With any chemical processing, there are risks involved because of the dangerous substances being handled. The results of major accidents, fires and chemical spillages are often seen in the news from across the world.
The need to reduce these accidents resulted in the Control of Major Accident Hazards (COMAH) Regulations being introduced in 2015.
The regulations are a series of safety laws designed to prevent major incidents involving chemicals, fuels and explosives. The hope is that they can protect both people and the environment from future disasters.
COMAH regulations apply to plants that use large volumes of hazardous materials, such as the petrochemical industry, biofuel processing and distilled spirit manufacturers.
Designing safety into processes is one way to reduce or mitigate the risks of using hazardous materials.
What Are The Major Risks In Petrochemical Processing?
Fire
Caused by the ignition of flammable material, it can have a domino effect if there is insufficient space between parts of the plant.
High-pressure leaks can cause jet fires, and spilt chemicals can cause pool fires.
Explosion
Caused by leaked flammable gases or overpressurised containers rupturing.
Toxic Gas Release
Either through damaged equipment, blocked pipes or outlets, overpressurisation of a container, or cooling system failures.
Risks To Human Health
Long-term exposure to certain chemicals can cause chronic health conditions in workers if not provided with the proper PPE. In rare cases, accidental exposure to toxic fumes can be fatal.
Corrosion, Erosion And Equipment Fatigue
Over time, plant equipment is subject to wear and tear, through chemical interaction, weather or use. All of these increase the risk of accidents.
Environmental Risks
Accidents can cause irreparable damage to ecosystems and biodiversity through air, water and soil pollution.
To avoid future crises, petrochemical companies design inherent safety into plant layouts and processes.
What Is Inherent Safety?
As defined by the Health & Safety Executive (HSE), the main principle of inherent safety is to remove the hazard completely.
Inherent safety design is a proactive way of using engineering to make chemical sites safer for workers and the environment. It was originally introduced after the Flixborough explosion in 1974.
The explosion was caused by a ruptured pipe, which leaked a large amount of cyclohexane. The vapour cloud caught fire and burned for several days, with eighteen fatalities on the site.
After the investigation concluded, Trevor Kletz, an ICI employee, wrote a paper that changed the way we design for safety on chemical sites.
It was entitled, “What you don’t have, can’t leak…” in reference to on-site inventory, and it paved the way for inherent safety design across the globe.
While there is no way to eliminate all hazards due to the nature of the industry, there are many methods of improving safety on-site.
How Can Inherent Safety Be Integrated Into Processes?
Changing The Hazardous Materials
The main method is to change the materials or the volume of the materials used in processes to less hazardous options.
However, it is not always possible to get the same quality end product by substituting a different chemical compound component.
Simplifying Systems
The benefit of this is that there will be fewer errors in production, therefore less chance of containment issues.
A simpler system may also be more efficient. For example, using a more efficient batch process could reduce the amount of hazardous materials needed, although this would depend on the output product.
Reducing Stored Materials
Implementing limits on the amount of hazardous inventory stored on site can immediately reduce the risk of accidents and loss of containment. This applies to the final product, its ingredients and any volatile catalysts required.
Plant Layout
The HSE has guidelines on how to design a safer plant. Although the design and build of a plan often involves a compromise between functionality and safety.
Some factors to consider include distances between plant equipment, interactions with existing infrastructure, access for emergency services and the proximity of homes to hazardous materials.
Fail-Safe Designs
Products or mechanisms that are engineered to respond to changes in systems and maintain safety by releasing pressure or initiating a shutdown.
What Are Examples Of Failsafe Design In The Petrochemical Industry?
Failsafes can mean the difference between business as usual and disaster, but many different types can be implemented as part of inherent safety design.
Valves
Valves are vital in the petrochemical industry, with so many dangerous and volatile substances in use.
They prevent leakage of gases and can reduce pressure in tanks and other containers. They are also used in pipelines and as inlet/outlet valves.
If power or pressure changes, that is when valves can kick in. An excellent example is a pressure relief valve for a gas tank.
Redundancies
Hardware redundancies and backups can be put in place for primary systems. For example, secondary power sources which take over when the main source fails.
Physical Failsafes
These are mechanical in nature, where a change in flow, pressure or surge in power kicks in. Examples include fuses, similar to domestic fuses, and dead man switches, which require the operator to be in constant contact or the system will shut down.
Safety Instrumented Systems
Often shortened to SIS, these systems detect unsafe conditions and automatically take the process or entire plant to a safe state. An example is an emergency shutdown system, which activates when a fire or gas leak is detected.
