In industrial and storage tank systems, maintaining safe pressure balance is critical to prevent catastrophic accidents. When tanks experience sudden overpressure or vacuum conditions, a specialized device—the Emergency Vent—acts as a vital safety mechanism. It ensures controlled venting to protect both the tank and the environment. In this guide, we’ll explain how an emergency vent works, why it’s essential for fuel tanks and storage tanks, and how to select the right type for your facility.
An Emergency Vent (also called an emergency relief vent or emergency pressure relief vent) is a safety device installed on tanks to prevent structural failure caused by excessive pressure or vacuum.
In normal conditions, the vent valve remains tightly sealed, keeping vapors or gases contained. However, when abnormal pressure levels are reached—such as during a fire, rapid product filling, or vapor expansion—the emergency vent hatch automatically opens to release excess pressure.
Common applications include:
Fuel tank emergency vent systems in oil depots and chemical plants
Emergency vent for storage tanks used in refineries and industrial facilities
Emergency relief valve tanks that handle volatile or flammable liquids
These vents are crucial components in a broader tank protection system, ensuring safe and continuous operations.
Overpressure occurs when gases or vapors expand beyond the tank’s design limits—often due to heat, chemical reactions, or fire exposure. Without a storage tank emergency vent, the internal pressure could exceed safe thresholds, leading to ruptures or explosions. The emergency vent quickly releases excess gases to maintain stability.
When product withdrawal or temperature drops cause internal pressure to fall below atmospheric levels, tanks can collapse inward. An emergency tank vent or vacuum relief vent opens inward to equalize the pressure, preventing structural deformation.
Regulations like API 2000, OSHA, and NFPA 30 require proper emergency venting of tanks to ensure worker and facility safety. Installing certified emergency relief hatches ensures compliance and reduces insurance risks.
Proper emergency venting reduces emissions and prevents liquid product from being forced out during venting events. A well-designed vent valve minimizes vapor release, protecting both your product and the environment.
In normal operation, the emergency vent hatch or emergency relief valve tank remains sealed. The internal pressure is stable, and no gas escapes. A sealing gasket ensures airtight closure to prevent vapor loss and contamination.
As tank pressure begins to rise, the system approaches the set pressure point (e.g., 6–10 kPa). The vent remains closed, but slight movement may occur in the pressure plate—this indicates readiness to activate. Operators can monitor this using pressure gauges or sensors.
When internal pressure exceeds the emergency pressure relief vent setpoint, the vent disc or hatch rapidly opens. This allows large volumes of vapor to discharge quickly, relieving tank pressure. High-flow capacity ensures the pressure stays within safe limits. This stage is crucial in fuel tank emergency venting, especially during fire exposure or vapor expansion.
If the tank experiences sudden cooling or product withdrawal, internal vacuum may develop. The vent valve opens inward, allowing external air to enter, thus preventing tank implosion. This dual functionality (pressure + vacuum) is key for emergency vent for storage tanks.
In a fire scenario, the emergency vent must handle extreme vapor expansion. The emergency relief hatch opens fully to release gases safely, preventing tank rupture. When combined with a flame arrester, it prevents external ignition from entering the tank.
Once the internal pressure normalizes, the emergency vent hatch automatically reseats. The seal ensures the system returns to a leak-free state. This automatic closure minimizes product loss and keeps emissions within limits.
To ensure proper performance:
Inspect sealing gaskets regularly
Check vent movement during pressure tests
Ensure no corrosion or blockage in the vent path
Test spring tension and setpoint calibration periodically
| Tank Type | Set Pressure (kPa) | Set Vacuum (kPa) | Typical Flow Rate (Nm³/h) |
|---|---|---|---|
| Fuel Storage Tank | +7 | -2.5 | 12,000 |
| Chemical Tank | +10 | -3 | 15,000 |
| LNG Tank | +15 | -5 | 20,000 |
These values vary depending on tank size, liquid type, and regulatory standards.
Case 1: A refinery tank avoided rupture during a fire thanks to its ZhenChao Emergency Vent that opened at 8 kPa.
Case 2: A storage tank collapsed inward due to a faulty vacuum vent — emphasizing the importance of dual-acting emergency relief vents.
Lesson: Regular inspection and reliable manufacturing are critical for safety.
Different tanks (fuel, chemical, LNG, or water) require specific vent materials and flow capacities. For fuel tank emergency vents, explosion-proof and flame-resistant materials are essential.
Consult your tank design or API 2000 to determine the appropriate set pressure and vacuum levels. The vent should activate just before the tank’s maximum allowable working pressure.
Select a vent with a flow coefficient (Cv) sufficient to relieve the expected gas volume. Undersized vents may cause delayed venting or insufficient protection.
Corrosive or volatile environments demand vents made from stainless steel, aluminum, or carbon steel with anti-corrosion coatings. ZhenChao Emergency Vent products use durable, weather-resistant materials for long service life.
For tanks containing flammable products, integrate emergency vents with flame arresters to prevent ignition.
An Emergency Vent is a vital safety device that protects storage tanks from dangerous overpressure or vacuum conditions. Choosing a reliable vent ensures safe operations and compliance with safety standards.ZhenChao, a professional emergency vent manufacturer and supplier, provides high-performance ZhenChao Emergency Vents designed for durability, efficiency, and easy installation. Whether you need an emergency relief vent, vent valve, or storage tank emergency vent, ZhenChao delivers trusted solutions for all industrial applications.
