341 type approval (D/G/H) (steam/gas/heating system) for heating systems according to EN 12828 / TRD 721

Safety valve to satisfy safety requirements in heating systems with flow temperatures of 120°C according to EN 12828.


THIES High-efficiency Safety Valves satisfy the German requirements of the following specifications: UVV- “Pressure Vessels“, AD Specification A 2 „Safety Valves“, the Technical Rules for Steam Boilers (TRD), SR Safety Valves and EN 12828.


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


Series 341 with closed bonnet.
Valve head is liftable. The pressure acts, via a ball, centrally onto the valve head. Corrosion-resistant spindle bushes ensure reliable and precise response of the valve.


Grey cast iron version: inlet and outlet according to 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 ".


Valve head with highly elastic seal and metal backing.
Leading to:

  • Better tightness.
  • Less sensitivity to fouling.
  • Reliable response due to metal backing.
  • High strength and high resistance owing to highly elastic seal embedded by vulcanizing.


Models 341                                                                       Order Code No.

  • Series 341 of grey cast iron PN 16                          341 GN
  • Series 341 of spheroidal graphite iron PN 40         341 GGG
  • Series 341 of cast steel PN 40                                 341 SNC