Fact Statement: The fire is still under investigation, and publicly available information has not yet confirmed the exact cause of the accident. Therefore, this article does not analyze the cause of the accident, nor does it attribute the accident to any specific valve, piping component, or equipment. Instead, it focuses on valve safety issues commonly involved in the commissioning of large-scale chemical facilities.
On August 25, 2026, a serious fire occurred at the Amur Gas Chemical Complex (AGCC) in the Amur Region of Russia’s Far East. As of August 26, the accident had resulted in 7 deaths, 152 injuries, and 9 people missing.
According to an official statement from AGCC, the fire occurred in the auxiliary process section of the plant’s pyrolysis unit, while the main project equipment was not damaged. This accident is deeply distressing and once again reminds us that, in natural gas chemical projects, the safety of auxiliary process sections, particularly the reliability of valves, is by no means an “auxiliary” issue.
An ethylene cracking unit is an extremely complex system with highly demanding process requirements. The cracking furnace is the heart of the unit, where natural gas or naphtha is cracked at temperatures above 800°C into basic chemical feedstocks such as ethylene and propylene.
The Auxiliary Technological Section, although not located at the center of the high-temperature reaction like the cracking furnace, is responsible for providing stable utilities and various auxiliary media for the entire unit, ensuring the continuous and safe operation of the main unit.
The auxiliary process section mainly includes the following seven subsystems:
1. Fuel Gas/Fuel Oil System: This includes fuel gas buffer vessels, knockout drums, fuel oil pumps, strainers, and burners, and is responsible for supplying stable and clean fuel to the cracking furnace.
2. Steam System: The core equipment is the Steam Drum, which generates and distributes the dilution steam, high-pressure steam, and other steam required by the unit.
3. Feedwater and Condensate System: This includes deaerators, boiler feedwater pumps, condensate recovery tanks, and other equipment responsible for supplying and treating qualified water for the steam system.
4. Compression and Refrigeration System: This includes multistage compressors, intercoolers, separators, and refrigeration compressors, which are used to compress and cool cracked gas and provide refrigeration for downstream separation.
5. Drying and Purification System: This mainly consists of molecular sieve dryers used to remove trace moisture from cracked gas and prevent freezing and blockage of downstream equipment at low temperatures.
6. Relief and Flare System: This includes flare knockout drums, flare tips, and other equipment used to safely burn and dispose of combustible gases discharged from the unit during startup, shutdown, or emergency conditions.
7. Decoking System: This includes decoking valves, decoking pipelines, and other equipment used to periodically remove coke deposits from cracking furnace tubes and restore heat-transfer efficiency.
Valves are the most numerous and diverse types of critical equipment in auxiliary systems. They perform important functions such as isolation, regulation, and control of the flow, pressure, and direction of process media. The following are typical valve types and their applications in auxiliary process sections:
This is one of the most representative valve types used in ethylene units. Its core applications are as a Transfer Line Valve (TLV) and a Decoking Line Valve (DLV), installed at the outlet of the cracking furnace. These valves are required to operate frequently under extreme conditions involving high temperatures of up to 700°C or above and process media containing coke particles, switching between normal production and decoking modes. The main technical challenges are valve sticking and coke accumulation inside the valve cavity.
Control valves are used in applications requiring precise flow regulation, such as fuel gas and feed flow control, dilution steam injection control, and compressor anti-surge control. Common valve types include Globe Valves and V-Ported Segment/Ball Valves.
Emergency shutdown valves are used to quickly and safely isolate process media in emergency situations. On fuel gas/fuel oil pipelines, a Double Isolation and Bleed configuration is generally adopted, meaning that a bleed valve is installed between two ESDVs to ensure absolute safety. Common valve types include Ball Valves and Gate Valves.
Ball valves are widely used in auxiliary systems. For example, in dryer systems, metal-seated ball valves are generally selected to cope with frequent switching operations and temperature fluctuations. Under operating conditions involving high differential pressure and frequent operation, metal-seated ball valves are also preferred to ensure performance and service life.
Check valves are used to prevent reverse flow of process media and protect critical equipment such as compressors. Large-diameter swing check valves are used on large pipelines.
For large-diameter applications requiring low pressure drop, butterfly valves are an efficient and economical option. For example, triple offset metal-seated butterfly valves are commonly used in flue gas or hot-air pipelines.
As the final safeguard, safety valves are installed on pressure vessels and high-pressure pipelines. They automatically open to relieve pressure when the system becomes overpressurized.
Transfer line valves and decoking line valves are installed at the outlet of cracking furnaces, where operating temperatures can reach 700°C or above and the process medium contains coke particles. Under these operating conditions, valves face two major challenges: sticking and coke accumulation inside the valve cavity. Once a valve is unable to open or close properly, operation of the entire cracking furnace will be affected. More dangerously, if the valve loses its sealing performance at high temperatures, leaked high-temperature cracked gas may cause a deflagration upon contact with air.
According to Russian media reports, the AGCC fire occurred during equipment depressurization operations. The commissioning stage is one of the most dangerous periods in a chemical project — equipment is exposed to actual process media for the first time, while temperature, pressure, vibration, and corrosion challenges occur simultaneously.
Historically, similar lessons are not uncommon:
● In 2021, during a shutdown and maintenance period at the No. 2 ethylene unit of the Olefins Division of Shanghai Petrochemical, the upstream and downstream valves of a blind plate on the cracking furnace feed pipeline were not closed, resulting in a deflagration accident.
● At a chemical plant in Shandong, China, a valve failure caused butadiene leakage, which resulted in a deflagration.
● At a naphtha cracking plant in South Korea, a fire was caused when butane gas leaking from a faulty valve was ignited by welding sparks.
These cases have one thing in common: valve failure was the first domino in the accident chain.
Under high-temperature and high-pressure operating conditions, the packing gland and sealing surfaces of a valve are the weakest points. Packing gland leakage can cause combustible media to escape directly into the surrounding environment, where contact with an ignition source may result in a fire. Failure of the sealing surfaces, resulting in internal leakage, may cause downstream equipment to become overpressurized or may expose personnel to poisoning or asphyxiation during maintenance.
Under high-temperature and high-pressure operating conditions, the packing gland and sealing surfaces of a valve are the weakest points. Packing gland leakage can cause combustible media to escape directly into the surrounding environment, where contact with an ignition source may result in a fire. Failure of the sealing surfaces, resulting in internal leakage, may cause downstream equipment to become overpressurized or may expose personnel to poisoning or asphyxiation during maintenance.
For high-temperature operating conditions involving coke particles, such as TLV/DLV service, high-end valves featuring a pressure seal structure — where higher pressure improves sealing reliability — an integrally forged valve body — with no weld seams and high strength — and hard-alloy hardfaced sealing surfaces — providing wear resistance and high-temperature resistance — must be selected. Valve selection should not be driven by price, but by full life-cycle reliability.
Valves and actuators used in natural gas chemical facilities should have the appropriate explosion-proof certifications, such as ATEX and IECEx. The fire-safe design of valves should comply with API 607 or API 6FA standards — meaning that under fire conditions, even if non-metallic seals fail, the valve can still maintain a certain level of sealing performance.
Based on lessons learned from historical accidents, valve inspections during commissioning should include at least the following:
Leak Tightness Test: Conduct shell tests and seat leakage tests to confirm that there is no internal or external leakage.
Operation Test: Confirm that the valve can fully open and fully close smoothly and that the actuator reaches the correct position.
Packing Gland Inspection: Confirm that the packing gland is properly tightened and check for any signs of leakage.
Internal Cleanliness Confirmation: Confirm that there is no welding slag, debris, or other construction residue inside the valve.
Explosion-Proof and Grounding Inspection: Confirm that the actuator explosion-protection rating and static grounding comply with requirements.
Safety Valve Set Pressure Verification: The set pressure should not exceed 1.1 times the maximum working pressure.
The sealing technology of high-temperature high-pressure valves is critical to preventing process media leakage:
Pressure Seal Structure: Uses internal system pressure to increase sealing force, providing more reliable sealing as pressure increases.
Hard-Alloy Hardfaced Sealing Surface: Cobalt-based hard alloy, such as Stellite, is hardfaced onto the sealing surface to provide wear resistance, high-temperature resistance, and galling resistance.
Corrosion-Resistant Nitriding Treatment of the Valve Stem: Improves the surface hardness and corrosion resistance of the valve stem.
Bellows Seal: Suitable for toxic and hazardous media and eliminates the risk of packing gland leakage.
The AGCC fire is a deeply distressing tragedy. Although the final cause of the accident is still under investigation, the fact that the fire occurred in the auxiliary process section is sufficient reason for us to reconsider the safety importance of auxiliary systems and their equipment within chemical facilities.
For the valve industry, every accident is a warning and also an opportunity for reflection. Particularly under high-temperature, high-pressure, and severe service conditions, ensuring product reliability is an essential requirement.
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