1 Introduction
At present, the use of coal mining face drainage pump, the special row of sediment products is blank. Regardless of how much sediment, is still commonly used in the traditional multi-stage centrifugal water pump. Therefore, serious wear and tear, water pump prematurely scrapped, not only increases the cost, but also often directly affect the production schedule.
As the coal face and tunneling face can not be set separately sedimentation of the water silo, can not be on-site removal of sediment and other solid particles, so to solve the problem of "water pump" row of sediment, temporarily only in the Improve the material properties of wearing parts to think of a way, but also in the final change in the structure of a big fuss about the drainage pump. This area of professional research work, has continued for many years, is still in tension.
The study found that the 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 remedy, you can find the ideal solution.
2 Determination of solid weight ratio of water samples collected in working face
After observation, the coal mining face water, the content of solid particles with the recycling operation of the content changes, and therefore, has a cyclical.
In general, at the end of the pre-mining preparation, before the start of coal mining operations, the minimum content of solid particles. Coal mining operations near the end of the most content. In order to reduce both collection times and problems, a water sample may be collected within 30 minutes prior to full mining and 30 minutes before the end of the coal mining operation. The location of the water samples collected in the coal mining face under the head, or in the slipway installed drainage pump own separate outlet.
In general, in the rock roadway heading face water, the drilling of multiple drilling before concentrating, the least content of solid particles. After blasting, the solid particles are most abundant in the last third of the time of the rock formation. Water samples were collected in each of the two periods. Acquisition location in the rake or rock loader within 10m after the work site, or in the face of the drainage pump their own separate outlet.
The water samples collected above, each weighing 2K0.2kg. After weighing, the use of filtration, with filter paper filter out all the solid particles of water. After drying, weighed the weight of solid particles, the water sample solid weight (percentage) than Caw:
Solids weight
Cow = --------------- H%
Solid, liquid mixture of the total weight
The solid weight ratio of the water sample is defined as "weight ratio solid concentration" in Caw et al., "Transport of Water in Slurry and Granular Materials" (Feixiang Jun, Chinese University Press, May 1994) and is used to transport Industrial slurry. This article referred to as the solid weight ratio, the site is sometimes referred to as the sediment weight ratio.
Under normal circumstances, when a face of the gushing water is less than 10m3 / h, solid weight ratio Cow increased significantly; gushing water is greater than 80m3 / h, solid weight ratio Cw significantly reduced
In the same mine, in a marked coal, rock water samples collected in large quantities, we can get the mine gushing water in the general law of the content of solid particles. And then according to the amount of water, rock characteristics and fragmentation degree of loose particles after the reaction of water and other further analysis of finishing, they can be used to guide the drainage design and drainage management. Table 1 is a set of comprehensive data obtained from the field.
Table 1
Project coal face driving face
(Before the end of the coal mining operation) (before the end of the rock operation)
Solids weight ratio Cw 0.83-5.48% 0.41-9.62%
3 multi-stage centrifugal pump wear and wear processes
3.1 multi-stage centrifugal pump wear parts
At present, the mining of multi-stage centrifugal pump is the most serious wear and tear parts of the balance plate, and then followed by impeller mouth ring, packing sets, the middle of the shaft hole bushings.
General solid particles will not wear the pump casing, the outer diameter of the impeller will not wear small, will not wear the blade short. Balance disk wear thinning, so that the direction of the rotor to the motor (forward) of the amount of channeling beyond the limit, resulting in chain damage. Impeller ring and wear the middle sleeve, the seal gap becomes larger, so that the centrifugal pump water shortage or no water, and sometimes mixed with a strong vibration.
3.2 balance plate wear process
The balance plate has the axial end beating, the pump body also has the axial end beating. Rotation of the balance plate a week, will go to an angle, the local axial clearance of the maximum gap or minimum gap.
The equilibrium state of the balance disc is dynamic, and the rotor of the pump will be pulsed in axial direction 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.
The axial clearance b0 has a local dynamic maximum clearance b0max and a minimum clearance b0min after the axial end face runout and the axial pulsation are superimposed.
It is assumed that the particle diameter of a solid K is A, which has already reached the high pressure region in front of the balance disk with the liquid, and
B0max> A> b0min
The solid K will be entrained in the axial gap of the balance disc by the liquid from the vicinity of the axial maximum gap b0max.
When the solid K has just stepped into the smaller distance S, the balance disc is moved to a position where the axial clearance b0 is less than A or the balance disk is back to a position where the axial clearance b0 is less than A. At this time, the balance disk will squeeze the solid K, the two will occur relative motion. The end surface of the balance disc is squeezed out by the solid K and is scraped out of the groove until the solid K is pulverized.
If the specifications of the high content of solid particles, it will follow the trend of succession, has been wrapped in, so that the end surface of the balance disc soon the first annular groove. As the abrasion progresses, the second channel and the third channel will appear in a little more than the first annular groove.
Nevertheless, when the amount of pump shaft channeling has not changed significantly, remove the balance disc can see these annular groove is generally concentric, arranged neatly. At the same time, the balance plate also appears similar to the groove.
The following phenomenon is worth noting:
When the particle diameter of the other solid W is B, it also reaches the high pressure region of the balance disk
B?
The solid W will be blocked against the high pressure region side of the balance disk.
At this point, if the size of solid particles with the liquid continue to flock to the plate in front of the high pressure area, particle size less than or equal to A solid particles with the flow through the axial gap. Solid particles with a particle size greater than or equal to B will be segregated here. We call this phenomenon "screening phenomenon."
When the "screened" to reach a certain number of solid particles, and blocking the entrance in the axial gap, the liquid pressure will rise, causing the rotor back to the pulsation, the axial gap instantly increased. At this time, these large-particle size of a large number of solid particles squeezed into the axial clearance of the disc, a "strong landing phenomenon." If this occurs in succession, the balance disc can be ground in a relatively short period of time.
3.3 impeller ring wear process
Impeller small to the pump shaft, the mouth ring radial runout; pump mouth ring hole radial runout also exist. Impeller rotation of a week, will go to an angle, the local ring mouth gap occurs the maximum gap or minimum gap.
The rotating pump shaft will bend and deform, resulting in maximum deflection.
This radial runout and superposition of the maximum deflection, the radial gap b ring will have a local dynamic maximum gap bmin and minimum clearance bmin. Likewise, the sealing surface of the mouth ring is squeezed by the solid particles, scraping out the groove.
However, if the material is the same, because the mouth ring gap does not appear as the balance plate as "pulsation" and solid particles "strong landing phenomenon", so the wear ring was significantly less than the balance plate. At this time, the mouth ring wear and balance plate, not the main contradiction.
However, it should be noted that in the multi-stage pump to remove the balance plate, the wear ring will rise to the main contradiction, to be taken seriously.
4 Remove the sediment from the bottom of the drain line
Drainage pipes, especially the large diameter permanent pipelines borrowed at the bottom, will settle the solid particles. These pass through the repeated water down the solid particles settled down a larger proportion of the surface spherical, relatively smooth. When the above-mentioned centrifugal pump water shortage, the flow rate decreased, the flow rate in the pipeline slowed down, will increase the settlement of solid particles. If the centrifugal pump flow to a certain critical value, the settlement of the solid particles will be countercurrent down, through the valve, full of pump chamber, not tens of minutes, will make this pump scrapped. We can do this in the field, or in the laboratory to do a simulation test to verify this phenomenon.
To this end, to calculate the minimum flow rate of the flow pipe, the general should be greater than 1m / s. In order to improve the flow rate, should be preferred diameter smaller drain.
Take the piping installation of the desilting submersible pump as an example (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 at the lowest point of the pipe bottom, Sand tube. In addition to sand control with a gate valve 5, when the water content of solid particles are more in place in the underground emissions. Each of the emissions of about 0.2-0.3m3 can be. In this way, you can promptly remove the settling of solid particles in the drainage pipe, to prevent accidental wear of centrifugal pump.
Experience shows that the rock excavation, adhere to the regular discharge of sand during the rock operations, generally extend the service life of centrifugal pump about 3-10%, and the back of the pump there is overhaul value, or make the repair easier.
In the automated drainage, the same should be added regularly remove the bottom of the drainage pipe of the auxiliary equipment,
If with the collection of water samples, timely analysis, sorting information, you can develop a more scientific approach to the use of pump maintenance, to maximize the life of centrifugal pump. Of course, this measure is best used in the design stage has been adopted.
5 cancel the balance plate of the new sand submersible pump
With a multi-stage centrifugal pump directly conveying water containing solid particles of mine water, the main spear has focused on the balance of axial force. Therefore, to extend the service life of pumps, cancel the balance plate, (or cancel the balance drum), has become an inevitable trend.
5.1 choice of wear-resistant materials
According to different purposes, various types of pump parts using different wear-resistant materials. Clean water pump for longevity, wear-resistant material is copper alloy; sewage pump began 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 in the river sand, wear-resistant material is rubber. Visible, "wear-resistant materials," the definition of a wide range.
Research and development of multi-stage desilting pump, to deal with is the hardness, there are angular "sand", to study the sand in the high-pressure, high-speed state of the pump erosion laws. 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 large to small order: balance disc, impeller ring, packing sets, bushings, guide vane, pump, impeller. As a result, sand pump selection of wear-resistant materials have a reference and basis, can be obtained from the following tips:
5.1.1 A variety of wearing parts should be made of high quality materials with different hardness. Among them, the use of high-hardness materials easy to wear, wear parts with low hardness of the material. In this way, both to prevent the emergence of weak links, but also reduce the cost.
5.1.2 Cancel the balance plate with the highest hardness of the material. The highest hardness of the material can be applied - tungsten cobalt alloy used in the impeller ring and hub on the ring, in order to obtain the longest life, the best value for money.
5.2 cancel balance plate approach - to improve single-stage pump head, instead of multi-stage pump
To improve the single-stage pump head to replace the previous two-stage, three-stage multi-stage pump, simple.
In 1988, with the head 70m, flow 100m3 / h, power 37kw single-stage double suction desilting pump to achieve this desire. The pump for the Quaternary quicksand dry well design, and later for the northern winter coal preparation plant waste remote remote control recycling (3km away, with the old open-air sediment slime).
1989, with a head 50m, flow 12m3 / h, to allow through the solid particle diameter of 10mm, power is only 4.0kw single-stage single suction desilting pump again to achieve this aspiration. Since then, the impeller and the pump body inside and outside the mouth ring are made of cemented carbide. The first alternative multi-stage centrifugal pump in the heading face drainage, "life expectancy increased by 5-8 times" (extracted from the pump 1991 ministerial "new product identification certificate"). Substituted multi-stage centrifugal pump power as much as 40kw, its high-pressure water used to drive the jet pump (commonly known as pump, water pumping sub) in the downhill drainage. Therefore, this small pump quickly spread, and award-winning.
After hundreds of coal mines in different geological conditions across the country after ten years of on-site inspection, proved that the sand pumping submersible pump technology program is feasible.
At present, the single-stage desilting submersible pump varieties, use has been greatly expanded, such as:
① used in coal mining face, the technical parameters can be achieved: head 95m, flow 168m3 / h.
② used in the tunneling face, the technical parameters can be achieved: head 85m, flow 158m3 / h.
The efficiency can reach 62.1%. Motor power 75kw.
5.3 cancel the balance plate approach two - impeller back to back installation, offset axial force
Impeller number is even, every two impellers back to back installation, cancel each other axial force, is a good way to completely remove the balance plate.
In 1995, with a four-stage multi-stage sedimentation submersible pump to achieve this vision. This pump, once in Gansu in one fell swoop to restore a flooded mine. The groundwater permeability of the mine, carrying the northwest surface of the sand into the underground, repeated use of ordinary centrifugal pump recovery, were ineffective.
The pump technical parameters: head 200m, flow 80m3 / h, efficiency 59.3%, power 185kw. Today, through unremitting efforts, but also adds a number of practical techniques, almost the original design to do a reborn improvement. Technical parameters have been revised: head 320m, flow 80m3 / h, power 185kw.
5.4 Desulfurization submerged pump structure
The submersible pump is vertical, can be placed on the ground, but also hanging installation. Pump and motor coaxial, motor in the upper, the pump in the lower part (lower pump).
The main feature of the structure is that the motor is located in the "air chamber".
"Air chamber" like an open "cup." The "cup" cup bottom up, cup down, into the water fixed. At this time, the "cup" of the air will not run away. The motor stator, rotor and upper and lower bearing bearings in the "cup", and then
The motor shaft from the "cup" mouth down, this is the sand submersible pump motor model.
With the "air room" protection, the motor stator, rotor, bearings and shaft seals are not with water and sediment in the water, acid and alkali salts and other harmful substances in direct contact. As a result, the motor can not be damaged even when submerged in water containing large amounts of sediment. In addition, the motor windings are casted with heat-resistant epoxy to cure them for long-term adaptation to downhole environmental requirements.
Motor shell is covered in the "water guide sleeve", the pump discharge of water, all from the motor and the water between the sets of water flow, the motor to achieve the "water cold." Thus, the desilting submersible pump can be exposed to the water surface.
The desilting submersible pump has single-stage single-suction type, multi-stage single-suction type and single-stage double-suction type, which eliminates the shaft seal of pump shaft on the pump casing, This is because:
(1) single-stage single-suction impeller suction upward, the lower end of the pump is closed.
② multi-stage single-suction type of the first impeller in the top, the first impeller suction upward, the lower end of the pump is closed.
③ single-stage double-suction impeller has the upper and lower suction port.
Allow the water to run dry - no damage to the motor and pump body. There is water, you can continue to drain, no one has to wait. This request, from the coal mine line, from the Coal Branch of the Shanghai Branch of the General Hospital after the research, making the design of the sediment pump at the beginning of this valuable subject according to the research, with its unique structure, the first product When it was born to achieve. Factory, the idling test must be Taiwan, even 75kw, 185kw is not out.
In the coal mine is to modernization, mechanization and equipment of their own today, people have begun to imagine the drainage automation. Demand for "water tank" of the pump, the demand along the roof boring, drainage in the low roadway automatically pumps, the demand for explosive atmospheres in the use of large-scale desilting submersible pumps, and so on, the voice is getting higher and higher. Therefore, the research of "multi-stage desilting pump" has been paid more and more attention. Since the advent of desilting submersible pumps, many design units, large and medium-sized coal mines have to cooperate with the study, a bold attempt to make contributions to this new thing.
Keywords:mine centrifugal pump, conveying solid, canceling balance plate, desilting subme
