Pressure Vessels

Pressure vessels are tanks that contain and store a wide variety of gases, fluids or vapors at pressure levels above 15 pounds per square inch (psi). Most often, pressure vessels, also called air pressure tanks, are used for applications pertaining to the food and beverage, chemical, pharmaceutical, plastics and oil and fuel industries.

Tanks are usually cylindrically shaped, and may be made from a variety of durable metals or high-strength plastics that can maintain their shape and properties under pressure. Examples include: stainless steel, zirconium, carbon alloy steel, titanium, niobium, nickel alloy(s) and fiberglass.

Pressure vessels are usually manufactured using one of three processes, which are: forging, brazing and welding. All three processes utilize heat to join metal pieces together, but they all use it differently. Forging forms metal parts through the application of heat and pressure; brazing refers to the process of joining two metals by filling the space between them with a non-ferrous metal, and in welding, two similar pieces of metal are heated until their edges melt together.

Metal used in any pressure vessel manufacturing process is usually first cold rolled, rather than hot rolled. Also, to increase tensile strength and temperature resistance, they’re also frequently tempered, quenched or galvanized. Before beginning any manufacturing processes, engineers must determine sensitive design components like pressure level, temperature, material components, size and shape.

Potential pressure levels range from 15 psi up to around 150,00 psi, while temperatures are often above 750°F and a vessel can weigh in from 20 to several hundred thousand gallons. Optional components engineers may consider include: stairs, ladders, detachable and removable lids, heating and cooling systems, sight glass for observation and agitation systems or propellers for mixing applications. Read More…

Leading Manufacturers

BEPeterson

Avon, MA | 508-436-7900

Gladwin Tank Mfg., Inc.

Gladwin, MI | 800-959-1152

E & H Manufacturing, Inc.

Charleston, WV | 304-344-9875

Mason Manufacturing LLC

Decatur, IL | 217-422-2770


In addition, engineers can base their designs on a number of different types of pressure vessels, such as process tanks, autoclaves, high pressure vessels, expansion tanks, water pressure tanks and vacuum tanks. Process tanks simply hold and store liquids. Autoclaves like grease kettles, on the other hand, use a combination of pressure and steam to create substance-producing chemical reactions.

The next example, high pressure vessels, are the strongest type available. Typically made of stainless steel and used with the highest psi, they offer the best corrosion, temperature and pressure resistance. Expansion tanks are found in every residential water heater, while water pressure tanks are found in wells. Finally, vacuum tanks provide important support to sewage applications.

To be considered a finished and functional tank, many pressure heaters must adhere to regulations by and be registered with the American Society of Mechanical Engineers (ASME). The ASME Boiler and Pressure Vessel Code and standards set out by others, like the American Petroleum Institute (API) help ensure worker and building safety; because tanks are under extreme pressure, even the tiniest leak could cause a large explosion with shrapnel damage.

Engineers may also take upon themselves to conduct mathematical and scientific studies to make sure that the design and construction of their pressure vessels meet requirements for appropriate size, shape, temperature, material and pressure levels. Pressure vessel testing and regular inspection is an important part of tank construction and maintenance.


Additional Reading…

A Brief History of Pressure Vessels

Pressure vessels, also known as ASME pressure tanks, are a type of industrial equipment that are used for storing vapors, gases, or fluids at a pressure different than the ambient pressure. As they have to withstand operating pressure of more than 15 psi, they have to follow and pass stringent government regulations.

Pressure vessels have application in mining, refineries, and military equipment such as submarines. They are used for storing a number of gases like chlorine, petroleum, and ammonia. For different applications, different types of vessels are available such as air pressure tanks, vacuum tanks, and heat exchangers.

Pressure vessels may look like a simple cylindrical container; however, over time, they have played an important part in industrialization. It is documented that pressure vessels were used even in the sixteenth century for hauling up heavy weights underwater. In 1495, Leonardo da Vinci came with the idea and designed air pressured containers for lifting purposes. However, the present day application of pressure vessels was not devised until the advent of steam engines. In steam engines, pressure vessels were used as boilers, where steam was produced and contained for powering the cylinder.

In all external combustion engines, pressure vessels were major equipment. However, pressure vessels were also the most unreliable part of external combustion engines, as the technology for manufacturing pressure vessels was in the formative stage. Moreover, the quality of materials used for making vessels was poor. The failure of pressure vessels was usually catastrophic, causing damage to the machines and killing operators. They were the source of explosions in an array of industries on a daily basis.

The first effort to modernize pressure vessels and improve their safety emerged in the United States. In 1911, American Society of Mechanical Engineers (ASME), which was established in 1880, came up with the idea of standardizing codes for making pressure vessels and presented the Boiler and Pressure Vessel Code (BPVC). In 1914, first rules and codes for constructing pressure vessels were printed.

Since industries needed pressure vessel that could withstand 10,000 psi, in 1919, a new design of pressure vessels came on the market. To endure such high pressure, steel wires were spirally wounded around the tank and rods gave additional reinforcement. With this design, there was no rupture of the pressure vessels even under stressful conditions.

At the same time, welding replaced rivets, as industries, such as chemical plants and petroleum refineries, needed pressure vessels that could endure high temperature too. BPVC recognized how welding could make pressure vessels stronger and thus, safer, so welding was included in the code. It was the beginning of the modern manufacturing technique, as nearly all of them use welding for joining metal plates in vessels.

Over time, to make pressure vessels safer, different testing techniques and methods were developed, and it became mandatory that all pressure vessels go through an examination. Traditional tests are mainly destructive; however, the modern tests are non-destructive. These new tests include radiography and phased array ultrasonic. Moreover, for making pressure vessels safer, assessing methods have also played a major role. Modern assessing methods, such as finite element analysis, can identify stress points.

 


 

Pressure Vessel Informational Video