LESER Type 431/433 Modulate Action Safety Valve

The LESER Type 431/433 is a flanged, spring-loaded safety relief valve designed for general industrial pressure relief across steam, gas and liquid service. The 433 is the closed-bonnet variant, the 431 is the open-bonnet equivalent, and the 433 PN 160 covers higher pressure applications up to 160 bar. The valve reaches full lift within a 10% pressure increase above set pressure and is characterised by low medium loss, which makes it suitable for applications where media cost or environmental release is a concern. A single trim covers steam, gas and liquid service, reducing the number of spare parts required across a fleet. The angle-type body is self-emptying to prevent residue build-up and reduce corrosion. The design uses no blow down ring, which simplifies service and prevents incorrect field settings. The one-piece spindle reduces friction and provides reliable operation across all service conditions. Available in cast iron, ductile iron, WCB carbon steel and CF8M stainless steel, with set pressures from 0.2 to 160 bar and operating temperatures from -270°C to +450°C depending on material. Certified to CE/PED 97/23/EC, DIN EN ISO 4126-1 and TÜV SV 577, with additional approvals from leading classification societies including Bureau Veritas, Lloyd's Register, DNV and Germanischer Lloyd.