Definition - What does Flapper Valve mean?
A Flapper valve is a check valve that contains a spring-loaded plate or flapper that allows the unidirectional fluid or gas flow and provides high performance sealing capabilities. It seals the opening when the fluid tries to flow back. The valve creates a watertight seal in storage tanks and ensures safe operations when used in high pressure and high volume environments.
Petropedia explains Flapper Valve
Flapper valves allow drilling fluids to be pumped in the downhole direction through the drill-string but they seal the opening if the fluid or gas attempts to flow back to the surface. The valve is usually is connected to the drill string and coiled tubing to control, regulate and direct the flow of liquids and gases. It operates by opening, closing or partially opening the passageway. The most common example of a flapper valve is the one that is found in a flush toilet. The valve holds water inside the tank before and after the toilet is flashed.