The American Society of Mechanical Engineers (ASME) is recognized as the leader in providing consensus standards relating to the field of mechanical engineering. The standards developed by ASME are in use as both best practice and regulatory requirements around the globe. For purposes of this FAQ, an ASME-rated tank is any brewing process tank where working pressures exceed 15 psi. In most cases, any brewing process tank operating above 15 psi must be designed and fabricated by strictly following ASME safety rules and regulations. The following information was prepared by the Brewers Association (BA) Maintenance and Engineering Subcommittee in collaboration with subject matter experts.
Pretty much every state adheres to ASME code. Check with your local jurisdiction.
This depends on tank geometry and pressure rating. The ASME code is divided into multiple sections that allow for different design criteria and pressures. Pressure vessels that are built for breweries will fall under AMSE Boiler and Pressure Vessel Code Section VIII Division 1. This section of the code relates to pressure vessel that a have a rating between 15 psi to 300 psi and have a diameter greater than 6 in (152 mm).
Non-ASME rated tanks need a PRV set to a pressure no greater than 15 psi. A secondary non-mechanical pressure relief device, like a frangible/rupture/burst disk, is advisable for any pressure tank. These are typically mounted to a tri-clamp ferrule or other fitting on the tank dome and are rated to rupture at a fixed pressure should the primary PRV fail to operate properly. A rupture disk is designed to be a one-time-use failsafe protection and will rupture should tank pressure or vacuum exceed the rating of the disk. It is much better for the disk to rupture than your tank. Non-ASME rated tanks need a PRV set at a pressure not greater than 15 psi.
When using a non-ASME rated tank for processes that require greater than 15 psi, risks include higher weld stress and potential premature weld failures (nozzle and manway weld joints are more susceptible to these failures). Deformation of the manway over time will cause leaks because the gasket does not correctly fit. In a worst case scenario an explosive failure of the manway, fitting, or weld seam can compromise the safety of workers. Violation of codes regarding pressure vessels can have far reaching implications—including tort liability, possible loss of insurance coverage, fines, and more—in the event of damage, injury, or loss from knowingly operating a tank that is not ASME rated.
A thicker gauge stainless steel used for construction, a design geometry that is conducive to higher pressures, and tank construction and weld seam inspections are all part of what make ASME-rated vessels different from non-rated vessels.
ASME code does not allow non-ASME rated vessels to be converted. It’s important to note that all ASME-rated vessels must be worked on by a National Board certified repair shop.
The BA Maintenance and Engineering Subcommittee recommends brewers use an ASME rated tank for any process that requires pressure above 15 psi.
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