OBJECTIVE :
The objective of this activity is to calculate the firewater demand required by the fixed fire protection systems for process plants as per OISD- 116.
ABBREVIATION & DEFINITION :
BEDP : Basic Engineering Design Practice
EPCC : Engineering, Procurement, Construction and Commissioning
LSTK : Lump Sum Turnkey
MMTPA : Million Metric Tonnes Per Annum
NFPA : National Fire Protection Association
OISD : Oil Industry Safety Directorate
PMC : Project Management Consultant
CODES & STANDARDS
The following codes and standards with latest code shall be followed for the calculation of the fire water demand calculation for any process plant.
OISD-STD-116 : Fire Protection facilities for Petroleum Refineries and Oil and Gas
NFPA-15 : Standard for Water Spray Fixed Systems for Fire Protection
Fire Water Demand Calculation :
The fire water demand for process unit to be estimated based on all the three alternates as per clause no. 2.5 of Annexure-I of OISD-116.
Alternate-I
Total unit area = 110 x 90 m2
Consider water rate @ 1 lpm/ m2 on area basis,
Water rate = (9900 x 1) lpm
= 594 m3/hr
Water for supplementary hose stream (including 1 HVLR) = 372 m3/hr
Total water rate = 966 m3/hr
Alternative – II
Consider a 10m x 10m portion of process unit area on fire. Provide water cover over an area of
30m x 30m at the rate of 10.2 lpm/ m2,
Water rate = (900×10.2) lpm
= 9180 lpm
= 551 m3/hr
Water for supplementary hose steam (including 1 HVLR) = 372 m3/hr
Total water rate = 923 m3/hr
Alternate – III
Water required for portion of unit area provided with fixed spray system (Extreme Hazardous Area)
Area assumed = 1000 m2
Water rate = 10.2 lpm/ m2
Cooling water required = 10200 lpm
= 612 m3/hr
Water for supplementary hose stream (including 1 HVLR) = 372 m3/hr
Total cooling water required = 984 m3/hr
Considering the maximum water under alternative I, II & III
Design flow rate = 984 m3/hr
