An ignitable liquid is hazardous sitting in storage; pumped, heated, mixed or sprayed, it is far more so. Liquid escaping from a pressurised line can become a spray fire within seconds, a pool fire spreading across the floor, or a vapour cloud explosion in an enclosed space. FM Global DS 7-32 Ignitable Liquid Operations is about preventing these scenarios in process areas using ignitable liquids, and limiting the damage when they occur.
Scope
The data sheet covers areas where ignitable liquids are transferred, dispensed, mixed, pumped, heated or used in a process: paint and chemical manufacturing, solvent recovery, filling and unloading stations, process tanks and the piping that connects them. Storage in portable containers is covered by DS 7-29, and certain special processes (spray booths, heat transfer fluids, hydraulic systems and similar) by their own companion sheets.
Fire Scenarios
| Scenario | How it arises | Main measure |
|---|---|---|
| Spray (jet) fire | Leak from a pressurised line, flange or gasket | Shorten the release; stop pressure and pumps |
| Pool / spill fire | Tank overfill, hose failure, container upset | Containment and emergency drainage |
| Running (three-dimensional) fire | Burning liquid falling from height or flowing between platforms | Solid platforms instead of grating, drainage, sprinklers |
| Vapour cloud explosion | Vapour building up in an enclosed space and igniting | Ventilation, ignition control, explosion venting |
Key Loss-Prevention Principles
1. Prevent the release
In process design the cheapest fire is the one that never starts. Welded metal piping, a minimum of flanges, avoiding glass sight gauges and unnecessary flexible hoses, protecting lines exposed to impact and leak testing after maintenance all reduce the chance of a release. Pump seals and flexible connections are the main sources of leaks on site.
2. Limit the duration and quantity of the release
This is perhaps the most distinctive point of the FM approach: the size of the fire is directly tied to the amount of liquid released. Automatic, fire-safe emergency shut-off valves at tank outlets, pumps stopped by fire detection or sprinkler waterflow signals, and emergency stop buttons reachable from the control room and the field all shorten the release. Sprinklers are designed to control the fire from a limited release; while the release continues, no sprinkler design is enough.
3. Containment and drainage
Curbs, sills, trenches and floor slopes keep spilled liquid within the process area and stop burning liquid flowing into neighbouring areas, cable trenches or under the building. The emergency drainage system must carry the largest credible release plus sprinkler and hose water to a safe collection point. Flame traps in the drainage line stop fire travelling along the drain.
4. Sprinklers and special protection
Sprinkler design in process areas is selected from the data sheet by liquid type, release scenario (spray or pool), ceiling height and whether drainage is provided. Some cases need foam-water systems or local water spray aimed at equipment. Shielded areas below platforms and equipment need their own sprinklers.
5. Ventilation and ignition sources
Mechanical ventilation keeps vapour below explosive concentrations. Hazardous area classification is carried out and electrical equipment is selected for those zones. Bonding and earthing against static electricity is critical, especially during transfer and filling. Hot work permits and management of change prevent ignition arising from operations. Hot surfaces (steam lines, exhausts, oven casings) should also be compared with the liquid's autoignition temperature; a sprayed liquid can ignite on a hot surface without any spark.
6. Building and explosion protection
Areas processing significant quantities of ignitable liquid are separated from the rest of the building by fire-resistant walls and preferably located against an exterior wall. Where a vapour cloud explosion is credible, explosion vent panels or damage-limiting construction are used.
How It Differs from NFPA 30 and ATEX Practice
NFPA 30 includes rules for processing facilities and dispensing, while standards such as NFPA 33 (spray application) and NFPA 34 (dip tanks) cover particular processes. In Europe the ATEX directives (2014/34/EU for equipment, 1999/92/EC for workplaces) govern hazardous area classification and equipment selection; Turkey has equivalent occupational health and safety regulations on explosive atmospheres. These rules focus mainly on preventing ignition.
The FM difference is that it accepts ignition cannot always be prevented and puts its weight on limiting release duration, drainage, and sprinkler control of that limited fire. At an FM survey, "does the emergency shut-off valve close on sprinkler waterflow?" matters as much as "is the equipment Ex certified?".
Field observation: the most frequent gap in process areas is pumps that are not stopped by fire detection or sprinkler waterflow. A pump that keeps running during a fire keeps feeding it.
Practical Checklist
- Likely release points (flanges, seals, hoses, gauges) are identified and reduced.
- Automatic, fire-safe emergency shut-off valves are fitted at tank outlets.
- Pumps and pressurised feeds stop on fire detection or sprinkler waterflow.
- Containment and emergency drainage are sized for the largest release plus firewater.
- Drainage lines include flame traps.
- Sprinkler design is selected from the data sheet by release scenario and ceiling height.
- Ventilation, hazardous area classification and Ex equipment are consistent.
- Bonding and earthing are tested regularly.
- The process area is fire-separated and explosion venting is provided where needed.
- Hot work permit and management of change procedures are in force.
Frequently Asked Questions
How does DS 7-32 differ from DS 7-29?
DS 7-29 covers storage in portable containers; DS 7-32 covers operations where liquid is transferred, mixed, heated or used in a process. Most sites apply both.
Why does release duration matter so much?
Fire size depends on how much liquid feeds it. As long as the release continues the fire grows; sprinkler design assumes a limited release.
Is Ex-certified equipment enough?
No. Ex equipment reduces the likelihood of ignition but does not answer the questions of release, drainage and extinguishment. FM expects all of these together.
How should emergency shut-off valves be verified?
Test periodically that the valve closes on its real trigger signal (fire detection, sprinkler flow switch or emergency stop) and measure the closing time. Closing it by hand alone does not prove the interlock chain works. Results are recorded and any fault is managed as an impairment.
Why can grated platforms be a problem?
Grating lets burning liquid fall to the levels below and creates a three-dimensional fire. Where liquid must be collected, solid platforms with drainage are preferred.
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Download MEP Calc on the App StoreFM Global Property Loss Prevention Data Sheet 7-32, Ignitable Liquid Operations; FM Global DS 7-29; NFPA 30; NFPA 33; NFPA 34; ATEX Directives 2014/34/EU and 1999/92/EC. This page is a summary in our own words, not the data sheet text. Download and design to the current revision from fmglobal.com.