Sanitary atmospheric tanks are often used in food processing to hold, mix, or store materials or liquid ingredients such as milk, juice, sauces, syrups, soups, and dressings. The term atmospheric refers to vessels designed to operate at or near ambient pressure, meaning the internal pressure is roughly equal to the surrounding air pressure.
In many cases, these tanks are used between processing steps to hold or blend products before the next stage. For example, milk may be stored before moving to another machine, juice ingredients may be mixed before bottling, and sauces or soups may be held until the line is ready. Sanitary atmospheric tanks can also be used to blend ingredients like cream, seasonings, and cheese to make a cheese sauce before packaging.
Typically constructed from stainless steel with sanitary finishes, atmospheric tanks are engineered with an emphasis on cleanliness, smooth internal surfaces, and configurations that enable effective cleaning or sterilization.
Since they are not subjected to significant internal pressure, atmospheric tanks are not subject to the same stringent requirements as pressure vessels, which are designed to handle fluids at pressures significantly above or below atmospheric levels.
By comparison, a pressure vessel certified to American Society Of Mechanical Engineers (ASME) is generally required for pressures above 15 psi (1 bar), or 0.5 barg and higher under European Pressure Equipment Directive (PED) regulations. Atmospheric tanks typically operate at pressures no greater than 1 psi (0.07 barg).
Nonetheless, pressure remains a critical factor. Even at low levels, atmospheric tanks must be equipped with proper venting systems to prevent excessive vacuum or overpressure that can arise from temperature fluctuations or during filling and emptying cycles. Without proper venting, a tank can collapse under vacuum or rupture due to overpressure.
Even normal ambient temperature variations, particularly in vessels installed outdoors or exposed to daily temperature cycles, can cause significant changes in internal pressure.
According to Geof Brazier, Director of Development, BS&B Safety Systems, LLC, protecting vessels from vacuum collapse or minor overpressure typically requires a rupture disk sensitive enough to activate at only a few inches of water column—just a fraction of a bar.
To address the need for a more streamlined approach for low pressure food processing applications, Brazier tasked BS&B’s R&D department to develop a new type of rupture disk, called the GHI™, which is capable of providing one-way or two-way (pressure and vacuum) relief. The disk is engineered to operate reliably at pressures so minimal they are comparable to the force of an ordinary sneeze.
The GHI (Gasketed Hi/Lo) rupture disk activates at extremely low burst pressures as low as 12.5 mbar/5 in water column in 4 in/100 mm sizes.
For more information, contact BS&B Safety Systems at 7455 East 46th Street, Tulsa, OK 74145-6379; call: (918) 622-5950; e-mail: sales@bsbsystems.com; or visit www.bsbsystems.com.