AS-C406 Customized Single Cartridge Mechanical Seal

This seal is single mechanical seal in cartridge form made as per drawing.

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What are the factors that affect the sealing performance of mechanical seals?
The tightness of the mechanical seal is its most important indicator. There are many influencing factors, including sealing structure, material, & how you manufacture it, how you install it, medium properties and how you use it, etc.If there is a problem in this link, the sealing performance will be affected. These factors can be divided into two categories: factors regarding the seal itself and the conditions of use.The seal structure, material and manufacture belong to the"seal itself", these factors are completed in the manufacturing plant, and the quality of the seal depends on the manufacturing plant. The installation, media properties and use, etc. belong to the range of “conditions of use”, and how to use it correctly depends on the user. This article only discusses the influencing factors that belong to the seal itself.

1. How does the load factor affect the sealing performance of the mechanical seal
From the point of view of sealing performance, the user would like the mechanical seal to have a larger load coefficient, which can ensure a higher specific pressure, and the stability and reliability of the mechanical seal are better. However, a large load coefficient means a lot of frictional heat. If it cannot be dissipated in time, the temperature of the sealing end surface of the mechanical seal will be too high. When it reaches the vaporization temperature of the medium, vaporization will occur, the liquid film will be destroyed, the wear will increase, and the service life will be shortened.Especially under high pressure working conditions, the use of unbalanced mechanical seals with a load factor greater than or equal to 1.0 is not allowed. However, for a balanced mechanical seal with a load factor less than 1.0, the sealing end face of the seal may be pushed away, and the stability is poor. In actual work, it is not desirable to generate too much heat, but also to have sufficient stability. After weighing the pros and cons,in the internal flow mechanical seal, the load factor is better between 0.75 and 0.85. Unbalanced mechanical seals (K=1.1~1.2) can also be used when the seal fluid pressure is low. According to the survey of several large petrochemical enterprises in China, the load coefficient is related to the properties of the medium. For heavier components and media that are not easy to vaporize, the load coefficient should be larger, and vice versa. The value of the load coefficient is not selected in isolation, but should be considered comprehensively with the specific pressure of the spring. .When the specific pressure of the spring is larger, the load coefficient can be smaller, otherwise it should be larger.

2. How does the specific pressure of the spring affect the sealing performance of the mechanical seal
The specific pressure of the spring is an important factor that promotes the fit of the sealing end faces of the mechanical seal. When the pressure is low when the pump is stopped and started, or the normal working pressure in the sealing chamber of the mechanical seal is low, or the pressure fluctuates greatly during work, the spring specific pressure becomes the main component of the end face specific pressure. The size of the specific pressure of the spring should be considered comprehensively according to the sealing structure, working conditions, medium properties and load coefficient. The larger the specific pressure of the spring, it is beneficial to the bonding of the sealing end face of the mechanical seal, improving the followability, and enhancing the sealing stability. If it is too large, the frictional heat will increase, the power consumption will increase, the wear will be large, and the service life will be shortened. If the spring specific pressure is too small, the leakage is large, and the sealing stability is poor. For the built-in internal flow seal, the spring specific pressure is between 0.1~0.25MPa. For medium with good lubricity, low speed or low pressure working conditions, the upper limit of spring ratio is taken, otherwise the lower limit is taken.

As mentioned earlier, it should also be considered in conjunction with the load factor.For the externally installed unbalanced seal, the specific pressure of the spring has a greater effect, which is the only force to make the sealing surface fit, and the specific pressure of the spring is much larger than that of the internally installed internal flow seal. When the medium pressure is around 0.1MPa, the spring specific pressure is 0.3~0.45MPa; when the medium pressure is 0.25MPa, the spring specific pressure should be 0.45~0.7MPa. In the agitator, due to its lower working speed, larger shaft swing and larger operating pressure fluctuations, the specific pressure of the spring should also be appropriately larger. For high-speed mechanical seals (mostly internal flow seals), although the sealing fluid with good lubricating performance is used, considering the followability of the seal, the specific pressure of the spring should be larger, generally 0.2~0.3MPa. At this time, the load factor is small.

3.How does the the roughness of the sealing end face affect the sealing performance of the mechanical seal
For ordinary mechanical seals, from a macroscopic point of view, under normal circumstances, the two end faces are parallel and in solid contact. From a microscopic point of view, any surface is uneven, that is, it has a certain roughness. It is usually said that two planes are in contact, but actually the high points of the two planes are in contact, but most of the surfaces are not in contact, and there are still certain gaps. The rougher the surface, the greater the gap height and the greater the leakage.In order to maintain a good sealing performance, a greater end-face specific pressure must be applied. As we all know, if the specific pressure of the end face is too large, it will inevitably increase the heat generated by friction, which is unfavorable. Therefore, certain requirements are put on the roughness of the sealing surface. This not only ensures good sealing, but also ensures a longer service life of mechanical seal.

4.How does the width of the sealing end face affect the sealing performance of the mechanical seal
For friction pairs of the mechanical seal with parallel seal faces, the width of the seal faces has little effect. In order to seal the pressure of 2MPa, only a width of 0.5mm is enough, and if the width of the sealing end face is increased too much for the sake of strength and rigidity, the heat generation will increase, the thermal deformation will be large, and eventually It leads to increased leakage, so the sealing end faces that is too wide is detrimental to the sealing performance of the mechanical seal.