ haulers that won the day.
“Their simplicity is one of the major factors about the TA400 that we really like,” says Moore. “It’s easy to maintain and service, so we are confident that it’s going to keep working. We find that once you have too many computers involved in running your machines then problems can start occurring.”
Before choosing its latest machine ISME not only visited the Terex Trucks facility in Motherwell, Scotland, but also saw the machines in action at an open cast mine in Scotland and at a product demonstration in Malaga, Spain. “We wanted something that’s robust and comfortable for the drivers,” explains Moore. “At the same time, fuel efficiency and environmental concerns played a part in choosing the right truck. And, of course, the back-up we get from the dealer also impacted our final decision.”
As part of its aftersales service, Sleator Plant provided a trainer who showed the operators the changes that had been made to the new machine, as well as explaining the new maintenance routine to the workshop staff.
There have been no problems running any of the machines. ISME keeps the trucks clean as an added safety precaution to reduce the risk of fire, while adhering to the maintenance and servicing schedule, as well as doing daily and monthly checks. The company operates its own workshop to carry out routine maintenance and servicing, with larger jobs, such as an engine overhaul, being carried out by Sleator Plant.
Keeping to the mine’s speed limit is a key factor in reducing wear and tear, as well as minimising fuel consumption. But the working conditions are still extreme, with the trucks having to cope with corrosive salt and dust, not to mention the temperatures inside the mine. “With all machines, it’s common that as they age there can be problems with the chassis because they really do take a pounding, but our oldest haulers are still operating after 25 years,” Moore adds.
More than a match for these conditions, the new TA400 is proving to be a success with ISME’s employees. “Truck driving is seen as one of the most important jobs in the mine, so it’s vital the operators have as much comfort as possible,” he continues. “When you get in, you don’t want to get out!
Trucks haul deep in Jordan
In other Terex news, its longstanding customer Comedat is putting the firm’s rigid dump trucks to work in phosphate mines in Jordan. Comedat, Jordan’s largest phosphate mining contractor, is using 90 Terex Trucks machines across three sites to mine phosphate in the north and south of the Middle Eastern country.
Used to help feed the world, the production of phosphate is generally consumed as fertiliser, and its annual demand is growing almost twice as fast as the human population. Although poor in water resources per capita, Jordan is rich in history and boasts plentiful supplies of phosphates. The kingdom is the fifth largest producer of phosphates globally with an estimated 1.3 billion tonnes of phosphate reserves.
The Comedat fleet is one of the largest fleets of Terex Trucks’ haulers in the world, consisting of a mixture of 100 ton (91 tonne) capacity TR100s and versatile 60 ton (54.5 tonne) TR60s.
The robust machines are required to work day and night, as Comedat operates 24 hours, seven days a week, 365 days a year. The trucks, which provide excellent rimpull thanks to a resilient drivetrain and rear axle configuration, are used to haul overburden removal, while others descend 56m below the surface to carry phosphate.