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Case
Tianjin Shihua Petrochemical Project: Surge Protection for Critical 220VAC Circuits
2026-04-15
Project Overview
Location: Tianjin, China
Industry: Petrochemical (refining & storage)
Application: Low-voltage 220VAC control and instrumentation circuits
Products Installed: Surge Protective Devices (SPD) + SCB (SPD specific disconnector)
Key Feature: Manual operation method retained for maintenance and emergency bypass
Tianjin Shihua Petrochemical Co., Ltd. （As Taihang valued customer）operates a large-scale refining and chemical complex in the Tianjin Economic-Technological Development Area (TEDA). The plant handles flammable liquids and gases, making lightning and surge protection not just an equipment issue – but a critical safety requirement.Industry: Petrochemical (refining & storage)
Application: Low-voltage 220VAC control and instrumentation circuits
Products Installed: Surge Protective Devices (SPD) + SCB (SPD specific disconnector)
Key Feature: Manual operation method retained for maintenance and emergency bypass
The Challenge
The plant's existing 220VAC control loops (powering sensors, actuators, and PLC cabinets) suffered from:
Frequent transient overvoltages caused by nearby lightning strikes and switching operations of large motors.
Occasional damage to input/output (I/O) cards, leading to unplanned process shutdowns.
Lack of proper coordinated protection between SPDs and upstream circuit breakers – resulting in nuisance trips or unprotected surges.
Additionally, the plant's electrical team required a solution that allows manual operation (e.g., manual disconnection/reset) during maintenance, without compromising surge protection.
Frequent transient overvoltages caused by nearby lightning strikes and switching operations of large motors.
Occasional damage to input/output (I/O) cards, leading to unplanned process shutdowns.
Lack of proper coordinated protection between SPDs and upstream circuit breakers – resulting in nuisance trips or unprotected surges.
Additionally, the plant's electrical team required a solution that allows manual operation (e.g., manual disconnection/reset) during maintenance, without compromising surge protection.
Our Solution
After a site survey, we deployed a combined SPD + SCB protection scheme on key 220VAC power supply lines feeding distributed control system (DCS) cabinets and field instrument junction boxes.
Products Used
The photo (attached) shows the installation inside a field instrument junction box – clearly marked with "SCB", "SPD", "Line voltage 220VAC", and "Manual operation method".
Enhanced safety – SCB prevents sustained arc faults if the SPD degrades, reducing fire risk in hazardous areas.
Manual operation capability – The built-in manual isolation feature allows loop testing and SPD replacement without powering down the whole control panel – critical for continuous processes.
Reliable 220VAC protection – Designed specifically for industrial control circuits, not just main distribution boards.
Easy retrofitting – Compact DIN-rail form factor fits into existing junction boxes.
SPD – Type 1 surge protective device, impulse current (In) 25kA, voltage protection level Up ≤ 2.3kV for 220VAC systems.
SCB – Specialized backup protector for SPDs, providing short-circuit breaking capacity up to 100kA, ensuring the SPD does not become a fire hazard under fault conditions.
Line voltage: 220VAC, single-phase.
Manual operation method: The assembly includes a manual disconnect/isolating switch (visible in the photo), allowing technicians to safely isolate the SPD/SCB module for inspection or replacement without de-energizing the entire panel.The photo (attached) shows the installation inside a field instrument junction box – clearly marked with "SCB", "SPD", "Line voltage 220VAC", and "Manual operation method".
Enhanced safety – SCB prevents sustained arc faults if the SPD degrades, reducing fire risk in hazardous areas.
Manual operation capability – The built-in manual isolation feature allows loop testing and SPD replacement without powering down the whole control panel – critical for continuous processes.
Reliable 220VAC protection – Designed specifically for industrial control circuits, not just main distribution boards.
Easy retrofitting – Compact DIN-rail form factor fits into existing junction boxes.
Why Choose Our SPD+SCB Solution for Your Petrochemical Facility?
IEC/EN 61643-11 & 61643-12 compliant – Suitable for global projects.
SCB coordination – No blind spot between SPD thermal disconnector and upstream fuse/MCB.
Manual operation option – Field-proven for maintenance-heavy environments like refineries, chemical plants, and pipelines.
Proven in China – Successfully deployed at Tianjin Shihua, Sinopec, and other major petrochemical sites.
