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Petroleum and Tank Farm Fire Safety — NFPA 30 and NFPA 11
Petroleum and fuel tank farms store very large volumes of flammable liquid in the open; a tank or dike (bund) fire, with its high radiant heat and potential to spread to adjacent tanks, is one of the hardest industrial scenarios. This article covers tank farm fire safety based on NFPA 30 (Flammable and Combustible Liquids Code) and NFPA 11 (the foam standard): tank types and the main fire scenarios (floating-roof rim seal fire, full surface fire, dike/bund fire, and boilover in crude oil), foam application methods (fixed foam chambers, floating-roof rim seal foam, subsurface injection, and foam monitors), the fluorine-free foam (F3/SFFF; AR-SFFF for alcohol/polar liquids) preference free of PFAS, water spray cooling that protects adjacent tanks, and 110%-capacity dike/containment with the water-foam infrastructure.
A-Pro Engineering
Petroleum and fuel tank farms store very large volumes of flammable liquid in the open. A tank or dike (bund) fire, with its high radiant heat and potential to spread to adjacent tanks, is one of the hardest industrial scenarios. This article covers tank farm fire safety based on NFPA 30 (flammable liquids) and NFPA 11 (foam); it is the storage companion to our petrochemical plant article.
Standards: NFPA 30 and NFPA 11
- NFPA 30 — sets the distances of tanks from each other and the boundary, the dike/bund arrangement, and the layout.
- NFPA 11 — defines the application rate, duration, and method of foam suppression.
To this are added NFPA 15 (water spray) for adjacent-tank cooling and NFPA 20 for the pump.
Fire scenarios
- Rim seal fire — most common in floating-roof tanks; occurs in the sealing zone around the roof, spreads to the whole surface if not tackled early.
- Full surface fire — in fixed (cone) roof tanks.
- Dike/bund fire — when liquid overflows a tank and ignites within the dike.
- Boilover — in wide-boiling-range liquids such as crude oil; water at the bottom suddenly vaporizes and ejects the burning liquid.
Each scenario requires a different foam method and cooling strategy.
Foam application methods
Per NFPA 11 the main methods are:
- Fixed foam chambers/pourers — gently pour foam onto a cone-roof tank surface.
- Rim seal foam system — distributes foam to the seal zone on a floating-roof tank.
- Subsurface injection — introduces foam at the tank bottom and lets it rise to form a blanket.
- Foam monitors/cannons — for dike fires and mobile response.
Systems can be fixed, semi-fixed, or mobile; on large-diameter tanks a fixed system + monitor combination is usually preferred. We covered foam design and expansion ratios in a separate article.
Fluorine-free foam (F3/SFFF, AR-SFFF for polar)
The AFFF/AR-AFFF foams formerly common contain PFAS (“forever chemicals”) and are being restricted by regulations such as EU REACH. As A-Pro we prefer fluorine-free (F3 / SFFF) foams; for water-miscible liquids such as ethanol, alcohol, and polar solvents, an alcohol-resistant fluorine-free foam (AR-SFFF) is used — because polar liquids break down an ordinary foam blanket. In a fluorine-free design, application rate, dosing, and liquid type are carefully matched.
Adjacent-tank cooling
One of the greatest dangers in a tank fire is the high radiant heat warming adjacent tanks (a BLEVE risk in pressure vessels) or a boilover spreading the burning liquid. Tanks around are therefore cooled with water spray (deluge) to keep the surface temperature safe. The cooling flow is calculated per NFPA 15 based on the exposed surface area — see our water spray cooling article.
Dike/containment and water infrastructure
Per NFPA 30, each tank/tank group is surrounded by a dike (bund); the dike volume is usually chosen as at least 110% of the largest tank. The slope and drainage inside direct flammable liquid to a safe collection point while separating rainwater. Because the water demand is very large, a reliable water source and fire pump are critical — we covered pump selection in our NFPA 20 article.
Suppression inside the dike (bund)
The dike is not only a basin that contains liquid — it is also a fire area that must be protected: when liquid accumulated here ignites, it forms a wide spill (pool) fire that heats the tank from below and rapidly worsens the situation. The dike therefore needs its own independent foam protection:
- Low-level foam pourers — fixed heads placed around the dike that gently spread foam over the dike floor.
- Fixed/semi-fixed foam monitors — water cannons sweeping the dike surface from above; multiple monitors on large dikes.
- Foam-water sprinkler/deluge — in-dike lines around critical equipment such as pump and dosing stations.
The application rate is calculated per NFPA 11 based on the dike’s surface area and liquid type; AR-SFFF is used for polar liquids. The aim is to blanket the dike fire early and cut off heat transfer to the tank.
Fire detection and alarm for the whole facility
In an open, large site a standard smoke detector is useless; detection is chosen by fire type and area characteristics:
- Optical flame detectors (UV/IR, multi-IR) — see a fuel fire within seconds on tank roofs and pump/manifold areas.
- Linear heat detection (LHD) cable — along the floating-roof rim seal zone, around the dike and along pipe racks; supported by point heat detectors.
- Leak/gas (LEL) detectors — at critical points to catch a leak before it becomes a fire.
- Manual call points, sirens/beacons — across the site.
All of this is gathered in a central addressable fire alarm panel. The panel communicates with SCADA/DCS to automatically open the foam/water spray deluge valves, start the pump and trigger emergency shutdown (ESD, ROSOV) — so the detection–alarm–suppression chain works in an integrated way. We covered detector selection and ATEX requirements in detail in our fire detection article.
Summary
Petroleum and tank farm fire safety is built on NFPA 30 + NFPA 11: fire scenarios that vary by tank type (rim seal, full surface, dike, boilover), the correct foam application method (fixed foam chambers, rim seal, subsurface, monitor), fluorine-free foam (F3/SFFF; AR-SFFF for polar), water spray cooling that protects adjacent tanks, in-dike foam suppression (low-level pourers + monitors), site-wide flame/heat/gas detection with addressable alarm and SCADA integration, and strong water infrastructure with a 110% dike/containment. We also covered which structure requires which system in our general article. At A-Pro Engineering we design foam, water spray, and water infrastructure for fuel terminals and tank farms in an integrated way; contact us for your project.
This content is for information purposes. Binding design must be produced project-by-project based on the actual conditions of the site and stored liquid and the editions of NFPA 30, NFPA 11, NFPA 15/20, and BYKHY in force.
© 2027 A-Pro Mühendislik. This is original technical content produced by A-Pro Engineering; all rights reserved. Copying, reproducing or republishing it in whole or in part without attribution and permission is prohibited.
Frequently asked questions
By what standards is a petroleum tank farm protected?+
The two core references are NFPA 30 (Flammable and Combustible Liquids Code) and NFPA 11 (Standard for Low-, Medium-, and High-Expansion Foam). NFPA 30 sets the distances of tanks from each other and from the boundary, the dike/bund (containment) arrangement, and the general layout, while NFPA 11 defines the application rate, duration, and method of the foam suppression system. To this are added NFPA 15 (water spray) for adjacent-tank cooling and NFPA 20 for the pump. In Türkiye, design is based on these standards together with BYKHY, the relevant environmental/OHS legislation, and the operator's specifications.
What scenarios occur in a tank fire?+
The main scenarios vary by tank type. In floating-roof tanks the most common is a rim seal fire in the sealing zone around the roof perimeter; if not tackled early it can spread to the whole surface. In fixed (cone) roof tanks a full surface fire occurs. Also, when liquid overflows a tank and ignites within the dike, a dike/bund fire forms. In liquids with a wide boiling range such as crude oil, a long-burning fire carries a boilover risk — water at the bottom suddenly vaporizes and ejects the burning liquid. Each scenario requires a different foam method and cooling strategy.
How is foam applied in a tank farm?+
Per NFPA 11 the main methods are: (1) fixed foam chambers/pourers — gently pour foam onto the surface of a cone-roof tank; (2) a rim seal foam system — distributes foam to the seal zone on a floating-roof tank; (3) subsurface injection — introduces foam at the tank bottom and lets it rise to form a blanket on the surface; (4) foam monitors/cannons — for dike fires and mobile response. Systems can be fixed, semi-fixed, or mobile. The method is chosen by tank type, diameter, and stored liquid; on large-diameter tanks a combination of fixed systems + monitors is usually preferred.
Can a fluorine-free option be used for tank foam?+
Yes, and it should be preferred. The AFFF/AR-AFFF foams formerly common contain PFAS ('forever chemicals') and are being restricted by regulations such as EU REACH. As A-Pro we prefer fluorine-free (F3 / fluorine-free, SFFF) foams; for water-miscible (polar) liquids such as ethanol, alcohol, and polar solvents, an alcohol-resistant fluorine-free foam (AR-SFFF) is used — because polar liquids break down an ordinary foam blanket. In a fluorine-free design, application rate, dosing, and the tank's liquid type are carefully matched. The aim is to avoid leaving a persistent pollutant in the environment while preserving effectiveness against fuel fire.
How are adjacent tanks protected?+
In a tank fire, one of the greatest dangers is the high radiant heat warming adjacent tanks and growing the fire (even a BLEVE risk in pressure vessels), or a boilover in crude oil spreading the burning liquid. Tanks around the burning tank are therefore cooled with water spray (deluge) systems to keep the surface temperature at a safe level and prevent ignition/deformation. The cooling-water flow is calculated per NFPA 15 based on the tank's exposed surface area. Where no fixed water spray exists, cooling is done with fire-brigade monitors; in both cases an adequate water source is critical.
How is a spill controlled in a tank farm?+
Per NFPA 30, each tank or tank group is surrounded by a dike (bund) to contain a possible leak/overflow; the dike volume is usually chosen as at least 110% of the largest tank's capacity, so that overflowing liquid stays under control and does not spread to neighbouring areas/water sources. The slope and drainage inside the dike are designed to separate rainwater while directing flammable liquid to a safe collection point. In a fire, the foam-water mixture and contaminated water are also managed with this collection system. Together with the foam and cooling infrastructure, the dike forms the basis of tank-farm safety.
How is a fire inside the dike (bund) extinguished?+
When liquid accumulated in the dike area around a tank ignites, it forms a wide spill (pool) fire that heats the tank from below and rapidly worsens the situation. The dike therefore needs its own independent foam protection. The main methods are: (1) low-level foam pourers — fixed heads placed around the dike that gently spread foam over the dike floor; (2) fixed/semi-fixed foam monitors — water cannons sweeping the dike surface from above, with multiple monitors on large dikes; (3) foam-water sprinkler/deluge — in-dike lines around critical equipment such as pump and dosing stations. The application rate is calculated per NFPA 11 based on the dike's surface area and liquid type; AR-SFFF is used for polar liquids. The aim is to blanket the dike fire early and cut off heat transfer to the tank.
How is fire detection and alarm set up in a tank farm?+
In an open, large site a standard smoke detector is useless; detection is chosen by fire type and area characteristics. Optical flame detectors (UV/IR, multi-IR) on tank roofs and pump/manifold areas see a fuel fire within seconds; a linear heat detection (LHD) cable or point heat detectors are laid along the floating-roof rim seal zone, and LHD is used along the dike and pipe racks. Leak/gas (LEL — lower explosive limit) detectors are placed at critical points to catch a leak before it becomes a fire. All of this is combined with manual call points, sirens/beacons and a central addressable fire alarm panel across the site; the panel communicates with SCADA/DCS to automatically open the foam/water spray deluge valves, start the pump and trigger emergency shutdown (ESD, ROSOV). This makes the detection–alarm–suppression chain work in an integrated way.
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