393 type approval (D) (steam), spring loaded according to EN 12828 - 1 bar / TRD 721

These safety valves are for blowing-off saturated steam from pressure generators.
THIES-Diaphragm High-efficiency Safety Valves meet the following German requirements: the AD Specification A 2 for „Safety Valves“, the Technical rules for steam boilers (TRD 721), the Safety Valves Code according to EN 12828.


Response overpressure: 1 bar.


Spring loaded, diaphragm type, high-efficiency safety valve, angled, with highly elastic seal and metal backing in valve head.


Series 393 with closed bonnet.
Valve head is liftable. Force is transmitted centrally at valve head via a ball. Corrosion-resistant spindle guides ensure reliable and precise response of the valve.


Flange connections:
Grey cast iron version: inlet and outlet as per DIN 2533 PN 16
Spheroidal graphite iron version and cast steel version:

  • inlet as per DIN 2545 PN 40
  • outlet as per DIN 2543 PN 16


The safety valves are provided with a drain plug:

  • up to DN 50 - R 1/4 ".
  • over  DN 65 - R 3/8 ".


Models 393                                                                  Order Code No.
Series 393 of grey cast iron  PN 16                              393 GN
Series 393 of spheroidal graphite iron PN 40               393 GGG
Series 393 of cast steel PN 40                                     393 SNC