What is a valve? Valve, in mechanical engineering, device for controlling the flow of fluids (liquids, gases, slurries) in a pipe or other enclosure. Control is by means of a movable element that opens, shuts, or partially obstructs an opening in a passageway. Valves are of seven main types: globe, gate, needle, plug (cock), butterfly, poppet, and spool. How do valves work? A valve is a mechanical device that blocks a pipe either partially or completely to change the amount of fluid that passes through it. Where ware control valves used? A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level. What are the different types of valves? Different types of valves are available: gate, globe, plug, ball, butterfly, check, diaphragm, pinch, pressure relief, control valves etc. Each of these types has a number of models, each with different features and functional capabilities. What are the different types of valves used for? Plug valves (seat valves), ball valves, & butterfly valves are the most common types of valves used in heating, ventilation, and air conditioning system. Other valves used in system of including knife gate valves, diaphragm valves, and gate valves. Different types of valves uses in different sectors. in this article mentioned 19 types of valves. 1. Globe valve 2. Gate valve 3. Ball valve 4. Butterfly valve 5. Diaphragm valve 6. Plug valve 7. Needle valve 8. Angle valve 9. Pinch valve 10. Slide valve 11. Flush bottom valve 12. Solenoid valve 13. Control Valve 14. Flow regulating valve 15. Back pressure regulating valve 16. Y-type valve 17. Piston valve 18. Pressure regulating valve 19. Check valve