Question 14 QMED01 - Junior Engineer

The Correct Answer is D **Why D (abrasion, dust, and dirt) is correct:** Valves in an air compressor rely on extremely precise seating (closing) to maintain pressure and prevent leaks. If the intake air is dirty, abrasive particles (dust, rust, carbon deposits, or other debris) are constantly pulled into the cylinder. These particles lodge themselves between the valve plate and the valve seat or cause physical damage (pitting, scratching, or wear) to the mating surfaces over time. This abrasion prevents the valves from sealing properly, leading directly to leaks, which reduces compressor efficiency and performance. **Why the other options are incorrect:** * **A) excessive discharge pressure:** While excessive pressure puts more stress on the valves, it is not a direct cause of *leaking* (failure to seal). Leaking is primarily a sealing issue. Extremely high pressure is more likely to cause premature failure of other components (like safety valves activating or gaskets blowing) or potential catastrophic structural failure, but the leakage itself is caused by poor sealing, not just the magnitude of the pressure attempting to escape. * **B) excessive compressor speed:** Running a compressor too fast increases operating temperature and mechanical wear, potentially reducing the lifespan of components, but it doesn't inherently cause the sealing surfaces of the valves to degrade or leak. High speed is a stress factor, but dust and dirt are the primary mechanism for sealing surface damage. * **C) irregular compression strokes:** Irregular strokes (often caused by internal mechanical issues like a bent rod or worn bearings) indicate a problem within the mechanism that *drives* the piston. While this mechanical malfunction can eventually damage the valve assembly (if the piston impacts the head, for example), the *cause* of leakage in a typical failing valve is the compromised sealing surface, which is usually due to foreign matter (D), not the irregularity of the stroke itself.