The present disclosure relates to controlling the direction of a fluid flow. More specifically, the present descriptions relate to control of fluid flow using check valves.
Check valves are one-way valves that permit a fluid to move through a valve in a first direction and restrict a backflow fluid flow through the valve in a second direction, which is generally different than the first direction.
Check valves can be used in many types of application, including, pumps, such as piston-driven and diaphragm pumps; fluid systems for industrial processes, including chemical and power plants; fluid control systems, such as irrigation sprinklers and drip irrigation; and in medical applications, such as check valves for the heart ventricles, and intravenous fluid delivery.
A check valve can include a valve that is generally shaped as a flat disk forming a diaphragm. The diaphragm can have a slit forming one or more valve segment. The valve segments can engage against each other in a closed position to resist fluid flow through the valve, and the valve segments can move, relative to each other, to open the valve and permit a fluid flow through the valve.
Check valves can have a normally-closed configuration where the valve is in a closed position to resist fluid flow through the valve. The check valve can move to an open position to permit fluid therethrough by a fluid pressure or engagement of a fluid against the valve. The pressure or force required to move the valve to the open position is known as the cracking pressure. The cracking pressure can be a pressure at the inlet, e.g., upstream, of the check valve at which a first indication of flow through the valve occurs. In some check valves, the valve is moved to an open position when a positive pressure differential is applied to the valve, for example, when a pressure upstream of the valve is greater than a pressure downstream of the valve.
In the open position, a check valve can permit fluid flow through the valve with minimal pressure loss. The check valve can move to the closed position when the positive pressure differential is decreased, removed, or reversed. In some instances, the inherent resilience of the valve enables the valve to move to the closed position. A negative pressure differential, e.g., when the fluid pressure downstream of the valve is greater than the fluid pressure upstream of the valve, can cause the valve to move to the closed position. In the closed position, a check valve can resist a backflow of fluid of at least 30 psi.