Boiler Safety Valve Relieving Capacity Calculator (ASME I)

Compute certified steam relieving capacity ($lb/hr$ or $kg/hr$), Napier formula sizing, orifice area selection, and $3\%$ accumulation limits per ASME Section I.

Safety Valve Setting & Orifice

Set Pressure P_set (psig):

Valve Location:

Superheated Steam Temp (°F): Applies if superheater location

ASME API Orifice Designation:

Certified Discharge Coeff K_d: ASME Section I derated (0.90 typical)

Overpressure Accumulation (%): ASME I strict limit = 3%

Certified Relieving Capacity Output

Certified Capacity (W_steam):

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Capacity in Metric Units:

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Relieving Pressure P_rel (psia):

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Superheat Correction Factor (K_sh):

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Reaction Force on Discharge Elbow:

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ASME Section I Code Status:

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ASME Section I Boiler Safety Valve Sizing

ASME Boiler and Pressure Vessel Code (BPVC) Section I strictly regulates overpressure protection for power boilers. Unlike ASME Section VIII (which permits $10\%$ to $16\%$ accumulation), Section I restricts maximum steam pressure rise during full load rejection to strictly 3% overpressure accumulation.

Napier Formula & Superheater Priority Setting

Steam relieving capacity is governed by the Napier formula: $$W = 51.45 \cdot A \cdot P_{relieving} \cdot K_d \cdot K_{sh}$$ To protect superheater tubes from burning out during overpressure, the superheater outlet safety valve is always set to lift before the drum safety valves, ensuring cooling steam continues flowing across superheater tube bundles.

Boiler Safety Valve Relieving Capacity Calculator (ASME I)

Safety Valve Setting & Orifice

Certified Relieving Capacity Output

ASME Section I Boiler Safety Valve Sizing

Napier Formula & Superheater Priority Setting

Frequently Asked Questions