Mechanical seal application characteristics Mechanical seal

Mechanical seal application characteristics




2020-01-14 09:25






There are two situations for the sealing of vacuum devices

One is that the seal separates a container filled with a liquid medium from the external vacuum space. In this case, the main function of the seal is to prevent the liquid medium from leaking into the vacuum space.

In another case, the seal separates the vacuum inner cavity from the outer cavity, and its function is to maintain the required vacuum degree. This situation is more complicated, because even a slight leakage of the surrounding gas medium into the vacuum chamber will reduce its vacuum degree. If corrosive gas leaks in, the vacuum equipment may be damaged.

In many cases, the degree of vacuum and the cleanliness of the vacuum space have a decisive influence on the quality of various processes carried out under vacuum conditions.
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There is nothing special about the structure of mechanical seals used in vacuum devices.

For the first case above, a metal bellows type single-end mechanical seal with good airtightness is usually used.

In the second case, a double-end mechanical seal is used. If a single-end seal is used, there must be a problem that the sealing end face cannot be lubricated.



First, the definition of mechanical seals and hydraulic seals:


Mechanical seals are one of the basic components of machinery with precision and complex structures, and are key components of various pumps, reaction synthesis kettles, turbo compressors, submersible motors and other equipment.

Its sealing performance and service life depend on many factors, such as type selection, machine precision, correct installation and use, etc.


Hydraulic seals have pressure requirements, and require a certain degree of smoothness on the joint surface. The sealing element is mostly made of rubber, and the sealing effect is achieved through the local deformation of the seal.


2. Classification of mechanical seals and hydraulic seals


Mechanical seal model: cartridge seal series, light mechanical seal series, heavy mechanical seal series, etc.


Hydraulic seals: lip seals, V-shaped seals, U-shaped seals, Y-shaped seals, YX-shaped seals and combined seals commonly used in hydraulic cylinders are mainly bud rings, grid rings and Ster seals.


3. Select seals


When purchasing seals for maintenance, most users will purchase according to the size and color of the sample, which will only increase the difficulty of purchasing, and may not be able to select the right product. The following procedures are recommended to improve the accuracy of purchasing seals:


1. Direction of motion - first determine the direction of motion where the seal is located, such as reciprocating, rotating, spiral or fixed.


2. Key points of sealing - for example, determine that the active point is a tie rod seal on the inner diameter or the active point is on a piston seal on the outer diameter, etc.


3. Temperature grade - consult the original machinery manual or evaluate the working temperature according to the actual working environment to determine the required materials. A description of the temperature classes can be found in the Notes to Production Users below.


4. Size - most users will buy according to the used old samples, but after a period of use, the original size of the seal will be greatly affected by factors such as temperature, pressure and wear, and the selection according to the sample can only be used as a reference , a better method is to measure the size of the metal groove where the seal is located, the accuracy will be higher.


5. Pressure level - check the relevant data from the original mechanical instructions, or infer the working pressure level by observing the hardness and structure of the original seal.