Safety Valve Discharge Capacity Calculation

Safety Valve Discharge Capacity Calculation

• Medium is Air or Gas
• Critical Condition:

1. Sub-critical Condition:

In the Formula:

Ws---The Discharge Capacity of Safety Valve, Kg/h

K---The Discharge Coefficient, related to the structure of safety valve, provided by the manufacturer, also can be selected upon the following:

Full Lift Safety Valve, K=0.75～0.81

Low Lift Safety Valve, K=0.2～0.3

Pd---The Discharge Pressure of Safety Valve (Absolute pressure)、Pd=1.1Ps+0.1MPa

Ps---The Set Pressure of the safety valve,  MPa

Po---The Outlet pressure of the safety valve, MPa

A----The minimum exhaust sectional area of safety valve,  mm²

Fully Lift Safety Valve, when,

Low Lift Safety Valve, when,

In the formula: h---the opened height of the safety valve, mm

 d₁---The minimum diameter of flowing area(throat diameter), mm

D---The diameter of seat ring, mm

C---Coefficient of gas property, (Reference to the table 1)

K---Absolute heat index of gas,

M---Mole Mass of gas, kg/mol

T---The Temperature of the gas, K

Z---The compressed coefficient of gas under the operation temperature and pressure.

• Medium is Liquid

In the Formula:

Kp---Overpressure regulating value

25% overpressure, Kp=1.0

20% overpressure, Kp=0.8

10% overpressure, Kp=0.6

Kv---Intensity Regulating Value

U---The absolute Intensity of the flowing medium temperature

.ρ---The liquid density at the valve inlet temperature, kg/m³

• P----The Pressure drop of the Inlet and Outlet Pressure, Mpa

,

Ps---Set Pressure, Pb---- Back Pressure (guage pressure)

• Medium is Saturated Steam

When the Saturated Steam is≥98%, the maximum working heat is 10℃

1. When  

   ,

1. When ,

Table1---The Coefficient of gas properties for different K value

Value C of the property coefficient of the gases of different valve k