When selecting mechanical seals used in food and beverage applications, what materials consideration should be made?
A mechanical seal provides dynamic sealing and static sealing of the pumped fluid. Image 4 shows a simple mechanical seal illustrating the product side and atmospheric side of the seal. The product is sealed to atmosphere by static seals along the pump shaft and in the housing, and the mating surfaces of the rotating and stationary faces seal dynamically.
IMAGE 1: Mechanical seal (Images courtesy of Hydraulic Institute)Materials selection is vital for mechanical seals and wetted components of a pump, because of corrosion, product contamination and chemical resistance.
This is of importance for pumps used in food and beverage applications because it prevents toxic particles from entering the pumped fluid. Nickel is suitable where resistance to caustic and other alkalis is required, and it is also useful for protecting product purity in the handling of foods and synthetic fibers. Nitrile, fluorocarbon, ethylene propylene and polytetrafluoroethylene (PTFE) materials are available in compounds suitable for use in food and beverage services. On the other hand, some grades of bronze are not acceptable for food service because of tin and lead content.
For more information on mechanical seals and their materials of construction, read “Mechanical Seals for Pumps: A Cost-Saving Guide to Proper Selection, Installation & Operation” at pumps.org.