One of our users has shared images of Mossmorran flaring, which started around 2:30pm, we have also received the following update from ExxonMobil regarding the flaring incident;

ExxonMobil can confirm that there has been a process upset at the Fife Ethylene Plant.

We are now working to return to normal operations and anticipate that the flaring will continue over the next 24 hrs.

We would like to apologise to the local communities for any inconvenience or concern they may have caused as a result of today’s flaring from the Fife Ethylene Plant, Mossmorran.

Whenever Mossmorran flares, traffic on the site increases, and one of the most popular search terms for the site is ‘How safe is Mossmorran?’

Unfortunately we do not know the full answer, however, we do have documents from Fife Council published in 2009, that highlights the procedures to be undertaken regarding any emergencies at Mossmorran and other top-tier COMAH sites operating in Fife. The four documents are a sobering read, and give indications of the potential risk from Mossmorran and other top-teir COMAH sites operating in Fife;

2.1 COMAH Top-Tier Sites in Fife
The COMAH off-site emergency plan is based around major accident hazards identified by Fife based operators in safety reports submitted to the Health and Safety Executive and Scottish Environment Protection Agency, which could affect people and the environment outside the
boundary of their establishments, or require the attendance of the emergency services in event of an emergency. Fife Council is required under Regulation10 to produce off-site emergency plans for the following top-tier COMAH establishments within its area as notified by the competent authority.

Organisation/ Location

  • Shell Expro Fife NGL Plant, Mossmorran
  • ExxonMobil Chemical Fife Ethylene Plant, Mossmorran
  • Shell Expro Marine Terminal, Braefoot Bay
  • ExxonMobil Chemical Marine Terminal, Braefoot Bay
  • Diageo Banbeath, Leven

2.6 Flammable Releases

These include flammable liquids, highly flammable liquids and extremely flammable gases and liquids based on relative flash point categories.

a. A release of flammable material may result in a fire or explosion. The consequences depend on the nature and quantity of the material released, whether it is ignited and time between release and any ignition. If the release is a volatile liquid or a gas not ignited immediately, it will form a cloud which may disperse over a long distance becoming diluted with air as it moves away from the point of release.

Eventually its concentration will fall below the substance’s lower flammable limit and so no longer present a fire hazard. The distance over which such a release may disperse depends upon the quantity, properties and state of the material, the nature of the release and the prevailing weather conditions.

The concentrations in the dispersing cloud may be estimated using appropriate computer programmes which combine a mathematical model of a physical description of cloud behaviour with data collected from experiments and incidents.

b. If a developed cloud is ignited, it may burn as a flash fire back to the point of failure. If a release from a broken pipe, leaking flange or a hole in a vessel is ignited immediately, it may burn as a jet fire or a pool fire. Models exist for estimating the quantity of material released over time and the size and thermal radiation from jet and pool fires.

c. Vapour cloud explosions (VCE) following a massive release of a gas or volatile liquid and boiling liquid expanding vapour cloud explosions (BLEVE), are low frequency, high consequence events. These may occur with certain flammable fluids under certain
accident conditions. Methods are available for estimating the size of a VCE or BLEVE fireball, the thermal radiation consequences and the levels of blast over-pressure.

d. A considerable range of possible accident scenarios exists involving the release of flammable materials with considerably different consequences and therefore different planned responses. Examples may be:

• A major fire, but with no danger of an explosion, for example, a fire in a non-crude oil storage tank: The hazards would be high levels of thermal radiation and smoke of long duration. Evacuation may be required from buildings close to the establishment
and directly exposed to severe thermal radiation. In addition, it may be necessary to evacuate areas severely affected by smoke.

• A major full surface fire in a large crude oil storage tank: There is the potential for a boil over to occur, which could propel burning tank contents upwards and outwards up to ten times the tank diameter involved, whether or not fire fighting is taking place. The evacuation of all non-essential personnel from within the area noted, and arrangements to deal with any possible escalation, should be included in any plans.

• A fire threatening a major item of plant or a storage tank containing hazardous materials: The safety report includes an assessment of the possible consequences of such an event, and identifies the area that may need to be evacuated. The planned response should give appropriate consideration to assessing the consequences.

• A fire threatening a major item of plant that develops too quickly to allow evacuation: Best advice for those in the vicinity may be to remain indoors away from windows and shielded from line of sight of the fire. There may be significant risks in attempting to evacuate if a BLEVE or fireball occurs with people in open.

• Cryogenic effects: The sudden release of certain fluids (e.g. ethylene) may cause severe local cooling of the atmosphere and persons caught in the cloud of released gas may suffer ‘cold burns’ or damage to the lungs. However, these kinds of releases can be highly visible and people are unlikely to enter the affected area.

• Asphyxiation: Releases of large amounts of gas or vapours (even non-toxic substances) at high concentration can cause asphyxiation due to exclusion of oxygen. However these conditions may only exist in close proximity to the point of failure.

• Noise: A high pressure gas release creates a great deal of very intense noise which causes damage to people’s hearing, albeit temporarily. A high pressure gas pipeline major failure may result in large numbers of people seeking medical attention for hearing problems. High noise levels can be very disorientating and may cause unexpected behaviour in people affected.

2.7 Explosives

An explosive means: A substance or preparation which creates the risk of an explosion by shock, friction, fire or other sources of ignition. A pyrotechnic substance is designed to produce heat, light, sound, gas or smoke or a combination of such effects through non-detonating self-sustained exothermic chemical reactions.

Some major catastrophic events occurring without warning, for example, the accidental detonation of solid explosives, or lighting strike. In these situations, it may not be possible to take any prior emergency action. However, most events are of very short duration. The main consequence of any explosion would be from the blast over pressure and its effects on people and buildings can be calculated.

Blast effects and Projectiles: The pressure blast at the time of an explosion can be significant in close proximity to source but its effect will diminish quickly over distance. In the event of a major explosion cover materials including building materials, rocks, soil, hardcore, etc. will be thrown at high velocity into the air. Also blast pressures as low as 1 p.s.i. (pound per square inch) can damage 90% of window glass and potentially cause fatalities and such pressure can be achieved at a considerable distance from the source.

There are processes with stored energy in pipelines conveying gas where there can be a significant hazard potential of the fluid. The failure of a pipeline carrying a liquid will have a much lower blast effect owing to the incompressible nature of liquids.

Gases conveyed as liquids and liquids with dissolved gases will have an immediate effect. The emergency response in these situations is to rescue, treat the injured, extinguish any secondary fires and mitigate any further damage.

2.8. Toxic Releases

Dangerous substances and preparations may also be categorised as being either Toxic or Very Toxic.

a. The consequences of toxic releases may be more difficult to accurately predict than those of flammable releases because they are more time dependent and variable according to the distance from the release and the weather conditions.

Operators should be able to estimate the concentrations and durations of gas clouds at various distances from the point of release. This information may then be used with human vulnerability models to calculate the distances at which toxic effects might be expected, and hence the area in which appropriate emergency measures might be needed. The operator should estimate dispersion distances for various foreseeable events based on the toxicology of the material involved.

b. Different events involving the release of toxic material may require different planned responses, for example:

• A slow or intermittent release, for example, through leaking relief valve: If it was expected that the release would not be controlled quickly, or would grow with time, the appropriate response might be to evacuate the people nearest to the establishment of release and most closely downwind of it, provided that this evacuation would increase their safety. The benefits from evacuation (shelter from the toxic release in the safe area) should outweigh any associated harm of being exposed to the toxic release during the evacuation process.

• A fire or mechanical damage that threatened an installation containing toxic material If the fire could not be controlled and if there was likely to be a reasonable period before ver-pressurisation or plant failure occurred, evacuation might be appropriate. Priority should be given to those nearest the plant and downwind.

• Rapid events with a limited duration, for example, the fracture of a component that could be isolated within a reasonable time

For events that have grown and can be rapidly controlled, the proposed emergency response should not include evacuation. Any toxic cloud formed would be of limited size and likely to drift past a particular spot relatively quickly. For members of the public, the best place to be located would normally be indoors, upstairs with doors (internal and external) and windows closed, in a room which faces away from the direction of the incident.

• A major event leading to a sudden release of a large quantity of toxic substance, which would form a large toxic cloud, for example, most of the contents of a storage tank escaping to the atmosphere through the failure of the tank shell:

Although the probability of such an event occurring should be extremely low, the consequences for people located close to the incident would be severe. The emergency response in these circumstances would be to rescue local people, treat the injured, make safe the affected areas and mitigate further releases.

c. In most cases, releases of toxic clouds tend to be hazardous down to much lower concentrations than flammable clouds, and therefore remain hazardous over greater distances when dispersing. In all cases, however, the hazard is greatest close to the source and near to the downwind plume. In many cases, the best course is not to attempt evacuation, but to go indoors, close the doors and windows and to switch off any ventilation and heating which draw air in from outside.

In addition, if this action if followed, people will be situated where they can receive communications via radio, television and telephone. Also, if the decision is taken to evacuate they are in a fixed location to be picked up and transported to a place of safety outside the immediate hazard zone.

After the toxic cloud has passed, it is essential to get people to open all doors and windows and then to go outside until their homes are adequately ventilated.

2.9 Causes of Plant/Equipment Failure

The most likely causes of plant and equipment failure are included in the following list which is not exhaustive:

• third party activities (accidental and deliberate, including sabotage)
• corrosion, internal and external
• mechanical failure, including: material defects, construction defects, including weld defects, fatigue, stress corrosion cracking, operational errors, maintenance problems, natural hazards, subsidence/landslip, earthquakes

The four documents are worth reading in full, as they show a wide comprehensive plan is in place in case of any major emergency at any of the top-tier COMAH sites in Fife which is reassuring, but they also highlight the potential risks of the various COMAH sites in Fife, allowing residents to make more of an informed choice of what risks they are willing to accept within their communities.

Meanwhile, the flare has reduced it’s size from the initial flaring event, which indicates that the ‘process upset’ is now under control by the staff at Mossmorran and any serious incident has been averted. One of our volunteers was near the site during the flaring event and managed to capture the following images;

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