A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve all the way in, and then turning the compressor over by hand. If the discharge valves are leaking, the high-side pressure gauge will show pressures which react in which way?
• Behavior of discharge valves in a reciprocating compressor • What happens to high-side pressure when the discharge line is blocked off • Difference between leak-by (small leak) and a tight, non‑leaking valve
• When you turn the discharge service valve all the way in, what are you isolating, and what happens to any gas that leaks past the discharge valves? • As you slowly turn the compressor by hand, think about whether each stroke is trying to move gas into a closed space or back toward the low side. • If the discharge valves are leaking, would the trapped high‑side pressure stay steady, build up, drop off, or swing up and down as each piston moves?
• Identify clearly which side of the system the high-side gauge is reading once the discharge service valve is shut. • Visualize one full revolution of the crankshaft and what happens to pressure on each stroke (compression stroke vs suction stroke). • Decide whether leaking discharge valves would cause pressure to equalize, to ratchet in one direction, or to oscillate around some value.
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