Idea from space inspires new way to reduce carbon emissions, fuel

Less carbon emissions means a more environmentally friendly way to drill, and less fuel use means cost savings.

You’re kicked back in your favorite recliner, watching a documentary on the Space Shuttle and suddenly they’re talking about on-board pneumatic systems. Who wouldn’t be excited?

A certain engineer was not only excited, he was inspired: “A compressor hasn’t got any air to compress in the vacuum of space, and I thought how much power does it take to rotate the compressor in a vacuum?” The answer? “Only enough power to overcome the frictional forces inside the compressor, such as bearings and rotor mesh friction.” He was on to something.

Now our engineer may sound like someone who needs to stop taking work home, but fortunately for his employer he hasn’t yet.

Grant Field, automation engineering manager for Sandvik Mining, recognized that operating in a vacuum could reduce engine load. Sandvik doesn’t operate on the moon, however. Field needed a way of creating a vacuum inside a compressor or, you might say, of creating “space” inside a compressor.

He thought of connecting a small compressor to the main compressor. Using the appropriate valves, he could evacuate the main compressor to isolate it. “Isolating” the compressor, Field explains, means isolating the inlet from the atmosphere and the outlet from the pressure in the receiver tank (where compressed air is stored at a higher pressure than the atmosphere). Field wrote a proposal based on his concept that showed a theoretical fuel savings of more than 30 percent. That got management’s attention.

First try
Sandvik developed the technology in-house using existing components, such as a compressor from an underground drill, modifying the components to suit the application.

“It took us around three months to identify the correct components and how to install them. It took a week to fit the parts to a machine. The concept worked on the first attempt,” Field says.

“We then spent another two months fine tuning the components and the programmable logic controllers to get the system to work as we wanted it to. Specifically, we wanted all of the components to be fail-safe. Our prime concern was that if any part should fail, the machine would either shut down or default to a condition that would not damage the main compressor or the other systems,” he says.

After successful testing of the concept on a DR460 rotary blasthole drill in the factory, they secured a prototyping site in Australia and continued development. After a year of successful field testing, Sandvik moved its compression management system (CMS) to production installations. The company now has more than 50 systems in operation.

The list price of the system is $180,000, plus installation. Two mechanics take three days to fit the hardware, and it takes one electrician two days to wire it. Once installed, programming and commissioning take about four hours. All of the original pneumatic controls are removed from the compressor, and new controls and evacuation compressor are fitted, along with new valves and wiring.

Fuel savings, according to Field, depend on the model of machine and drilling conditions. In most applications, the average savings is between 20 and 35 percent. This is a direct reduction in fuel consumption, translating to thousands of gallons of fuel, a significant amount of money and hundreds of tons of carbon emissions every year.

“The larger the machine, the greater the savings and the faster the payback,” Field says. “Savings can be predicted mathematically by knowing the volume of air and pressure that’s delivered. We know these figures because we measure and control them with the system.”

Field testing started with “early adopters” (mine sites that use new technology before it is fully proven). Now field data proves the company’s claims.

“Our investigations show we have reduced compressor downtime events up to 80 percent. Standard pneumatic regulation on the compressor can be troublesome in cold or in high-humidity applications. CMS replaces all pneumatic regulation with electronic valves and controls that have proved reliable and make start-up easier.” (Note: Electronic valves are less susceptible to cold and humidity because they do not use air to regulate them.)

The company did considerable research and testing of the concept before implementation, so there were few surprises. On-flow benefits, such as extended engine and compressor life owing to reduced load, are difficult to quantify.

“Engine life is directly proportional to fuel burn. The engine manufacturers provide maintenance-related tasks and a rebuild schedule that are based on fuel burn. Any savings in the fuel burn rate extends the interval between these tasks and ultimately reduces operating costs,” Field says. This also applies to the operating life of the compressor, which is based on average load. If the load is reduced by 30 percent, compressor life is increased proportionately.”

Sandvik has more than 1,000 rotary blasthole drills working around the world, and retrofitting all of them would take a substantial amount of time. As more field results back up their claims, the number will grow. CMS is available as a factory-fitted option or as a retrofit to units in the field. However, before the retrofit can take place, the unit must be audited and, if required, certain tasks completed to ensure achieving the stated benefits. Currently the system is only available on Sandvik drills.

The company might want to consider installing a flat-screen TV in Field’s office.

Patrick G. Mahoney, a freelance writer based in Cleveland, writes extensively on engineering and other technical topics.