API - Pressure relief valves | LESER
API Pressure Relief Valve from LESER

Pressure relief valves according to API 526 with standardized capacities and dimensions

  • Compliance with API 526
  • Diverse selection of high-alloy materials available as standard
  • Longer lifetime due to hardened discs, partly stellited seats and integrated shielding of the optional bellows
  • Single trim: Identical internal parts for S/G/L for cost-effective maintenance
  • LESER Nanotightness: Exceeds the tightness requirements of API 527 by 50%


LESER API safety valves are designed, marked, produced and approved according to the requirements of the following regulations:

  • LESER CE Approvel
  • LESER ASME Approvel
  • LESER EAC Approvel
  • LESER Chinese TS Approvel

Valve Types

Type 526

Fulfillment of API 526

DN 25 - DN 200 (1" - 8")

Technical specifications API

Nominal Diameter at Inlet
DN 25 - DN 200 | 1" - 8"
Actual Orifice Diameter d₀
14 mm - 161.5 mm | 0.551 in - 6.36 in
Actual Orifice Area A₀
154 mm² - 20,485 mm² | 0.239 in² - 31.75 in²
0.12 bar - 413.7 bar | 2 psig - 6,000 psig
Temperature (in accordance with DIN EN)
-268 °C bis 538 °C | -450 °F bis 1,000 °F
Body Material
1.0619, 1.4408, 1.7357 | SA 216 WCB, SA 351 CF8M, SA 217 WC6, SA 352 LCB, SA 351 CF3M, SA 995 Gr 4A CD3MN (Duplex), SA 494 M35-1 (Monel), SA 494 CX2MW (Hastelloy)
Valve Connection
Flange in accordance with ASME B 16.5 or DIN EN 1092
Bellows Material (optional)
Load Type
Urea Plant

Case study

LESERs safety valves increase reliability and performance of Urea plants


Chemical plant

LESER Solution:

API and Best Availability

Customer since:

over five years

Quantity of Valves Supplied:

more than 1800

LESERs solution against corrosion 
In the last 10 years LESER, The Safety Valve Company, from Hamburg in Germany has installed more than 1800 safety valves in Urea plants located in almost all countries in the world.

Of these 1800 more than 320 are equipped with LESER steam flushing system assuring no clogged situations of the outlet line and no condensation and erosion corrosion of the seat area.
More than 70 Safety Valves are designed with a standardized block body design 3J4 and the LESER flushing system with the following benefits:
  • Material of all medium wetted parts can be in high corrosive resistant  composition
  • Constant temperature of nozzle higher than condensation temperature of the carbamate solution to avoid negative corrosion effects and material structure effects of sealing surface
  •  Metal to metal sealing with LESER Nanotightness process for sealing surfaces with roughness and flatness at measuring range of 100 nm 
  • 360°-flushing of main valve body to avoid any crystallization in case of blow off situation
  • One steam supply point needed for the LESER flushing, even if heating  jacket is preinstalled to heat outer area of block body with minimized steam consumption Urea 

And the synthesis sections of already four lines in urea plants are equipped with the LESER Supplementary Loading System enabling these plants to operate the synthesis pressure very close to the set pressure leading to higher conversion figures and 75% lower emissions in case of a blow off situation

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