Basic Knowledge of Marine Valves: Marine valves are devices used to control fluid flow rate, pressure, and flow direction. The fluids being controlled may be liquids, gases, gas–liquid mixtures, or solid–liquid mixtures. A marine valve typically consists of a valve body, valve bonnet, valve seat, closing member, actuating mechanism, sealing elements, and fasteners. The control function of a marine valve is achieved by using an actuating mechanism or the fluid itself to drive the closing member to move up and down, slide, swing, or rotate, thereby changing the cross-sectional area of the flow passage. Basic knowledge of marine valves reveals that their applications are extremely broad and closely related to everyday life; for example, the faucet on a water supply pipe and the pressure-reducing valve on a liquefied petroleum gas stove are both types of marine valves. Marine valves are also indispensable components in various types of machinery and equipment, including internal combustion engines, steam engines, compressors, pumps, pneumatic transmission systems, hydraulic transmission systems, vehicles, ships, and aircraft.