Defining ASME Pressure Vessels

These pressure vessels have the job of containing liquids, gases, or vapors at pressures generally above 15 psig. They are often used in the petroleum refining industry and other industries that process chemicals. They may be used as storage tanks or boilers. Each tank has its own pressure and temperature limits built into the design.

The ASME code provides details on the design of these pressure vessels to ensure they can handle the chemicals placed inside them. Designers and builders must follow the design requirements and fabricate the vessels according to code. They are required to test and inspect the vessels after construction to receive certification for both fired and unfired vessels.

While an inspection prior to installation is critical to determine the safety of the vessel, re-inspections should be done every five years or after any major repairs. An inspection should be detailed and involve the following:

• Evaluation of the thickness of the vessel

• Inspection of the pressure release valves

• Stress analysis

• Hydrostatic pressure test

• Surface inspection

• Insulation examination

• Inspection of joints and welds

• Inspection of structural connections

These vessels are built according to the ASME Boiler and Pressure Vessel Code.

Repairing Pressure Vessels

All repairs for pressure vessels should follow requirements from the National Board Inspection Code or NBIC. This code includes installation, inspection, and repairs and alterations. Before a repair can take place, it must be determined if the work will fall under these requirements. Certain simple and standard repairs don’t fall under the NBIC requirements. For instance, when you change out a pressure switch or low water cutoff, it wouldn’t be under the NBIC code. However, replacing nozzles or installing mounting clips would be under the NBIC code.

When searching for a company that will perform repairs, they must be able to meet the requirements of the NBIC. They should have a Certification of Authorization. The NB mark is used with the fabrication of the vessel, but for repairs you would need the R mark, indicating repairs.

The codes governing fabrication and repair are very similar, but there are key differences. This includes both in testing and documenting. An example is with the U1 or U1A form that must be submitted at the time of fabrication. No such form is needed with a repair. A nameplate is required showing the date of fabrication. A second nameplate is necessary to show the date of repair.

It’s important to work with a company that knows the subtle differences in fabrication and repair and can ensure your vessels are in compliance while maintaining all requirements and documentation for their life. Great River Industries not only designs and fabricates pressure vessels, we provide ongoing maintenance and repairs for them throughout their useful life. Great River Industries builds and maintains pressure vessels that meet the ASME code. These vessels comply with industry regulations and are tested prior to installation and use.