Liquid Sizing Formula calculates either the required relief area or flow capacity for liquid service. This ASME-approved method accounts for liquid properties and pressure differential to ensure safe pressure relief while preventing wasteful oversizing.
| Parameter | Description | Typical Values |
|---|---|---|
| Mass Flow Rate (W) | Relief capacity required (kg/hr) | 100 - 100,000 |
| Upstream Pressure (P) | Set pressure plus overpressure (kPa absolute) | > 0 |
| Back Pressure (Pc) | Pressure at valve outlet (kPa absolute) | > 0 |
| Density (ρ) | Liquid density at flowing conditions (kg/m³) | 700 - 1500 |
| Constant (2407) | Derived from unit conversion factors for flow rate, pressure, and density | Fixed |
Proper liquid relief sizing prevents catastrophic equipment failures in chemical plants, refineries, and other liquid-handling facilities. Undersized valves can't relieve excess pressure, while oversized valves may cause system instability. This calculation ensures safety devices function as intended during liquid overpressure events.
ASME BPVC Section VIII and API RP 520/521 mandate liquid relief calculations. The 2407 constant incorporates unit conversions and assumes turbulent flow. Typical overpressure is 10% for conventional valves and 21% for balanced bellows valves.
Accurate liquid relief sizing is essential for safe industrial operations. This calculation ensures proper protection against overpressure while optimizing system design. Always verify results against applicable codes and consider actual liquid properties at relief conditions.