subject: What Is The Driving Force For Sealing And Stopping The Pump Seal [print this page] Vice impeller dynamic seals and sealing devices stop packing and mechanical seals can be overcome certain deficiencies, a simple structure, reliable sealing, fluid does not leak point advantage is now in the metallurgical and petrochemical industries to be more universal application.
Vice impeller dynamic pump seal (also known as centrifugal sealing fluid power seals, etc.) can be divided into closed and the Deputy Vice-blade impeller seal. When the pump rotates, the impeller is generated out of the liquid pressure P, then the flow of exports, but also pressure to fill rooms, so that media leaks out. However, the Deputy Vice-impeller blades and the role that it had a centrifugal force P1 'or P2'. The direction of the impeller produces the opposite direction the pressure P out. Therefore, the liquid can leak out of the top back. That is formed in the seal cavity, "such as sealing" or "vacuum seal" so that the pump during operation to leak. Because parking seals, pump in the parking can be sealed when.
1. Deputy blade computing sealed
After the cover in the impeller plane for several radial ribs open bars, this is the deputy leaves. It maintained a small pump shell gap, the liquid is also similar to the impeller angular velocity of rotation, rather than vice leaves no time for the angular velocity as half. This makes the role of fluid pressure in the packed chamber Department reduced.
In the absence of the role of vice leaves, the back cover panel liquid pressure distribution ABEF. We know that when the impeller when the deputy leaves the pressure variation is a parabola, shown in Figure 3, in KG. The resulting pressure value GKFG area.
Pump seal has two parts:
1. Sealing rings. As the liquid is high-pressure centrifugal pump impeller exit, the entrance is a low-pressure, high pressure liquid through the gap between the impeller and the pump suction leakage flow back into the office, you need to install the Split Seal ring. Its role is to reduce leakage between the impeller and the pump loss; on the other hand protect the impeller and the pump body to avoid friction.
2. Shaft seal. In the pump shaft and the gap between the pump casing, to prevent outflow of fluid pump, or to prevent air leakage into the pump, the need for sealing.
Multi-stage centrifugal pump is a pump to a fixed blade housing contains the ballast devices fixed rotation, and contrary to the existing structure of multi-stage centrifugal pump. The pump is less due to internal sealing parts, sealing wire is small and basically eliminate internal leakage, can increase the volumetric efficiency; as axial force is small, eliminating the need for balance device can improve the pump efficiency; with the same technical specifications of existing multi-stage centrifugal pumps ratio, small size, light weight, materials, provincial, simple structure, easy to manufacture. As the degree of rotor steel to produce more centrifugal pumps to be higher lift for the development of multi-level mud considerable significance.
Used to pump on the improvement of mechanical seals
In 2004, the engineering and maintenance department to find a solution. Systems engineers typically determine mechanical seal leakage as a function of whether the primary criterion for normal. In some applications, the leak could lead to extremely serious consequences, but the situation is not always the case. Steam generator feed water is generally not dangerous, and controlled processing system leak, should ensure that access to power plants and water supply by supply systems for processing and reuse.
In the case of the installation of the new seal and renovation of parts, the original seal in the first year of operation, almost no visible leakage. However, stop and restart after a water pump, seal leakage began to increase, until the management of closed loop fluid temperature warning system issued a temperature alarm, the pump stopped running maintenance and repair.
Most of the device seals the root causes of the failure lies in its lack of a fixed axial movement meter seal parts, this is because the pin of the beat to produce anti-rotation slot glitch caused. Since the two metal parts of all the material and hardness are similar to each burr with the pumps running and gradually increased. But after burr with a file, and then seals the pump can be installed back to resume its sealing function.
Understanding of the power plant operation and details of all the parameters, the Fox made the recommendation improve the seal, including the minimum number of controlled leakage. As Doel3 ~ Doel4 of big size and operation to pump speed 4000 ~ 4820r/min, speed of conversion circumference 55m / s, for this type of pump, the requirements of the mechanical seal is very high. With slightly higher leakage rate into the seal design to ensure that the sealing surface of the seal interface to remain stable within the liquid film, thereby reducing friction and heat. To improve the lubrication helps to reduce the surface wear, it can also reduce vibration inside the tiny seal parts.
The new proposed DHTW mechanical seals, the ideal laboratory test conditions in the leakage rate 300cm3 / h. Then multiplied by the value of the coefficient a 3 to 5, and stable operation of the pump used to calculate the actual leak. Usually the reasons for increasing pump leak associated with external factors, including vibration, instant Wo operational changes, but the seal design stage or in the laboratory test often can not take into account these factors.
Preliminary Design Department, the company first sealing solutions for the new first draft. In order to pump on these important mechanical seals used in a good old interchangeability, thus not Jihua right Beng's hardware modifications, Congerquebao the Wanquan of interchangeability. Once the preliminary design is complete, will use advanced computer modeling software to predict the mechanical properties of the sealing surface and thermal deformation and the expected value of seal leakage. Use for many years designing high-end mechanical seal parts experience, combined with applications over the years Gezhong experience of laboratory testing, Fox has developed a precise and reliable finite element analysis of Mo Xing. The accuracy and practicality of this model allows engineers in a relatively short period of time design used under harsh working conditions of mechanical seals.
Mechanical seals the surface under the influence of certain factors occur in various forms of distortion. Two main factors are caused by hydraulic pressure and temperature distortion. Hydraulic pressure will usually result in concave deformation, thus blocking the fluid film seal gap and seals the surface of the liquid will change the static pressure distribution. This situation will lead to friction within the sealing gap energy increases, changes in temperature distribution in turn lead to the opposite convex and concave deformation of thermal deformation. Between rotating and stationary seal gap sealing surface shape changes will result in changes in the shape of the liquid film. When the seal gap between the sealing surface shape change, the sealing surface between the liquid film width can be changed and will not change the leakage rate of sealing. Fox fine-tuning for specific operating conditions seals to ensure the curve within the mixed lubrication and hydrodynamic lubrication way to achieve stability on the border between the sealing operation. The curve illustrates the sealing surface and the coefficient of friction between the seal and the sealing surface spacing between, from left to right boundary lubrication, mixed lubrication and hydrodynamic lubrication. In the mixed lubrication and hydrodynamic lubrication of the border between f and h each curve corresponding Y coordinate values are relatively small, which is to ensure low friction coefficient and low seal leakage. Curve of this region in the run to ensure low friction coefficient and low seal leakage.
In production before the new mechanical seals, new solutions through a wide range of tested, using the real from the power plant to pump Lai simulation as realistic site conditions. Now developed a test plan to verify the new sealing solutions for all requirements under working conditions.
1. After a period of time to run the average leakage rate of 300cm3 / h;
2. No sealing surface, broken or in contact with the surface deformation of the sign;
3. Graphite sealing surfaces of constant wear rate of 25um / h.
Seal design testing and evaluation through 1000h to 300r/min.800 r/min.2000 r / min and 4400 r / min speed and 4Mpa sealing pressure test conditions, and the introduction of heat to simulate the seal from the pump to water. As the speed of sealing surface is the main cause of thermal deformation, and sometimes need to compromise in the design.
Low speed in 300r/min under seal to the surface of the test showed that the wear of graphite increased. In the joint review of the test results, that the need to increase the low speed under seal wear mitigation. Conclusion has been reached in laboratory conditions, the leakage rate of 500 cubic centimeters per hour.
After completion of laboratory testing, detailed measurement data, the introduction of new leakage rate, the surface components of the wear rate is very low. Using this design, seals will have expected life of eight theory.
The company also developed a detailed user seals the cooling system proposed amendments that Plan23. As the first seal at a relatively high temperature sealing cycle to run, so need to install new seals and efficient cooler, and replace the larger diameter pipe connected to lower flow resistance seal.
