Selection of industrial control computers for explosion-proof scenarios

Selection of Industrial Control Computers for Explosion - Proof Scenarios

Understanding Explosion - Proof Environment Classification

Explosion - proof environments are classified based on the frequency and duration of the presence of explosive substances. The International Electrotechnical Commission (IEC) and the European Electrotechnical Commission divide hazardous areas into three main zones: Zone 0, Zone 1, and Zone 2.

Zone 0 represents areas where explosive gases are continuously or for long periods present. For example, the interior of closed containers in some chemical production processes. In this zone, the risk of explosion is extremely high, and only the most stringent explosion - proof equipment can be used.

Zone 1 is where explosive gases may occasionally occur during normal operation of equipment. An example is the area around gas discharge ports. The probability of explosion in this zone is lower than in Zone 0 but still requires reliable explosion - proof measures.

Zone 2 is an area where explosive gases only exist briefly under abnormal conditions. Well - ventilated laboratories can be considered as Zone 2 environments. The risk of explosion in this zone is relatively low, but appropriate explosion - proof equipment is still necessary.

Explosion - Proof Types and Their Applicability

There are several main explosion - proof types for industrial control computers, each with its own characteristics and applicable scenarios.

Flame - Proof Type (Ex d)

The flame - proof type uses a sturdy enclosure to withstand the pressure generated by an internal explosion and prevent the flame from spreading to the external environment. The enclosure has strict requirements for gap size and thickness. For instance, in a chemical plant, where there are large amounts of explosive gases in the production workshops, flame - proof industrial control computers can be installed. These computers can contain an internal explosion within the enclosure, ensuring the safety of the surrounding environment and personnel. The flame - proof type is suitable for Zone 1 and Zone 2 environments, especially when dealing with relatively high - pressure and high - energy explosive gas mixtures.

Intrinsic Safety Type (Ex i)

Intrinsic safety type limits the voltage and current of the circuit to ensure that the electrical sparks and thermal effects generated under normal and fault conditions cannot ignite the explosive mixture. It is further divided into ia and ib levels. The ia level means that the equipment will not cause ignition under normal operation, one fault, and any combination of two faults. The ib level can ensure non - ignition under normal operation and one fault condition. Intrinsic safety type is mainly used in environments with a high concentration of dust, such as coal mines. In a coal mine, where there is a large amount of coal dust that can easily cause an explosion, intrinsic safety industrial control computers can effectively prevent the occurrence of explosions by limiting the electrical energy. This type is suitable for Zone 0 environments and can also be used in Zone 1 and Zone 2 with appropriate protection measures.

Pressurization Type (Ex p)

The pressurization type involves filling the interior of the equipment with a protective gas and maintaining a positive pressure to prevent external hazardous gases from entering. This type is often used in precision equipment such as analyzers. In a petrochemical plant, some analytical instruments need to operate in a safe environment. By using pressurization - type industrial control computers, the internal pressure can be kept higher than the external pressure, ensuring that explosive gases do not enter the equipment and cause damage to the precision components inside. It is mainly applicable to Zone 1 and Zone 2 environments where high - precision operation is required.

Key Considerations for Selecting Explosion - Proof Industrial Control Computers

When selecting explosion - proof industrial control computers, in addition to considering the explosion - proof type and the applicable zone, several other factors need to be taken into account.

Environmental Adaptability

The industrial control computer should be able to withstand the physical challenges of the explosion - proof environment. This includes resistance to high and low temperatures, humidity, vibration, and shock. In an outdoor oil and gas storage and transportation facility, the temperature can vary greatly between day and night, and there may be strong winds and vibrations. The selected industrial control computer should be able to operate normally under these harsh conditions. It should have a wide operating temperature range, such as from - 20°C to 60°C, and good anti - vibration and anti - shock capabilities to ensure stable performance.

Ingress Protection (IP) Rating

The IP rating indicates the degree of protection against the ingress of solid objects and liquids. For explosion - proof environments, a high IP rating is often required. In a dusty environment like a grain processing plant, an IP6X rating is necessary to prevent dust from entering the equipment and causing short - circuits or component damage. In areas where there is a risk of water splashing or immersion, such as in some food processing plants, an IPX4 or higher rating is required. A high IP rating ensures the long - term reliable operation of the industrial control computer in the explosion - proof environment.

Communication and Data Processing Capabilities

The industrial control computer should have sufficient communication and data processing capabilities to meet the requirements of the explosion - proof environment. In a large - scale chemical production plant, there may be a large amount of data from various sensors and equipment that need to be collected, processed, and transmitted in real - time. The industrial control computer should support multiple communication protocols, such as Ethernet, RS - 485, and Modbus, to ensure seamless connection with other devices. It should also have a powerful processor and sufficient memory to handle complex data processing tasks, enabling real - time monitoring and control of the production process.