Introduction

Hydraulic demand calculation is one of the fundamental steps in the design of fire protection systems. This calculation determines the flow rate and pressure required to ensure that suppression systems operate effectively during a fire event.

Main Parameters

To determine the hydraulic demand, the following must be considered:
• application density
• hazard area
• minimum pressure at devices
• friction losses

Required Flow Rate Calculation

The required flow rate is calculated by multiplying the application density by the protected area:

Q = D × A

Where:
Q = required flow rate
D = application density
A = protected area

Practical Example

Assume:
hazard area: 400 m²
density: 6.5 L/min·m²

The required flow rate would be:
2600 L/min

This value serves as the basis for sizing:
• fire pumps
• piping
• valves

Conclusion

A proper hydraulic demand calculation ensures that the system delivers sufficient extinguishing agent at the critical moment of a fire.

References

NFPA 13 — Standard for the Installation of Sprinkler Systems
NFPA 20 — Standard for the Installation of Stationary Pumps for Fire Protection
NFPA 24 — Standard for the Installation of Private Fire Service Mains

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