Bearing mechanical seal structure type selection is an important step in the design aspects must first conduct a survey: ① operating parameters - media pressure, temperature, shaft diameter and speed. ② Medium features - concentration, viscosity, corrosive, with or without solid particles and fiber impurities, is it easy to vaporization or crystallization. (3) host work characteristics and environmental conditions - continuous or intermittent operation; host installation in indoor or outdoor; around the atmosphere of nature and the temperature change. ④ host allowable leakage seal leakage direction (internal leakage or leakage) requirements; life and reliability requirements. ⑤ hosts limit the size of the seal structure. (6) the stability of operations and production processes.

1 according to the operating parameters p, v, t selection

    Where p is the sealed chamber at medium pressure, depending on the size of the p-value can initially determine whether to select a balanced degree of structure and balance. NSK Bearings for the high medium viscosity, good lubricity, p ≤ 0.8MPa, or low viscosity and poor lubricity of the medium, p ≤ 0.5MPa usually use non-equilibrium structure. p-value exceeds the above range, considering the selection of a balanced structure. 15MPa, the structure of the general single-end balance is difficult to meet the sealing requirements, the choice of face seal series.     " b="当p＞15MPa时，一般单端面平衡式结构很难达到密封要求，此时可选用串联式多端面密封。">When p> 15MPa, the structure of the general single-end balance is difficult to meet the sealing requirements, the choice of face seal series.

    υ is the peripheral speed of the average diameter of the sealing surface, according to the size of the υ values ??to determine whether the elastic element with the axis, that is, the spring rotary or spring static structure, general υ <20 ~ 30m / s can spring Rotating higher speed conditions, could easily cause strong vibrations due to unbalance of the rotating parts, preferably in the spring static structure. P and υ values ??are high, considering the selection of the hydrodynamic pressure structure.

    t is the medium temperature of the seal cavity, FAG bearings based on the size of t to determine the secondary seal material, the sealing surface of the cooling method and its auxiliary systems. Temperature t in the range of 0 ~ 80 ℃, the auxiliary ring is usually chosen nitrile rubber O-ring; -50 ° C ≤ t <150 ° C, can be used according to the corrosive medium strength of the fluorine rubber, silicon rubber or PTFE ethylene forming filler ring: temperature <-50 or t ≥ 150 ° C, rubber and PTFE will produce low-temperature embrittlement or high-temperature aging, can be used metal bellows structure. Medium turbidity higher than 80 ℃, usually in a sealed areas must follow the high temperature to consider cooling measures must be taken at this time.

2 according to the media characteristics of selection

    Less corrosive media, usually selected the built-in mechanical seals, SKF bearings face the stress state and the media leaks direction than the external rational. Spring selection is more difficult for the strong corrosive medium, the choice of external or PTFE bellows mechanical seal, but generally only applies to p ≤ 0.2 ~ 0.3MPa.

    Easy crystal, easy to solidification and high viscosity of the medium should be used in the structure of the spring rotation. Because of the small spring clogging solids, high viscosity media will make a small spring axial compensation move blocked.

    Flammable, explosive, toxic media, in order to ensure that the media does not leak, you should use the double-end structure of the sealing liquid (insulating liquid).

    The working parameters and dielectric characteristics of the selected structures are often only a preliminary program, INA bearings finalized must also consider a host of features and some special requirements for sealed. For example, the rocket motor seal life is just a few minutes, but requires a short period of time is absolutely no leakage. The host ships sometimes in order to obtain more efficient space, very stringent requirements on seal size and installation location is often Another example is the drainage pump on the submarine, the submarine in the ups and downs of the process, the pressure fluctuated widely. In these cases, you can not structure the conventional selection criteria, specially designed for specific conditions, while taking the necessary supporting measures.


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