How are Pressure Vessels Classified?

How are Pressure Vessels Classified

Pressure vessels are used in a wide range of industries for various purposes. There are different types of pressure vessels that are classified on the basis of several criteria. In today’s blog post, we will take a close look at the types of pressure vessels, the classification of pressure vessels, and the material selection for pressure vessels.

What are Pressure Vessels?

Pressure vessels are enclosures that are capable of holding gases, vapours, and liquids at a huge pressure difference compared to ambient pressure. These are used in a wide range of industries including the food processing industry, chemical industry, oil and gas industry, and petrochemical industry, among others. Some examples of pressure vessels include heat exchangers, reactors, and separators.

Classification of Pressure Vessels

Pressure vessels are typically categorized into the following classifications:

  • Pressure classification
  • Shape classification
  • Role classification
  • Dimension classification
  • End construction

Keep reading below to learn more about the various types of pressure vessel classifications. 

1). Pressure Classification 

Pressure vessels can be classified on the basis of pressure levels. These pressure levels include ultra-high pressure, high pressure, medium pressure, and low pressure.

2). Shape Classification

When it comes to shape or geometry, you will find that there are spherical vessels and cylindrical vessels. Spherical vessels are typically used to store high-pressure fluids where their spherical shape ensures even distribution of internal and external stresses. On the other hand, cylindrical vessels have a cylindrical shell and a number of heads. A cylindrical shape is the most widely used as it is cheaper to produce; however, they are not as strong as spherical-shaped vessels.

3). Role Classification

Pressure vessels may also be classified on the basis of their role in the process such as a reaction container, heat exchange container, storage container, transportation container, or separation container. A reaction container is used for carrying out physical and chemical reactions whereas a heat exchanger is used for completing heat exchange. 

Meanwhile, a separation container is used for gas separation or gas purification or medium exchange.  A storage and transportation vessel is used for the storage and transportation of media or for balancing and buffering the pressure.

4). Dimension Classification

Pressure vessels are also classified on the basis of the thickness of the shell. If the wall is less than 1/10 of the shell diameter, the vessel is known as a thin shell. If the wall thickness is higher than 1/10 of the shell diameter, it is called a thick shell vessel. The thin shell vessels are used in pipes, tanks, and boilers whereas thick shells are used as gun barrels, tanks, and high-pressure cylinders.

5). End Classification

This classification is based on the end construction which can be open-ended or close-ended. A piston is an example of an open-end construction whereas a tank would be a close-ended vessel.

Material Selection for Pressure Vessels

Pressure vessels are constructed using a wide range of materials. The material is chosen based on several criteria such as corrosion resistance, strength requirements, ease of fabrication, ease of maintenance and budget.

Needless to say, the chosen material must be capable of withstanding certain levels of internal and external stresses The material should also be capable of withstanding the environment where it is going to be installed. It is not easy to fabricate pressure vessels using any material. Material needs to have proper weldability and machinability.

Some of the common materials used for the construction of pressure vessels include:

1). Stainless steel — It is a type of steel with chromium content ranging from 10.5 to 30% with trace amounts of nickel and lower carbon content. Stainless steel has excellent corrosion and chemical resistance properties. It has higher elasticity and ductility as compared to carbon steel.

3). Carbon steel — Carbon steel has a carbon content of up to 2.5% and it is known for high tensile strength which makes it useful for various applications. However, it is difficult to bend into certain shapes due to its high tensile strength and is more prone to corrosion as compared to stainless steel.

3). Aluminium — It is a material with a high strength-to-density ratio. It is also much cheaper and easier to fabricate as compared to stainless steel. On top of that, it has excellent corrosion resistance but it is not suited for high-pressure applications.

4). Titanium — It has excellent strength along with corrosion resistance. Its melting point is also higher than aluminium and steel which makes it suitable for high-temperature applications. Its high thermal conductivity makes it the perfect material for heat exchangers.

Final Thoughts

To conclude, pressure vessels are used in a wide range of industries. They can take form as a variety of shapes and are classified on various basis as explained above. When it comes to choosing a material for constructing a pressure vessel, it should be chosen on the basis of strength, corrosion resistance, and other end requirements.

Register Your Pressure Vessel Design

The pressure vessel design registration and verification make sure that your pressure vessel meets the required standards. The registration process is focused on equipment safety. Design registration is also mandatory for certain types of pressure vessels.

Sherwood Design and Engineering is a premier design and manufacturing agency of pressure vessels that meet the required standards. Our team can also make recommendations for engineers to ensure final inspection and sign-off before registration.

Give us a call at (02) 9437 3566 or leave an enquiry if you would like to learn more about our pressure vessel engineering design and support services.