Fabrication of pressure vessel

Welding can be divided into three main categories: fusion welding, pressure welding, and brazing.

(1) Fusion welding

A welding process involves a process in which the workpieces to be welded are locally heated to melt, and then condensed to form welds in order to join the pieces together. This includes arc welding, gas welding, electro slag welding, electron beam welding, laser welding, etc. A fusion welding process is one of the most widely used welding methods today, and most low-carbon steels and alloy steels are welded using this method. In addition to metals, special fusion welding can also be used to weld non-metals such as ceramics and glass.

(2) Pressure welding

There are a variety of ways in which welding can be accomplished, including using pressure, heat, or a combination of both. As a result of its heating, the metal is softened so that the atoms are close to the distance of mutual attraction, which is essentially different from the heating that occurs during the fusion welding process, in which the metal is deformed by applying pressure in order to plastically deform it. There are many types of pressure welding, including resistance welding, friction welding, ultrasonic welding, cold pressure welding, explosion welding, diffusion welding, and magnetic force welding. As a result, it has a small welding deformation, less cracks, and an easy automation process.

(3) Brazing

An integral welding method is a welding method where the solder with a lower melting point than the base metal is heated to melt, but at a temperature that is lower than the melting point of the base metal, and then the molten solder fills the weld, wets the base metal, and diffuses into the base metal, resulting in an integral welding method being formed. It is important to understand that there are two main types of brazing: brazing and soldering. During brazing, the temperature is greater than 450 °C, and the tensile strength is greater than 200 MPa, which means that the temperature is greater than 450 °C. In order to weld carbide turning tools and geological drills, silver-based and copper-based solders are often used, which are suitable for situations where there is high working stress and a high ambient temperature, such as when welding carbide turning tools and drilling holes in rock. The temperature of the soldering process is less than 450°C, and the tensile strength is less than 70MPa, which makes it suitable for environments with a low level of stress and low working temperatures, such as the tin soldering of circuits.

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ASME Codes and Their Impact on Pressure Vessel Manufacturing

ASME’s Boiler and Pressure Vessel Design Code (BPVC) is designed to guide mechanical engineers in designing, constructing, and maintaining pressure vessels. A number of crucial design specifications are outlined in the BPVC, such as safe operating pressures, temperature & heat issues, safety parameters, corrosion reduction, and crash modes.

Each division of ASME Section VIII defines the standard terms and specifications required to manufacture pressure vessels.

1. DIVISION I – 

Division I contains appendices that detail additional design guidelines, nondestructive analysis techniques, and pressure vessel approval standards, some of which are mandatory.

It also contains guidelines for using the single ASME certification mark with the U, UM, and UV designators. Appendix A in Division II summarizes the main components of design and construction. 

There are general requirements for pressure vessels in Appendix B of Part I, including minimum sizing provisions, material designations, and non-destructive gas testing methods. In Division II, appendix C provides guidelines and criteria for the safe use of ASME code symbols.

As follows, this division is further divided into three subsections:

• Subsection A – 

This document describes all the customary requirements for construction materials, designs, openings and pillars, markings and reports, overpressure protection, and temperature stabilization.

• Subsection B – 

All specifications relating to pressure vessel manufacturing are included. This subsection also discusses ASME vessel fabrication techniques such as welding, forging, and brazing. In order to gain a clear understanding of the materials to be used, the fabrication sequence, the design, inspection, and other factors involved.

• Subsection C – 

Materials used for pressure vessel manufacturing are specifically discussed in this subsection. When building a pressure vessel from typical materials such as carbon steel, low alloy steel, high alloy steel, cast iron, non-ferrous metals, etc., this subsection contains all the obligatory specifications.

2. DIVISION 2 – 

This division includes all mandatory requirements pertaining to the design, fabrication, engineering, and pressure vessel testing of pressure vessels, which are required to withstand internal or external pressure. It also covers materials, design, and nondestructive examination procedures for pressure vessels.  10.3.1 Boiler, Pressure Vessel, and Pressure Piping Code. 

For boilers and pressure vessels to be used anywhere in the United States, this code specifies the materials required. As well as boiler and pressure vessel design, this code also covers nondestructive examination techniques, the requirements for construction documents, and standard detail drawings. Among other things, it regulates design calculations for boiler systems used in transportation (such as marine propulsion engines). 

Division 2’s standards allow for higher stress intensity values than Division 1, but are much more meticulous. Division 2 also applies to pressure vessels occupied by humans, primarily diving vessels. As with Division 1, Division 2 includes guidelines on how to use the single ASME certification mark for both U2 and UV.

3. DIVISION 3 – 

Whether the pressure is internal or external, Division 3 applies to pressure vessels exceeding 10,000 psi. Division 3 does not specify a maximum pressure limit for Section VIII divisions preceding it, nor does it specify a minimum pressure limit. Every owner or operator of a pressure vessel must prove that the vessel is not hazardous if its pressure is not limited by Division 3. 

In order to prove that a pressure vessel does not contain any hazardous quantities of gas and vapor, the owner or operator must provide clear and convincing evidence. A temporary operation permit may be obtained for an installation that is subject to a pressure-vessel hazard classification under Section 2.101.

A single ASME certification mark with U3 and UV3 designations is also prescribed.

Why Should You Consider ASME Pressure Vessels for Your Facility

• SAFETY – 

By complying with ASME Code, pressure vessels are manufactured according to stringent criteria and quality guidelines. In its 12 sections, ASME’s Code addresses every aspect of the fabrication of a pressure vessel, regulating the entire process of producing safe and efficient pressure vessels.

• QUALITY – 

Safety is delivered by quality. Pressure vessels are made safer, more secure, and more efficient with ASME’s regulatory codes. As well as validating the quality and efficiency of equipment, ASME compliance contributes to environmental sustainability.

• HOMOGENEOUS – 

The ASME code provides consistency across international markets and industries because these are standardized codes and regulations.

Fabrication of Pressure Vessels

By forging, rolling, and welding the metal sheet, the vessel’s shell and its heads are constructed. In accordance with the above-mentioned factors, the thickness of the metal sheet is the wall thickness. To ensure the pressure vessel serves its purpose, auxiliary equipment, and devices, as well as accessories, are installed:

• It is usually welded perpendicularly to the shell or head and away from the weld lines so that feed, products, and utilities can be introduced and discharged.
• During operation, pressure relief valves provide safety
• Stirred reactor vessel jackets for heating or cooling
• Supports that allow the material to expand during operation, such as saddles, skirts, or legs

Why Should You Consider ASME Pressure Vessels for Your Facility

• SAFETY – 

By complying with ASME Code, pressure vessels are manufactured according to stringent criteria and quality guidelines. In its 12 sections, ASME’s Code addresses every aspect of the fabrication of a pressure vessel, regulating the entire process of producing safe and efficient pressure vessels.

• QUALITY – 

Safety is delivered by quality. Pressure vessels are made safer, more secure, and more efficient with ASME’s regulatory codes. As well as validating the quality and efficiency of equipment, ASME compliance contributes to environmental sustainability.

• HOMOGENEOUS – 

The ASME code provides consistency across international markets and industries because these are standardized codes and regulations.

Fabrication of Pressure Vessels

By forging, rolling, and welding the metal sheet, the vessel’s shell and its heads are constructed. In accordance with the above-mentioned factors, the thickness of the metal sheet is the wall thickness. To ensure the pressure vessel serves its purpose, auxiliary equipment, and devices, as well as accessories, are installed:

• It is usually welded perpendicularly to the shell or head and away from the weld lines so that feed, products, and utilities can be introduced and discharged.
• During operation, pressure relief valves provide safety
• Stirred reactor vessel jackets for heating or cooling
• Supports that allow the material to expand during operation, such as saddles, skirts, or legs

Selection of materials for pressure vessels

Selection of the appropriate material for pressure vessels is based on the following criteria:

• The materials must be able to withstand specific internal and external pressures, and structural stresses during the pressure vessel’s lifetime.
• As a pressure vessel is expected to be reliable in harsh environments, corrosion resistance is one of its most important characteristics.
• During the lifecycle of the pressure vessel, materials, fabrication, and maintenance costs need to be considered. Economic analyses are conducted to determine which material is most cost-effective. In order to determine if acquiring a pressure vessel is profitable, the Return on Investment must be evaluated.
• Fabrication and maintenance of pressure vessels must be easy. Since metal sheets are shaped into pressure vessels, they must be machinable and weldable.
• There must be a wide range of standard sizes available in the region of the pressure vessel manufacturer for pressure vessel materials. There must be a wide range of standard sizes available in the region of the manufacturer for pressure vessel materials.

Welding and Fabrication of Pressure Vessels

The ASME BPVC Standards Section VIII governs pressure vessel manufacture (and fabrication) and comprises 3 divisions. The first division covers both mandatory and non-mandatory requirements for designing and fabricating techniques and material selection alternative rules for the construction and welding of parts of pressure vessels.

Types of Vessels Pressure According to their Purpose

• The term ‘storage vessel’ refers to a pressure vessel that temporarily holds liquids, vapors, and gases. Storage vessels are used to hold fluids during a later vessel function or to store finished products like compressed natural gas (CNG) and liquid nitrogen. why does a gas fill a vessel completely?
• They are commonly used in the food, pharmaceutical, energy, and bioprocessing industries to transfer heat between two or more fluids. The operation of heat exchanger equipment depends on the thermal and flow properties of the fluids involved in heat exchange, as well as on the thermal property of the conductive partition (for indirect contact heat exchangers). A heat exchanger experiences stress due to the temperature difference between the hot and cold fluids, as well as internal pressure.
• Typically, boilers are heat transfer devices that are equipped with an enclosed vessel that allows heat to transfer from the source to the fluid. They use fuel, nuclear or electrical power as their sources of heat. Their primary purpose is to heat liquids. It is common for the fluid to undergo phase transformation into vapor inside the boiler. Various heating applications and power generation use the vapor generated by the boiler. In steam boilers, steam is generated at high pressure to accelerate the blades of the turbine. Therefore, the boiler vessel must be very strong in order to withstand such high pressures and thermal stress. For most materials, strength decreases as the temperature increases.
• Process vessels are pressure vessels that undergo a wide range of industrial processes, including mixing, agitating, decanting, distillation, mass separation, and chemical reactions. The change in the internal pressure of a process vessel depends on the nature of the process carried out and the transformation of the substances involved. 

Applications Of Fabrication of pressure vessel

• Oil & Gas
• Power Generation
• Off-Shore
• Chemical & Petrochemical
• Geothermal
• A wide range of sectors
• Including food and beverage
• Plastic and polymer resins, rubber, military and defense
• Water and filtration of chemical
• Wastewater and treatment of water
• Pharmaceuticals, oil, fuel, and energy
• All Pressure Vessel Industries