Note:

This formula is used to calculate the minimum orifice area required for steam, air, or dry gas under critical flow conditions. It is mainly used in safety valve sizing to ensure proper gas discharge.

Explanation of Parameters:

• Mass Flow Rate (ṁ): The amount of gas passing through per hour.
• Isentropic Exponent (C): A factor that represents gas properties.
• Coefficient of Discharge (Kdr): A correction factor for real-world efficiency.
• Relieving Pressure (P₀): The absolute pressure at which the gas is released.
• Specific Volume (ν): The volume occupied by 1 kg of gas at given conditions.
• Constant Value (0.2883): This is a derived factor used in gas flow calculations, particularly for critical flow conditions. It plays a key role in determining the minimum orifice area.

BS EN 4126 is a European standard that specifies requirements for safety relief valves used to protect pressurized systems by safely discharging excess gases or steam, preventing overpressure and ensuring system safety.

Real-life Applications:

• BS EN 4126 Valves: This formula is used in pressure relief valves according to the BS EN 4126 safety standard.
• Boilers: Ensures excess steam is released safely.
• Fire Safety: Used to prevent pressure buildup.
• Compressed Air Systems: Helps in HVAC and industrial air management.

Conclusion:

This calculation ensures that gases can be safely discharged under high pressure, preventing explosions or system damage.