• Toxic gas mixtures and liquid streams, sour products, pyroforic material, H2S - hydrogen sulphide;
• Corrosive chemicals, acids, caustic soda, Toxic processing chemicals, Bromine, Chlorine, Ammonia - the HazMat list goes on;
• Large volumes of highly flammable liquids that maybe processed at pressures and temperatures well above atmospheric conditions and above the liquids boiling point at atmospheric pressure. Any leak to atmosphere will vaporise rapidly and can, under certain conditions, ignite spontaneously;
• Vapour cloud explosions have provided the largest onshore damage loss in the history of hydrocarbon processing and chemical industries.
Recognising the risks involved it becomes immediately clear to the industry that our aim must be to eliminate the possibility of a minor incident developing into one of catastrophic proportions. The basis of a safe plant design is to eliminate foreseeable risks of fires and explosions.
What about HAZOPS?
Safe design practices must be the aim of every facility operator, ensuring that plant layout, process design and operators are fully optimised so that in the event of a loss of containment, major gas release or fire, the process can be shut down as quickly as possible.
HAZOPs, studies of plant design looking at inbuilt safety features, isolation depressurisation and emergency shut-down facilities, are carried out in the early stages of plant design.
Prevention is the obvious key to designing against the effects of catastrophe.
The influence of COMAH
Today, fire hazard management legislation drives us forward. In the UK, this legislation is known as COMAH and it has put pressure on management to produce documentation under safety Management Systems.
This requires Hazard identification, the assessment of onsite/offsite risks to personnel, society and the environment. Also required is Hazard Evaluation and hazard Control, demonstrating safe working practices, the competency to deal safely with any emergency incident. Supported by municipal fire authorities and mutual aid companies, legislation now requires that major fire/safety exercises be conducted on a regular basis.
Using minimum manpower - a result of the current climate of cutbacks and downsizing - petrochemical plant personnel are expected to direct the firefighting and emergency response strategy towards early detection, effective control and extinguishment.
Moving towards early detection systems must be a way forward. The formation of an undetected cloud of flammable or toxic vapour is probably the most hazardous situation which can develop in a hydrocarbon processing unit.
It’s worth remembering that fixed detectors, firefighting equipment, remote and manual monitors and deluge systems are vulnerable to explosion damage. We must ensure that suitable back-up equipment is readily available both on-and-offsite.
The early stages of any incident are critical and it’s imperative that each site has a fast response. This should be provided by properly-trained and suitably-equipped emergency response personnel who understand the philosophy of ‘sizing up’ - whether to cool or not, protecting exposures, extinguishing or whether to leave it to burn under control.
On many sites, the first response may be the works fire brigade (if one exists), plant operators or maintenance personnel who should have received training onsite by suitably qualified instructors. I am often told that training is expensive. I believe that ignorance is far more costly.
Fewer workers to cope with emergencies
Within the European Union, the directive issued in 1996 on the control of major accident hazards involving dangerous substances has been the catalyst to ensure that operators clearly demonstrate to society that they are able to manage and control all hazards that might occur on their site.
With the current over-refining capacity in Europe, refineries have been forced to reduce costs as much as possible, maintenance costs has been a high priority but in looking at cost reduction, downsizing (manpower) comes to the fore.
Because of reduced manpower the numbers of personnel on site available for Emergency Response activities has reduced considerably. To supplement this reduction, petrochemical plant has introduced additional fire and gas detection, with further installation of CCTV in those identified critical areas within the complex, without immediate human surveillance, e.g. hot oil pumps (AIT) 350°C, compressors, offsite LPG Pumps, Transfer Pump Houses.
Once a release of hydrocarbon vapour or a fire is detected, the design of the facilities must be such that containment can be achieved quickly and the possibility of escalation reduced to a minimum.
Factors affecting the ability to accomplish this include realistic plant design layout, process equipment spacing, drainage, isolating valve location and operation, passive protection, spill containment by use of toe-walls and active fire protection.
Rapid containment involves a realistic assessment of the probable scenarios, remedial action, and manpower and equipment availability.
All kinds of fire and chemical disasters are out there, just waiting to happen. The question is - could you cope when such an incident occurs?