Classification of explosive gases at construction sites of petrochemical enterprises
Generally, explosive gases at construction sites of petrochemical enterprises are classified into three categories:
The first category is mine methane; the second category is explosive gases and vapors; the third category is explosive dust and fibers.
Under standard test conditions, explosive gases are classified based on their maximum experimental safe gap and minimum ignition current ratio, and grouped by their ignition temperature. When installing instruments, electrical equipment, and materials in explosive and fire hazard locations, they must comply with the current national or ministerial issued explosion-proof quality standards and technical appraisal documents, as well as have the factory certificate of explosion-proof products. At the same time, ensure that there are no external damages and cracks. The protective tubes should be selected from national standard thick-walled galvanized steel tubes.
Zoning of petrochemical hazard locations
The zoning of petrochemical hazard locations mainly depends on the level of the release source and the frequency of the appearance of explosive mixtures. Release sources are classified into continuous-level release sources, first-level release sources, and second-level release sources based on their characteristics and frequency of appearance.
Continuous-level release sources, such as the surface of flammable liquids in fixed roof storage tanks not covered with inert gas, are expected to release for a long time or frequently in a short time. First-level release sources, such as the seals of pumps, compressors, and valves that release flammable substances during normal operation, are expected to release periodically or occasionally during normal operation. Second-level release sources, such as the seals of pumps, compressors, and valves that do not release flammable substances during normal operation, are not expected to release under normal circumstances. Even if they release, it is only an occasional and short-term release.
Based on the frequency of the appearance of explosive mixtures, the explosive environment is divided into Zone 0, Zone 1, and Zone 2. Zone 0 is an environment where explosive gas mixtures continuously or long-term appear, such as the internal gas space of closed containers and storage tanks. In actual design, Zone 1 rarely exists, and most cases belong to Zone 2. Zone 1 is an environment where explosive gas mixtures may appear during normal operation. Zone 2 is an environment where explosive gas mixtures cannot appear during normal operation or even if they appear, it is only for a short time.
Dust-proof capacity requirements of feedback switches in the petrochemical industry
In the petrochemical industry, the dust-proof capacity of feedback switches is crucial. In a complex production environment, dust particles may interfere with the normal operation of feedback switches. To ensure the stable operation of feedback switches, their dust-proof capacity needs to reach a high standard. Generally speaking, high-quality feedback switches should have a good sealing structure to prevent dust from entering the interior. For example, some feedback switches use special dust-proof materials to make the shell, effectively blocking the invasion of dust. In addition, special treatments are also carried out at interfaces and gaps to enhance the overall dust-proof effect. In practical applications, in some production areas with a lot of dust, if the dust-proof capacity of feedback switches is insufficient, it may easily lead to problems such as poor contact and signal transmission errors, thereby affecting the monitoring and control of the entire production process.
Water-proof capacity requirements of feedback switches in the petrochemical industry
In the petrochemical field, the water-proof capacity of feedback switches cannot be ignored. Due to the possibility of liquid leakage and spraying during the production process, feedback switches must have good water-proof performance. Usually, feedback switches with excellent water-proof capacity will adopt strict packaging processes and water-proof sealing materials. For example, some feedback switches use rubber sealing rings to prevent moisture from entering the interior, and some have water-proof coating treatment on the shell surface to improve water-proof performance. In some working environments with high humidity or easy access to water, if the water-proof capacity of feedback switches is poor, it may lead to problems such as short circuits and equipment damage, thereby affecting the normal progress of production.
Usage limitations of contact feedback devices in explosion-proof occasions
In explosion-proof occasions, contact feedback devices have some obvious usage limitations. Since most of them are composed of mechanical limit switches and have mechanical contact parts, sparks are prone to occur during operation. Therefore, when using contact feedback devices in flammable and explosive environments, explosion-proof shells need to be installed, which not only increases the volume and weight of the equipment but also makes the operation very cumbersome. Moreover, if the valves operate frequently, the accuracy and lifespan of contact feedback devices will decrease. For example, in some petrochemical production sites, due to the frequent switching operations of valves, contact feedback devices may not be able to meet the requirements of long-term stable operation.
Application conditions of non-contact feedback devices in explosion-proof occasions
Non-contact feedback devices have unique application conditions in explosion-proof occasions. They generally adopt NAMUR proximity switches, overcoming the disadvantage of sparks prone to occur in contact feedback devices. However, when using non-contact feedback devices in explosion-proof occasions, safety barriers need to be matched, which increases the cost. But from the perspective of safety and stability, non-contact feedback devices are still widely used in some explosion-proof occasions with high requirements for accuracy and stability. For example, in some petrochemical storage areas with extremely strict explosion-proof requirements, non-contact feedback devices can exert their advantages to ensure the safety of the production environment.
Advantages of fiber optic valve position feedback devices in flammable and explosive sites
Fiber optic valve position feedback devices have many significant advantages in flammable and explosive sites. Firstly, it uses optical signal transmission and there is no electrical signal, fundamentally avoiding the possibility of electrical sparks and achieving intrinsically safe explosion-proof. Secondly, fiber optic valve position feedback devices adopt non-contact measurement and will not affect performance due to mechanical wear of components. They are economical, durable, and not easily damaged, especially suitable for harsh environments. Furthermore, the optical signal transmission distance is long and the anti-electromagnetic interference ability is strong. The maximum transmission distance can reach 5 kilometers, and it is not subject to any electromagnetic interference on the transmission path, ensuring the accurate and stable transmission of signals. For example, in flammable and explosive areas of petrochemical industries, fiber optic valve position feedback devices can precisely monitor the status of valves and provide a strong guarantee for production safety.
In conclusion, the explosion-proof requirements for feedback switches in the petrochemical industry are very strict. Different types of feedback switches have their own characteristics and limitations in explosion-proof occasions, and need to be selected and applied based on specific production environments and requirements to ensure the safety and stability of the production process.