Safeguarding Petrochemical Conveyors: A Case Study in Instrumentation and Lightning Protection
In the midst of a substantial supply expansion program, Power Quality was tasked with implementing lightning protection measures for a conveyor system, including transfer towers, substation earthing, and the crossing of high-voltage power lines. Amidst these efforts, a request emerged to investigate recurring damages to the conveyor’s emergency stop system, leading to a critical discovery that would enhance the system's resilience against lightning and electromagnetic interference.
A nearby conveyor was experiencing repetitive damages to its pull key system, which is essential for emergency stoppage in critical situations. This system's failure not only posed a significant safety risk but also threatened to disrupt the continuous operation of the conveyor, highlighting the need for an urgent and effective solution.
Within minutes of inspecting the conveyor’s second combiner box, Power Quality’s team uncovered a fundamental issue: the communication cable’s shielding was not earthed. The absence of a proper connection due to the cable gland’s failure to secure the screen/shielding to the local earth point was identified as the culprit. This oversight caused the shielding to function as an antenna for electromagnetic events, particularly lightning, allowing energy to couple onto the cable’s cores and create excessive potentials at both ends.
The discovery revealed how the unintended antenna effect of the cable shielding led to repeated lightning-induced damages. The electromagnetic energy from lightning strikes, instead of being safely dissipated into the earth, was channeled into the conveyor’s electronic systems. This misdirection caused significant surges that the system was not designed to handle, leading to the recurrent failures of the emergency stop mechanism.
To address this critical issue, Power Quality implemented a corrective measure by properly grounding the communication cable’s shielding. This intervention involved the installation of a dedicated wire connecting the screen/shielding to the local earth point, thereby neutralizing the antenna effect and preventing electromagnetic energy from coupling onto the cable's cores.
The corrective measures taken significantly mitigated the risk of lightning-related damage to the conveyor's emergency stop system. By ensuring the proper grounding of the cable shielding, the team not only enhanced the system's operational reliability but also reinforced safety protocols, ensuring the well-being of personnel and the integrity of the petrochemical conveyor operations.
This case study underscores the critical importance of detailed attention to all components of industrial systems, especially in environments where the risk of lightning and electromagnetic interference is high. It highlights the necessity of thorough inspections and the value of specialized expertise in diagnosing and resolving complex technical issues. As industries continue to evolve, the lessons learned from this project serve as a testament to the ongoing need for vigilance and innovation in protecting essential infrastructure.
