A minute spark in an oil & gas field, refinery, or chemical plant could trigger fires or explosions, resulting in huge damage to equipment and the environment and – even worse - potential loss of life. As a result, end users in industries with these types of hazardous environments will continue to deploy specialized automation products and systems designed to prevent electrical or other sparking.
Over the past several years, the proliferation of digital networks at the field level has changed the role of and demand for hazardous area components. Other technologies such as the Internet of Things (IoT) and Industrial IoT are pushing change in this area even faster with new field-mounted sensors and edge devices. Space limitations in the control room also encourage end users to install more components in hazardous plant and field areas. At the same time, increasingly stringent safety regulations and standards for explosion protection are driving users to obtain automation (and other) products with certifications for use in hazardous areas.
Hazardous Environment Automation Equipment
Plant or field areas that are exposed to potentially ignitable concentrations of flammable gas, vapor, or dust where an electrical spark could cause a hazardous explosion are classified as “hazardous” areas. Generally, explosions are caused by a combination of combustible substances (oil, gas, dust, etc.), explosive atmosphere (air/oxygen), and a source of ignition. Potential sources of ignition in the plant area include electrical installations; adiabatic compression and shock waves; electric stray currents; cathodic corrosion protection; electrostatics; flames; hot gases; hot surfaces; ionizing radiation; and electromagnetic waves.
The three basic methods of protection are: explosion containment (Ex d); segregation (Ex p, Ex m, Ex o, Ex q); and prevention, including both intrinsic safety (Ex i) and increased safety (Ex e). The intrinsic safety prevention method has been gaining wide acceptance especially in Europe and North America where, according to recent ARC market research, it is currently experiencing phenomenal growth. This is largely because the intrinsic safety approach allows maintenance to be performed without first having to shut down the power (and thus without interrupting production).
Major Industries Prone to Unexpected Explosions
In most process plants, it’s not possible for all automation system components to be installed in non-hazardous areas. As a result, some form of protection is required to prevent fires and explosions that could occur when a hazardous gas and energy source combine. Fortunately, there are standards and associated products that - if properly designed, installed, and maintained - virtually eliminate the risk of an accidental explosion in hazardous areas.
Process industries, including (but not limited to) upstream, midstream, and downstream chemical, oil, and gas, face numerous hazardous situations with the potential to cause huge explosions. Examples of actual incidents include well-publicized explosions at a Xiangshui chemical plant at Chenjiagang Chemical Industry Park in China, a boiler explosion in a packaging plant in Bangladesh, Tri-Chem Industries in the US, Yibin Hengda Science and Technology Company in China, a BASF plant in Germany, the Skikda refinery in Algeria, and BP’s Texas City Refinery in the US. Lack of information, leading to the inability to identify and understand hazardous locations, often contributes to these types of incidents.
User Challenges – Lack of Skilled Workforce
End user organizations continue to face a shortfall of qualified personnel. In many cases, they have brought this situation upon themselves through multiple rounds of layoffs, early retirements, and other ongoing efforts to reduce the size of their engineering, operations, and maintenance staffs. As a result, the pool of qualified personnel continues to shrink, as fewer members of the new workforce perceive process automation, process engineering, chemical engineering, or similar technical fields as attractive career paths. It can take two years to train a new hire effectively in the field of automation, and, once trained, it may be difficult to retain that individual.
This “brain drain” leads to some interesting problems in the process industries, including the inability to find qualified personnel to keep manufacturing plants up and running. On the positive side, the new digital infrastructures can provide secure remote access to data and tools to enable the diminishing pool of experienced personnel to support the less-experienced workers remotely.
The other major challenge for end users is being able to perform maintenance safely in hazardous areas without first isolating the power source of equipment. As previously mentioned, use of intrinsically safe equipment or intrinsic safety barriers make this possible.
Energy Limiting or Prevention Method – Intrinsically Safe (IS) Systems
Intrinsic safety, a low-power protection technique for safe operation of electrical equipment in hazardous areas, limits the voltage, current, and stored energy to a level below the minimum required for ignition during both normal and abnormal operation of the equipment. It provides a way to safely route electrical signals in Zone 0 locations (where ignitable concentrations of flammable gases or vapors are present continuously or for long periods of time). In the event of a short or arcing anywhere in the circuit, there will be insufficient energy to cause an explosion, so the equipment in the IS system can be worked on while electrically live.
In signal and control circuits, which operate with low currents and voltages, the intrinsic safety approach simplifies circuits and reduces installation cost compared to other protection methods. However, intrinsic safety protection is only used for low-power applications, which is a disadvantage.
Explosion-proof or Flameproof (Ex d) Approach
With the explosion-proof approach for hazardous areas, enclosures must be able to contain any explosion that might originate within its housing from igniting gases or vapors and prevent transmission of the explosion to the atmosphere around the enclosure.
Equipment certified for use in hazardous areas must be capable of withstanding an explosion caused by sparks, electrical arcs, or high temperatures. The explosion-proof enclosures are designed so that hot gases generated during an internal explosion are cooled below the ignition temperature of the surrounding flammable atmosphere as they escape through the joints of the housing. In addition, the external surfaces of the enclosure must not become hot enough to ignite the surrounding atmosphere.
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Keywords: Hazardous Area Automation, Intrinsic Safety, Explosion Proof, HMI, Remote I/O, Industrial IoT, ARC Advisory Group.