Aside from floating roof tanks, atmospheric tanks and pressure vessels are also commonly used to store industrial liquids. Both have characteristics, pressure limits, and functions tailored to the company’s operational conditions and needs.
Before making a decision, you need to understand the difference between atmospheric tanks and pressure vessels. Read the full article below to gain a comprehensive understanding of the differences between those two before choosing the right option.
Understanding Atmospheric Tanks and Pressure Vessels
A pressure vessel is a storage container designed to hold fluids at internal or external pressures that differ from atmospheric pressure. A fluid refers to any substance that flows easily, changes shape, and conforms to the shape of its container.
Unlike atmospheric tanks, pressure vessels are specifically engineered to withstand higher pressures, making them suitable for various industrial processes that require pressurized operating conditions.
In industrial applications, pressure vessels are used to store or contain gases, vapors, or liquids that require specific pressures and temperatures.
Meanwhile, atmospheric tanks are storage vessels designed to hold fluids at pressures close to atmospheric pressure.
Atmospheric tanks are widely used in various industrial operations, particularly for storing liquids at low pressure.
In industrial operations, atmospheric tanks are widely used to store various types of liquids, such as raw water, process water, liquid fuels, oil, lubricants, and various chemicals that are stable at atmospheric pressure.
The Differences Between Atmospheric Tank vs. Pressure Vessel
Atmospheric tanks and pressure vessels are both used as fluid storage facilities in industry. However, they have fundamental differences in terms of design, operating pressure, construction, and safety systems. These differences determine the types of fluids and operating conditions suitable for each tank. Here is the explanation:
1. Design
Atmospheric tanks are designated to operate at pressures very close to atmospheric pressure. Therefore, they are typically constructed as vertical cylinders with a fixed roof, floating roof, or open top. This type of tank is also equipped with a ventilation system to maintain pressure balance during both filling and emptying processes.
Conversely, pressure vessels are designed to withstand much higher internal and external pressures. They are generally designed as horizontal or vertical cylinders with heads shaped like ellipses, hemispheres, or torispheres.
Additionally, pressure vessels usually have thicker walls than atmospheric tanks and are equipped with various safety components, such as pressure gauges, nozzles, and other monitoring instruments.
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2. Operating Pressure
The difference between atmospheric tanks and pressure vessels can also be seen in their operating pressures. Atmospheric tanks are designed only to store fluids at pressures close to atmospheric pressure.
According to the API 650 standard, atmospheric tanks are generally designed for internal pressures of up to approximately 2.5 psi (17.2 kPa) above atmospheric pressure.
During operation, pressure changes inside an atmospheric tank are relatively small and typically result from filling, emptying, or temperature changes. A venting system ensures that the internal pressure remains within design limits, preventing overpressure or vacuum conditions that could damage the tank.
Meanwhile, pressure vessels are designed to withstand higher internal and external pressures. They are generally shaped like horizontal or vertical cylinders with elliptical, hemispherical, or torispherical heads.
This shape helps distribute the pressure-induced stress more evenly across the vessel’s surface, allowing the structure to withstand the pressure load better.
Therefore, every pressure vessel has a Maximum Allowable Working Pressure (MAWP), which is the maximum pressure allowed at the top of the vessel for safe operation under normal temperature and operating conditions.
3. Distribution Methods
Another difference between atmospheric tanks and pressure vessels lies in the method used to distribute or transfer fluid from inside the tank to the process system. In atmospheric tanks, fluid is generally distributed without relying on internal pressure, but rather by using a pump or gravity.
Meanwhile, pressure vessels can utilize internal pressure to force the fluid out through the piping system. This pressure aids distribution, allowing the fluid to be delivered to the point of use without always relying on a pump, although the need for a pump still depends on the required pressure and system configuration.
4. Materials and Structure
Atmospheric tanks and pressure vessels also differ in terms of materials and construction. In atmospheric tanks, the material commonly used is carbon steel plate with sufficient yield strength to support the load of the stored liquid.
The structure of atmospheric tanks is designed to withstand hydrostatic pressure resulting from the height of the liquid column as well as external loads such as wind and earthquakes. Therefore, plate thickness is generally determined based on the height of the stored liquid, rather than on internal pressure calculations.
Meanwhile, pressure vessels must be able to withstand higher internal and external pressures. Therefore, the selection of materials and wall thickness must be determined based on design pressure and temperature, fluid properties, allowable stresses, and joint efficiency.
Generally, materials used to manufacture pressure vessels include carbon steel, alloy steel, or other materials that meet design requirements.
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5. Ventilation and Sealing Systems
Atmospheric tanks are equipped with ventilation systems that allow air or vapor to enter and exit during filling, emptying, or temperature changes to maintain the internal pressure close to atmospheric pressure while preventing damage caused by overpressure or vacuum.
Atmospheric tanks are generally equipped with normal vents for standard operating conditions and emergency vents that activate during emergencies, such as a pressure surge caused by heat exposure during a fire.
Meanwhile, pressure vessels use a sealed system to maintain the internal pressure of the vessel. Therefore, these tanks do not have open vents like atmospheric tanks.
Instead, pressure vessels are equipped with a pressure relief valve (PRV), which opens only when the pressure inside the tank exceeds the design limit.
Entrust Your Chemical Storage Needs to CDI!
Understanding the difference between atmospheric tanks and pressure vessels is a crucial step in determining a storage system that is safe, efficient, and suited to the characteristics of the fluid.
However, aside from choosing the right tank, you also need a partner that can provide reliable storage infrastructure and logistics services backed by reliable operational standards.
To support those needs, PT Chandra Daya Investasi Tbk (CDI), through its subsidiary PT Redeco Petrolin Utama (RPU), provides integrated port and chemical storage solutions.
RPU operates over 70 tanks with a total storage capacity of over 125,000 m³. These facilities are supported by two docks, each with a length overall (LOA) of 200 meters, capable of serving vessels up to 35,000 DWT with a draft of 10 meters.
Additionally, RPU also operates a Centralized Filling Station (CFS) designed to handle tank trucks of various types and sizes, as well as a Customer Order Service (COS) that helps customers plan product pickups according to their operational needs.
In terms of safety, the RPU facility has implemented international standards for fire protection and operational safety. The facility is also equipped with oil booms that can be used to help manage potential oil spills in the operational area.
As #YourGrowthPartner, CDI and RPU are committed to providing safe and efficient logistics services for various industrial sectors.
With the support of our integrated facilities and services, trust CDI and RPU with your company’s logistics needs. Contact us to get the best offer for your business!
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