Manufacturing Pressure Vessels and Tanks

The primary uses of pressure vessels are for holding storage, processing materials and heat exchangers.

Storage Tanks

Typically manufactured with carbon steel, storage tanks are used for storing liquid and gases, under pressure, for common utilities such as fuel oil, natural gas, propane or liquified hydrogen. 

Heat Exchange 

A very common type of pressure vessel are Heat Exchangers. These pressure vessels are used for repeatable functions of heating, chilling or condensing. 

Process Vessels

Specialized designed drums, reactors or columns or gravity separators are used to create a process in a controlled environment. These processes may be a desired chemical reaction, breaking down materials or joining multiple products together. 

Pressure Vessel Fabrication

The construction of a pressure vessel begins with engineering CAD drawings and a design concept that meets ASME (American Society of Mechanical Engineering) Boiler and Pressure Vessel code requirements. The design phase derives and compares the hoop and longitudinal stress formulas based on basic pressure, wall thickness and stress assumptions.

The geometric solution to minimize strain is to create a spherical pressure vessel. However, this is a difficult task that is not very cost effective. Therefore, the solution and vessel shape we see most commonly is a cylindrical shape with a convex or curved head at each end. The cylindrical section of the vessel is developed using a strong material, usually steel, to distribute the pressure strain.

Welding Process

When fabricating a pressure vessel, there are different types of welding processes

used to join pieces together with the use of heat or pressure. Submerged Arc Welding (SAW) is characterized by the use of continuously-fed solid wire electrode which provides an arc that is totally covered by a layer of granular flux. The biggest advantage of SAW is its high deposition rate. It can typically deposit weld metal more efficiently than any of the more common processes.

Gas Tungsten Arc Welding (GTAW) is a versatile welding process that provides the highest quality weld by using a non-consumable tungsten electrode. This method is mostly used for precise, small welds on stainless steel and other materials like aluminum, magnesium and copper alloy.

Gas Metal Arc Welding (GMAW) or “MIG” welding is another popular process. Gas Metal Arc Welding is characterized by a solid wire electrode, which is fed continuously through a welding gun. An arc is created between this wire and the workpiece to heat and melt the base and filler materials. Once molten, the wire becomes deposited in the weld joint. When fabricating pressure vessels, we use MIG/GMAW and TIG/GTAW, with a Sub Arc Welding approach.

Testing and Inspection

In order to meet ASME (American Society of Mechanical Engineering), ANSI (American national Standards Institute) and ASTM (American Society for Testing and Materials) standards, pressure vessels undergo rigorous testing and inspection. Some welding inspections a vessel must pass include X-ray, ultrasonic, visual testing, magnetic particle testing and dye penetrant. Another common requirement for pressure vessels is passing a hydro test. Determining which testing methods are used depends on the type of job the vessel will be used for, but these practices are critical to safety and quality. C4 has CWI’s on staff with ASNT and NDT certifications to ensure all inspection requirements are met.