PRP PRESSURE VACUUM RELIEF VALVE PIPED AWAY details:

Pressure vacuum relief valve piped away
Model PRP is used for pressure and vacuum relief where vapours must be piped away. Special pallets in the Model PRP housing virtually eliminate the intake of air and the escape of vapours except during normal tank breathing, thus reducing the loss of product and protecting the tank from possible damage. Escaping vapors are piped away through a flanged outlet connection. This helps to provide increased fire protection and safety.

Product features
Size 50mm-300mm
Pressure settings 355pa to 1750 pa
Vacuum settings -295pa 
With piped away