When selected correctly, all types of mechanical seals will thrive. First, understanding what they are is critical.
Mechanical Seal engineering is used throughout all industrial processes. The different types of mechanical seals are available in multiple designs.
An end-face mechanical seal is a device used on a rotating shaft to keep fluids in and contaminants out. It prevents the fluid moved through an asset, most often a centrifugal pump, from leaking. These seals are located in the asset’s stuffing box or seal chamber. This is the area of the pump where the pump shaft connects to the drive (an electric motor, for example).
Except for air seals, which will be discussed later, most mechanical seals consist of two flat faces installed perpendicular to the shaft. One of the faces is mounted stationary to the seal chamber housing. The other face rotates with the shaft to provide the primary seal. Axial mechanical force and fluid pressure maintain the contact between the seal face materials. This contact prevents leakage and retains the fluid within the pump.
Three types of mechanical seals are used in process equipment:
A cartridge-mounted, end-face mechanical seal is a self-contained unit that houses the sealing components—a gland, sleeve, and hardware. A cartridge seal allows the unit to be preassembled and preset by the manufacturer. With the manufacturer handling these tasks, installation, and maintenance are simplified. Cartridges may be equipped with one or two seals, depending on the application’s requirements.
Component, end-face mechanical seals consist of a separate rotating member and a stationary seat that mount in a gland or housing. Since they are not preset, installation and maintenance are more complicated than cartridge seals. Installing these requires experienced technicians who can properly install and adjust them.
Air seals are non-contacting, pneumatic devices engineered to seal rotating shafts. These seals are primarily installed in dry powder or slurry applications. They use small amounts of air or inert gas to protect against product loss, emissions, and contamination. This air is throttled to create positive pressure and an effective seal.
The type of seal chamber affects the seal design and type chosen.
The correct bore size must be known to ensure that the ideal mechanical seal type is selected.
Most mechanical seals have five parts:
Knowing the mechanical seal types and the parts that make them up is only the beginning. Assessing the application, installation, and operation (with leakage limits) helps determine which seal type will be selected and how well it will perform in the system. This important decision factors into overall system reliability.
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