Fire Safety in Petroleum Refineries and Fertilizer Plants - Code of Practice
2003 Edition

According to IS 15394, LPG storage spheres and hydrocarbon tanks must adhere to specific spacing requirements to ensure fire safety. Groups of spheres or tanks are limited to a maximum of six vessels with an aggregate capacity not exceeding 15,000 cubic meters, maintaining at least 50 meters separation between different groups. Additionally, groups should be spaced by (R + 30) meters, where R represents the sphere's radius. Individual horizontal pressure tanks (bullets) require a minimum 50-meter gap, which can be reduced to the tank diameter if concrete partition walls with overhead water spray systems are installed. Tanks must be arranged in staggered rows to reduce the risk of cascading failures, and diking and drainage provisions must comply with Clause 12.15 to prevent accumulation of leaked liquids under spheres.

IS 15394 mandates that all load-bearing supports for storage tanks, vessels, heaters, piping, and process equipment must possess fire protection to their full load-bearing height, typically requiring a minimum of 3 hours of fire resistance. For pipe racks located within 7.5 meters of major equipment such as heaters and pumps, both vertical and horizontal members should be fireproofed for 3 hours; those between 7.5 and 15 meters require 2 hours of protection. Pipe racks beyond 15 meters generally do not need fire protection unless under special circumstances. Cantilever pipe racks are prohibited. Supports of fin fan coolers above pipe racks must have at least 2 hours of fire resistance, while vessels with significant liquid content above pipe racks require 3 hours. Elevated horizontal tank supports are preferably concrete or masonry, and steel legs for spherical tanks should have 2 to 3 hours of fire protection.

The standard specifies a minimum fire water pump capacity of 410 cubic meters per hour at 8.8 kg/cm² pressure, maintaining a residual pressure of 7 kg/cm² at the most remote point continuously. Fire-water mains should be sized to deliver this flow and pressure to the main plant areas. Design flow rates consider the largest two simultaneous demands, including a cooling flow of 10 liters per minute per square meter of tank shell area for tanks on fire, 5 lpm/m² for tanks within the (R+30) meter radius, and 3 lpm/m² for tanks beyond that radius. Foam systems must be installed on the largest tank roofs, supported by hydrants and monitors delivering specified flow rates at the required pressure. Water storage capacity must cover at least nine hours of firefighting at full pump output, with seawater use allowed as a backup.

IS 15394 requires that control rooms situated in hazardous zones be designed to resist blasts, particularly those within 120 meters of hydrocarbon or hydrogen units. Minimum separation distances are 15 meters for single process units and 30 meters when multiple units are involved, with a preference for maintaining 30 meters to reduce fire and shrapnel risks. Control rooms must be single-storied without rooftop equipment, located on the plant's edge adjacent to roads or parking areas, and built on elevated plinths. They must have at least two exits with independent, unobstructed escape routes, and incorporate blast resistant baffle walls with 45° or 90° overlaps at opposite doors. Exhausts from toxic gas analyzers should be routed outside these rooms. The design anticipates a static overpressure of 3 MPa to ensure structural integrity under blast loads.

To prevent vapor migration during fires, IS 15394 recommends installing fire stops or water seals within industrial sewer and drainage systems, effectively blocking vapor transmission through openings in vulnerable sections. Sealed segments of the sewer must be properly vented to prevent pressure build-up and potential seal failure, especially where light materials may enter the system. Particular attention is necessary at the junctions of building drains with industrial sewers to ensure tight sealing and adequate venting. Additionally, sewer systems should be sized to handle both normal runoff and firefighting water overflow, avoid mixing stormwater with process drains, provide sufficient slope for drainage, use separate localized drains for incompatible chemicals, and include emergency control valves operable on instrument air or nitrogen during power outages.