The LESER Type 811/821 Pilot-Operated Safety Relief Valves are designed for precision pressure relief and environmental safety in high-pressure industrial systems. The Type 811 features pop action for rapid gas relief, while the Type 821’s modulate action ensures proportional opening, reducing emissions and noise for vapor, gas, and liquid applications. Fully compliant with API 526, these valves offer exceptional tightness up to 97% of set pressure and operate reliably up to 426 bar. Their robust design and integrated backflow preventer make them ideal for critical applications in petrochemicals, energy, and LNG/LPG industries, prioritizing both safety and environmental responsibility.
| Parameter | Type 811 (Pop Action) | Type 821 (Modulate Action) |
|---|---|---|
| Set Pressure (CE) | 2.5–256 bar (36–3705 psig) | 1–426 bar (15–6179 psig) |
| Set Pressure (ASME) | 2.5–256 bar (36–3705 psig) | 1–689 bar (15–10000 psig) |
| Temperature Range (CE) | -45°C to 200°C (-49°F to 392°F), Special: -162°C to 300°C | -45°C to 200°C (-49°F to 392°F), Special: -162°C to 300°C |
| Temperature Range (ASME) | -49°F to 392°F, Special: -259.6°F to 572°F | -49°F to 392°F, Special: -259.6°F to 572°F |
| Nominal Diameter at Inlet | DN 25–DN 200 (NPS 1–NPS 8) | DN 25–DN 200 (NPS 1–NPS 8) |
| Actual Orifice Diameter (d₀) | 11–180 mm (0.433–7.087 in) | 11–180 mm (0.433–7.087 in) |
| Actual Orifice Area (A₀) | 95–25446.9 mm² (0.147–39.443 in²) | 95–25446.9 mm² (0.147–39.443 in²) |
| Flange Rating Inlet | PN 10–PN 250, ASME Class 150–1500 | PN 10–PN 400, ASME Class 150–2500 |
| Body Material | 1.0619, 1.4408, SA 216 WCB, SA 351 CF8M, SA 352 LCB, SA 494 M35-1 (Monel), SA 494 CX2MW (Hastelloy) | 1.0619, 1.4408, SA 216 WCB, SA 351 CF8M, SA 352 LCB, SA 494 M35-1 (Monel), SA 494 CX2MW (Hastelloy) |
| Seat Gasket | Soft sealing, metallic, sealing plate | Soft sealing, metallic, sealing plate |
| Load Type | Medium-controlled | Medium-controlled |
The LESER Type 811/821 valves excel in precision pressure relief for critical industries:
Its modulate action opens proportionally to overpressure, minimizing product loss and emissions.
Yes, they handle pressures up to 426 bar (6179 psig) for Type 821 and 256 bar (3705 psig) for Type 811.
It enhances safety by preventing reverse flow, integrated as a standard component.
Yes, the supplementary loading system allows function testing and adjustment without downtime.
Options include Monel and Hastelloy for corrosion-resistant applications.
For more information about the LESER Type 811/821 Safety Relief Valves, pricing, or to request a demo, contact our team:
