Q
Kind of mechanical seals which is divided into several ?
A

Kind of mechanical seals which is divided into several 

1.push mechanical seal and non-push mechanical seal

Push-type mechanical seal refers to the secondary seal of the mechanical thrust along the shaft or sleeve to compensate for the wear of the sealing surface of the mechanical seal, usually the spring-loaded mechanical seal.
A non-push mechanical seal for secondary sealing is secured to the shaft of the mechanical seal, typically a bellows mechanical seal.
2.balanced and unbalanced mechanical seal type mechanical seal
The mechanical seal seals the pressure acting on the ring to form a closing force, and the liquid film is formed between the opening force of the end face. Load factor K> 1, sealed unbalanced mechanical seal. General unbalanced mechanical seals can only be used for low pressure. When the pressure is greater than a certain limit, the liquid film between the sealing surfaces will be extruded. The film in the lubrication loss and the role of high load, sealed mechanical seal is about to be destroyed. Unbalanced mechanical seals can not be balanced by the action of the liquid on the end face of the face and the pressure increases as the fluid pressure increases.
Load factor K <1, the seal is balanced mechanical seal. Balancing the mechanical seal shaft seal the built-in step, so that the radial inner seal surface extension movement, but does not reduce the width of the sealing surface. The seal opening force is constant, but due to the presence of a large torus exposed to the liquid, a considerable portion of the closing force is balanced. Balance Mechanical Seal External Seal Balanced Method Other Force In the opposite direction, on the other hand has the same built-in mechanical seal. In this case, increase the share of the hydraulic closing force to offset the mechanical seal between the film opening forces. The balanced mechanical seal can be partially balanced by the end face of the liquid surface effect, with the pressure increasing slowly as the fluid pressure increases. General non-balanced mechanical seals can only be used for low pressure, but the lubrication performance is poor, low boiling point, easy to medium steam and high speed conditions, even under low pressure should also use balanced mechanical seal. As the mechanical seal is not balanced, the mechanical seal chamber when the pressure increases, the seal between the liquid film will be squeezed out, the mechanical seal surface quickly damaged. Balanced mechanical seals can be used for a variety of pressure conditions.
3.no pressure double pressurized mechanical seal double mechanical seal
Single mechanical seal only a pair of friction, simple structure, easy manufacturing, easy disassembly, generally only set the flushing system, no external seal liquid supply system.
The double mechanical seal (formerly known as the double mechanical seal) means that there are two pairs of friction pairs, the structure is complex, the need for external sealing liquid supply system, pressurized double mechanical seal through the high than 0.5 ~ 1.5bar medium pressure isolation chamber fluid, Block, lubrication, etc., in the internal seal of the liquid seal. No pressure double seal (formerly known as series seal) means that there are two pairs of friction pairs, the structure is complex, the need for external sealed liquid system, no pressure double sealed sealed chamber buffer is not pressurized, the process medium lubrication internal sealing effect.
In general, the preferred use of single mechanical seal, single mechanical seal structure is simple, easy to use, low prices. However, in the following cases, the preferred dual mechanical seal is preferred.
(1) toxic and dangerous media.
(2) high concentration of H2S.
(3) low temperature volatile media (such as liquefied petroleum gas, etc.).
With the increasing importance of health, safety and environmental protection, the number of non-pressurized double mechanical seals increases year by year. The non-pressure sealed double mechanical seal can be used for toxic and volatile dangerous media such as vinyl chloride, carbon monoxide and light hydrocarbons The Sealed double mechanical seal (first seal) without pressure is the main seal, the equivalent of single-ended built-in mechanical seal, single mechanical seal by the media lubrication and was sealed to play. The sealed chamber is filled with a water tank to seal the liquid without pressurization. The non-pressure dual mechanical seal, once the inner seal fails, results in an improved pressure seal chamber that can be displayed, recorded or alarmed by a sealed tank gauge. At the same time there is no pressure outside the seal double mechanical seal and sealed shell can play before the role of liquid leakage.
For some harmful particulate media (corrosive or very powerful medium), consider the following methods:
(1) Use appropriate environmental control measures such as cleaning the + line with cyclone flushing system.
(2) using a double mechanical seal.
Pressure double mechanical seal blocking fluid pressure higher than the medium pressure, so that the pump medium does not enter the sealed room. Pressure sealed within the double mechanical seal to prevent the isolation, the liquid into the pump room. Thus, when transporting this viscous abrasive and high temperature medium, the double mechanical seal is pressurized inside the seal because there is no exposure in the medium and may not be expensive for alloy production. Pressure outside the seal double mechanical seal can only play a role in isolation of liquid leakage to the atmosphere.
4.built-in mechanical seal and external mechanical seal
Built-in mechanical seal: mechanical seal installed in the sealed chamber.
External mechanical seal: refers to the mechanical seal installed in the sealed room outside.
Due to the built-in mechanical seal effect is better than the pressure to increase the pressure, the built-in mechanical seal leakage direction and centrifugal force in the opposite direction, it is usually made of built-in mechanical seals. Only when there is corrosive media, and because I do not want to consider the use of pressurized dual mechanical seal, consider the choice of external mechanical seal.
5.rotating mechanical seal and mechanical seal fixed
The rotary mechanical seal compensating part rotates with the shaft mechanical seal.
The static mechanical seal compensating member does not rotate with the shaft mechanical seal.
Usually the rotating mechanical seal is made, but at a large shaft diameter, high speed, the sealing peripheral speed is 25 m / s, the centrifugal force is large, and because the spring needs to balance the other rotating elements to produce high stirring power consumption is also large, Use a static mechanical seal. In addition, if the medium is easily crystallized while stirring, it is also recommended to use a static mechanical seal.
6.single, multi-spring mechanical seal mechanical seal spring
Single spring mechanical seal, simple structure, can play a role in the spring, but the surface pressure is not uniform, not suitable for high-speed operation.
Multi-spring mechanical seals, complex structure, can not play a role in the spring, and even high-speed operation will face pressure. In general, it is recommended to use a multi-spring mechanical seal.

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