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Tanks vs Pressure Vessels: Types, Applications, and Materials

Publication Date : 2023-06-19

Keywords: Pressure Vessel ASME

By Mat Khaloobagheri



Pressure tanks and vessels are available in a wide range of shapes and sizes, catering to the specific requirements of different industries. These specialized containers are engineered to withstand high pressures, typically exceeding 15 pounds per square inch gauge (PSIG), and are capable of safely storing gases, vapors, and liquids under these elevated pressures. On the other hand, storage tanks are primarily used for the containment of various liquids. Whether it is water, oil, gasoline, diesel, or chemicals, storage tanks provide a secure environment for the preservation and handling of these substances. While each type of tank possesses its own distinct properties and applications, they all play a crucial role in facilitating the safe and efficient operations of diverse businesses across various sectors. By ensuring the proper storage and containment of materials, pressure tanks and vessels contribute to the integrity, reliability, and regulatory compliance of industrial processes, safeguarding both personnel and the environment.


What is a Storage Tank?

In the realm of storage, a "tank" commonly refers to a metal or plastic container designed to store liquids for varying durations, spanning from short to extended periods, all while maintaining atmospheric pressure (typically around 15 pounds per square inch gauge, or 15 PSIG) and temperature. These tanks can range in size significantly, ranging from compact containers holding just a few gallons to massive reservoirs capable of accommodating substantial volumes of liquid.


Storage Tank Applications

Tanks serve as storage vessels for a diverse range of substances, including water, oil, gasoline, diesel, and various chemicals. The choice of materials used in tank construction is dependent on the specific cargo being stored. Certain liquids have the potential to react with specific metals, necessitating the use of alternative materials such as plastic or concrete. Steel is commonly employed for larger tanks due to its advantageous combination of strength, affordability, widespread availability, and malleability. On the other hand, smaller tanks often utilize plastic materials as they offer a cost-effective solution despite being heavier compared to steel. The selection of the appropriate tank material ensures the safe containment and preservation of the stored substances.


Type of Storage Tanks

There are different types of tanks available, each with its unique design and functionality:

Bladder Tank: A bladder tank is equipped with a rubber or synthetic rubber bladder that serves as a water storage compartment. As the bladder fills with fluid, the air trapped within the tank gets compressed, exerting pressure on the water and maintaining a consistent pressure level. This design is commonly used to store water and ensure pressure maintenance.

Diaphragm Tank: In contrast to bladder tanks, diaphragm tanks feature a flexible diaphragm that divides the steel tank into two separate chambers. One chamber is dedicated to holding water, while the other contains air. As water enters the tank and fills the water chamber, the air chamber applies pressure on the water, keeping the pressure stable. Diaphragm tanks are frequently utilized to maintain a steady pressure in water systems.

Air-over-Water Tank: Air-over-water tanks, also referred to as galvanized or stainless steel tanks, function by having air occupy the upper portion of the tank while fluid, typically water, occupies the lower section. The air exerts pressure on the water, ensuring consistent pressure levels as long as water remains within the tank. When water is drawn out of the tank, the pressure decreases. These tanks find applications in various settings where pressure maintenance is crucial.

These different tank types offer versatile solutions for storing fluids, each designed to meet specific requirements and ensure effective pressure management.


What is a Pressure Vessel?

Irrespective of the ambient pressure, a pressure vessel is a sealed storage container capable of accommodating liquids, gases, or vapors at pressures exceeding 15 pounds per square inch (PSI). These vessels undergo rigorous manufacturing processes and must be operated within specified temperature and pressure thresholds due to the inherent hazards associated with stored energy.


Pressure Vessel Applications

Pressure vessels find applications in various industries such as the pharmaceutical industry, food and beverage manufacturing industry, dairy and brewery industry, and cosmetics industry. These vessels are subject to comprehensive regulations and standards that govern their design, construction, installation, testing, inspection, and certification. Among these regulations, the American Society of Mechanical Engineers (ASME) standards are widely recognized and accepted as the primary guidelines for ensuring the safety and compliance of pressure vessels.


Types of Pressure Vessels

Heat Exchanger: Heat exchangers facilitate the transfer of heat between two or more fluids. They are widely utilized in industries such as food processing, pharmaceuticals, energy production, and bioprocessing. The efficiency and performance of heat exchanger equipment are influenced by factors such as the temperature, flow rate, and thermal properties of the fluids involved, as well as the conductive partition's thermal characteristics in the case of indirect contact heat exchangers. The temperature difference between the hot and cold fluids, along with the internal pressure exerted by the fluids, places stress on the materials used in the heat exchanger.

Boiler: Boilers serve as heat transfer devices that utilize fuel, nuclear energy, or electricity as heat sources. Typically, they consist of enclosed vessels that facilitate the flow of heat from the source to a fluid. Boilers are predominantly employed for heating liquids, and within the boiler, the fluid often undergoes a phase transition from liquid to vapor. The steam produced by the boiler is utilized in power generation and various heating applications. Steam boilers operate at high pressures to drive turbine blades efficiently, necessitating strong boiler vessels capable of withstanding the elevated pressures and heat stress. It is important to note that the strength of materials generally decreases with increasing temperature.

Process Vessel: Process vessels encompass a broad category of containers used in industrial operations such as agitation, mixing, decantation, distillation, mass separation, and chemical reactions. The specific process employed and the nature of the chemicals being processed can impact the internal pressure changes within a process vessel.

Chemical Reactors: Chemical reactors are enclosed pressure containers that contain and/or stir the reactants, products, and catalysts involved in a chemical reaction. These reactors are equipped with agitators or stirrers to facilitate the mixing of reactants and enhance molecular interactions. Baffles are often incorporated to prevent fluid spinning and establish a suitable flow pattern inside the reactor.



To conclude, the distinction between tanks and pressure vessels lies in their design, functionality, and intended applications. Tanks primarily serve as storage vessels for liquids, with various materials such as steel and plastic used depending on the stored substance. They come in different types like bladder tanks, diaphragm tanks, and air-over-water tanks, each tailored to specific requirements. Pressure vessels, on the other hand, are sealed containers capable of accommodating liquids, gases, or vapors at pressures exceeding 15 PSI. They find applications in industries such as pharmaceuticals, food and beverage, and energy production. Heat exchangers, boilers, process vessels, and chemical reactors are examples of pressure vessel types, each designed to meet specific needs while adhering to rigorous regulations and safety standards. Overall, both tanks and pressure vessels play vital roles in maintaining the integrity, safety, and efficiency of industrial processes across diverse sectors.


Looking for Help?

If you are looking for an expert pressure vessel designer, look no further than Acetake Group Inc. We’ve been designing tanks and vessels for over 15 years and our state-of-the-art designing capabilities enables us to deliver robust vessels that stand the test of time.

Check out one of our recent ASME pressure vessel design and fabrication projects and contact us today to discuss your next pressure vessel project.


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