Passive Fire Protection focuses on the protection of structures in the process areas and outlines the general requirements for passive fire protection and active fire protection of structures in light of the active fire protection requirements. “Passive Fire Protection” as used herein predominantly refers to fire proofing with materials that may be sprayed, toweled, or brushed on structures or equipment. The philosophy is to limit the requirements for passive fire protection coating as far as possible based upon results of risk assessments.
The passive fire protection system should be considered for the following, if required, based on Fire & Explosion or other safety study:
- Temporary Refuge
- Process Deck
- Riser Balcony Support (as applicable)
- Other Structures
- Temporary Refuge
- Central Control Room (CCR)
Risk Management for Passive Fire Protection
The application of passive fire protection should be considered an integral part of risk management. Passive fire protection is typically provided as the last barrier following efforts to prevent an incident from occurring, detecting the incident, and combating an incident with active means of fire protection. Common objectives for the use of passive fire protection include:
- Protection of occupied buildings and/or buildings containing emergency systems, structures, or process equipment
- Protection of the temporary refuge to achieve the required endurance period
- Protection of escape routes, embarkation stations, and means of evacuation
The typical requirement that the provision of Fire Protection for any of the above purposes should have clear benefits, and that there should be an identifiable link between risk reduction and the provision of passive fire protection. A risk cost-benefit analyses may be used as a basis to accept or reject passive fire protection where there is an identified link between the application of passive fire protection and risk reduction.
Passive fire protection should be considered for the protection of identified critical buildings, process train, or structural components if:
- There is an identified link between the escalation of a fire scenario and the exposure of personnel, loss of emergency systems, or loss of all alternative escape routes, the temporary refuge, or means of evacuation within the required endurance period for each, and it can be demonstrated that this link can be broken by the application of passive fire protection
- Scenarios could result in oil release to the environment where the fire duration would be within the rating of passive fire protection.
- The risk reduction gained by providing passive fire protection is judged risk cost effective.
Passive fire protection should not be considered for catastrophic type scenarios that could impact the environment where it is clear that the fire duration likely should outlast the rating of typical passive fire protection.
Asset protection through the application of passive fire protection is not a project objective.
Jet versus Pool Fire
Load bearing steel members that upon collapse may directly or indirectly impair escape to the temporary refuge, the integrity of the temporary refuge itself, or evacuation of the installation may be protected by either deluge or passive fire protection if the hazard is liquid hydrocarbons (pool fire). Jet fire (“J”) rated passive fire protection is required if jet fires represent a credible threat to the collapse of load bearing steel members leading to impairment of escape to the temporary refuge, integrity of the temporary refuge, or evacuation. J rating is required to withstand jet fires for 120 minutes.
If deluge protection is chosen for structural protection, the deluge system should comprise of suitable nozzles arranged to ensure coverage of all exposed sides of the steel members. If it is credible that steel members could be totally engulfed by flames, the deluge nozzles may be staggered on both sides while ensuring the required density of spray.
Where scenarios have been identified in which structural failure could impair primary escape routes, the temporary refuge, or means of evacuation, the structure should be protected to ensure enough time before collapse.
The failure of non-critical components is acceptable; therefore, it may be necessary to identify the critical steel members that need to be protected (such as in a frame or truss structure). Structural collapse analyses should be carried out on a project basis for structures that are deemed critical from the perspective of escape and evacuation.
The primary temporary refuge is located in the accommodations. The accommodations are not likely for a process fire to result in a fire underneath the quarters causing structural collapse. As a result, there is no identified need for passive fire protection of temporary refuge support structures, but decks and bulkheads should comply with SOLAS and Class Requirements.
The temporary refuge is separated from process areas/fire locations by distance. A transverse coaming across the breadth of the main deck should be provided to prevent oil spills and consequent pool fires from reaching the temporary refuge.
The Temporary refuge (e.g. CCR and the Emergency Response Room) and its associated walls should be upgraded in accordance with Class requirements. In general, windows should not be retained on the external forward wall of the temporary refuge function rooms/spaces (e.g. muster areas, equipment room, and CCR).
Any additional fire or blast protection requirements for external boundaries should be determined by project specific fire and blast loads analysis.
Process Deck Structures
Each process module is supported by steel structures that upon failure may result in the deformation and collapse of the process deck. This may lead to escalation of the fire scenario due to subsequent breach of piping and damage to process equipment.
In order to minimize the potential of jet fire impingement onto the process deck support structures, pressurized gas lines should not be located underneath the process level deck.
Plated process decks with open drains prevent understructures from exposure to pool fires fed by liquids from the process train above. The deck foam system provides protection against fire radiation exposure of deck supports against running/pool fire on the deck.
Process equipment includes all systems on the raised modules (process deck). Key elements for risk management in these areas include:
- Minimization of leak and ignition sources
- Equipment spacing to reduce the likelihood of local escalation
- Provision of plated process decks for areas with oil process/separation inventories, and open drain system to collect spills to minimize the chance of liquids flowing to adjacent modules or the deck below
- Deluge coverage of vessels containing significant quantities of hydrocarbon
- Blowdown system for the evacuation of gas from the process train to the flare
Given the distance between the process areas and the temporary refuge with its lifeboats, fire on the process deck is not considered a direct threat to personnel while sheltering in the temporary refuge or manning the lifeboats. Escape from the process areas should be completed before escalation would be expected. The application of passive fire protection to process vessels, their nozzles, their supports and ESD valves is therefore considered protection against financial loss. The release of liquid hydrocarbons from one or more failed vessels would drain to the process deck and, via the deck drains, to the Open Drain Sump Tank. It is therefore not likely that significant quantities of hydrocarbons would flow overboard. However, the scenario is considered in the deck support section above, and for which it is recommended that the process deck support structure should be provided with deluge coverage.
Elevated/ Mezzanine Decks
Some process modules should incorporate elevated mezzanine and/or access decks. Escape from these areas should be completed before collapse would occur, and there is no identified link between the localized escalation of fire that could result and the safety of personnel while within the temporary refuge or during evacuation via the lifeboats. Thus, there is no identified need for fire protection of these structures from a personnel risk standpoint.
Emergency Response Procedures should clearly state that elevated deck structures may fail in case of fire, and may represent a real and direct hazard to members of the fire team.
Riser Balcony Structure (as applicable)
Escape from the riser balcony area should be completed within minutes before any significant structural failure would occur. General water deluge coverage should be provided as an aid to escaping personnel by area cooling and any knockdown effect on the smoke.
Riser fire is clearly the worst-case scenario in terms of fire severity and duration. All piping and manifolds should be isolated from the risers by riser ESDVs and provided with blowdown to limit the amount of fuel available to feed a fire.
Passive protection of the production and gas riser connectors and ESD/PSD valves should be evaluated by project specific fire and blast loads analysis. To ensure ease of access for NDT testing and inspections, any protection required should be designed to be removable.
Collapse of the helideck due to fire could impair the temporary refuge and/or means of evacuation. There are, however, no other fuel sources identified that could cause a serious hydrocarbon fire at the base of the helideck other than the fuel onboard a helicopter.
The helideck should be provided with a drain system to prevent any fuel spilled from falling to the base of the helideck. Furthermore, personnel would be evacuated from the quarters in case of a crash, and the scenario is not considered one that would require emergency evacuation of the installation. Thus, there is no identified need to provide structural protection against fire for the helideck support structure.
Other Elevated Structures
Elevated structures onboard the facility includes the flare tower, the deck cranes, and the provision crane.
The flare tower is typically located next to the process deck. Flare tower collapse caused by fire before personnel have been able to escape the process deck is deemed extremely unlikely. The tower should be located where it is unlikely for liquid hydrocarbon spills would not accumulate to collect. Structural protection of the flare tower against fire is not envisaged; this should be confirmed by project specific fire load analysis during detail design.
Deck cranes should be located to serve the production deck laydown areas in locations. It is not envisaged crane collapse from fire exposure is a credible scenario as contributor to personnel risk, and passive fire protection or fixed deluge protection of the deck crane pedestals is not expected. This should be subject to confirmation in project specific fire analysis during detail design.
Provision Crane (if present)
The collapse of the provision crane in case of a pool fire caused by a crude oil transfer/export manifold leak is considered credible. Unless this scenario is identified as a significant contributor to personnel risk, passive fire protection or fixed deluge protection of the deck crane pedestal is not considered justified.
Similar to the protection of structures, fire protection of process equipment should be provided if it is found this protection may prevent local escalation that could:
- Affect personnel risk through impairment of escape routes, the temporary refuge or means of evacuation
- Lead to the release of significant hydrocarbons to the sea
Production deck buildings including Lab, Stores, Workshop, Electrical Switchgear Building, external and internal walls, decks, and ceilings should be specified as a minimum in accordance with Class requirements according to their function and adjacent spaces.
Any additional fire or blast protection requirements for external boundaries should be determined by project specific fire and blast loads analysis in detail design.
The bulkheads, decks and ceilings, together with external and internal walls should be built to SOLAS requirement at the time of construction of the vessel. All modifications to the accommodations should meet present SOLAS and Class requirements.
Central Control Room with Emergency Systems
Class requirements for “structural fire protection” should be considered in the design, including requirements to Control Stations (which includes Central Process Control Rooms). These requirements apply to both bulkheads and decks.