The safety relief valves are manufactured according to the “DIRECTIVE 2014/68/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment”. This instruction sheet shows what requested by the Annex I, article 3.4 of the above mentioned Directive. Safety relief valves control the pressure of the generators or heating systems in which they are installed. When the pressure reaches the setting value, the valve begins to open the obturator, discharging the fluid in the atmosphere. In this way, the system pressure is limited avoiding it from reaching dangerous working values. Safety relief valves protect the system from overpressures caused by: - eccessive increase of system temperature - wrong sizing of the closed expansion vessel - malfunction or damage of the closed expansion vessel membrane - damage/leakage of the charging/filling unit with system pressure increase as a consequence - hole in the sanitary heat exchanger in boilers for instantaneous domestic hot water production with system pressure increase as a consequence. Safety relief valves automatically close when the pressure decreases to the reseating pressure value, which is 20% lower than the valve setting value.