Selection criteria for safety valves

The selection of a safety valve is a critical process that depends on several key factors. These include the operating pressure, operating temperature, set pressure, type of medium, and discharge capacity. Here’s a detailed guide on the criteria and principles for selecting the appropriate safety valve:

Safety Valves

Safety Valves

Nominal Pressure Determination: The operating pressure dictates the nominal pressure of the safety valve.

Temperature Range: The operating temperature determines the suitable temperature range for the safety valve.

Set Pressure Range: The calculated set pressure value decides the spring or lever set pressure range.

Material and Structure: The type of medium influences the material and structural design of the safety valve.

Throat Diameter: The discharge capacity calculation determines the throat diameter of the safety valve.

Conditions for Safety Valve Selection

When selecting a safety valve, the following conditions must be clearly defined:

Operating Conditions: This includes the type of medium, actual working pressure, and temperature.

Pressure Specifications: The opening pressure (set pressure), discharge pressure, and reseating pressure are crucial for the manufacturer to set the valve as per user requirements, or the discharge capacity and valve opening height.

Selection Principles

Gas or Steam Discharge: Use a full-lift safety valve.

Liquid Discharge: Use either a full-lift or a micro-lift safety valve.

Water Vapor or Air Discharge: A safety valve with a lever is suitable.

High Pressure and Temperature Gases: For set pressures above 3 MPa and temperatures exceeding 235°C, use a safety valve with cooling fins to prevent direct erosion of the spring by the discharged medium.

Atmospheric Discharge: Use an open bonnet safety valve for media that can be safely discharged to the atmosphere. Use a closed bonnet safety valve for media that cannot be discharged to the atmosphere.

Toxic or Corrosive Media: Use a bellows safety valve for highly toxic, highly corrosive, or extremely dangerous media.

High Back Pressure: Use a back pressure balanced safety valve or a pilot-operated safety valve.

Critical Applications: In some important applications, two safety valves may be installed as mutual backups. The inlet and outlet shut-off valves of these safety valves should have a mechanical interlock device to ensure the required discharge area of the vessel is maintained at all times, including during maintenance.

As an expert in the field of piping systems, Haihao Group not only produces a variety of piping system supporting products, but also is proficient in the installation and maintenance knowledge of various piping systems, and actively shares it with customers. If your piping system project requires related products, please feel free to contact us.

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