Breather Valves 

Breather valves are primarily for protection – keeping and maintaining the pressure/vacuum, thereby helping the valves or storage systems from imploding.

Breather valves would help breathe in and out, in doing so, maintaining desired pressure and vacuum.

They are designed to prevent vapour loss, maintain pressure without any buildup or losing pressure and storage bucking.

There is pressure and vacuum buildup inside storage systems due to process and thermal changes. This can easily damage and burst the storage systems. While vacuum would be created during pumping out of liquid and it would result in further flow of the liquid from getting drawn out, hence buckling down the storage systems.
Maintaining and managing excess pressure or vacuum created inside the storage system is very important and can be controlled through valves.

Weighted pallet are used that lifts at set pressure and vacuum allowing smooth and seamless flow capacity through the valve