What Is a Mechanical Seal?

Mechanical seal refers to the prevention of fluid leakage by at least one pair of end faces perpendicular to the rotation axis under the action of fluid pressure and the spring force (or magnetic force) of the compensation mechanism and the cooperation of the auxiliary seal. Device.

Machinery Seal

Mechanical seal refers to the prevention of fluid leakage by at least one pair of end faces perpendicular to the rotation axis under the action of fluid pressure and the spring force (or magnetic force) of the compensation mechanism and the cooperation of the auxiliary seal. Device.

The elastic loading mechanism and auxiliary seal are mechanical seals of metal bellows.

Mechanical seals rely on a pair

Shaft seal box

In the past, shaft seal boxes containing mechanical seals were designed for

The first is to use the "

The seal ring is the general name of the moving ring and the static ring (the same applies hereinafter), and is the most important component of the mechanical seal. The sealing ring largely determines the service performance and life of the mechanical seal, so it puts forward some requirements for it.

Have enough strength and stiffness

Under working conditions (such as pressure, temperature, and

During installation

1. Great care must be taken to avoid installation deviations during installation

(1) The tightening gland should be at

Before you start

1. Comprehensively check whether the mechanical seal, the installation of auxiliary devices and pipelines are complete, and whether they meet the technical requirements.

2. Perform a static pressure test before starting the mechanical seal to check whether there is any leakage in the mechanical seal. If there are many leaks, the cause should be investigated and eliminated. If it still does not work, it should be removed for inspection and reinstalled. The general static pressure test pressure is 2 ~ 3 kg / cm2.

3.Press the rotation direction of the pump

Mechanical seals and other equipment due to long-term high-torque mechanical movement, the gear box meshing gap becomes larger, causing greater noise and equipment vibration. In addition, the sealing part is operated under high speed and high temperature for a long time, and oil leakage occurs from the sealing part. The leakage caused by the seal is caused by the following reasons: 1. Leakage due to quality problems of the oil seal; 2. Improper lubrication management, resulting in excessive oil addition or dry grinding due to lack of oil; 3. Damage to the seal during repair and maintenance causes seal failure 4. Oil level exhaust holes are blocked due to excessive pressure, etc. The above problems not only affect the continuous and safe operation of production equipment of the enterprise, but also cause large consumption of enterprise costs. ^[1]

There are two cases of the sealing of the vacuum device. One is that the sealing member separates a certain container filled with the liquid medium from the external vacuum space. In this case, the main role of the seal is to prevent liquid medium from leaking into the vacuum space. Another situation is that the seal separates the vacuum inner cavity from the outer cavity, and its role is to maintain the required degree of vacuum. This situation is more complicated because even if the surrounding gas medium leaks into the vacuum chamber slightly, it will reduce its vacuum. If corrosive gas is leaked in, the vacuum equipment may be damaged. In many cases, the degree of vacuum and the cleanness of the vacuum space have a decisive influence on the quality of various processes performed under vacuum conditions. The mechanical seal used in the vacuum device is not special in structure. For the first case mentioned above, usually a metal bellows type single-end mechanical seal with good air tightness is used. In the second case, a double-end mechanical seal is used. If a single-end seal is used, there is bound to be a problem that the sealed end face cannot be lubricated.

It is difficult for people to distinguish between mechanical seals and hydraulic seals, and they often think that they are the same thing.

First, the definition of mechanical seals and hydraulic seals:

Mechanical seals belong to one of the basic mechanical components with precise and complex structure, and are the key components of various pumps, reaction synthesis kettles, turbine compressors, submersible motors and other equipment. Its sealing performance and service life depend on many factors, such as selection, machine accuracy, correct installation and use.

Hydraulic seals have pressure requirements, and require a certain degree of smoothness of the joint surface. Sealing elements are mostly rubber, and the sealing effect is achieved by local deformation of the seal.

Classification of mechanical seals and hydraulic seals

Mechanical seal models: 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 hydraulic cylinders are commonly used in combination with seals, such as bud-shaped rings, Gree rings and step seals.

Third, choose the seal

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

1. Movement direction-first determine the movement direction of the seal, such as reciprocating, rotating, spiral or fixed.

2. Seal points-For example, determine whether the active point is a rod seal with an inner diameter or a piston seal with an active point on the outer diameter.

3. Temperature grade-consult the operating instructions of the original machine or evaluate the working temperature according to the actual working environment to determine the required materials. For the description of the temperature grade, please refer to the note for production users below.

4. Size-Most users will choose the old samples used, but after using for a period of time, the original size will be greatly affected by factors such as temperature, pressure and wear. The selection based on 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, and the accuracy will be higher.

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