Introduction
Pressure vessels are containers specifically designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Pressure vessels are a critical component of process industry, and the design, construction and maintenance of them are regulated by legislations and codes. As they are used in a wide range of application areas, such as chemical, pharmaceutical, oil and gas, their material of construction should depend on their application. Generally, steels are commonly used for the fabrication of pressure vessels due to their strength properties and good weldability.
Steels for Pressure Vessels
Steels for pressure vessels are classified in accordance to their strength which is determined by the percentage of carbon in the steel. Low carbon steels, such as AISI 1010 to AISI 1020 have lower strength compared to other types, but they can still be used in low-pressure applications. Medium carbon steels, such as AISI 1030 and AISI 1040 have better strength, wear resistance and ductility. High carbon steels, such as AISI 1045 to AISI 1050, provide good strength, ductility and excellent weldability properties. Additionally, stainless steel should be used for applications where corrosion resistance is important. Common austenitic stainless steels are grades 304 and 316.
In moderate and low temperature services, steels AISI 1020 and AISI 1045 are used in steel vessels. For applications that require higher mechanical properties, such as process vessels, steels AISI 4140 and AISI 4145 are used. Moreover, for high temperature services, steels AISI 4130 and AISI 4140 are recommended.
Regulations and Codes
In addition to materials of construction, the design and construction of pressure vessels should be in accordance to their application and their environment. These requirements have been developed through sets of regulations and codes, such as American Society of Mechanical Engineers (ASME) and International Organization for Standardization (ISO), and they should be followed. The pressure vessels should be designed and constructed to withstand operating pressures, temperatures and loads, so that their users receive the expected performance. The pressure vessels should have passed tests and inspections, so that their design, construction, operation and maintenance are in compliance with the regulations and codes.
In summary, pressure vessels are majorly constructed with steels due to their excellent strength and weldability features. The steels used for the fabrication of pressure vessels should depend on the application and their environment. For moderate and low temperature services the steels AISI 1020 and AISI 1045 are used, whereas for higher temperature services the steels AISI 4130 and AISI 4140 are recommended. Furthermore, the design and inspection of pressure vessels should be in accordance to relevant regulations and codes set by organizations, such as ASME and ISO, for the safe operation of the vessels.
Conclusion
Pressure vessels play a crucial part in process industry and their construction should be based on their application and their environment. Steels are common materials used for the fabrication of pressure vessels due to their strength and weldability. Low carbon steels, such as AISI 1010 to AISI 1020 are suitable for low-pressure applications, while medium carbon steels, such as AISI 1030 and AISI 1040 and high carbon steels, such as AISI 1045 to AISI 1050 are commonly employed for applications that require higher mechanical properties. Moreover, stainless steel should be used for corrosion-resistant applications. In addition to the materials of construction, the design and construction of pressure vessels should also comply with relevant regulations and codes set by organizations, like ASME and ISO, for the safe operation of the vessels.
