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Reprinted from 512720510 at 11:35 on December 7, 2010 Reading (loading. ..) Comments (0) Category: Personal Diary
Chapter 2 shaker operating principle and operating parameters
present, linear vibrating screen is widely used in the mining industry, especially in the coal preparation plant, commonly used in the coal off the mud, dehydration, medium and screening operations, this paper describes the method for determining the kinetic parameters.
2.1 works
different linear vibrating screen to rotate by simultaneous dual-excitation imbalance vibrator, vibrator eccentric mass in the 2 groups m1 = m2, to synchronize the reverse operation. In the instantaneous position, the 2 groups along the centrifugal force generated by eccentric mass vibration direction of the force is always superimposed with each other, and in its normal, the component of centrifugal force always cancel each other to form a single direction of the exciting force, the screen box for reciprocating linear vibration. Trajectory to the horizontal screen box into a 45 °, the part of the vibration shaker part supported by the supporting device 4, under the action of the exciting force, the material in the screen surface as a continuous ramp up throwing, when the material is loose in the toss , met with the screen surface when the collision, the small particles through the sieve,
timberland kids, in order to achieve the classification of materials, dehydration, mud, off the purpose of referrals. Works shown in Figure 8.
Figure 8 Schematic diagram of the work
2.2 motion parameters
Kinematics
linear vibrating screen to determine kinematic parameters including the amplitude A,
timberland boots sale, frequency of vibration n, screen surface inclination angle α and the vibration direction of β, these parameters directly affect the linear shaker screening efficiency and processing power, it is necessary reasonable choice.
2.2.1 amplitude A
amplitude selected according to the material to be screened to select the size and nature. For the larger particle size materials, selection of larger amplitude; for fine-grained materials, smaller amplitude. Linear vibrating screen amplitude A = 3.5 ~ 6 mm.
2.2.2 screen surface angle α
screen surface and the horizontal angle between the screen surface is called angle. Screen surface angle and vibration sieve screening efficiency and capacity are closely related. With the increasing inclination of screen surface, the movement of materials in the sieve surface speed, along with increased capacity; but the material stays in the screen surface of shortening the time screening efficiency. Linear vibrating screen for more than 50 mm sieve materials is, α = 5 ~ 10 °; for the following 40 mm, the fine screening material when α = 0 °; for off mud, off medium, dehydration, α =- 5 ~ 0 °.
2.2.3 Vibration direction angle β
vibration direction line and the screen surface is called the angle between the direction of vibration of angle β. β is small and the material movement speed, high capacity, easy to screen for materials; β value of the large, slow movement of materials, adequate screening, suitable for difficult materials. The range of linear vibrating screen β = 30 ~ 60 °, for all domestic vibrating screen to take β = 45 °. This value is not only a good performance to adapt to a variety of screening, but also get the best speed and high productivity.
2.2.4 work to determine the frequency and amplitude of work
work to determine the frequency and amplitude of the shaker work process effect is usually determined by the vibration intensity, vibration intensity Once identified, we must choose the right amplitude and frequency. Typically used for grading operations generally use low-frequency vibrating screen large amplitude; for dehydration, medium should be used shaker operating frequency of small amplitude; for small particles of sticky wet screening operations of materials should be used in low frequency and large amplitude. Practice shows that the operating frequency vibrating screen not less than 700 r / min. Taking into account the different uses of different screen machine, screening machine to control the operating frequency of 800 ~ 900 r / min. When the vibration intensity of 4 and 4.5, the amplitude A screening machine in the distribution and frequency of n shown in Figure 9.
Figure 9 the amplitude and frequency allocation chart
2.2.5 vibration strength to determine
screen box
mechanical index is the largest ratio of acceleration and acceleration due to gravity, ie K = Aω2/gn. The value is an important indicator of that vibration intensity, K value greater the greater the mechanical dynamic load suffer more conducive to the improvement of process indicators, but high values will lead to a substantial increase in acceleration and inertial force, is bound to create screen machine the life of declining.
2.2.6 Vibration Angle and material along the screen surface speed
vibration direction angle determined from the speed of the material along the screen surface to consider, the best angle and direction of vibration on mechanical index. On a large hard or corrosive materials screening, orientation angle β should be large, fragile nature of the material orientation angle should be small. Generally take β = 35 ~ 50 °. General design of the shaker vibration direction angle is 45 °.
2.3 design
vibrating screen is a screen box, vibrator, support equipment and transmission components.
2.3.1 screen box structure
screen box is the main working parts screen machines, which support the vibrator, passing the exciting force, the material to withstand impact. Load characteristics required screen frame has sufficient strength, stiffness, and good dynamic performance. Large screen machine screen box is the main component side, strengthening the beam, side beam and the beam out of material. Side by block plate cutting, through the torsional shear type high strength bolts and bearings connected with the strengthening ribs, the side panels form a spatial network structure. The side without any seam, thus avoiding the thermal residual stress generated by processing. Including the installation of the drive beam beam vibrator and the next beam. Consider the connection with the vibrator and side, driver beams of the word thick steel plate welded duplex structure, with better mechanical properties. OC beam structure with good rigidity and are sealed in the above allocation of the Ministry of baffles, baffle and bolt hole is not sealed portions of beams to prevent the liquid into the sealed beam caused by corrosion, reduce machine life. Components into the overall design of longitudinal bracket without welding. Feed box lined on both sides of the surface and covered with screen box corrosion resistant materials to prevent wear and corrosion. Connection between the main components of torsional shear type high strength bolts are used.
2.3.2 vibrator
large vibrating screen with box-type vibrators, external eccentric selection of the overall structure, which has the advantage of light weight, compact structure, transmission parts lubricated concentrated, easy to guarantee the overall accuracy, anti-song performance, highest security. Box of high quality ductile iron, long life and very durable; to increase stability and reduce transmission of noise, using high-precision helical gear drive gear; to overcome the axial force of helical gears, bearings, double row with the import spherical roller bearings, bearings and reliable splash oil lubrication, bearing life can be greatly improved; in order to prevent oil spills box, sealed with a reliable seal double frame structure,
mens timberland boots, this device can work in harsh environments and from to protection; box using a special magnetic oil plug,
cheap timberland boots, inside the metal box is used to capture the fines; in operation, the vibrator can be easily adjusted on the eccentric weight block, according to the requirements of higher screen machines or more exciting force and low amplitude.
2.3.3 support device and the damping device
supporting device supporting device into the metal coil spring, rubber spring supporting the spring supporting device and composite device. Taking into account both a rubber composite spring linear spring,
timberland outlet, the spring resistance of the advantages of larger, but also with a metal coil spring load capacity advantages. Generally believed that the resonance zone in the past has low amplitude, no longer need dampers, its stability and carrying capacity than rubber spring, although higher than the natural frequency of the metal spring, but lower than the rubber spring, and have simple structure, the noise and low. Therefore determine the selection of composite spring supporting device.
2.3.4 transmission
screen machines with non-linear transmission device, the device is fixed in a cylindrical motor frame. Deceleration by the triangle belt motor, then the power transfer through the bearing to the vibrator, you can effectively compensate for vibration sieve and parking caused by radial resonance.
2.4 component material selection
main components of the choice of material in the coal preparation plant, vibrating screen cracking and breaking the beam side phenomenon, mostly caused by the stress concentration, there is the strength of the inadequacy, in addition, members of poor stability of materials also contributed to the Screen Machine one of the reasons of poor reliability. Therefore, the main components of the material shaker is not only a higher intensity,
timberland boots, more importantly, have a certain toughness and weldability, without any defects. The pressure vessel steel is such a 20g steel, due to its application in the manufacture of boilers and other pressure vessels, related to personal safety, it is also an absolute guarantee of the performance and stability. The main components of the sieve plate all with high quality boiler plate 20g. Small screen machines generally use Q235A steel, welding of the material is good.
2.5 screen machine dynamic performance test modal analysis
screen machine dynamic performance test modal analysis to further understand the dynamic performance of screening machines, large-scale mining on the vibrating screen prototype experimental modal analysis. 0 ~ 50 Hz bandwidth using the random vibration testing method, testing both sides of the structure of the static plate response Z direction, Z direction obtained on both sides of the frequency response curves plate (see Figure 10).
Z
Figure 10 side direction of the frequency response curve
frequency response curve can be seen through: one side order natural frequency of 4.0 Hz, the other order natural frequency of 23.4 Hz, while the screen machine working frequency of 14.2 Hz, natural frequency and frequency difference of 9.2 Hz This shows that the dynamic performance of screening machines better stiffness.
test test amplitude and vibrator shaker working temperature directly affect the reliability of the two indicators, in accordance with the a difference of not more than 0.75 mm, screen box symmetry points on both sides of plate should not exceed the difference between the amplitude of 0.5 mm; vibrator bearing maximum temperature should not exceed 75 ℃, the temperature rise should not exceed 45 ℃. After the screening mechanism SZKX4248 into its test run, the amplitude test the choice of site shown in Figure 11, the test values shown in Table 2.1.
Figure 11 tests the choice of site
Figure
amplitude of the test value
Table 2.1
measuring point
1
2
3
4
5
6
amplitude mm
4.6
4.7
4.5
4.5
4 .. 3
4.4
we can see from the data in Table 2.1, the amplitude of sieve machine both sides of the symmetry points difference 0 ~ 0.1 mm. Difference before and after the maximum amplitude of the ipsilateral 0.3 mm.
Chapter 3 the main parameters of the selection and calculation
3.1 shaker excitation force identification
exciting force P = MAω2
where M --- the part of the vibration of the shaker part of the quality,
A --- sieve working amplitude,
ω --- work sieve vibration frequency,
3.2 eccentric and quality determine the radius of gyration
turning radius and the eccentric block to determine the quality of the block under the eccentric shape and size shown in Figure 12, the manual can be found from the eccentricity
l = eYS = 38.179 (R3-r3) sinα (R2-r2) α
where R, r --- eccentric eccentric parts, the inner radius, mm;
α --- angle, usually taken α = 60 °.
single eccentric eccentric mass
m = 18Prω2
shaker amplitude can be adjusted to increase the use of the main eccentric way of weight plates, according to the actual needs of production, changes in weight plates to achieve a reasonable amplitude.
Figure 12 eccentric structure
3.3 Determination of excitation center
excitation center of the screen to determine the symmetry of the structure according to established perpendicular to the screen surface flat
surface coordinates, the origin of coordinates in the screen box, select the bottom left corner. Figure 13.
Figure 13 Calculation of excitation centers
coordinate system
x = Σ (Wi, xi) ΣWi
y = Σ (Wi, yi) ΣWi
where Wi --- i-weight of a component, N;
ΣWi --- i a component weight of the total, N.
the direction of the exciting force screen machines do not coincide with the screening machine but the overall center of gravity offset a certain distance, the actual center of gravity determined on the basis of the calculation based on the distribution characteristics of the material on the screen made the appropriate adjustments. The value of the size of the offset D are not included in detail, the screen unit offset D = 250 ~ 300 mm.
3.4 Calculation of screening materials production
Q = 3600BHVmρ
where Q ---- shaker output, t / h
H ------- shaker in the screening material thickness, m
Vm ------ material speed, m / s
3.5 vibrating motor power
vibration system power consumption mainly in the emphasis of the journal inertial force caused by friction on the damping and various other self-consumption and electrical consumption.
emphasis on inertia: p0 = Σm0ω2R; (1)
emphasis on consumption of friction power revolution: A = fp0πd; (2)
where, f-journal friction coefficient, usually 0.0025 ~ 0.01; d-main journal diameter (m).
vibrating motor power required N = KAn / (60 × 102) (kW) (3)
where, n-motor speed (r / min); K --- consider other power storage coefficient, often taking 1.2 to 1.5. N-type vibration motor with the power of choice. By (1) (2) (3), we can determine the vibration of the motor parameters required to select their models.
3.6 shaker in the spring selection
The total spring stiffness of isolation
:
Ky =
where m --- body mass, kg
Z ---- frequency ratio, Z = w / wn. usually taking = 3-5
wn --- natural frequency, y - vertical coordinate of the displacement, m
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