Duckbill/Umbrella/Flapper/Dispensing Check Silicone Rubber One Way Valve
Cracking pressure – Refers to the minimum pressure differential needed between the inlet and outlet of the valve at which the first indication of flow occurs (steady stream of bubbles). Cracking pressure is also known as unseating head (pressure) or opening pressure.
Reseal pressure – Refers to the pressure differential between the inlet and outlet of the valve during the closing process of the check valve, at which there is no visible leak rate. Reseal pressure is also known as sealing pressure, seating head(pressure) or closing pressure.
Back pressure – a pressure higher at the outlet of a fitting than that at the inlet or a point upstream
A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a ball. In some ball check valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials; in some specialized cases out of highly durable or inert materials, such as sapphire. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with balls of (artificial) ruby and seats made of sapphire[6] or both ball and seat of ruby,for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with ball valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
