Exam Question
(a) Explain how oil carry over occurs in starting air compressors. (6)
(b) State how the problems of oil carry over are minimized. (4)
(c) State THREE factors that contribute to air start line explosions in diesel engines. (6)
Class 4 (4th Engineer)
MEKG
📅 Sep 2022
Reference Answer
### (a) How Oil Carry Over Occurs in Starting Air Compressors (6 Marks)
Oil carryover is the phenomenon where lubricating oil from the compressor's running gear and cylinders is entrained in the discharge air stream and deposited in the air receivers and starting air lines. This occurs through several mechanisms:
1. **Mechanical Atomization**: The crankshaft and connecting rods moving at high speed in the crankcase splash the lubricating oil, creating a fine mist or aerosol. If the crankcase oil level is too high (overfilling), this effect is exacerbated, generating a dense oil-laden atmosphere within the crankcase.
2. **Defective Piston and Scraper Rings**:
Oil carryover is the phenomenon where lubricating oil from the compressor's running gear and cylinders is entrained in the discharge air stream and deposited in the air receivers and starting air lines. This occurs through several mechanisms:
1. **Mechanical Atomization**: The crankshaft and connecting rods moving at high speed in the crankcase splash the lubricating oil, creating a fine mist or aerosol. If the crankcase oil level is too high (overfilling), this effect is exacerbated, generating a dense oil-laden atmosphere within the crankcase.
2. **Defective Piston and Scraper Rings**:
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