What are the four types of check valves?

1. Swing check valve: This type of valve consists of a hinged disc that swings open to allow fluid or gas to flow in one direction and swings closed to prevent backflow. The disc is typically held in place by a hinge, and the valve closes when the flow of fluid or gas stops.

2. Lift check valve: A lift check valve operates by using a piston or a ball that lifts off its seat to allow fluid or gas to flow in one direction. When the flow stops or reverses, the piston or ball drops back onto its seat, preventing backflow.

3. Inline check valve: An inline check valve is a simple, one-way valve that allows fluid or gas to flow in one direction only. It consists of a spring-loaded disc or ball that closes when the flow stops or reverses, preventing backflow.

4. Diaphragm check valve: A diaphragm check valve uses a flexible diaphragm that flexes to allow fluid or gas to flow in one direction and flexes back to its original position to prevent backflow. The diaphragm can be made of various materials, such as rubber, plastic, or metal, depending on the type of fluid or gas being handled and the pressure and temperature of the system.

Each of these types of check valves has its own unique advantages and disadvantages, and the choice of valve depends on the specific requirements of the system and the fluid or gas being handled.