What type of valve is designed to prevent the collapse of a pipe?

The type of valve designed to prevent the collapse of a pipe is the air-and-vacuum relief valve. This valve plays a crucial role in water distribution systems by allowing air to enter the pipeline when there is a negative pressure condition, such as during a sudden change in flow or in the event of a pipe break. When water flow decreases rapidly, a vacuum can form, which can create a collapsing force on the walls of the pipe. The air-and-vacuum relief valve helps to alleviate this potential issue by admitting air, thus equalizing the pressure inside the pipe and preventing it from collapsing under external pressure.

Unlike pressure relief valves, which are designed to release excess pressure, and check valves, which allow flow in only one direction, the air-and-vacuum relief valve specifically addresses the problem of negative pressure conditions. Isolation valves are used to shut off the flow of water for maintenance or other purposes but do not protect against collapse due to vacuum conditions. Therefore, the air-and-vacuum relief valve is essential for maintaining the structural integrity of the piping system by ensuring that it does not experience harmful negative pressure.