- While pusher seals operate by using axially mounted springs on shaft sealing assemblies, which allows them to produce fixed pressure, nonpusher mechanical seals use sealed bellows to apply pressure. That is why they are also called bellow seals. They can tolerate high and low temperatures and do not require a secondary seal. These types of seals are available in different sizes and configurations. Pusher and nonpusher mechanical seals have a simple mechanism so it is not difficult to work with them. Neither of these seal types is designed to tolerate much misalignment and vibration. Examples of pusher seals are Dura RO and Crane Type 9T, while nonpushers include Dura CBR, Crane 215 and Sealol 680.
- Use a balanced mechanical seal in situations when there is liquid, especially if this liquid has poor lubricity and high vapor pressures. Balanced mechanical seals can tolerate high pressures. Dura CBR, PBR and Crane 98T are examples of balanced mechanical seals. Unbalanced ones are Dura RO and Crane 9T and they are also useful in situations when there is high vibration and misalignment, but they have a low pressure limit.
- Conventional mechanical seals are also called standard mechanical seals. Dura RO and Crane Type 1 are standard seals which require setting and alignment of the seal. These seals are often used for retrofit of pumps and compressors, but you need to make some engineering and maintenance effort.
- Cartridge seals provide lower maintenance costs because they offer a whole mechanical seal package that can fit into cartridge type housing. These types of seals also reduce the setting mistakes that can happen because there is no need for all the setting measurements for their installation. Today, pump builders often incorporate these cartridge mechanical seals into their new products in order to make maintenance easier for themselves.
Pusher and Nonpusher Mechanical Seals
Balanced and Unbalanced Mechanical Seals
Conventional Mechanical Seals
Cartridge Mechanical Seals
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