LO 6-5 Identify and describe the hazards associated with engines as ignition sources and outline control practices

Aftertreatment systems performing a regeneration are another way a diesel engine can become an ignition source and fire hazard. During exhaust regeneration events, the exhaust system temperatures rise to over 1000° F (538° C), becoming hot enough to ignite dry grass, paper, and any debris in contact with the exhaust pipe. Landfills and the interior of factories are two common places where this hazard can start a fire Figure 28. Similarly, spark arresters are used in off-road applications when hot carbon particles can exit the exhaust and ignite forest fires or grass fires. The spark arresters generally consist of screens at the exhaust pipe tip or layers of metal discs that the spark must pass across at the tip, which cools and quenches sparks.

FIGURE 06-28: The exhaust tailpipe outlets are double walled to allow the circulation of cooler air around the tip to reduce its temperature.

When working on diesel engines, whether it is in a shop, broken down on a job site, or outdoors, controls for ignition hazards include:

• Establishing acceptable areas, boundaries, and entry routes for vehicles and machines’ combustion to avoid potential flammable gases
• Marking off and enforcing acceptable traffic routes through hazardous locations
• Installing automatic overspeed shutdown devices on engines
• Installing exhaust spark and flame arrestors
• Inhibiting the operation of the aftertreatment system anytime it is indoors or around potentially flammable waste or products
• Flushing out charge air coolers and intake air systems, if the intake air system has oil accumulations, subsequent to a repair but before starting an engine