🔍 Key Concepts

• Diesel engine crankcase explosions and how they develop in stages • Difference between a primary and secondary explosion inside an enclosed space • Role of flammable oil mist and crankcase relief valves in limiting damage

💭 Think About

• Think about what physically happens first when oil mist ignites in the crankcase: is pressure already built up, or is it just starting? • Consider which event would occur after hot spots have continued and pressure has had time to rise inside the crankcase. • Ask yourself: in which stage is there more accumulated gas and pressure available to be released suddenly?

✅ Before You Answer

• Clarify in your mind which event happens first in time and which happens after pressure has built up. • Recall which explosion type engine designers try to prevent from becoming violent by using crankcase relief doors/valves. • Before choosing, be sure you can explain in your own words why one stage would be more destructive than the other.