This Fire Water Demand & Pump Sizing spreadsheet from 3D-LABS follows API standards and gives instant, checkable results for practising engineers — no manual derivation required.
This spreadsheet calculates fire water demand and pump sizing for industrial plants per NFPA 15 (Water Spray Fixed Systems), NFPA 20 (Centrifugal Fire Pumps), OISD-116 (Fire Protection Facilities for Petroleum Depots, India), and IS 15105:2002. It determines the required fire water flow rate, storage volume, pump rated flow, head, and driver power — the four values required for fire water system procurement packages.
What standard does this calculation follow?
NFPA 15:2017 (Standard for Water Spray Fixed Systems for Fire Protection), NFPA 20:2019 (Standard for the Installation of Stationary Pumps for Fire Protection), OISD-116 Rev 2 (Oil Industry Safety Directorate, India), IS 15105:2002 (BIS India), and API RP 2001 (Fire Protection in Refineries).
What formula is used?
Fire water demand: Q_total = Q_spray + Q_monitors + Q_hose_streams (litres/min). Spray density per NFPA 15: minimum 10.2 L/min/m² for process vessels, 6.1 L/min/m² for cable trays. Pump rated flow = 1.5 × design flow (NFPA 20 redundancy). Net positive suction head required: NPSHr from pump curve; NPSHa = ha – hvp – hf – he ≥ NPSHr + 0.6 m safety margin.
Frequently Asked Questions
What fire water spray density is required for a process vessel per NFPA 15?
Per NFPA 15:2017 Table 7.4.2, the minimum water spray density for cooling LPG/flammable liquid vessels is 10.2 L/min/m² of exposed surface area. For transformer protection: 6.1 L/min/m² on vertical surfaces. For cable trays: 6.1 L/min/m² per NFPA 15-7.3. Apply to the total exposed surface area including top heads and shell.
What is the OISD-116 requirement for fire water storage volume?
OISD-116 Clause 4.2 requires fire water storage volume for a minimum 4-hour fire fighting duration at peak demand flow rate. For petroleum depots: V = Q_peak × 240 minutes (4 hours). A system requiring 500 m³/hr peak flow needs 500 × 4 = 2,000 m³ storage minimum. Replenishment rate must restore storage within 24 hours.
How many fire pumps are required per NFPA 20?
NFPA 20:2019 Clause 4.26 requires: one main pump + one standby pump of equal capacity. For facilities over 6,000 L/min (1,585 gpm), two main pumps plus one standby (each at 100% rated capacity) are recommended. One pump must be diesel-driven (independent of electrical supply per NFPA 20 Clause 4.25). Pumps must deliver 150% of rated flow at no less than 65% of rated head.
What’s Included
An instant Excel download with the complete formula set, a worked numerical example, and reference to the governing standard — ready to adapt to your own project inputs.
