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How to adjust and control the vibration of decanter centrifuge

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How to adjust and control the vibration of decanter centrifuge

Processing any equipment will definitely produce tolerances. The higher the processing accuracy, the smaller the tolerances, but the processing cost is greatly increased. The decanter centrifuge is designed to use a variety of knowledge to achieve a certain processing error, so that the decanter centrifuge's vibration is controlled within the normal range. However, if the user uses it improperly, it will destroy this design balance and cause serious accidents. Only when the working speed of the decanter centrifuge is not the critical speed, the rotor can move smoothly. For low-speed decanter centrifuges with a low working speed, the critical speed is generally increased as much as possible, so that the decanter centrifuge operates below the critical speed. The shaft of this decanter centrifuge is very thick and has high rigidity, which is called a rigid shaft. When the speed requirement is very high, reduce the critical speed as much as possible. The shaft is made thinner and the rigidity is small. It is called a flexible shaft. Modern decanter centrifuges all use flexible shafts.

The critical speed is related to the decanter centrifuge and the rotor used. A decanter centrifuge can be equipped with several kinds of rotors, so when designing a decanter centrifuge, the tolerance of the decanter centrifuge's vibration reduction design to various rotors should be considered. The working range of the decanter centrifuge is very wide, from several thousand revolutions/minute to tens of thousands revolutions/minute. The higher the rotation speed at which the decanter centrifuge vibration occurs, the greater the danger. Once the vibration occurs at high speed, the decanter centrifuge should be stopped at the fastest speed down gear, and all personnel should leave the scene quickly to avoid personal injury in the event of shaft breakage. Never cut off the power. Once the power is cut off, the brake (rapid deceleration) will be gone and the rotor will stall very slowly. Accidents are generally caused by improper operation of the decanter centrifuge, such as the rotor is not placed on the main shaft, the rotor cover is not covered, the swinging basket of the rotor is not placed, etc. Modern decanter centrifuges generally have unbalanced protection functions. That is, once the vibration of the rotor is greater than a certain size when the decanter centrifuge is started, the decanter centrifuge will automatically slow down and stop. The decanter centrifuge with this performance sometimes misses the report and cannot ensure that no accidents will occur.

Decanter centrifuge rotor machining errors and decanter centrifuge installation errors will cause the rotor centroid to deviate from the decanter centrifuge main shaft to varying degrees, therefore, vibrations will occur when the rotor rotates, and these vibrations will be inherent to the decanter centrifuge drive system at certain specific speeds The frequency resonates, causing strong vibration of the entire system. The speed at which this phenomenon occurs is called the critical speed. The rotor will cause vibration when rotating at high speed, but the flexible shaft has an "self-aligning effect". The principle of action is that the rotor produces a disk effect when rotating at high speed, and the elastic reaction force when the flexible shaft bends pulls the rotor that deviates from the geometric centerline of the main shaft back to the geometric centerline of the main shaft, and the vibration disappears. Of course, the amount of unbalance existing in the rotor at this time must also have a certain limit, beyond which the vibration will not disappear.

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Requirements of lubricating oil for decanter centrifuge

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During daily operation some wear will occur to the decanter centrifuge. So maintenance is imperative in order to extend the service life of the equipment. Lubricating oil must be used regularly. Below we introduce the precautions for adding lubricating oil to the decanter centrifuge.

The decanter centrifuge has two main components that need to be lubricated. One is the bearing and the other is the reducer. The bearing is greased, commonly known as butter; the reducer is lubricated, that is, gear oil. Butter is grease. One of the main quality indicators for evaluating grease is the freezing point. Freezing point is the maximum temperature when the oil is not flowing under the specified conditions. The freezing point of butter is higher than normal temperature. When the heating temperature exceeds the freezing point, it can melt and flow. The melted butter can lubricate the bearings, reduce the friction between the components, reduce wear, and have the effect of cooling.

Gear oil should have good abrasion resistance, load resistance and suitable viscosity. In addition, it should have good thermal oxidation stability, anti-foam resistance, water separation performance and anti-rust performance. Gear oil is a lubricating oil with excellent performance. Gear oil is a kind of important lubricating oil mainly composed of petroleum lubricating base oil or synthetic lubricating oil, which is added with extreme pressure anti-wear agent and oily agent.

1. The lubricating oil should have a certain stability. In the working environment of some decanter centrifuges, the temperature difference between day and night is large. If the oil is poor, it will cause the formation of a lubricating film, which will not play a lubricating role. In order to prevent the occurrence of fire, lubrication should also have flame resistance.

2. The selected lubricating oil should have certain thermal stability and oxidation resistance. Because the oil tank of the decanter centrifuge is small, the amount of lubricating oil is necessarily small. Moreover, the long-term operation of the decanter centrifuge will increase the temperature of the bearings and other parts, so the lubricating oil needs to be thermally stable.

3. The working environment of the decanter centrifuge will be contaminated by dust, moisture and other impurities. Therefore, there are requirements for lubrication such as anti-rust and anti-corrosion functions. When impurities are contaminated in the lubricating oil, its performance will not be greatly affected. It does not affect the normal operation of the equipment as standard. Butter is usually added once a shift, gear oil is added at least once a week, and needs to be replaced once a month. So as to meet the maintenance needs of decanter centrifuge.

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Common causes and solutions of decanter centrifuge vibration

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Common causes and solutions of decanter centrifuge vibration

 

If the vibration is too severe during the use of the decanter centrifuge, it will cause the fatigue damage of the drum in advance, the connection bolts will be loose and broken, and even the differential will separate from the drum, causing an accident and affecting the service life.

 

1. During the maintenance and assembly, the score lines of the drum are not aligned; the accuracy of the dynamic balance is destroyed. Solution: Realign the reticle.

2. The lubricating oil deteriorates. Solution: Replace as described in the instruction manual.

3. The main bearing fails. Solution: replace the bearing.

4. The inner ring of the main bearing loosely cooperates with the shaft. Solution: Repair or replace the end cap.

5. The screw conveyor bearing fails. Solution: replace the bearing.

6. The bolts of the liquid outlet and the slag outlet are not tightened or the pipes are rigidly connected. Solution: Tighten the bolts, and change the elastic flexible connection of the pipeline.

7. Loose flange head of the decanter centrifuge causes vibration of the differential. Solution: replace the flange head or used small end cover.

8. The differential is damaged (generally caused by lack of oil). Solution: replace the differential parts.

9. After the stop, the valve is not tightly closed and the material is fed, which causes the accumulation of material in the drum and the partial weight. Solution: wash in water, when the accumulation of material is serious, use the counter-clockwise steering wheel to drive the auxiliary pulley of the differential after stopping to discharge the material. After the accumulation of material is discharged, it can be put into use again.

10. The joints of rotating parts are loosely deformed. Solution: Check and repair.

11. The replacement of the new parts has a poor dynamic balance. Solution: adjust or replace.

12. The related parts are worn seriously. Solution: Replace and repair.

13. The material accumulated in the casing rubs against the outer drum. Solution: clean up or flush regularly.

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Rotating speed difference of decanter centrifuge

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The rotating speed of the decanter centrifuge drum can be adjusted steplessly in a relatively large range. By adjusting the rotating speed, the separation factor of the decanter centrifuge can be controlled to adapt to different mud requirements. Generally speaking, the larger the sludge particle and the greater the density, the lower the separation factor, and the higher the separation factor.

The initial settling sludge generally only needs a small α value to obtain a better dewatering effect. Although the digested sludge particles become smaller, due to the increased density, the required α value is basically equivalent to that of the primary sludge. The density of activated sludge is small, and the size of sludge particles is also small. To obtain a higher dewatering effect, a larger α value is required. The higher the SVI value of the activated sludge, the larger the required α value. The longer the sludge age, the larger the required α value. The activated sludge in the expanded state generally requires a high-speed decanter decanter centrifuge to dehydrate. The required α value of mixed sludge depends on the proportion of activated sludge. The higher the ratio of activated sludge, the greater the required α value. When the mud quality is unchanged, increasing the value of α can increase the recovery rate of dehydrated solids and improve the clarity of the separation liquid. As the value of α increases, energy consumption also rises, so unless a high solids recovery rate is required, an excessively high value of α is not required.

GN dewatering decanter centrifuge is P series decanter centrifuge with beach angle of 11 degrees. GN P series decanter centrifuge is usually used dewatering and thickening purpose. It is widely used for maximum dewatering requirements of municipal and industrial wastewater sludge. The dewatering decanter centrifuge is designed for easy separation material include large particle size, high density difference of solid and liquid, low viscosity, high concentration, high treatment capacity and higher dryness than clarity. The materials like sludge or wastewater containing fine particles usually need to be added with flocculants to gather the fine particles condensed into large ones, and then dewatered with P series decanter centrifuge.

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The use and value of manure processed by decanter centrifuge

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The first use of manure for electricity generation is relatively mature technology. Use cow dung to generate electricity and make substitutes for biogas and coal. For example, in dairy farms, the annual electricity generated by the fermentation of dried cow manure processed by a cow manure decanter centrifuge can save 1.2 million yuan in electricity costs. In addition, cow dung sticks and cow dung honeycomb coal can also be developed in a certain place. Cow dung sticks made of cow dung are used as fuel, and the combustion value is high. Cow dung honeycomb coal is compressed with cow dung and coal at a ratio of 4:6, which solves the problem of honeycomb coal. Pollution of the atmosphere. Solid-liquid separation equipment.

The second use of manure

    Manure can also grow Agaricus bisporus and straw mushrooms. The cow dung produced by the milk buffalo is used for biogas power generation. The produced biogas slurry can be made into liquid fertilizer, and the fertilizer is sold for more than 3,000 yuan a ton. The milk produced by milk buffalo is about 4 yuan, but the fertilizer can sell for 100 yuan. This shows that the use of cow dung can not only increase the economic income of cattle farmers, but also bring many economic and social benefits. In order to solve the problem of farming wastewater pollution and build an environment-friendly farming base, the company's leaders attach great importance to pollution control work, and entrusted our unit to design a plan for the fecal sewage solid-liquid separation treatment project. In order to complete this work with high quality, the decanter centrifuge.

    The dried cow dung dehydrated by the cow manure decanter centrifuge can also be used as feed for many animals. The cow manure contains minerals and various nutrients, including organic matter, total nitrogen, crude protein and other nutrients.

After the manure is processed by the decanter centrifuge, according to the similar project investigation and the information provided by the owner, the sewage mainly comes from cow urine and ground washing wastewater, and contains manure and urine.

According to the requirements of the owner, it is necessary to treat about 300 tons of manure sewage produced by 4000 cows every day, and the moisture content of the dried cow manure after treatment is about 60%-70%. The excrement processed by the decanter centrifuge can greatly increase the income of the enterprise, and truly turn waste into treasure.