Class 4 (4th Engineer) MEKG 📅 Nov 2022

Exam Question

(a) State why air compressor suction and delivery valves should seat promptly. (4)

(b) Explain the effect on the compressor if the air is induced into the cylinder at a temperature higher than normal. (4)

(d) Explain why pressure relief devices are fitted to the waterside of cooler casings and their normal set values. (4)

Reference Answer

### (a) Why Air Compressor Suction and Delivery Valves Should Seat Promptly (4 Marks)
Prompt seating of compressor valves is critical for ensuring maximum efficiency, reliability, and safety. Delayed seating directly compromises the compressor's performance in several key areas:
1. **Prevention of Backflow and Maximizing Volumetric Efficiency (η_vol)**:
* **Suction Valve**: If the suction valve is slow to close at the beginning of the compression stroke (as the piston moves from BDC to TDC), a portion of the inducted air will be pushed back into the suction manifold. This reduces the mass of air trapped in the cylinder for compression.

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