A check valve , also called a non-return valve, is a mechanical device that normally allows fluid to flow through it in only one direction. The force of upstream fluid creates high differential pressure across the interior valve body, and it then allows forward streams to pass through.
An important concept in check valves is the cracking pressure, which is the minimum upstream pressure required for the valve to operate. Typically, the check valve is designed for a specific cracking pressure. Check valves are useful in several different types of devices. They stop flooding in water-related devices such as sump pumps and water heaters. They also protect equipment that can be harmed by the reverse flow of material, such as control valves, strainers and flow meters. In addition, check valves can stop material from constantly flowing backwards when a device is off, which can save power and protect the parts of the device.
There are several types of check valves. Some of the more popular include ball check valves, diaphragm check valves, dual-door check valves and clapper check valves. Most of these valves work in a similar way, but no one type of valve is good for all applications. Each of these check valve types has its advantages and disadvantages depending on the application.