LPG storage and transfer facilities need carefully planned fire protection because LPG is stored under pressure and can rapidly form a flammable vapour cloud following a release. Fire exposure can also heat pressurised vessels, increasing internal pressure and placing the vessel shell under severe thermal stress. A reliable LPG tank fire protection system therefore brings together early detection, emergency isolation, fixed water spray, deluge systems, hydrants, monitors, fire-water pumps and sufficient fire-water storage. The same approach applies to loading and unloading areas, where tank trucks, loading arms, hoses, manifolds and transfer connections introduce additional release points.
Why LPG Facilities Need Dedicated Fire Protection
Unlike many liquid fuels stored close to atmospheric pressure, LPG is held as a liquid under pressure. Once released, part of the liquid can flash rapidly into vapour and form a flammable cloud.
The main concerns around LPG installations include:
- Rapid vapour generation after loss of containment
- Fire exposure to storage vessels and tank trucks
- Radiant heat affecting nearby equipment
- Rising vessel pressure during external fire exposure
- Loss of vessel-shell strength under prolonged heating
- Escalation from one LPG item to adjacent equipment
Fixed water spray is primarily used to cool exposed equipment and limit heat absorption. It does not replace emergency isolation or other fire-fighting systems; instead, it forms one part of the overall protection strategy.
Fire Protection Design for LPG Storage Tanks
Above-ground LPG storage vessels, often referred to as LPG bullets, are generally protected using a fixed medium-velocity water-spray system. For installations governed by OISD-STD-144, above-ground LPG storage vessels require automatic heat detection, remote/local deluge operation and a minimum water-spray density of 10.2 L/min/m².
A typical system consists of:
- Fire-water distribution piping
- Isolation valves
- Deluge valve
- Spray rings or distribution headers
- Medium-velocity spray nozzles
- Automatic and manual activation arrangements
The nozzle layout should cool the vessel shell, dish ends, underside and other surfaces exposed to fire or radiant heat. Adequate total water flow alone does not mean the vessel is properly protected. Nozzle position, spray angle, overlap and operating pressure determine whether water actually reaches the required surfaces.
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Fire Protection Design Methodology for LPG Tanks and Loading/Unloading Bays
Fire-protection design should begin with the facility layout and credible fire scenarios rather than immediately selecting pipe sizes or nozzles.
1. Establish the Design Basis
Collect essential inputs such as vessel dimensions, operating conditions, LPG inventory, equipment layout, loading-bay arrangement, available fire-water pressure and applicable project standards.
2. Identify the Governing Fire Scenario
Determine which credible event produces the highest fire-water demand. This may involve a vessel exposed to fire, cooling of nearby vessels, a loading-bay incident or simultaneous use of fire-water monitors and hoses. For OISD-STD-144 installations, vessels located within 30 m from the periphery of the affected LPG vessel are included when establishing the applicable single-risk water-flow requirement.
3. Determine the Protected Surface Area
Calculate the surface requiring cooling, considering the cylindrical shell, dish ends, lower portions and any other exposed surfaces included in the applicable design basis.
4. Calculate the Water-Spray Requirement
The basic relationship is:
Required Water Flow = Protected Surface Area × Water Application Density
Where 10.2 L/min/m² applies, this density is multiplied by the relevant protected surface area.
5. Develop the Spray Arrangement
Arrange the spray rings, headers and nozzles to provide consistent coverage. Check nozzle spacing, spray angle, orientation, overlap, obstructions and dish-end protection.
6. Verify the System Hydraulically
Confirm that every nozzle receives adequate flow and pressure after allowing for pipe friction, elevation differences, fittings, valves and deluge-system losses. The final arrangement must demonstrate both sufficient water quantity and effective surface coverage.
Step-by-Step Design of an LPG Tank Sprinkler Ring
A sprinkler ring is the distribution arrangement that supplies cooling water to spray nozzles positioned around the LPG vessel.
A practical design sequence is:
- Determine Vessel Dimensions – Obtain vessel diameter, cylindrical length and dish-end geometry.
- Calculate Protected Area – Determine the surface requiring cooling.
- Calculate Spray Flow – Apply the required water-spray density to the protected area.
- Select Spray Nozzles – Choose suitable nozzles based on flow, spray angle, discharge characteristics and operating pressure.
- Arrange the Rings – Position sufficient rings or headers to cover the shell, underside and vessel ends.
- Check Hydraulics – Confirm adequate pressure and discharge at the hydraulically remote nozzle.
The aim is not simply to place a pipe around the LPG bullet. The ring and nozzle arrangement must provide consistent cooling without significant dry areas.
Water-Spray Demand Calculation
The initial water-spray demand is based on the protected surface area and the applicable water application rate.
Water-Spray Flow = Protected Surface Area × Application Density
The total fire-water demand, however, may be higher than the calculated sprinkler-ring flow.
The hydraulic assessment may also need to consider:
- Adjacent LPG vessel cooling
- Loading and unloading gantry protection
- Fire-water monitors
- Hydrants and hose streams
- Pipe friction losses
- Deluge-valve losses
- Elevation differences
The governing fire scenario should therefore be used to establish final fire-water flow, pump capacity and network pressure.
Fire Protection for LPG Loading and Unloading Bays
Loading and unloading operations involve regular connection and disconnection between fixed LPG piping and tank trucks. This makes transfer points particularly important when developing the fire-protection layout.
Potential leakage locations include:
- Loading arms
- Flexible hoses
- Liquid transfer connections
- Vapour-return lines
- Manifolds
- Isolation valves
- Tank-truck fittings
The water-spray system should protect both the tanker and the critical transfer equipment. Typical coverage includes the tanker shell, upper and lower surfaces, dish ends, tyres, manifold and loading/unloading connections. OISD-STD-144 specifically requires the medium-velocity spray system at tank-lorry gantries to effectively cover tank-truck surfaces, tyres, manifolds and dish ends.
Three-Tier Water-Spray Arrangement
| Spray Tier | Protection Purpose |
| Upper Tier | Cools the upper surface of the LPG tanker and reduces heat exposure. |
| Middle Tier | Provides lateral cooling along the tanker shell and side surfaces. |
| Lower Tier | Protects lower vessel surfaces, tyres, manifolds and transfer areas. |
OISD-STD-144 requires at least three tiers of medium-velocity sprinklers for LPG tank-lorry gantries. Final nozzle spacing should be based on actual tanker dimensions and required spray coverage.
Fire-Zone Arrangement for Loading Bays
Loading and unloading gantries can be divided into separate deluge zones to direct fire-water only where it is needed. Proper zoning improves hydraulic performance, system response, maintenance flexibility and area isolation. Under OISD-STD-144, up to eight tank-lorry bays may be treated as one risk area, with each zone served by an independent deluge system.
Fire Detection and Deluge Activation
Rapid detection is essential because an LPG release can develop quickly.
A typical sequence is:
Heat/Fire Detected → Alarm → Deluge Valve Opens → Water Spray Activates → Cooling Begins
The protection philosophy should also coordinate the water-spray system with:
- Fire & Gas Detection System
- Emergency Shutdown System
- LPG isolation valves
- Plant alarm system
- Emergency-response procedures
Where practicable, emergency isolation reduces the continuing LPG release while the water-spray system limits heat exposure to the equipment.
Overall Fire-Water Demand
The fire-water system should be sized for the most demanding simultaneous fire scenario, not only the LPG sprinkler-ring demand. The calculation should include vessel cooling, loading-bay deluge, hydrants, monitors, hoses and hydraulic losses.
Under OISD-STD-144, the system should also consider 288 m³/h for two monitors or supplementary hoses and maintain at least 7.0 kg/cm² residual pressure at the remotest point of application, making hydraulic verification essential.
Fire-Water Pumps and Storage
Fire-water pumps should be capable of supplying the governing demand while maintaining the required network pressure.
The design should consider:
- Required pump flow
- Discharge pressure
- Fire-water storage duration
- Pump redundancy
- Reliable power sources
- Jockey-pump arrangement
- Emergency operating conditions
Fire-water storage, pumps and distribution piping should therefore be designed as one integrated hydraulic system.
Standards Used for LPG Fire Protection
| Standard / Code | Application |
| OISD-STD-144 | LPG storage, handling and loading/unloading installations |
| OISD-STD-116 | Fire protection for refineries, petrochemical complexes and oil & gas processing facilities |
| NFPA 58 | Requirements for Liquefied Petroleum Gas (LPG) systems and installations |
| API 2510 | Design and construction of LPG storage and handling facilities |
| API RP 2510A | Fire-protection considerations for LPG storage facilities |
Current OISD editions: OISD-STD-144 – August 2026 and OISD-STD-116 – June 2025. The applicable code hierarchy should be defined in the project design basis before detailed engineering.
Common LPG Fire-Protection Design Issues
Common design problems include poor nozzle orientation, incomplete vessel coverage, inadequate dish-end and tanker protection, incorrect deluge zoning, low remote-nozzle pressure and undersized piping. Coordination between the detection, deluge and ESD systems should also be checked. Reviewing spray coverage and hydraulic performance together helps identify these issues before construction.
Key Design Considerations
A reliable LPG fire-protection system should deliver four essential functions:
- Early Detection – Identify fire or abnormal heat quickly.
- Emergency Isolation – Reduce or stop the continuing LPG release.
- Effective Cooling – Protect exposed vessels, tankers and associated equipment.
- Escalation Prevention – Limit heat exposure to neighbouring equipment.
Together, these functions support a practical protection philosophy:
Conclusion
Effective fire protection for LPG tanks and loading/unloading bays requires coordinated design of water demand, nozzle coverage, deluge zoning, hydraulic performance, detection and emergency isolation. Loading and unloading areas should also provide adequate protection to the complete tanker and critical transfer equipment.
iFluids Engineering supports clients with practical LPG fire-protection solutions, including water-spray and deluge-system design, fire-water demand assessment, hydraulic analysis and technical review.
Frequently Asked Questions
A sprinkler ring supplies cooling water to spray nozzles arranged around the LPG vessel. Properly designed coverage limits vessel heating during fire exposure and helps reduce escalation risk.
The initial flow is calculated from the protected surface area and applicable water-spray density. Hydraulic calculations are then used to verify actual pressure and flow throughout the distribution system.
Not necessarily. The required number and position of rings depend on vessel geometry, nozzle characteristics and the coverage achieved over the shell, underside and dish ends.
Multiple spray tiers allow cooling water to reach the upper, middle and lower portions of the tanker. This provides more complete protection than an overhead-only arrangement.
Yes. Hydraulic analysis confirms pipe sizing, pressure losses, available nozzle pressure and the ability of the system to deliver the required water demand under the governing fire scenario.