SPECIAL TOPIC: EMISSION CONTROL IN TANKS
Hazardous Storage Tank Pressure Protection and Emissions Control
This article discusses the essential equipment necessary to safeguard low-pressure storage tanks from pressure change events, addressing the challenges posed by new standards, narrow operating ranges and the need for precise system component coordination. It also provides valuable insights into effective tank protection strategies, focusing on operational safety and minimized environmental impact.
By Omar Cruz, Emerson
While storage tanks can safely store thousands of barrels of product, they are sensitive to overpressure or vacuum conditions, both of which can lead to product loss or excess emissions. Tank ruptures or implosions can result when the tank ' s design limits are exceeded.
One straightforward solution is to install large vents on a tank, allowing it to release pressure or relieve the vacuum freely. This approach works well for tanks storing non-hazardous materials but poses significant safety and environmental risks for tanks containing volatile organic compounds. These tanks need a more sophisticated array of protection devices to ensure product quality, operational safety and minimal environmental impact. Tank protection solutions might include a combination of tank blanketing regulators, pressure vacuum relief valves, gauge hatches, emergency vents and other equipment.
Meeting new emission requirements
There is a wide range of storage tank designs, but this article concentrates on low-pressure storage tanks holding liquids that are stable at room temperature. These tanks usually have a fixed roof construction that creates a vapour space between the stored liquid and the top of the tank. High-pressure and cryogenic tanks are beyond the scope of this article.
With these types of tanks, regulating the internal pressure within vacuum and pressure design limits is critical. Many storage tanks can sustain a vacuum of only a few inches of water, and the maximum pressure may be one PSI or less. Operation even slightly beyond design pressure or vacuum can result in immediate and catastrophic damage( Figure 1).
12 FUGITIVE EMISSIONS JOURNAL • APRIL 2025