The new model SCF-RFP-D, entirely made in ductile cast iron epoxy coated with internal components in stainless steel, allows the release of air pockets in working conditions and the entrance of large quantities of air, in case of pipe bursting or draining phases. The air discharge velocity is maintained within a safety level by means of an exclusive CSA anti-surge mechanism to prevent water hammer. Its special features have been designed to guarantee the proper operation in pressurized sewage systems avoiding unwanted blocks and deposits.