Pressure vessels are utilized in different industries for retaining gases and liquids at varying temperatures and pressures. The majority of these materials contain massive amounts of energy that, if not appropriately handled, can result in containment loss or catastrophic breakdown. Failure of a vessel which works under extreme pressure can result in gas leaks, fires, and even explosions.

The numerous examples of pressure vessels include hot water system tanks, boilers, heat exchangers, and industrial mixers. In comparison to industrial tanks, the most common household heater is smaller in size, and it contains no chemical dangers, only plain hot water. Even the most basic pressure vessels, such as water heater tanks, can be prone to explosion.

The applications of pressure vessels are undoubtedly in great demand. Although many individuals are not familiar with the purpose of pressure vessels, their usage is fundamental to our industrial operations throughout the world. This guide will cover everything you need to know about pressure vessels, including designs, components, and classifications.

What Exactly is a Pressure Vessel?

A pressure vessel is a solid, leak-tight container, usually spherical or cylindrical, designed to keep fluids such as liquids or gases at a pressure that is significantly different from the ambient pressure. They are commonly made of stainless or carbon steel and welded together from plates that have been rolled into a hemispherical shape.

In some cases, other materials, such as non-metallics, copper, aluminum, and others, are also employed as pressure vessel materials. The majority of pressure vessels are long cylinders with two heads at each end. However, they can also come in a conical or spherical design.

Uses for Pressure Vessels

While pressure vessels are common even in household applications (hot water heaters, air compressors, propane tanks, etc), they have far more extensive uses in the industrial world.

Storage Vessels

The most typical use for pressure vessels is as a storage vessel. The applications include holding gases or liquids under high pressure, such as chemicals like ammonia, petroleum products, water or air. All storage vessels are designed to properly keep a specific substance that would be affected if exposed to another element or the outside air.

Process Vessels

A process vessel is a pressure vessel in which a process, such as chemical reactions, occurs, resulting in a fundamental change in the pressure vessel’s total contents. Examples of processes include removing features from an existing product to produce something new, breaking down a product into one or more other products, and combining one or more products to create a new product.

Heat Exchangers

Another common type of pressure vessel is a heat exchanger. Heat is frequently a waste product that must be eliminated from an industrial process or is necessary to enable a chemical reaction. Heat exchangers allow heat to be removed from one process and utilized in another, independent process.

Main Components of a Pressure Vessel


The shell casing is a component that creates the tank’s wall and keeps the contents at the prescribed pressure. Welding numerous plates together result in a conical, spherical, or cylindrical shape with a uniform rotational axis. In some pressure vessels, the shell is also insulated because it is sensitive to the condition and temperature of the tank’s contents.


The head is responsible for the vessel’s end closure components. They are available in a range of shapes, including semi-elliptical, dished, and spherical. Unlike flat heads, their curving characteristic makes the head able to withstand much greater pressures, allowing for a sturdier, slimmer, lighter, and less expensive design.


The nozzle is a cylinder-shaped component that connects the head and shell of a pipe system. It makes getting things in (Inlet) and out (Outlet) of the vessel, as well as attaching instruments, easier. The manway of a vessel is also considered a nozzle.


The support is the portion that acts as a foundation for the pressure vessel’s weight. There are several forms of support, and you can determine their application through the tank’s inclination and size. Here are a few examples:

  • Lug supports – are ideal for vertical tanks that aren’t too tall and have a medium diameter.
  • Leg supports – assist small vertical vessels in maintaining their stability.
  • Saddle supports – feature a classic U-shape and support the weight of horizontal vessels.
  • Skirt supports – have a cylindrical shape and are excellent for supporting vertical tanks.

Classifications of Pressure Vessels

Pressure vessels can be categorized in a variety of ways. The following are some of their classifications:

Geometrical Shapes

The most common vessels in this category are cylindrical and spherical pressure vessels. Spherical vessels are preferable for storing high-pressure fluids. Despite their higher price, they have a strong structure that distributes pressure uniformly in the tank. On the other hand, cylindrical vessels are less expensive to manufacture. They are not as durable as their spherical counterparts due to their weak points. To alleviate this issue, you can design and fit them with hemispherical ends.


Dimensions include both thin and thick shell vessels. The wall thickness of thin shell tanks is less than 1/10 the diameter of their shell. On the other hand,  the wall thickness of the thick shell is higher than a tenth of the shell’s diameter. Dimensions vary depending on type of vessel and the amount of storage required.

Storage Vessels

Storage vessels come in a wide variety of diameters and heights depending on the barrels and gallons a company needs. Below is just a small sample of those dimensions.


Heat Exchangers

Heat exchangers can vary in size depending on the size, weight, temperature, and water information. Below is just an example of those dimensions.


End Construction

In the end construction, usually involves either open-ended or closed-ended pressure vessels. In open-ended containers, fluid pressure creates hoop stress, such as in pipes. While in closed-end vessels, such as tanks, pressure is due to the circumferential and longitudinal stress.

Rely on NDT Tanknicians

At NDT Tanknicians, we embrace the tough challenge set in place to be certified by entities such as the Environmental Protection Agency (EPA,) American Petroleum Institute (API,) Steel Tank Institute (STI,) American Society for Nondestructive Testing (ASNT,) and the National Association of Corrosion Engineers (NACE,) to name a few. We are only as good as the service we provide, and we go the extra mile to ensure all of our personnel are trained to industry standards.

We’re capable of providing top-to-bottom coverage for all of your Storage Tank requirements; servicing a broad spectrum of clientele, both small and large. Our ability to streamline an entire project gives us an edge over the competition by providing our clients with the peace of mind and convenience of trusting one service provider to become familiar with all of their current and future needs, rather than half a dozen. This keeps costs to a minimum, quality control consistent and communication among crews seamless. Request your quote today.