Types And Applications Of Mechanical Seal Faces

By Author: Wilber Whitfield
Total Articles: 72
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Mechanical seal faces, also known as face seals, are used for leakage control in industrial applications where rotating equipment such as mixers and pumps are in use. They help prevent liquids and gases passing through the equipment from seeping out into the surrounding environment. The concept and components used in these seals are discussed below, along with the possible types of face seals.

If the sealing action was not present, liquids would be able to seep out through the gap between the outer pump casing and the rotating shaft inside. It follows, therefore, that seals used must have two components in contact with each other even as one of them is rotating with the shaft while the other is stationary and embedded into the casing. The contact is maintained despite this sliding motion with the help of a spring and hydraulic pressure, which can be from the sealed liquid within.

Face seals can have many varying designs using different materials. The component that is stationary must be hard, and is usually made of tungsten carbide. The rotating component has to be softer, and is commonly made of carbon graphite.

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... mechanism generates a lot of wear due to the constant friction of the sliding components, and this has to be minimized with a lubricant. Technically, the lubricant is known as a film fluid and has to be stable enough for the extreme and rugged working conditions that heavy industrial equipment is used in. This ensures the seals will last at least as long the pump itself.

The two basic types of face seals are a simple spring loaded component unit and a more complex and preassembled ceramic unit. The former has two sub-types which are known as pusher and non-pusher. The pusher type has a dynamic secondary seal such as an O-ring that can move with the shaft, while the non-pusher has a static secondary seal fixed on the shaft or the sleeve.

All put together, even the most basic unit with four sealing points has at least seven components. Both the stationary and rotating components have sealing members. It will also need a spring and a gland plate, and there is also a clamp ring. Regardless of the type, design and materials used, all such seals will be built to comply with A. P. I. Standard 682.

Cartridge seals are generic and preassembled. They are preset at the factory and come ready with everything from the seals to the gland plate, shaft sleeve and everything else required for the unit to work. It simply has to be inserted into the pump, with no further installation or settings required. It is often used in rotating equipment where the design makes it is hard to install the sealing components separately while manufacturing the equipment.

Mechanical seal faces find major applications in industrial and agricultural equipment and machinery that need to be used in harsh conditions and are subjected to sustained wear and tear. It can be found in an excavator or bulldozer, and will come in just as handy for axles, heavy trucks, combines, mining equipment and tunnel boring tools. It is also the ideal choice in applications such as gearboxes, wind energy generators and mixers where the seal needs to be functional for the lifetime of the product.

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