MEK workshop in Heilongjiang Petrochemical Plant heat pump P403, model CHZE100-250B, the transmission medium for the HTF. Leakage has always been an issue that we are striving to solve since it was started in 1998. Together with the well-known domestic manufacturers of bellows seals, such as Closure Seal, North Carbon Seal, and Positive Seal, a set of seals is installed to run continuously for the best continuous operation Month began to leak, the general 7,8 days began to smoke, a year down only a seal on the cost of a 160,000 yuan, plus relief pressure relief, the direct economic losses caused by leakage of more than 10 million, a serious threat MEK workshop safety and sanitation. After the structural analysis of the seal, it was found that the main problem lies in that the process medium (heat conducting oil) deposits carbon between the two friction end faces, partially leaks and accumulates outside the stationary seal ring. As time passes, Coking gradually increased, and finally static ring face contour, thus virtually changing the mechanical seal PV value caused by leakage. Chengdu Yitong Technology Co., Ltd. dry gas seal technology in the successful application of industrial pumps to solve this problem. The seal is the use of hydrodynamic principles, through the open end of the seal face dynamic pressure seal groove to achieve the non-contact operation of the seal face, therefore, the seal friction material is not limited by the PV value, compared with the mechanical seal, dry gas seal advantages: (1) long service life, stable and reliable operation. (2) The sealing power consumption is small, only about 5% of the contact seal. (3) Compared with other non-contact seals, dry gas seal gas leakage is small. (4) can achieve zero overflow of the medium, is an environmentally friendly seal. (5) seal auxiliary system is simple, reliable, use does not require maintenance. Dry gas seal structure principle shown in Figure 1, by the rotating ring, static ring, spring, ring, and spring seat and sleeve composition. Figure 2 is a dry gas seal rotating ring diagram. Fig.1 Schematic diagram of dry gas sealFig.2 Schematic diagram of dynamic pressure groove on dry gas seal face Rotary ring sealing surface is polished and polished, and hydrodynamic groove with special function is machined on it. Dry gas seal Rotating ring rotation, the seal gas is sucked into the dynamic pressure groove from the outer diameter towards the center of the radial direction toward the seal weir flow. Due to the throttling effect of the sealing weir, the gas entering the sealing surface is compressed and the pressure of the gas is increased, so that the sealing surface is pushed away by this pressure. The flowing gas forms a thin gas film between the two sealing surfaces It replaces the normal sealed liquid seal between the two films). According to the theory of gas dynamics, when the gap between two end faces of dry gas seal is 2 ~ 3mm, the gas flow layer through the gap is the most stable. Therefore, the thickness of gas film is generally selected to be about 3mm. When gas static pressure and spring force are formed When the closing force and the film reaction force are equal, the thickness of the film is very stable. Under normal conditions, the closing force (spring force and medium force) acting on the sealing surface is equal to the opening force (film reaction force), and the sealing work is in a stable working clearance. When subjected to external interference and the thickness of the gas film decreases, the gas film Reaction force increases, the opening force is greater than the closing force, forcing the sealing work to increase the gap back to normal. On the contrary, if the thickness of the seal film increases, the film reaction force decreases, the closing force is greater than the opening force, the sealing surface and interference return to normal, so long as within the design range, when the external interference disappears, the film thickness You can revert to the design value, so anti-pump ability is very strong. Therefore, the gas seal formed between the dry gas seal surface has a certain stiffness of the gas film, the greater the rigidity of the gas film, dry gas seal anti-pump (interference) the stronger the more stable and reliable seal operation. Dry gas seal performance is mainly reflected in the stability of the seal operation (that is, life) and seal the contradiction between the amount of leakage. The direct factor that affects the amount of dry gas seal leakage is the dry gas seal film thickness that is the working clearance formed between the seal faces during dry gas seal operation. 1, the structure parameters of the seal (1) hermetically sealed dynamic pressure groove shape, the logarithmic spiral groove produces the strongest hydrodynamic pressure effect, using it as the dry gas sealed dynamic pressure groove and the formation of the largest gas film stiffness, dry gas seal The best stability. (2) When the depth of dynamic pressure groove dry gas seal and the dynamic pressure groove depth of dry gas seal are the same order of magnitude as the gas film thickness, the rigidity of the sealed gas film is the largest. (3) the number of dynamic pressure sealed dry gas tank, dynamic pressure tank width, dynamic pressure tank length. 2, the operating parameters of the seal leakage (1) The larger the seal diameter, the higher the speed, the greater the speed of the seal ring, the greater the leakage of dry gas seal. (2) In the case of certain sealed working gap, the higher the sealing gas pressure, the greater the gas leakage. (3) The influence of the medium temperature on the seal leakage is due to the influence of temperature on the medium viscosity. The increase of the medium viscosity, the dynamic pressure effect and the increase of the film thickness increase the resistance to flow through the gap between the seal faces Temperature, medium viscosity on the seal leakage is not significant. Since the P403 retrofit started with a dry gas seal in October 2002, the pump was operating in a very stable condition with no leaks. The pump movement before and after the movement in Table 1. Table 1 before and after the transformation of the pump operating conditions can be seen from Table 1, only a power-saving, according to 300 days a year, saving about 120,000 yuan, although the higher requirements of clean nitrogen supply system increased costs (about 2 Million), but in comparison is negligible, part of the sealed nitrogen into the HTF system after venting, part of the direct discharge into the atmosphere, will not cause any air pollution, is a kind of environmentally friendly seal. Because this kind of seal replaces the traditional "liquid blockage" with "gas blockage", it requires relatively high gas pressure, the dry gas pressure is 0.2-0.3MPa higher than the pressure in the sealed chamber and the gas contains impurities less than 3μm , Sealed nitrogen is strictly prohibited interruption or less than the pressure in the sealed chamber and pump reverse operation, otherwise it will damage the sealing surface caused by leakage. 3. Conclusions The successful application of dry gas seal technology on this pump has provided a new way of high-quality and environment-friendly leak prevention for petrochemical systems, especially those with high requirements on toxic and harmful medium leakage, which not only save money but also reduce maintenance The frequency and labor intensity of workers are new technologies worth promoting.
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Product name |
Decorative embossed sandwich panels polyurethane sandwich panel/pu foam sandwich panel |
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Metal board |
0.0.3mm |
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Core material |
Hard Polyurethane foaming(for insulation) |
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Back layer |
Aluminum foil |
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Standard Size |
L3800*W380*H16(mm) |
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Packing Size |
L3850*W415*H135(mm) |
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Quantity |
8pcs /pkg or as you request |
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Length |
3000-6000mm(1000mm, MOQ>500sqm) |
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Weight |
3.7Kg/sqm |
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