Electric mining vehicles use rubber products for environmental sealing, thermal transfer, and thermal and acoustic insulation. Like traditional diesel-powered equipment, electric mining vehicles need door and window seals, floor mats, and headliners. Electric mining trucks and tunneling equipment also need molded rubber parts like grommets and silicone hose connectors. In addition, anti-vibration mounts that use rubber-to-metal bonding are found in both electric mining vehicles and diesel-powered ones.
Where electric mining vehicles differ, of course, is that they are battery-powered. Typically, this battery has a specialized chemistry and contains thousands of cylindrical cells. Thermal runaway remains a risk, but these battery cells are separated by fire-resistant insulation. Plus, the risk of a battery fire in electric mining vehicles is overstated, according to Cooler Than Ice, a recent article about electrification and battery safety in International Industrial Vehicle Technology (iVT) magazine. Nomex®, a flame-resistant aramid polymer, can be easily slotted between battery cells and comes in long thin sheets.
Battery Gaskets for Electric Mining Vehicles
Nomex® has greater thermal and chemical resistance than either nylon or Kevlar, but it’s not the only polymer that’s used for battery sealing and insulation. Silicone foams and polyurethane foams are converted into battery cover gaskets from either sheet materials or extrusions. Silicone and polyurethane both have excellent heat resistance and can mate with battery cover plates while filling surface discontinuities. Closed-cell silicones are also used for battery pack gaskets because they can withstand high temperatures and seal out water, dust, moisture, and other contaminants.
Elastomers such as BISCO® silicones and PORON® polyurethanes can maintain close contact between the cooling plate and the battery, but alternatives to these Rogers Corporation materials are emerging – and with significantly shorter lead times. The batteries for electric mining vehicles also use thermal gap pads that are pre-cut to specific shapes and sizes. These rubber products combine good thermal performance with ultra-high compressibility for low-stress, high-conformability to mating surfaces. Often, silicone is used because it combines high-temperature protection with environmental resistance.
Thermal and Acoustic Insulation for Safety and Comfort
In electric mining vehicles, rubber foams that provide thermal insulation can be applied to the doors and roofs of cabins. With their semi-open cellular structure, polyimide foams are a good choice because they minimize heat flow. They also help to reduce acoustic vibrations from onboard traction motors. For the vehicle headliner, polyimide foams that that keep out the cold and keep in heat (or vice versa) are used. Dense polyimide foams are also installed beneath the cabin floor to provide a thermal barrier against heat coming from underfloor battery packs.
Polyimide foams that are less dense can be installed between the cabin floor and traction motors to provide acoustic insulation. Some of these materials are designed to produce low levels of smoke – and no toxins – in the event that a battery cell short circuits and starts to heat up uncontrollably. Silicone foams can also be used, but some produce off-gassing. Because underground mining is both hot and hazardous, designers want materials that can withstand extensive testing at temperatures in excess of 50°C (122°F).
Rubber and the Future of Electric Mining Vehicles
Although concerns about battery safety remain, electric mining vehicles reduce the risk of fire because they have significantly fewer hot surfaces. With diesel-powered equipment, the splash of fuel or oil on hot surfaces such as exhaust pipes can cause fires to occur either aboveground or underground, both of which are part of mining operations. Importantly, electric mining vehicles also reduce emissions and heat in underground mines and tunnels. In turn, this reduces the need for ventilation and cooling. Of course, electric vehicles are also quieter, and that promotes occupational health and safety.
Elasto Proxy is a fabricator and distributor of rubber products that serves the heavy equipment and electric vehicle industries. As companies like Caterpillar develop electric mining trucks, we’re ready to supply them with all of the rubber parts that are needed for a build. In addition to door and window gaskets, Elasto Proxy can supply you with molded rubber products and thermal, acoustic, and thermal-acoustic insulation. For one-stop shopping that strengthens your supply chain, contact Elasto Proxy.