Most pressure vessel manufacturing covers industry-standard vessels with common shapes, sizes and pressure ratings. Minor changes required to suit specific requirements are usually easy to accommodate.

But from time to time, customers request unique customized pressure vessels designed for specific purposes where a standard design will not suffice. When this happens, the designer needs to go back to the drawing board and design the vessel from scratch. Here are a few examples of custom pressure vessels that are difficult to manufacture.

Corrosive Duty

Many chemicals are corrosive, and the fabrication of pressure vessels for such applications must be preceded by a rigorous study of corrosion-resistant materials, taking into account that corrosion rates differ depending upon chemical concentration and temperature. During fabrication, welding specifications must be closely followed, especially with regard to post-weld treatment to ensure that welds don’t corrode.

High Temperature Applications

High temperature pressure vessels are potentially hazardous because of risks associated with the release of high temperature products. Detailed HAZOP studies should be undertaken as part of the design to ensure potential issues and failure modes are understood. Attention must be given to the risk of high temperature creep and material fatigue, and rigorous manufacturing processes must be applied.

High Pressures

Pressure vessels designed for high pressures fall under an alternative set of ASME VIII rules. A key aspect of high pressure design is the use of thick and heavy sections, which involve greater difficulties with cutting, bending and welding. Additionally, pressure vessel design is more complex and requires high expertise.

Large Physical Size

Large vessels are difficult to fabricate because of the need to support and position components during fabrication. Care must be taken to ensure the vessel is not damaged and is properly supported during production. Large vessels are usually manufactured in a horizontal position although designed for vertical installation.

Jacketed Vessels

Jacketed vessels are difficult to manufacture because of limited internal access, which means that welding has to be performed from outside. This is exacerbated if there are numerous internal partitions in the jacket.

When a customized pressure vessel is required, it’s essential to select designers and fabricators who have requisite experience with similar vessels and of the exotic manufacturing techniques required. Don’t be fooled by fabricators who promise to undercut everyone else’s price; it’s likely they don’t have appropriate experience and skills, and you may end up with a dud.