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Common forms of dynamic seals in seven mechanical designs
Source: | Author:佚名 | Published time: 2026-06-30 | 15 Views | 🔊 Click to read aloud ❚❚ ▶ | Share:

Today, we will mainly introduce seven common forms of dynamic seals in mechanical design, including packing seals, mechanical seals, dry gas seals, labyrinth seals, oil seal seals, power seals, and spiral seals.


The sealing problem of moving equipment always exists with the operation of the equipment. Today, we have compiled various commonly used sealing forms, usage ranges, and characteristics on moving equipment, so that everyone can have a deep understanding of the sealing problem.




 

1、 Packing seal

 

Packing seals can be divided into:

Soft packing seal

Hard packing seal

Molding packing seal


1. Soft packing seal

Soft packing type: packing


The packing is usually woven from relatively soft thread like materials, filled into the sealing chamber with square shaped strips, and pressed by the pressure cover to compress the packing. The packing is pressed against the sealing surface (the outer surface of the shaft and the sealing chamber), generating a radial force for sealing effect and achieving the sealing effect.


Applicable occasions for soft packing: The selection of packing material for packing determines the sealing effect of the packing. Generally speaking, the manufacturing material of packing is affected by the temperature, pressure, and acidity of the medium on site. When selecting the material of packing, the surface roughness, eccentricity, and linear velocity of the mechanical equipment in which the packing works also need to be considered.

a. The characteristics of graphite packing are high temperature and high pressure resistance, corrosion resistance, excellent sealing performance, and stable and reliable performance. It is one of the most effective products to solve high temperature and high pressure sealing problems.

b. Aramid packing is a kind of high-strength organic fiber, which is dipped in polytetrafluoroethylene lotion and lubricant.

 

c. Polytetrafluoroethylene packing is made from pure polytetrafluoroethylene dispersed resin as raw material, first made into a raw material film, and then twisted and woven into packing Commonly used in valves and pumps with high cleanliness requirements and strong corrosive media, such as food, pharmaceuticals, papermaking, and chemical fibers.


2. Hard packing seal

There are two types of hard packing seals: split ring and split ring.



2、 Mechanical seal

 

The machine seal consists of two parts: a rotating component and a stationary component (as shown in the figure below), with the stationary ring surface serving as the main sealing surface.

Mechanical seal, also known as end face seal, is defined according to relevant national standards as a device that prevents fluid leakage by maintaining contact and relative sliding between at least one pair of end faces perpendicular to the axis of rotation under the action of fluid pressure and the elastic (or magnetic) force of the compensation mechanism, as well as the cooperation of auxiliary seals.

 

3、 Dry gas seal

Dry gas seal, also known as "dry running gas seal", is a new type of shaft end seal that uses slotted sealing technology for gas sealing, and belongs to non-contact sealing.


Features: Good sealing performance, long lifespan, no need for a sealing oil system, low power consumption, simple operation, and low maintenance costs. Dry gas seal, as a maintenance free sealing system that does not require any sealing end face cooling or lubricating oil, is replacing floating ring seal and labyrinth seal as the main seal for high-speed centrifugal compressor shaft seals in the petrochemical industry.


Applicable occasions: Centrifugal compressors and other high-speed fluid machinery, suitable for working conditions where a small amount of process gas leaks into the atmosphere without harm, such as air compressors, nitrogen compressors, etc.


4、 Maze seal

迷宫密封是在转轴周围设多个依次排列的环行密封齿，齿与齿之间形成一系列截流间隙与膨胀空腔，被密封介质在通过曲折迷宫的间隙时产生节流效应而达到阻漏的目的，是离心式压缩机级间和轴端*基本的密封形式，根据结构特点的不同，可分为平滑式、曲折式、阶梯式及蜂窝式等四种类型。 

 


1. Smooth labyrinth seal

The smooth labyrinth seal has two types of structures: integral and embedded. It has a simple structure and is easy to manufacture, but the sealing effect is poor.  


2. Tortuous labyrinth seal

The zigzag labyrinth seal is also divided into two structures: integral and embedded. Its characteristic is that the extension height of the sealing teeth is different, and the high and low teeth are arranged alternately. The matching shaft surface is a specially designed concave convex groove. This structure, which matches the high and low teeth with the concave convex groove, turns the smooth sealing gap into a zigzag shape, thus increasing the flow resistance and improving the sealing effect. The disadvantage is that it can only be used in cylinder bodies or partitions with horizontal dividing surfaces, and the sealing body also needs to be made into a horizontal dividing type.  


3. Staircase labyrinth seal

The stepped labyrinth seal is structurally similar to a smooth labyrinth seal, and its sealing effect is similar to that of a tortuous labyrinth seal. It is commonly used at impeller cover plates and balance disks.  


4. Honeycomb labyrinth seal

The sealing teeth of the honeycomb labyrinth seal are welded into a honeycomb shape to form a complex expansion chamber. Its sealing performance is superior to general sealing forms and is suitable for situations with large pressure differences, such as the balance disk seal of centrifugal compressors. The manufacturing process of honeycomb labyrinth seals is complex, with high sealing strength and good sealing effect.  


5、 Oil seal sealing

Oil seal is a self tightening lip seal with a simple structure, small size, low cost, easy maintenance, and small resistance torque. It can prevent medium leakage, external dust and other harmful substances from entering, and has a certain compensation ability for wear. However, it is not resistant to high pressure, so it is generally used in pumps in low-pressure situations.


6、 Power seal

When the pump is running, the pressure head generated by the secondary impeller balances the high-pressure liquid at the outlet of the main impeller, thereby achieving sealing. When parking, the auxiliary impeller does not work, so a parking sealing device must be equipped at the same time to solve the possible pump leakage that may occur during parking. The sealing structure of the secondary impeller is simple, reliable, and has a long service life. The pump can achieve no leakage during operation, so it is often used in pumps that transport impurities.


7、 Spiral seal


Spiral seal is also a type of power seal, which is machined with spiral grooves on the rotating shaft or on the bearing sleeve of the shaft, and a sealing medium is filled between the shaft and the sleeve. The rotation of the shaft causes the spiral groove to produce a pump like conveying effect, thereby preventing the leakage of the medium. The sealing ability is related to the helix angle, pitch, tooth width, tooth height, effective length of teeth, and the gap size between the shaft and the sleeve. Due to the absence of friction between seals, it has a long lifespan. However, due to the limitations of structural space, its spiral length is generally short, which limits its sealing ability. When the pump is used at reduced speed, its sealing effect will be greatly reduced.