Abu Dhabi Gas Liquefaction Company Ltd Job Training Mechanical Technician Course Module 9 Compressors
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- Figure 4.25
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> + = valve open < + = valve closed Gas pressure (opening force) Spring force (closing) Figure 4.24: Forces Acting on a Valve Gas pressure (closing force) Flow direction Personnel & Training Division Job Training—Mechanical Technician Compressors/Rev. 0.0 Page 34 of 90 Figure 4.25: Valve Operation (a) Suction stroke—Gas enters cylinder through open suction valve Suction port Discharge port Suction valve open Discharge valve closed Piston on suction stroke Springs Springs Opening force big Total closing force small Opening force small Total closing force big (b) Compression stroke—Gas leaves cylinder through open discharge valve Suction port Discharge port Suction valve closed Discharge valve open Piston on compression stroke Opening force small Total closing force big Opening force big Total closing force small The suction valve opens when gas force in the suction port is greater than the gas force in the cylinder plus the spring force. This happens when the piston is on the suction stroke—when suction port pressure exceeds cylinder pressure. The discharge valve opens when gas force in the cylinder is greater than the gas force in the discharge port plus the spring force. This happens when the piston is on the compression stroke—when cylinder pressure exceeds discharge port and suction port pressure. Figure 4.25 shows forces on the valves during the suction and compression stroke. Personnel & Training Division Job Training—Mechanical Technician Compressors/Rev. 0.0 Page 35 of 90 (a) Joined Rings (b) Separate Rings Download 0.5 Mb. Do'stlaringiz bilan baham: 
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