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.
Dervos provides high performance check valve products, including Swing check valve, Lifting check valve, Titling check valve, External check valve, Wafer check valve etc. Check valve, non-return valve or one-way valve is a kind of mechanical device and a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction.