Article Photos: Fracking for natural gas being powered by it, too 2/7

In this photo made on Thursday, Jan. 17, 2013, the truck and trailer rig with a huge converted engine that runs a pump used in extracting gas from wells, sets outside the Cummins Bridgeway facility in Gibsonia, Pa. The unit on the front of the trailer cools the 50 litre, 16 cylinder Cummins diesel engine that occupies the center of the trailer. The pump for the fracking fluid is at the rear. Oil- and gas-field companies from Pennsylvania to Texas are experimenting with converting the huge diesel engines that operate pumps that propel millions of gallons of water, sand and chemicals down a well bore in the fracturing process to break apart rock or tight sands that trap natural gas. (AP Photo/Keith Srakocic)