Offshore facilities

Offshore facilities are dramatically different from onshore facilities because instead of being spread out the equipment is segregated essentially into compartments or separated into a complex of platforms. Offshore facilities pose critical questions of personnel evacuation and the possibility of total asset destruction if prudent risk assessments are not performed. A through analysis of both life safety and asset protection measures must be undertaken. These analyses should be commensurate with the level of risk a particular facility represents, either in personnel exposed or financial loss. An unmanned wellhead platform might only require the review of wellhead shut-in, flowline protection and platform ship collisions to be effective, while manned drilling and production platforms may require the most extensive analysis. 

Generally the highest risks in offshore facilities are blowouts, transportation impacts and process upsets. Where inadequate isolation means are provided for either wellheads or pipeline connections to the installation considerable fuel inventories will be available to an incident. 

The helidecks of offshore facilities are usually provided at the highest portion of the offshore installation for avoidance of obstructions during aircraft maneuvering and available space. As a result the roof of the accommodation is typically selected. The location also facilitates evacuation of personnel from installation by helicopter due to its proximity to the highest concentration of personnel. This enhances one of the avenues of escape from the installation but also exposes the accommodation to several hazards. The accommodation becomes subject to the hazards of helicopter crashes, fuel spillages, and incidental helicopter fuel storage and transfer facilities. 

Because of the inherent hazards associated with helideck operations they should be provided with 

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Where space and weight are considerations (such as on an offshore facility) plate separators may be used to dehydrate crude to evacuation specification. Packs of plates are used to accelerate extraction of the water phase by intercepting water droplets with... 

Hydrocylones have become common on offshore facilities and rely on centrifugal force to separate light oil particles from the heavier water phase. As the inlet stream is centrifuged oil particles move to the centre of the cyclone, coalesce and are drawn off upwards, while the heavier water is taken out at the bottom. 

The function of offshore production facilities are very much the same as those described for land operations. An offshore production platform is rather like a gathering station hydrocarbons have to be collected, processed and evacuated for further treatment or storage. However, the design and layout of the offshore facilities are very different from those on land for the following reasons ... 

Artificial islands could be regarded as platforms but fall somewhere between land and offshore facilities. 

While RP14C provides guidance on the need for process safety devices, it is desirable to perform a complete hazards analysis of tlie facility to identify hazards that are not necessarily detected or contained by process sLifety devices and that could lead to loss of containment of hydrocarbons or otherwise lead to fire, explosion, pollution, or injury to personnel. The industry consensus standard, American Petroleum Institute Recommended Practice 14J, Design and Hazards Analysis for Offshore Facilities (RP14J), provides guidance as to the use of various hazards analysis techniques. 

The requirements of both PSM and SEMP are, from a practical standpoint, identical and thus, SEMP can easily be applied to onshore facilities as well as offshore facilities. The basic concepts of SEMP are as follows ... 

In the ease of an offshore facility, electrical power is generally ge ated on site by engine- or turbine-driven generator sets using natural or diesel as fuel. Most installations are designed to handle the total e tri. 1 even if one generator is out of service. To minimize the siz st quipment, some facilities have a system to automatically f... 

Heatric (UK) Compact heat exchangers for offshore facilities, hydrogen production 4 tons per year [1]... 

The most expensive initial investment of any capital project is the investment in space to provide a facility. For onshore on offshore facilities the amount a space a facility occupies directly corresponds to increased capital costs, however these should still be balanced with the need for adequate separation, segregation and arrangement protection principles. 

In oil and gas facilities, these effects can be generally related to flame velocity, where this velocity is below 100 m/s (300 ft./s), damage is considered unlikely (Note This is generally within the limits of confinement normally found in offshore facilities). The size of a vapor cloud or plume in which such velocities can occur has been experimentally investigated at the Christian Michelsen Institute (CMI, Norway). The experiments demonstrated that flames need a "run-up" distance of approximately 5.5 meters (18 ft.) to reach damaging speeds. Therefore vapor clouds with dimensions less than this may not cause substantial damage. This is a much over-simplification of the factors and variables involved, but does assume the WCCE of congestion, confinement and gas concentrations. 

Generally offshore facilities and major process plants onshore represent considerable capital investment and have a high number of severe hazards associated with them (blowouts, ship collisions, line and vessel ruptures, etc.). They normally cannot be easily evaluated with a simple safety checklist approach. Some level of "quantifiable evaluation" reviews are usually prepared to demonstrate that the risk of these facilities is within public, national, industry and corporate expectations. 

Specialized studies are investigations that attempt to verify the ability of a facility to perform effectively during an emergency, generally by mathematical estimates. They are used extensively to justify the necessity or deletion of a safety system. The most common studies are listed below however every facility is unique and may require it s own investigative requirements (e g., for an offshore facility - the potential for ship collisions). For example, for a simple unmanned wellhead... 

Additional specialized studies are sometimes specified for offshore facilities. These may include the following, depending on the type of facility under review ... 

The ideal situation for offshore facility is to locate the accommodation on a separate installation jacket that is spaced as far as practical from the production processes and the process platform oil or gas pipeline risers. Inclusion of the facility control room can also be conveniently provided in the accommodation increasing personnel safety and providing a cost benefit. 

Subsea pipeline emergency isolation valves for offshore facilities are provided where a risk analysis indicated topside isolation may be considered vulnerable. They should be protected from ship impacts, anchor dragging, flammable liquid spills and heavy objects that may be dropped from the offshore facility. 

In some cases radiation shields are provided to protect against heat effects from fire incidents and operation requirements. The shields usually are of two styles either a dual layer wire mesh screen or a plexy-giass see through barrier. The shields provide a barrier from the effects of radiant heat for specific levels. They are most often used for protection against flare heat and for barriers at fixed firewater monitor devices, most notably at the helidecks of offshore facilities. 

Exit routes and doors from all facilities should be provided according to the requirements of NFPA 101. The minimum width of all exit routes should not be less than a standardized width, 1.0 meter (39 inches) being commonly adopted. Where low occupancy rooms are provided in offshore facilities near process areas, a secondary emergency escape hatch is provided as an alternative means of escape in addition to the normal means of egress. 

Areas of the North and South Atlantic, and North and South Pacific present continual extreme and hostile ambient conditions that make survival exposed to such conditions a very limited probability with adequate protection measures. In these locations the probability of survival is increased with the provision of a fixed safe refuge rather than the provision of an immediate means of escape. For offshore facilities historical evidence indicates that both helicopter and lifeboat mechanism may be unavailable in some catastrophic incidents. Remote onshore facilities may also experience severe winter conditions that also render this philosophy applicable. 

All fixed fire suppression system control valves should be located out of the fire hazard area but still within reach of manual activation. For high hazard areas (such as offshore facilities), dual feeds to fire suppression systems should be considered from opposite areas. For onshore facilities, firewater isolation valve handles should not be contained within a valve pit or a below grade enclosure within the vicinity of hydrocarbon process facilities, since heavy process vapors travel from the process and may settle inside. 

Isolation - It has been shown that the addition of isolation valves at periodic intervals is not as cost effective as prevention measures such as thickness inspections or tests. However all pipelines should be provided with a means for emergency isolation at it entry or exit from a facility. Offshore facilities may be particularly vulnerable to pipeline incidents as the Piper Alpha disaster has shown. In that accident a contributing factor to the destruction was the backfeed of the contents of the gas pipeline to platform once the topside isolation valve or piping lost its integrity. Further isolation means (i.e., a subsea isolation valve SSIV) were not available. 

Iceland could also develop wind power with coastal or offshore facilities. A study indicated that 240 wind power plants could produce the electricity needed to replace fossil fuel from vehicles and fisheries. 

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