The LESER Type 811/821 Pilot-Operated Safety Relief Valves are engineered for high-efficiency pressure protection in demanding industrial applications. The Type 811 features a rapid pop action for abrupt opening, ideal for gas applications, while the Type 821 offers modulate action for proportional opening, minimizing product loss and noise in vapor, gas, and liquid systems. Both valves comply with API 526 standards, ensuring 100% compatibility with high-pressure systems up to 426 bar. With exceptional tightness up to 97% of set pressure and robust construction, these valves are perfect for industries like chemical processing, oil and gas, and LNG/LPG operations.
| 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 are optimized for high-pressure safety applications:
Type 811 offers pop action for abrupt opening in gas applications, while Type 821 uses modulate action for proportional opening, reducing emissions and noise.
Yes, both Type 811 and 821 meet API 526 standards for full compatibility.
Yes, they support back pressures up to 70% of set pressure, outperforming spring-loaded valves.
They are certified to ASME Sec. VIII Div. 1, PED, DIN EN ISO 4126-4, AD 2000-Merkblatt A2, AQSIQ, EAC, and classification societies (LR, RINA, DNV GL, BV).
They maintain tightness up to 97% of set pressure, with increasing closing forces near set pressure.
For more information about the LESER Type 811/821 Safety Relief Valves, pricing, or to request a demo, contact our team:
