The term “Fire Protection” as used herein includes active and passive fire protection.
This section, Active Fire Protection outlines the intended use of active (water and/or foam) systems to prevent or mitigate credible topsides fire scenarios. The ABS “Guide for Building and Classing Facilities on Offshore Installations” provides further details regarding the arrangement of structural fire protection within the quarters. NFPA guidelines should be followed.
The active fire protection system should consist of the following.
- Firewater system
- Foam system
- Gaseous fire extinguishing system
- Water mist system
- Portable fire extinguishers
Firewater available for topsides process facilities and hull, should be provided from a dedicated firewater system distributed throughout the facilities. The distribution system should include a ring main with cross connections and dedicated feeds to consumers. The ring main with cross feeds should be provided with manual isolation valves to allow isolation for maintenance of a section. The valves should be located or equipped to allow operation from main deck, and their locations should be properly marked.
At least one Jockey Pump should be provided to maintain the fire main pressurized. Additional means for pressurization should be considered.
Two independent and self-contained diesel / hydraulic or diesel / electric driven firewater pump units should be provided, connected to the common firewater ring main and located as far apart as reasonably practical. The pumps should satisfy the requirements in NFPA 20 in terms of flow characteristics and starter arrangements. Each unit should be sized to supply 100% of the total firewater demand at desired flow and pressure corresponding to the “maximum firewater demand case” for the topsides process facilities. The fire pumps should start automatically upon confirmed detection of fire or low ring main pressure. Remote and local means for manual start of either pump should be provided. Pump performance curve should be selected to meet the flows and pressure needed for major fire scenarios.
If located adjacent to the hazards, the pumps should be protected by a fire with a blast wall and a solid floor. The pumps should be protected against topsides fires and explosions.
Hydrants / Hose Stations
Existing hydrants and hose stations should be utilized as much as possible. Additional hydrants/ hose stations should be provided to ensure coverage of the new areas on the facilities.
Hydrants and hose stations should be arranged to ensure that fire fighters can cover all areas from different directions with two separate hose streams.
Foam hydrant stations should be provided in areas where liquid hydrocarbon fires can occur.
Deluge System for Topsides Production Areas
Deluge systems should be provided for the production process areas.
The primary intent of the deluge systems is to cool process equipment to reduce the risk of escalation of fire and to prevent the impairment of evacuation routes and systems. Production process equipment includes hydrocarbon vessels, pumps, heat exchangers, and other hydrocarbon handling systems and their saddles / supports. Gas handling equipment, such as compressor skids, where the liquid hydrocarbon inventory is small and can effectively be removed from the fire via blowdown to the flare should not be provided with deluge systems.
The deluge systems should be activated automatically upon confirmed fire in the zone (module) where the fire is detected as well as in the neighboring zones (modules). The associated deluge valves should have the option for remote and local manual release and should physically be located at some distance from the fire zone.
The use of foam with the deluge systems for production process systems coverage should be assessed based on the type of process decks chosen (solid versus grated), the requirements to property protection, and any impact from liquid hydrocarbon fires that may be mitigated through foam application.
Premix Foam System
A foam generation and distribution system should be provided in accordance with Class, Regulatory, and SOLAS requirements. This system should supply the existing fire monitors and the deluge systems underneath the process deck modules with premixed foam from a distribution main. Existing foam tank(s) located in the foam room and the foam main header line should be evaluated for reuse for this service. The pump should be powered from the emergency switchboard.
The foam tank capacity should be sized with capacity to deliver foam to the entire process deck area in accordance with Class and project requirements.
Activation of the foam supply should be via manual local control from the Foam Room or manual remote-controlled valves operated from the Central Control Room (CCR).
Cargo Tank Deck System
The existing firewater / foam monitors for process areas should be maintained for open deck protection. Foam nozzle systems should be provided underneath the process modules where the existing foam monitors cannot reach.
Similar to the deluge systems for the process modules, these systems should be zoned and activated remotely upon a confirmed fire. The associated deluge valves should have the option for remote and local manual release and should physically be located at some distance from the fire zone.
Premixed foam should be supplied to this system and should be grouped into zones, similar to the process module systems.
Firewater/foam monitor(s) should be provided at the offloading station(s).
Foam monitors protecting the helideck should be provided with dedicated foam concentrate tanks to ensure immediate supply of foam for the initial stage of a fire. The foam monitors should also be supplied premix foam from the central foam tank for extended fire fighting.
Firewater/foam monitors should be arranged at the helideck in accordance with regulatory and class requirements.
Alcohol Resistant Foam
Alcohol resistant foam concentrate should be provided in areas where Aqueous Film Forming Foam (AFFF) would be unsuitable. Only one type or Manufacturer of foam concentrate should be used to eliminate incompatibility issues. (e.g. Methanol fire hazards). If methanol is stored within the facilities, then alcohol resistant foam should be used throughout the vessel.
Water spray nozzles should be installed to spray water onto the lifeboats located outsides of the accommodations. Water spray nozzles should be considered (by safety study) to provide a water screen forward of the lifeboat embarkation areas. Water spray should be activated manually.
Gaseous Fire Extinguishing Systems
Manually operated carbon dioxide (CO2) or other suitable gaseous or water mist fire extinguishing systems should be used as appropriate.
Gaseous fire extinguishing systems should be installed in electrical and instrument equipment rooms, machinery rooms, pump room, etc. in accordance with regulatory and Class requirements.
The use of water mist fire fighting systems should be evaluated for areas where such systems are appropriate.
Portable Fire Extinguishers
Portable extinguishers should be provided in sufficient numbers per area and at strategic locations throughout the facilities as dictated by Class requirements to include the CCR, radio room, corridors etc.