LEC Emissions Control Systems 3 — Questions and Answers
Question 1: Which federal regulation establishes the primary emissions standards for in-use locomotive engines in the United States?
- 49 CFR Part 229
- 40 CFR Part 1033 (Correct answer)
- 49 CFR Part 238
- 40 CFR Part 86
Correct answer: 40 CFR Part 1033
40 CFR Part 1033 contains EPA's emissions standards specifically for locomotives and locomotive engines, covering both new and in-use engines.
Question 2: What effect does exhaust gas recirculation (EGR) have on combustion temperature?
- It increases peak combustion temperature
- It has no effect on temperature
- It lowers peak combustion temperature to reduce NOx formation (Correct answer)
- It raises temperature to burn off particulates
Correct answer: It lowers peak combustion temperature to reduce NOx formation
EGR dilutes the intake charge with inert exhaust gases, lowering peak combustion temperatures and thereby reducing NOx formation.
Question 3: A locomotive engineer observes visible black smoke during a throttle notch increase. Which emissions issue does this most likely indicate?
- Excess DEF injection
- Rich fuel mixture causing incomplete combustion (Correct answer)
- SCR catalyst failure
- Low coolant temperature
Correct answer: Rich fuel mixture causing incomplete combustion
Black smoke indicates incomplete combustion of diesel fuel, often caused by a rich fuel-air mixture, a clogged air filter, or injector problems.
Question 4: Under EPA regulations, how often must in-use locomotives undergo emissions testing?
- Every year
- Every 2 years
- Every 92 days or at each periodic inspection
- Only at major overhaul (Correct answer)
Correct answer: Only at major overhaul
Under 40 CFR Part 1033, locomotives are subject to emissions testing at the time of remanufacture or major overhaul, not at routine annual inspections.
Question 5: What is the role of an oxidation catalyst in an after-treatment system when the exhaust temperature is below its light-off temperature?
- It operates at full efficiency
- Its conversion efficiency is significantly reduced (Correct answer)
- It switches to passive DPF mode
- It injects extra DEF to compensate
Correct answer: Its conversion efficiency is significantly reduced
Catalytic converters require minimum light-off temperatures (typically 200–300°C) to activate; below this threshold, conversion efficiency drops sharply.
Question 6: Which type of emission is primarily responsible for the blue-gray smoke sometimes seen from locomotive exhaust?
- Unburned hydrocarbons from fuel combustion
- Oil being burned in the combustion chamber (Correct answer)
- Excess DEF crystallization
- Carbon monoxide release
Correct answer: Oil being burned in the combustion chamber
Blue-gray smoke indicates engine oil is entering and burning in the combustion chamber, often due to worn piston rings or valve seals.
Question 7: When an SCR system detects ammonia slip, what does this mean?
- Not enough DEF is being injected
- Excess ammonia is passing through the catalyst unreacted (Correct answer)
- The NOx sensor has failed
- The DPF requires regeneration
Correct answer: Excess ammonia is passing through the catalyst unreacted
Ammonia slip occurs when excess urea/ammonia is injected beyond what the catalyst can react with NOx, allowing unreacted ammonia to exit the exhaust.
LEC Emissions Control Systems 3
Which federal regulation establishes the primary emissions standards for in-use locomotive engines in the United States?