Burner coal tar pump is a pump and motor together, together with the submerged pump work. Compared with the general horizontal or vertical sewage pump, the burner coal tar pump clearly has the following advantages: (1) compact structure, small footprint. As the submarine liquid work, the pump can be installed directly in the sewage tank, without the need to build a dedicated pump room to install the pump and motor, saving a lot of land and infrastructure costs. (2) easy installation and maintenance. Small burner coal tar pump can be freely placed, large coal tar pumps are generally equipped with automatic coupling device can be automatically installed, installation and maintenance is quite convenient. (3) continuous operation for a long time. Due to the coaxial pump and motor shaft, the short shaft and the light weight of the rotating parts, the load on the bearing (radial) is relatively small and the life expectancy is much longer than that of the normal pump. (4) small vibration and noise, low temperature motor, no pollution to the environment. It is because of the above advantages, the burner coal tar pump by people of all ages, the use of more and more wide range, from the original purely used to transport edible oil can now transport a variety of domestic sewage, industrial waste oil, construction sites row Oil, liquid feed and so on. In municipal engineering, industry, hospitals, buildings, restaurants, oil construction and other industries play an important role. 1, impeller and shell materials and conditions Ch/Product-33.html a sewage treatment plant with a burner coal tar pump 7 to 9 months, ZYB heavy oil coal tar pump operation The performance obviously decreased phenomenon, after disintegration found that the impeller damage is serious, while the entire part of the shell surface corrosion is not serious. Pump design parameters: speed 1450r / min, flow 200mVh, head 22m, power 22kW, impeller and shell material for the HT200, the measured chemical composition is shown in Table 1. Operating conditions when the working medium for domestic sewage, acidic microstrip; containing solid particles. 2, corrosion characteristics 2.1, the corrosion of the impeller The corrosion of coal tar pump impeller shown in Figure 1, only a few months to run the average wear depth of the impeller has reached 3-5mm, cavitation pits 4-6mm deep, 5mm short blade wear Above, the flow guide part of the impeller is seriously thinned and the amount of thinning is 2-4 mm. The scaly pattern and the honeycomb pattern interact on both sides. The front pattern is large and deep, the pattern on the back is small and shallow, and the direction of the scaly pattern points to the oil flow The direction of flow. A semicircular scour hole appears on the radial circumference of the impeller mouth ring. Impeller oil side of the blade and the diaphragm thinning, the edge was uneven blade. 2.2, shell corrosion Inside the shell there are impact wear ring groove marks, the original wall thickness of 8mm, thinning to 6mm after erosion, the damage is not very serious, but the impact of wear and tear at the entrance is more serious. In some places appear deep grooved stripes. Analysis of impeller failure From the macroscopic analysis, the impeller failure is the direct cause of serious thinning of the blade, through the impeller conditions and damage analysis shows that the cause of thinning of the blade is due to the emergence of a serious wear and tear Corrosion caused by the high-velocity oil in the solid particles of the grinding effect of accelerating the corrosion of the material surface, the impeller there is a clear grinding zone, impact zone and cavitation zone. Insulation asphalt pump due to the different parts of the impeller flow velocity and flow conditions, so the media on the impeller mechanical force is not the size and direction, resulting in uneven wear and tear on the surface morphology. In this main performance for the two forms of erosion and cavitation. 3.1. Effect of Solid Particles on Abrasion The solid particles in the sewage oil are the main reasons for accelerating the over-flow components of the coal tar pump in the combustor. The abrasion damage is caused by the relative velocity of oil flow and cavitation. Hard particles with a certain kinetic energy in the high-velocity solids-laden oil flow repeatedly wear and tear on the surface of the overcurrent component and wear and tear. The wear amount of the solid particles to the overcurrent component can be estimated by the following equation. From the above formula, The wear on the overcurrent component is mainly caused by the effect of the relative speed of the oil flow. Solid particles increase the incidence of cavitation and reduce the cavitation resistance. Firstly, the physico-chemical properties and fluidity of solid particles are different from that of clear oil. The viscosity of solids-laden oil flow decreases, the fracture resistance is poor, and the heat transfer oil pump increases the probability of cavitation. Second, the solid particles will be entrained with air bubbles in the oil to increase the vapor nucleation, the probability of cavitation increases. In addition, there is a significant difference between the mass and inertia of the solid particles and the oil. The trajectory of the solid particles deviates from the flow line of the oil stream to distort the flow field. Due to the additional velocity of the solid particles caused by the flow resistance and the inertial force, Whirlpool, causing local pressure decreases, increasing the probability of cavitation occurs. Cavitation pits can severely damage the smoothness of the surface of the overcurrent component and aggravate the wear of the solid particles. Domestic and foreign scholars have done a lot of experimental studies on the relationship between solid particles and cavitation. The simulation tests show that the cavitation strength of solid particle flow is 4-16 times of the cavitation strength of pure oil when the other conditions are the same, Pump in the oil and oil in the operating data analysis also confirmed this conclusion. In the guide part of the blade, the angle between the oil flow direction and the blade is less than 45 degrees, and the grinding effect is obvious. The characteristics of this region are that the blade is uniformly thinned, the fish-shaped stripes with a certain direction appear, and the furrow shape is smooth Stripe; at the tip of the impeller into the oil side of the blade, the oil flow direction and the metal surface angle greater than 45 degrees, the region characterized by the blade and the front cover the local material loss of the junction area, which is due to high solids Under the repeated impact of the particle oil flow, the weak part of the material will be firstly destroyed to form pores and pits, or the microcracks along the grain boundaries of some small flaky sand grains will expand along the grain and finally form the intergranular distribution The fatigue crack, causing the grain fatigue spalling, thus exacerbating the material loss. The edge of the blade is uneven blade, for three reasons: First, the high-speed movement of the impeller to the solid particles in the sewage thrown to the tail edge of the blade, ZYB-B adjustable pressure residue pump leaves the blade edge of the solid Particle concentration is greater than the average concentration; Second, the impeller at the tail of the line speed is greater, the test shows that the flow of solid particles relative to the impeller surface movement speed is higher, the more serious the loss of material; third is in this area by steam The effect of erosion further accelerates the wear and tear of the trailing region of the blade. 3.2, the impact of cavitation Cavitation area is located in the impeller vane outlet area of ​​the back oil side. This area sponge-shaped honeycomb, there are intensive horseshoe pit and long deep furrows, smooth pit wall, the top was blade-shaped. When the impeller turns at a high speed, a large number of small vacuum bubbles are generated due to the local negative pressure on the back of the blade. After the negative pressure is reduced, small bubbles annihilate and release energy, and some of the energy is directly transferred to the metal matrix while the other part is transferred to the solid particles. That part of the energy passed to the metal is continuously absorbed by the material to develop microcracks into fatigue cracks, which in turn cause the grains to loosen and fall off, forming early pocketed cavities. The microcracking of the material surface is mainly caused by the material's own defects, impacts and penetration of solid particles. The energy transferred to the solid particles accelerates the solid particles. Partially accelerated solid particles of the KCB gear pump impact or slide across the metal surface at various angles to form small-angle grinding and high-angle impact damage. The sand entering the cavitation pits The results showed that the cavitation pits were continuously enlarged and merged. The staggered two cavitation pits formed a blade-like structure at the top of the pits, and the inner wall of the cavitation pits was smooth. 4, improve the program From the above analysis shows that the main factor affecting the service life of the impeller is the design parameters of the impeller and materials. Without reducing the corrosion resistance of the impeller, it is the most effective way to prolong the service life of the impeller by improving the wear resistance and corrosion resistance and optimizing the design parameters of the impeller. (A) in the design, the solid particles on the flow surface of the wear process is a composite wear, that is, cutting wear and deformation wear exist at the same time, the total amount of wear: We can see from the above equation, the greater the speed, Small, then the total wear and tear greater, so in the design process, to ensure flow, lift the same circumstances, increased impeller inlet diameter, reduce the relative speed of oil flow, improve flow conditions, reduce turbulence and appropriate thickening The geometrical dimensions of the impeller front and rear covers. (B) is to improve the surface finish of the impeller to reduce the formation of cavitation and cavitation. (C) is the use of anti-wear materials with good corrosion resistance, wear and tear due to corrosion of metal materials is the result of wear and tear caused by mechanical forces and medium corrosion. Therefore, the use of both corrosion and wear-resistant materials will be an effective preventive measures, based on a comprehensive analysis, the choice of martensitic stainless steel 2Cr13, after quenching, high hardness, good corrosion resistance. (D) Epoxy diamond coating on the impeller surface protection, 3GR three screw pump epoxy resin, curing agent, toughening agent, thinner and filler mixing mortar, smear on the surface of the impeller and volute. Bottom and base metal knot strength 400 ~ 450kg / cm, the middle layer of tensile strength 130kg / cm2, compressive strength 500kg / cm2, shear strength 300kg / cm. Emery as adjuvant, epoxy resin as the main agent of the bonding material, and the wear resistance of emery better, so the combination of the two showed a strong adhesive force, oil resistance and anti-sediment wear resistance, and Has a strong impact resistance. 5. Conclusion According to this plan, after comprehensively reforming the coal tar pump of the burner, the whole impeller has no obvious corrosion after six months of operation and the effect is good. Only the protective coating on the surface of the impeller comes off, but it does not affect the normal use of the pump, Achieved the desired effect. In summary, YCB arc gear pump abrasion is mainly due to high-speed solid particle flow over-current components of the wear and tear damage, followed by cavitation and wear joint destruction. Therefore, the fundamental measure to prevent the abrasion of the pump is to try to reduce the relative velocity of the solid particle oil flow on the surface of the overcurrent component. Supplemented with the necessary anti-erosion material and protective coating, the effect is more obvious. For cavitation damage, this can be prevented by optimizing the oil design.
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