View all search results

Flanged Safety Relief Valves

Safety & Pressure Relief Valves

banner image

LESER Type 431/433 Modulate Action Relief Valve

product image

LESER Type 431/433 Modulate Action Relief Valve

Inlet Connections

DN 15 - DN 150 | 1/2" - 6"

Pressure Rating

0.2 - 40 bar | 2.9 - 580.15 psig
PN 16 - PN 40 | CL150 - CL300


PN 16 - PN 40(CL150 - CL300)
PN 16 - PN 40(CL150 - CL300)


PED/ DIN EN ISO 4126-1, PED/ AD 2000-Merkblatt A2, AQSIQ, EAC

  • Applications

    LESER – Modulate Action Safety Valves provide the ultimate solution for all industrial applications with steam, gasses, and liquids.

    Series 433 standard safety valves acc. to definition AD 2000-Merkblatt A2 are ideal relief valves for medium mass flows. Their greater proportional range leads to a constant mode of operation and relief of pressure peaks for liquids in particular.

    Typical applications for LESER Modulate Action Series 433 safety valves are:

    • Chemical industry
      – recycling facilities: Low medium loss
      – piping with long line lengths
      – two-phase flow
      – waste gas purification systems on the outlet side
    • Heat-transfer oil systems
    • Liquids protection
      – metering pumps
      – hydraulic systems
      – pulsating operating pressures
    • Machine building (OEM)
      – piston compressors with small and medium capacities
    • Overflow function
    • Thermal expansion
      – protection of pipeline segments
      – sealed storage tanks


  • Features

    General design feature
    LESER – Modulate Action Safety Valves offer a large number of models, materials, and accessories for adaptation to any application:

    • 11 valve sizes from DN 15 to DN 150 – 1/2″ up to 6″ with connection possibilities for the respective application
    • Nominal pressure ratings from PN 16 to PN 160 / Class 150 to Class 600 fulfil most pressure requirements
    • Orifice 0.2 x D to > 1.1 x M cover all common performance requirements.
    • The required material for the application can be chosen from the large choice of body materials, for example:
      – 0.6025 / cast iron (Series 433)
      – 0.7043 / ductile iron
      – 1.0619 / WCB
      – 1.4408 / CF8M
    • Centre to face dimensions acc. to DIN 3320
    • Set pressures from 0.2 to 160 bar qualify Modulate Action safety valves for all industrial systems
    • Operating temperatures from -270 to 450 °C make use possible in numerous applications
      • compact construction and low weight for easy handling
      • same nominal inlet and outlet diameter
      • identical construction for steam, gasses and liquids
    • (single trim) reduces the number of required spare parts and facilitates cost-effective maintenance
    • Construction without a blow down ring guarantees easy service and prevents incorrect settings of the blow down ring
    • The one-part spindle reduces friction, guarantees optimal guidance and reliable operation under all operating conditions
    • The self-emptying angle type body prevents residue and reduces corrosion
  • Options

    LESER – Modulate Action safety valves can be individually adapted to the applications with a multitude of accessories.
    Examples are:

    • Discs with soft seal (O-ring) fulfill increased demands of functional tightness
    • Stellited or hardened metal seat surfaces of disc and seat reduce the wear and increase the service life
    • Balanced bellows for compensation of the back pressure and to protect the moving parts
    • Heating jacket for heating the safety valve when protecting cold stiff media
    • Each component can be constructed of an alternative material according to customer specifications
  • Datasheets