Safety Relief Valves for Natural Gas Systems

Relief Valves

USG safety relief valves are engineered to protect gas systems from dangerous over-pressurization in transmission, distribution, metering, and industrial applications. When regulators, bypass valves, or other pressure-control devices fail or leak, relief valves provide a critical last line of defense by automatically venting excess pressure to the atmosphere and maintaining system integrity.

Designed for large-capacity relief applications, USG mechanical relief valves offer dependable performance, rugged construction, and economical installation. They are widely used in natural gas systems where pressure buildup during low-load or off-peak conditions can otherwise lead to unsafe operating conditions.

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Product Documents

Safety Relief Valve Features

  • Large-Capacity Pressure Relief: Designed to safely discharge excess gas volume and maintain pressure below predetermined limits.

  • Mechanical, Spring-Operated Design: Opens automatically when system pressure exceeds the set point and reseats tightly when pressure returns to normal.

  • Roll-Out Diaphragm Technology (Model 257-S): Minimizes pressure buildup above set point while delivering maximum relief capacity and accurate repeatability.

  • Angled, High-Flow Body Design (Models 250-S & 250-DW): Large exit areas support high flow rates and allow valve removal without disturbing piping.

  • Weatherproof & Watertight Construction: Suitable for indoor or outdoor installations in utility and industrial environments.

  • Ball-Check Diaphragm Sentry (Select Models): Maintains relief protection in the event of diaphragm failure.

Benefits

  • Improved System Safety: Protects downstream piping, meters, and equipment from over-pressurization events.

  • Reliable Final Pressure Protection: Provides a dependable safeguard when regulators or bypass valves fail.

  • High Discharge Capacity: Supports large gas volumes in distribution and industrial applications.

  • Simple Installation & Operation: No external power or controls required. It operates automatically based on system pressure.

  • Long Service Life: Heavy-duty materials and proven designs ensure dependable performance over decades of service.

Capability

USG safety relief valves are designed for a wide range of gas system protection requirements.

  • Application Types: Gas distribution systems, district regulator stations, metering sets, city gate stations, industrial gas systems

  • Gas Compatibility: Natural gas, propane (LP gas), nitrogen, dry COâ‚‚, air, and other non-corrosive gases

  • Installation:

    •  Indoor or outdoor installations

    •  Typically installed vertically with discharge piping to a safe vent location
      (Not recommended for buried service)

  • Relief Pressure Ranges: From ounces of pressure through high-psi relief applications (model dependent)

Specifications

Available Models

  • Model 257-S: Spring-operated safety relief valve featuring a roll-out diaphragm and double-ported soft-seat valve for large-capacity relief with minimal pressure buildup.

  • Model 250-S: Spring-loaded safety relief valve with angled body and deep molded diaphragm for high flow capacity.

  • Model 250-DW: Dead-weight loaded safety relief valve offering precise relief pressure control for low-pressure applications.

Construction

  • Body Materials: Cast iron (ASTM A126 Class B)

  • Diaphragm: Buna-N with fabric reinforcement (model dependent)

  • Valve Trim: Soft-seat designs for tight sealing and reliable reseating

  • Housing & Internal Components: Heavy-duty construction for durability, corrosion resistance, and long-term reliability

Pressure & Size Ranges

  • Pipe Sizes: 2", 3", and 4" (NPT and ANSI flanged configurations available)

  • Relief Pressure Ranges: Approximately 2 oz to 100 psi, depending on model and spring selection

  • Maximum Working Pressure: Up to 175 psi (model dependent)

For detailed sizing guidance, capacity tables, spring selections, and dimensional data, refer to the product documents above.