The Emergency Relief Vent is used for the relief of excess pressure as emergency breathing of cone roof tanks. Emergency breathing may be necessary in case of failure of the existing normal pressure valve or when its capacity is no longer sufficient due to an extremely high heat flow e.g., in the event of fire in neighboring tanks. When positioned on the flanged seat, the Emergency Vent provides an effective vapor-tight seal. Under emergency fire conditions, the cover can pivot open on its hinge and provide required relief, preventing damage to the tank due to excessive internal pressure. When tank pressure is reduced, the cover automatically recloses. The hinged design allows the use of a level principal counterweight. The design allows convenient access through the manhole opening for tank inspection and maintenance. Design and lightness of unit permit easy, convenient handling for inspection and maintenance. Opening of hinged cover allows access to tank through the seat area.
Emergency vents allow for the rapid release of pressure buildup due to fire exposure, thermal expansion, or chemical reaction.
Without this pressure relief, tanks may rupture or explode, causing massive environmental and human safety hazards.
API 650 requires tanks to be designed with consideration of such scenarios, referencing API 2000 for appropriate vent sizing.
Emergency venting is critical in fire scenarios (e.g., external fire heating tank contents).
These vents allow overpressure relief when normal vents are insufficient, preventing BLEVE (boiling liquid expanding vapor explosion).
In certain conditions like rapid filling, overheating, or exposure to sunlight, the vapor space can generate high pressure.
Emergency vents handle extreme cases beyond the capability of normal vents.
By avoiding excessive pressure differentials, emergency vents help:
Reduce stress on tank walls and roof
Prevent deformation or collapse
Extend the service life of the tank
A vented emergency pressure scenario avoids unplanned shutdowns and costly downtime.
Enables safer operations even in unanticipated conditions.
Although emergency vents may release vapors, their presence ensures a controlled release rather than an uncontrolled rupture.
Helps operators stay in line with environmental and occupational safety regulations (e.g., OSHA, EPA, local codes).
Emergency vents are typically passive devices (like rupture disks or spring-loaded hatches), requiring no power or manual operation.
This makes them reliable in power failure or emergency situations.
Emergency Venting Types
For set pressures less than 500 mm W.G., only weight is used to adjust the equipment at the required set pressure. Weight Loaded Emergency Vent is divided into simple, inverse and long arm based on the set pressure and material.
For set pressures more than 500 mm W.G., due to the increase in cover thickness, spring is also used to adjust the equipment at the required set pressure in addition to weight.
| Size | 10″ to 36″ |
| Model No. | 3800 & 3850 |
| Type | Weight or Spring Loaded |
| Connection | Flanged-Class #150 |
| Body Material | Carbon Steel
Stainless Steel 304 Stainless Steel 316 |
| Cover
And U-channel Material |
Carbon Steel
Stainless Steel 304 Stainless Steel 316 Aluminum |
Emergency venting events typically release volatile organic compounds (VOCs) or hazardous vapors into the atmosphere.
This contributes to air pollution, greenhouse gas emissions, and potential health risks to nearby populations and ecosystems.
Sustainability Consideration:
Reduce frequency and likelihood of emergency venting through better tank design, pressure control, and early detection systems.
Emergency vents are often triggered by fire scenarios, releasing flammable vapors that may worsen the fire or cause explosions.
This poses risks to human safety, wildlife, and can cause long-term environmental degradation.
Mitigation Strategies:
Use of inert gas blanketing systems to reduce flammability.
Installation of flame arrestors and gas recovery systems.
Emergency venting may result in loss of stored product (e.g., crude oil or chemicals), leading to:
Soil and water contamination
Wasted resources
Carbon footprint of replacement production
Sustainable Alternatives:
Vapor recovery units (VRUs) can be coupled with vents to capture and recycle vapors.
Secondary containment systems to prevent ground contamination.
