Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/185325
maintenance | continued crankshaft, same rods and rod bearings. The surfaces that need to be lubricated are the same." Oil filters are also the same as used in the diesel engine, he says. Assuming the fueling station is configured correctly, a fuel-water separator is not necessary, since natural gas fuel is dry, House says. There is a fuel filter that should be drained daily, he says, but this is for other contaminants. The fuel filter also protects against the possibility of oil contamination from the compressor in the fuel station, House says. As for oil analysis, look for the same things as you would in a diesel lube oil analysis, House says, including wear metals, total base number, total acid number, and contamination. Exhaust aftertreatment Natural gas engines meet the same exhaust emissions standards as diesel engines, but because CNG and LNG burn cleaner, they generate fewer pollutants in the combustion process. "The engines we produce today use a three-way catalyst. It's very simple and maintenance free, much like what's on your automobile, just a little bigger," House says. "We don't have a DPF, and we don't use SCR." This arrangement is particularly well suited to applications that involve a lot of slow speed operation and frequent starts and stops, he says. Pressurized systems Although Cummins-Westport does not make the pressurized fuel tanks that hold natural gas (that's done by truck upfitters) there is a requirement for periodic fuel tank inspections, House says. Most companies get their technicians trained and certified to do this. And there is another required tank inspection any time a truck has been in an accident, he says. Pressure regulators step down the fuel pressure to an average of 150 psi at the engine, House says. "It's regulated in the on-board fuel system and then we further regulate it as it comes into the engine. There are also shutoff devices that you close when working on the system to prevent your fuel from escaping into the atmosphere." Unlike traditional diesel engine and even today's gasoline engines, the Cummins-Westport design does not have fuel injectors. "We have an on-engine fuel regulator and a fuel control valve. Then there's intake air that's controlled by a butterfly throttle. It's similar to the old carbureted engines," House says. "Very simple in design and componentry. And you don't have injectors to adjust." Plugs and valves Diesel mechanics may take a while to get used to it, but these natural gas engines do have spark plugs and they have to be replaced on a recommended change interval. Spark ignited natural gas engines run a bit hotter even than gasoline engines, so it's important to stick to the published spark plug change intervals, House says. Another important maintenance consideration is adjusting the intake and exhaust valve lash. "Sometimes in the diesel world, people get a little lax with that," House says. "With some of the new technology it seems not as important. But it's extremely important to do on a natural gas engine, especially for knock control." EW Bringing your shop up to code YOU MAXIMIZE YOUR INVESTMENTS WITH CARETRACK. THAT'S SMART. Smart works. See how: volvoce.com/CareTrack/ew Volvo Construction Equipment Depending on your local building code, you may need to make some changes to your shop to work on natural gas fueled trucks and equipment. Check with an architect and your local fire marshal to find out what you may need to do to meet the National Fire Protection Association Code, the International Building Code and the National Electrical Code as well as the NFPA 58 Liquefied Petroleum Gas Code and the NFPA Code for Motor Fuel Dispensing Facilities and Repair Garages. The codes may vary depending on where you live, but in any case, the local fire marshal will have the final say-so. EW 36 October 2013 | EquipmentWorld.com EW1013_Maintenance.indd 36 9/24/13 1:55 PM