Concrete pump can not pump fault handling skills

The choice of mechanical seal configuration is an important step in the design cycle and must be investigated: Operating Parameters - Dielectric Pressure, Temperature, Shaft Diameter and RPM. Media characteristics - concentration, viscosity, corrosive, with or without solid particles and fiber impurities, whether easy to vaporize or crystallization. Host operating characteristics and environmental conditions - continuous or intermittent operation; host installed in the room or open air; the surrounding atmosphere and the temperature changes. Host on the seal of the allowable leakage, leakage direction (internal leakage or leakage) requirements; life expectancy and reliability requirements. ⑤ host the size of the seal structure restrictions. ⑥ operation and production process stability. 1. According to the working parameters p, v, t selection p here refers to the pressure at the seal cavity media, according to the size of the p value can be initially determined whether to choose a balanced structure and the degree of balance. For medium viscosity, good lubricity, p ≤ 0.8MPa, or low viscosity, poor lubricity of the media, p ≤ 0.5MPa, usually use non-balanced structure. p value exceeds the above range, should consider the use of balanced structure. When p> 15MPa, the general single-end balanced structure is difficult to meet the sealing requirements, this time can be used in series multi-face seal. υ refers to the circumferential surface of the average diameter of the sealing surface speed, according to the value of the value of υ determine whether the elastic element with the shaft rotation, that is, using spring or spring stationary type structure, the general υ <20 ~ 30m / s can be spring- Under higher speed conditions, it is better to adopt the spring static structure due to the unbalanced quality of the rotating parts that causes strong vibration. If p and υ values ​​are high, consider the choice of hydrodynamic structure. t is the temperature of the medium in the sealed chamber, the material of the secondary seal, the cooling method of the sealing surface and its ancillary system are determined according to the size of t. Temperature t in the range of 0 ~ 80 ℃, the auxiliary ring is usually selected nitrile rubber O-ring; -50 ℃ ≤ t <150 ℃, depending on the corrosiveness of the medium, the choice of fluorine rubber, silicone rubber or PTFE Ethylene molding packing ring: temperature <-50 or t ≥ 150 ℃, the rubber and PTFE will produce low temperature brittle cracking or high temperature aging, this time can be used metal bellows structure. Medium turbidity higher than 80 ℃, in the field of sealing usually take into account the high temperature, this time must take appropriate cooling measures. 2. According to the characteristics of media selection of less corrosive media, usually use built-in mechanical seal, the end of the state of stress and media leakage than the external sense of direction. For strong corrosive media, the selection of the spring or Teflon bellows mechanical seal is more difficult because of the spring material selection. However, generally only p≤0.2 ~ 0.3MPa is suitable. Easy to crystallize, easy to set high viscosity medium, should be used in large spring rotating structure. Because small springs are easily clogged with solids, high-viscosity media can obstruct small spring axial compensation movements. Flammable, explosive, toxic media, in order to ensure that the media is not leakage, should be used sealed liquid (barrier fluid) double-sided structure. The structure selected according to the above working parameters and medium characteristics is often just a preliminary solution. Ultimately, the characteristics of the host and certain special requirements for sealing must also be considered. For example, a rocket engine has a seal life of only a few minutes, but it requires absolute leak-tightness over a short period of time. In order to obtain more effective space, sometimes the hosts on the ships often place very strict requirements on the size and installation position of the seals. For example, the drainage pumps on the submarine have great pressure changes during the ups and downs of the submarine. Under these circumstances, the standard structure can not be chosen conventionally, and the specific conditions must be specially designed and the necessary auxiliary measures taken.