At present, the drainage pump used in the coal mining face, the special sediment discharge product is blank. No matter how much sediment, commonly used is still the traditional multi-stage sub-level centrifugal pump. Therefore, serious wear and tear, pump premature retirement, not only increased costs, but also often directly affect the production schedule.
As coal mining face and heading face can not be set separately sediment sediment silos, sand and other solid particles can not be removed in situ, so to solve the problem of using "clean water pump" sediment discharge, the only temporary To improve the performance of wearing parts to think of ways to achieve the final drastic changes in the structure of the drainage pump big fuss. Professional research work in this area has lasted for many years and is still under intense work.
The study found that solid particles on the centrifugal pump wear, in a particular environment, to comply with a certain law. To show this law in front of us, the right medicine, we can find a better solution.
1, the working face water samples collected solids weight ratio measured by the observation, coal mining surface gushing water, the content of solid particles with the recovery cycle changes in the content of the operation, therefore, has a cyclical nature.
Under normal circumstances, before the end of mining preparation, coal mining operations began, the least solid particles. Coal mining is about the end of the content. When collecting water samples, in order to reduce the number of acquisitions, but also to explain the problem, can be collected within 30 minutes before the official mining, mining once again within 30 minutes before the end of the mining operation. Collecting water samples at the coal mining face under the head, or in the slip-road installation of the pump's own separate outlet.
In general, in the gushing water of the rock drift driving face, the solid particles content is the least before the multiple drilling machines concentrate the drilling. After blasting, solid particles were the most abundant in the last third of rock-out operations. Water samples were collected during these two periods. The collection site is within 10m after the working site of the scraper or rock loader or the drainage outlet of the drain pump at the working surface.
The water samples collected above, each weighing 2kg ± 0.2kg. Weigh the weight, the use of filtration, filter out all the solid particles in the water sample with filter paper. After drying, weighed out the solid particle weight, then the water sample solid weight (percentage) Cow than:
Solid weight Cow = -------------------- H%
The solids weight ratio of the total heavy water sample of the solid and the liquid mixture, Cow, is defined as "the weight concentration of the solid concentration in the slurry and granular material transport hydraulics (Fei Xiangjun, Press University Press, May 1994) ", Used to convey industrial slurry. This article referred to as solid weight ratio, the scene sometimes used to call the sediment weight ratio.
Under normal circumstances, when the gushing water of a working face is less than 10m3 / h, the solid weight ratio is obviously increased; the gushing water is more than 80m3 / h, and the weight of solid is significantly reduced than Cow in the same mine. In a large number of water samples collected, we can get the mine gushing water solids in the general rule. According to the characteristics of gushing water, the characteristics of rock mass and degree of fragmentation, the reaction of loose particles with water, further analysis and sorting can be used to guide drainage design and drainage management. Table 1 is a comprehensive set of data obtained from the field.
Table 1
Project coal mining face heading face
Coal mining operations are about to end before the end of rock operations Solid Weight ratio Cow 0.83-5.48% 0.41-9.62%
2, the heart pump wear parts and wear process 2.1 multi-stage centrifugal pump wear parts At present, the mine wear the most serious parts of the multistage centrifugal pump balance plate, and then followed by the impeller mouth ring, packing sets, the middle of the shaft hole lining Set and so on.
General solid particles will not wear the pump casing, will not wear a small diameter wheel, it will not wear short leaves. Balance plate wear thinning, the rotor to the motor direction (forward) channeling overrun, resulting in chain damage. After the impeller mouth ring and middle sleeve wear, the sealing gap becomes larger, so that insufficient or no centrifugal pump water, and sometimes mixed with a strong vibration.
2.2 Balance plate wear process Balance plate with axial end beating, pump body balance plate also has axial end beating. Balance plate rotation for a week, will turn to a certain angle, the local maximum axial clearance gap or minimum clearance. The equilibrium state of the balance disc is dynamic, and the pump rotor pulsates axially before and after a certain equilibrium position. When the operating point changes, the rotor will automatically move to a new equilibrium position for axial pulsation. After the axial end face beating and axial pulsation superposition, the axial clearance b0 has the local dynamic maximum clearance b0max and the minimum clearance b0min.
Assuming that the particle diameter of a solid K is A, the solid K will be entrained by the liquid in the axial direction of the balance disc from near the maximum axial clearance b0max as the liquid reaches the high pressure zone in front of the balance disc, and b0max> A> b0min Within the gap. When the solid K has just stepped over a small distance S, the balance disc is shifted to the position where the axial clearance b0 is smaller than A, or the balance disc is being pushed back to a position where the axial clearance b0 is smaller than A. FIG. At this time, the balance plate will squeeze the solid K, the two will be relative movement. The balance disk end will be pushed out of the indentation by the solid K and will be scraped out of the recess until the solid K is ground. If the specifications of the high content of solid particles, will be in line with the trend of the past, continue to be wrapped in, so that balance plate soon appear the first ring groove. As the abrasion aggravates, the second trench and the third trench will appear one after another slightly larger than the first annular trench.
In spite of this, when the pump shaft channeling amount has not changed significantly, remove the balance disc can be seen that these annular grooves are generally concentric, arranged neatly. At the same time, a similar groove appears in the balance board.
The following phenomenon is noteworthy:
When the particle diameter of the other solid W is B, also reaching the high pressure zone of the balancing disc, and B≥b0max, the solid W will be blocked on the high pressure zone side of the balancing disc. At this moment, if the solid particles of different sizes are flocking to the high pressure zone in front of the balance disc, solid particles with a particle diameter of less than or equal to A will flow through the axial gap with the liquid flow. Solid particles with a diameter greater than or equal to B will be separated here. We call this phenomenon "sieving phenomenon."
When a certain amount of solid particles are "screened" and blocked at the entrance to the axial gap, the pressure of the liquid will increase, causing the rotor to pulsate backward, causing the axial gap to increase momentarily. At this time, these large particles of solid particles took the opportunity to squeeze into the balance plate axial clearance, a "strong landing phenomenon." If this happens one after another, the balance pan can be thinned in a short period of time.
2.3 The wear process of the impeller mouth ring Small impeller mounted to the pump shaft, the radial existence of its mouth ring beating; pump mouth ring hole radial runout also exists. Impeller rotation a week, will turn to a certain angle, the local mouth ring radial gap maximum gap or minimum clearance. Rotating shaft will bend, resulting in maximum deflection. After the radial runout and the maximum deflection are superimposed, the radial clearance b of the mouth ring has a local maximum dynamic clearance bmax and a minimum clearance bmin. Similarly, the sealing surface of the mouth ring will also be squeezed by the solid particles, scraping out of the groove. However, if the material is the same, the wear of the collar is significantly less than that of the balance disc because the mouth ring gap does not "pulsate" like the balance disc and "strong landing" of the solid particles. At this moment, the wear of the mouth ring is not the main contradiction compared with the balance disc. However, it should be noted that in a multi-stage pump with unbalanced discs, wear of the orbital ring will rise as the main contradiction and must be taken seriously.
3, clear the drain at the bottom of the sediment
Drainage pipes, especially the bottom of large diameter permanent pipes that are borrowed separately, will settle solid particles. The diameter of these solid particles after repeated sedimentation of water than the larger, spherical surface, more smooth. When the above mentioned centrifugal pump insufficient water, the flow decreased, the flow velocity slowed down, will increase the settlement of solid particles. If the flow of the centrifugal pump is reduced to a certain critical value, the settling solid particles will flow countercurrently down through the valve and fill the pump chamber, which will void the pump in less than a few minutes. We can test it in the field or do a simulation test in the laboratory to verify this phenomenon. To this end, the minimum flow rate to be calculated when the flow rate value within the pipe, the general should be greater than 1m / s To increase the flow rate, should be preferred to use smaller diameter pipes.
Taking the example of pipe installation of a submersible submersible pump (see Figure 1), a short pipe can be connected to the pipe between the check valve 1 and the gate valve 4 of the centrifugal pump or to the lowest point on the bottom of the pipe - except Sand tube. The desilting pipe is controlled by another gate valve 5, which discharges underground in the well when there is a large amount of solid particles in the water. Each discharge of about 0.2-0.3m3 can be. In this way, you can promptly remove the settlement of solid particles in the drainage pipe to prevent accidental wear and tear centrifugal pump.
Experience has shown that rock excavation, insisted on regular discharge of sediment during rock out operations, generally extend the service life of centrifugal pumps about 3-10%, and make the pump out there overhaul value, or make overhaul easier.
In the automatic drainage, the same should be added regularly remove the bottom of the drain sediment auxiliary equipment, if with the collection of water samples, timely analysis, finishing information, we can develop a more scientific use of the pump maintenance methods to maximize the extension of the centrifugal pump life. Of course, this measure is best used at the design stage.
4, to cancel the balance plate of the new sediment submersible pump with multi-stage centrifugal pump centrifugal water directly transported with solid particles of mine water, the main spear has focused on the balance of axial force. Therefore, to extend the life of the pump, cancel the balance disc, or cancel the balance drum), has become an inevitable trend.
4.1 Selection of wear-resistant materials Depending on the application, all kinds of pump parts with different wear-resistant materials. Clean water pump for long life, wear-resistant material is copper alloy; sewage pump starting in the discharge pulp, wear-resistant material is only ordinary cast iron. Slurry pump is a single-stage pump, wear-resistant material is high chromium cast iron; sand pump sand in the river, wear-resistant material is rubber. Visible, "wear-resistant materials," the definition of a wide range.
Research and development of multi-stage sediment pumps, to deal with is the hardness, angled "sand", to study the sand in high pressure, high-speed state of the law of pump erosion. Therefore, the choice of "wear-resistant material" is even more important.
The following parts of the same material, according to the degree of damage from big to small order: balance disc, impeller mouth ring, packing sets, bushings, vanes, pump body, impeller. Thus, sand pump selection of wear-resistant materials have learned and based on which you can get the following tips:
4.1.1 All kinds of wearing parts should use high-quality materials with different hardness. Among them, easy to wear the use of high hardness of the material, easy to wear parts with low hardness materials. In this way, both to prevent weaknesses, but also reduce costs.
4.1.2 Cancel the balance plate with the highest material hardness. To the highest hardness of the material can be used at present - tungsten cobalt carbide used in the impeller lip and sleeve, in order to obtain the longest service life, the best value for money.
4.2 to cancel one of the balance plate approach - to improve the single-stage pump head, instead of multi-stage pump to improve the single-stage pump lift to replace the previous two-stage, three-stage multi-stage pump, simple and easy.
In 1988, with a head 70m, flow 100m3 / h, power 37kw single-stage double-suction suds submersible pump to achieve this desire. The pump is designed for quarrying of Quaternary sediment and then used for remote remote control recycling of coal washery wastewater in the northern North China in winter (3 km away from the old open-air sediment slime).
In 1989, this was achieved again with a single-stage single suction sump submersible pump with a lift of 50 m and a flow rate of 12 m 3 / h, which allowed passage through a solid particle with a diameter of 10 mm and a power of only 4.0 kW. Since then, both the impeller and the inner and outer rings of the pump body have been made of cemented carbide. The first alternative to multistage centrifugal pumps in the tunnel excavation face drainage, "life expectancy 5-8 times" (excerpt from the pump 1991 ministerial level "new product certification certificate"). Multistage centrifugal pump was replaced as much as 40kw, its high-pressure water is used to drive the jet pump (commonly known as pump, water pumping) in the downhill drainage. As a result, this small pump is rapidly gaining popularity and has won numerous awards.
Hundreds of coal mines with different geological conditions across the country have been tested on site for 10 years, proving that this type of technical solution for submersible submersible pumps is feasible.
At present, single-stage sediment submersible pump varieties, uses have been greatly expanded, such as:
① used in coal mining face, the technical parameters can be reached: head 95m, flow 168m3 / h.
② used in driving face, technical parameters can be reached: head 85m, flow 158m3 / h.
Efficiency can reach 62.1%. Motor power 75kw.
4.3 Cancel balance plate approach two - impeller mounted back to back, offset the axial force The number of impeller is even, each two impeller mounted back to back, offset each other axial force, is a good way to completely cancel the balance disc.
In 1995, a four-stage multi-stage submersible submersible pump to achieve this idea. This pump, once in Gansu, recovered a flooded mine. The mine ground permeable, carrying the Northwest surface sediment into the well, many times with the ordinary centrifugal pump recovery, did not work.
The pump technical parameters: Head 200m, flow 80m3 / h, efficiency 59.3%, power 185kw. Nowadays, through unremitting efforts, it has added a number of practical techniques to improve the original design almost completely. Technical parameters have been revised as: head 320m, flow 80m3 / h, power 185kw.
4.4 Sediment submersible pump structure Introduction The above sand submersible pump is vertical, can be placed in place, but also hanging installation. Pump and motor coaxial, the motor in the upper part of the pump in the lower (under the pump).
Drainage submersible pump structure of the main features are:
a, the motor placed in the "air room" in the "air room" like an open "teacup." The "cup" bottom of the cup up, cup mouth down, into the water fixed. At this time, the "cup" of the air will not run away. Place the motor stator, rotor, and upper and lower bearing supports in the "teacup" in advance, and then extend the motor shaft downward from the "cup" port. This is the motor model for the submersible pump. With the "air chamber" protection, the motor stator, rotor, bearings and shaft seals are not in direct contact with water and sediment, acid and alkali salts and other harmful substances. Therefore, the motor will not be damaged even if it is submerged in water with a large amount of sediment. In addition, the motor windings with heat-resistant epoxy casting, curing it for long-term adapt to the underground environment requirements Motor cover is shrouded in the "water guide sleeve", the pump discharge water, all from between the motor and the water guide sleeve, Motor to achieve a "water cooler." In this way, sand submersible pump can be exposed surface work.
The above-mentioned sediment submersible pump single-stage single-suction, multi-stage single-suction, single-stage double-suction three forms, eliminating the need for pump shaft casing in the pump important wearing parts - shaft seal, This is because:
① single-stage single suction impeller suction upward, the lower end of the pump is closed.
② multi-stage single suction head impeller at the top, the first stage impeller suction upward, the lower end of the pump is closed.
③ single-stage double-suction impeller has two suction ports.
b, to allow water to spin - will not have any damage to the motor and pump body.
With water, you can continue to drain, without someone waiting. This requirement, from the coal mine line, made by the Shanghai Branch of Coal Research Institute made after making the design of the submersible sand pump at the beginning of this valuable subject to tackle key issues, with its unique structure, in the first product It was born. When leaving the factory, idling test must be made in Taiwan, even 75kw, 185kw nor out.
In coal mines are modern, mechanized and equipped themselves today, people have begun to imagine the drainage automation. Demand for "water tank" pump, the demand along the roof dredging, automatic drainage in the low waterway pump, demand in the explosive environment of the use of large-scale desilting submersible pumps, and so on, louder and louder. Therefore, "multi-stage sediment pump" research has received widespread attention. Since the advent of submersible submersible pumps, many design institutes, large and medium-sized coal mines have worked together to make bold attempts to contribute to this new life.
Single-stage, multi-stage "submersible sand pump" and horizontal multistage "sand discharge centrifugal pump" structure, technical parameters and on-site feedback information and other details, the future will be introduced to the reader.
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