LNG Fire Protection: Dry Chemical Systems & Safety

Dry chemical, particularly potassium bicarbonate, is a primary extinguishing agent for LNG fire hazards because it can rapidly interrupt combustion without adding heat to the cryogenic liquid. Water and foam have different roles: water is primarily used for cooling surrounding equipment and controlling radiant heat, while high-expansion foam can help control large LNG pool fires and vapor movement.

Understanding an LNG Fire

LNG is primarily methane stored as a liquid at approximately -260°F (-162°C). When released, it rapidly vaporizes because surrounding surfaces are warmer than the liquid. The resulting vapor can initially remain close to the ground before warming and becoming buoyant.

An LNG release can produce several fire scenarios, including flash fires, pool fires and jet fires from pressurized equipment or transfer lines. The fire protection system therefore has to address both the immediate flame and the continuing release of fuel.

How NFPA 59A Applies to LNG Fire Protection

NFPA 59A provides the fire protection framework for LNG facilities, including the evaluation of site hazards, credible release scenarios, fire control methods and required equipment. The specific protection strategy is developed from the facility's fire protection evaluation rather than from a single universal extinguishing system.

Typical LNG facilities use several layers of protection. Dry chemical systems are positioned around transfer and process areas, water systems provide cooling and exposure protection, and high-expansion foam may be used for large impoundment areas where pool fires can develop.

Why Potassium Bicarbonate Is Used for LNG Fires

Potassium bicarbonate, commonly known as Purple K, extinguishes fire by interrupting the chemical chain reaction that sustains the flame. It does not depend on cooling the LNG itself, which is important because applying water directly to an LNG pool can increase vaporization.

Potassium bicarbonate is particularly effective against Class B hydrocarbon fires and provides rapid flame knockdown. It is therefore commonly selected for LNG transfer areas, process equipment and other locations where a pressurized release or running fuel fire needs rapid suppression.

Monoammonium phosphate is generally less attractive for LNG process areas because of its residue and its lower Class B performance compared with potassium bicarbonate. The final agent selection should always follow the applicable listing, hazard evaluation and system design requirements.

Where Different Fire Protection Systems Fit

LNG Transfer Arms, Jetties and Truck Loading

Transfer arms, hoses, flanges and loading connections can produce running spills or pressurized releases. Dry chemical is used for rapid flame knockdown, while water spray protects surrounding equipment and structures from heat.

A 1,000 lb or 2,000 lb dry chemical skid with a hose reel can provide mobile operator-controlled protection at a loading area. Fixed dry chemical systems can provide broader coverage where the hazard and facility layout require permanent protection.

Impoundment Basins and Sumps

An LNG spill that reaches an impoundment can develop into a pool fire. High-expansion foam can be used to control the fire, reduce radiant heat exposure and influence vapor behavior. The foam is not a substitute for dry chemical where rapid flame extinguishment is required.

For large impoundment fires, the response strategy may instead involve controlled burn-down depending on the facility's emergency procedures and hazard assessment. Extinguishing the flame without stopping the release can create an unignited vapor cloud, introducing another serious hazard.

Process and Vaporizer Areas

Pumps, vaporizers, compressors and associated pipework can experience jet fires or spill fires. Dry chemical is suited to rapid flame knockdown, while water spray protects nearby vessels and structural steel from excessive heat.

Emergency shutdown and isolation remain critical. Extinguishing a jet fire without isolating the fuel source can leave an uncontrolled gas release that may ignite again.

LNG Storage Areas

Storage tank protection focuses heavily on controlling exposure and protecting associated equipment. Water spray can cool exposed surfaces and piping, while dry chemical protection can be provided around platforms, valves and other credible ignition or release points.

Specifying a Dry Chemical System for LNG

The system specification should begin with the facility's fire protection evaluation. The design needs to establish the credible release scenario, protected area, application requirements, discharge duration, nozzle reach and environmental conditions.

Salus Global dry chemical skids are available for industrial applications in 350, 1,000 and 2,000 lb capacities. The systems use nitrogen as the expellant and can be configured with potassium bicarbonate for LNG and other Class B hazards.

For larger or permanently protected areas, a fixed dry chemical powder system can provide engineered coverage through a network of piping and discharge nozzles.

Maintenance of LNG Dry Chemical Systems

Dry chemical equipment needs regular inspection to remain ready for service. Routine checks should verify the condition of the agent, cylinders, valves, hoses, nozzles and associated components, with maintenance performed according to the applicable system listing and fire protection standard.

Coastal LNG terminals also require appropriate corrosion protection because salt exposure can affect equipment, valves and enclosures. Material selection, coatings and regular inspection should therefore be included in the system specification.

Frequently Asked Questions

Can you put water directly on an LNG fire?

Water is not normally applied directly to an LNG pool because it can increase vaporization. Water is instead used for cooling surrounding equipment, controlling radiant heat and protecting exposed structures.

Why is high-expansion foam used for LNG?

High-expansion foam can help control an LNG pool fire by reducing radiant heat and influencing vapor behavior. It is primarily a fire-control and exposure-protection measure rather than a replacement for rapid dry chemical extinguishment.

What size dry chemical system does an LNG transfer area need?

The required capacity depends on the credible release area, application requirements, discharge duration, nozzle coverage and facility fire protection evaluation. Transfer areas may use 1,000 lb or 2,000 lb skids, while larger facilities may require engineered fixed systems with greater agent capacity.

Salus Global dry chemical skids are UL listed and assembled, filled and inspected at our facility in Texas. Call +1 360 901 9828 or email info@salusglobal.co.