Is the grading accuracy of quartz sand screening equipment unqualified?
Professional manufacturers offer you accurate troubleshooting and solutions
In the production process of quartz sand, the screening equipment is
responsible for grading the crushed and sand-making materials according to the
particle size to produce finished products that meet the needs of different
industries (such as sand for glass manufacturing, sand for construction, and
electronic grade high-purity sand). The screening accuracy directly determines
the product quality. If the classification accuracy is not up to the standard,
it will not only cause the product to be "shoddy" and affect the sales, but also
increase the production cost and time cost due to rework of a large number of
non-conforming products. As a professional manufacturer engaged in the field of
quartz sand production equipment for many years, we have found in the practice
of a large number of projects that the problem of screening accuracy is not
caused by a single factor, which needs multi-dimensional troubleshooting from
material characteristics, equipment status, conveying and feeding system, etc.
The following will be elaborated for you.
Material property deviation: "natural deficiencies" affect the screening
effect
The raw material characteristics of quartz sand are the basic factors
affecting the screening accuracy. If the raw material is improperly pretreated,
it is difficult to make up for the fine subsequent screening.
Uneven particle size of raw materials: "hidden dangers" in crushing and
pretreatment
Problem performance: the particle size range of raw material is too wide, and
the fine particles (such as<0.1mm) and coarse particles (>1mm) are mixed
seriously, resulting in that the fine particles are easy to "bridge" in the
coarse particle gap during the screening process, blocking the screen mesh,
greatly reducing the screening efficiency, and the particle size deviation of
finished products is large. For example, a large amount of fine powder below
0.1mm and coarse particles above 0.8mm are mixed in the 0.3-0.5mm grain size
sand that should be screened.
Troubleshooting method: use a particle size analyzer to test the whole sample
of raw materials and draw a particle size distribution curve. If the peak width
of the curve is too wide (the normal particle size distribution of raw materials
should be relatively concentrated), or through the screen mesh number, screen
and test step by step, it is found that the proportion of a certain particle
size interval is far more than expected, and the particle size can be judged to
be uneven.
Solution: optimize the crushing process, and adopt the combination of
multi-stage crushing+fine screening. For example, use a jaw crusher for coarse
crushing, then use a cone crusher for medium crushing, and finally use a sand
making machine for fine crushing. Besides, add a vibrating screen between the
crushing links to timely screen the materials with qualified particle size, and
control the particle size of raw materials entering the screening equipment
within a narrow range; If existing equipment cannot be adjusted, a pre-screening
process may be added prior to sieving to remove oversize or undersize
particles.
Improper moisture content: too high or too low "add up"
Problem performance: when the moisture content of quartz sand is too high
(>8%), the particles are easy to be agglomerated and cannot pass through the
screen screen smoothly, resulting in serious blocking of the screen screen,
sudden reduction of the screening efficiency, and the particle size of the
agglomerated materials is uneven after screening; When the water content is too
low (<2%), the electrostatic effect of quartz sand particles will be
enhanced, and the quartz sand particles will be adsorbed and agglomerated
mutually, which will also affect the screening accuracy, and generate a large
amount of dust and pollute the working environment.
Troubleshooting method: check the moisture content of the material with a
fast moisture meter and compare it with the moisture content range (generally 4%
- 6%) required by normal production; Observe the material flow state during the
screening process. If the material "accumulates" and "slides slowly" on the
screen surface and the screen mesh has obvious adhesive, the water content is
probably too high; If the site is dusty and the material mobility is poor, the
moisture content may be too low.
Solution: when the moisture content is too high, add drying equipment (such
as roller drier), accurately adjust the drying temperature and time according to
the material output and moisture content, and reduce the moisture content to the
appropriate range; If the water content is too low, spray water for humidifying
before feeding (spray water evenly with atomizing nozzle to control the
humidifying amount), or install static eliminating device (such as ion air bar)
in the screening equipment to neutralize static electricity and improve the
material mobility.
Excessively cohesive material: impurities "tamper" with sieving
Problem performance: if the material contains clay, organic matter and other
cohesive impurities, during the screening process, these impurities will wrap
the quartz sand particles, so that the particles are mutually bonded to form
large particle aggregates, resulting in blocking of the screen mesh, reducing
the screening accuracy, and the content of impurities in the finished product
exceeds the standard. For example, the building sand is mixed with clay to
affect the strength, and the glass sand contains organic matter to affect the
transparency.
Troubleshooting method: carry out chemical analysis on materials and detect
the content of clay, organic matter and other cohesive impurities (ignition
method, chemical titration method, etc.); Observe the appearance of the
material. If there is obvious "caking" or "sticky" phenomenon, or there is
sticky attachments on the screen screen after screening, it can be preliminarily
judged that the cohesiveness is too strong.
Solution: pre-treatment process shall be added before screening, such as
"scrubbing+grading" process. Adhesive impurities on the surface of quartz sand
shall be removed by mechanical scrubbing, and then impurities and quartz sand
shall be separated by hydraulic classifier; For materials with high content of
cohesive impurities, add appropriate amount of dispersant (such as sodium
hexametaphosphate, add 0.1% - 0.3%) to reduce the surface tension of materials,
enhance particle dispersion and improve the screening effect.
Problems of the screening equipment itself: "chain off" of core components
and operating parameters
The screen state, installation accuracy and vibration parameters of the
screening equipment directly determine the screening capacity. Any deviation in
any loop will greatly reduce the grading accuracy.
Sieve aperture and abrasion: the screen is not accurate
Problem performance: Improper selection of screen aperture, such as too large
screen mesh (too small aperture), will lead to low material passing rate,
greatly reduced output, and part of qualified particle size materials are
wrongly screened; The screen screen is seriously worn after long-term use, the
aperture is enlarged or damaged, so that the large particle materials that
should be intercepted pass through the screen screen and mix into the qualified
products, resulting in particle size exceeding the standard. For example, the
aperture of the 0.5mm screen screen is expanded to 0.8mm after abrasion,
resulting in a large number of coarse particles mixed into the 0.3-0.5mm
finished sand.
Troubleshooting method: measure the mesh diameter with a standard mesh
diameter gauge and compare it with the equipment design requirements (the error
shall be controlled within ± 5%); Check the appearance of the screen regularly
for signs of wear such as breakage, deformation, wire-drawing, etc. Pay
particular attention to the edges of the screen and areas of frequent material
impact.
Solution: according to the grain size requirements of the produced quartz
sand, accurately select the mesh diameter. For example, for the production of
0.2-0.4mm quartz sand, select 40-70 mesh mesh; When the screen is slightly worn,
repair the damaged part with repair agent (such as wear-resistant rubber repair
agent); In case of serious abrasion, replace with a new screen with the same
specification in time, and ensure that the screen is flat without wrinkle and
deflection during installation.
Screen installation and tension: "loose and collapse"
Problem performance: the screen is not installed flatly, with folds,
depressions or bulges, and the materials flow unevenly on the screen surface,
which is easy to accumulate locally, resulting in incomplete screening; The
screen tension is insufficient and the screen shakes violently during operation,
which not only affects the screening accuracy, but also accelerates the wear of
the screen and shortens the service life. Meanwhile, the equipment vibrates
abnormally and generates large noise.
Troubleshooting method: Observe the material flow state on the surface of the
screen screen when the equipment is running. If the material appears "drift" and
"accumulation", the screen screen may not be installed flatly; Use the tension
tester to measure the screen tension (generally the tension shall reach
80-120N/cm). If the tension is lower than the standard, it means that the
tension is insufficient.
Solution: reinstall the screen, use special tools (such as screen strainer)
during installation, ensure that the screen is laid on the screen frame
smoothly, the edge is closely fitted with the screen frame, and firmly fixed
with bolts or clamps; Regulate the screen tension. Gradually increase the
tension to the standard range by adjusting the tension device (such as screw and
spring) on the screen frame. After installation, carry out the no-load test run
for 5-10 minutes to check whether the screen is stable.
Improper setting of equipment vibration parameters: low vibration
"misalignment" efficiency
Problem performance: the vibration frequency, amplitude and inclination of
the vibrating screen are not reasonable. If the vibration frequency is too high,
the materials stay on the screen surface for too short time, and the materials
are discharged before the screen is screened, resulting in insufficient
screening; If the vibration frequency is too low, the materials cannot be
effectively loosened and layered, which also affects the screening effect;
Excessive vibration will lead to fierce material fluctuation and "short circuit"
(materials will fall off the screen surface quickly and not be screened fully);
Too small amplitude makes it difficult for materials to pass through the screen;
Excessive inclination of screen surface, fast sliding speed of materials and
insufficient screening time; Too small inclination will cause material
accumulation and affect the screening efficiency.
Troubleshooting method: measure the vibration frequency and amplitude of the
equipment during operation with a vibration tester, and compare them with the
recommended values in the equipment specification; Measure the inclination of
the screen surface with a protractor (generally, the inclination of the straight
vibrating screen is 5 ° - 15 °, and the inclination of the round vibrating
screen is 15 ° - 25 °) to judge whether it is within a reasonable range.
Solution: According to the material characteristics and screening
requirements, optimize the vibration parameters by adjusting the angle of
eccentric block of the vibration motor (changing the amplitude) and the power
frequency (changing the vibration frequency), such as processing fine quartz
sand, appropriately reducing the amplitude and increasing the frequency; The
inclination angle of the screen surface shall be adjusted, and fine adjustment
shall be made gradually (1 ° - 2 ° each time) during the operation of the
equipment, and the material screening effect shall be observed until the optimum
state is reached. Generally, the optimal parameter combination shall be
determined through multiple tests.
Conveying and feeding system abnormality: "upstream" instability and
downstream disorder
The feeding state of the sieving equipment directly affects the sieving
accuracy. If the conveying and feeding system is faulty and the materials cannot
enter the sieving equipment evenly and stably, the sieving effect will be
affected.
Inadequate feed rate and uniformity: Difficult to screen "binge on
drinking"
Problem performance: the feeding speed is too fast, exceeding the processing
capacity of the screening equipment, the materials are piled too thick on the
screen surface, the bottom materials cannot contact the screen mesh, resulting
in incomplete screening, and a large number of qualified materials are
discharged with the unqualified products; The feeding speed is too slow, the
idling time of equipment is long, and the capacity is reduced; Uneven feeding,
"strip" and "block" distribution of materials on the screen surface, stacking of
materials in some areas, and idle screen in some areas, seriously affecting the
screening accuracy and efficiency.
Troubleshooting method: Observe the material flow rate at the outlet of the
feeder and compare it with the rated feeding capacity of the screening equipment
(which can be obtained through the equipment specification) to determine whether
the feeding speed is appropriate; A camera is installed above the feeding
opening of the screening equipment to observe the distribution of materials on
the screen surface. If the materials are not evenly distributed, local
accumulation or sparse areas can be clearly seen.
Solution: adjust the feeder parameters, such as the amplitude and frequency
of the vibrating feeder or the rotating speed of the belt conveyor, and control
the feeding speed to match the processing capacity of the screening equipment
(generally, the feeding capacity is 80% - 90% of the rated processing capacity
of the equipment); Optimize the structure of the feeder, and add a distributor
(such as a separating plate and a spreading roller) at the outlet of the feeder
to evenly disperse the materials into the screening equipment; At the same time,
automatic control system is installed to adjust the feeding speed in real time
according to the stacking height of materials in the screening equipment to
ensure stable feeding.
Unreasonable design of conveying system: material "churning" precision
reduction
Problem performance: in the conveying process of the conveying equipment, due
to the unreasonable slope and turning radius of the conveying belt, or the
conveying distance is too long, the material appears "gravity flow", "stacking"
and "caking" during the conveying process, and the material state is abnormal
when entering the screening equipment, affecting the screening accuracy;
Improper connection between conveying equipment and feeding port of screening
equipment, such as unmatched size and position deviation of feeding port,
resulting in material leakage, screen impact, screen damage and screening
effect.
Troubleshooting method: check the layout and structure of the conveying
equipment, and measure whether the gradient of the conveying belt (generally no
more than 15 °) and the turning radius (generally no less than 10 times of the
material particle size according to the material characteristics and conveying
speed) meet the requirements; Observe the flow state of materials on the
conveyor belt for abnormal accumulation and caking; Check the connection between
the conveying equipment and the feeding port of the screening equipment, and
check whether there is leakage or dislocation.
Solution: redesigning the layout of conveying equipment, adjusting the
gradient and turning radius of conveying belt to ensure stable conveying of
materials; Shorten the conveying distance and reduce the retention time and
turbulence of materials during conveying; Optimize the connection between the
conveying equipment and the feeding inlet of the screening equipment, adjust the
size and position of the feeding inlet, install the deflector, etc., so that the
materials can enter the screening equipment smoothly and accurately to avoid
leakage and impact.
Equipment maintenance and operation environment: "maintenance after tomorrow"
is indispensable
Screening accuracy will be affected by aging of parts, failure of control
system and temperature and humidity change of production environment after
long-term operation of screening equipment.
Equipment aging and component wear: "aging" is difficult to be accurate
Problem performance: after the equipment is used for a long time, the
vibration motor, bearing, screen frame and other parts are aging and worn, and
the power of the vibration motor is reduced, resulting in unstable vibration
frequency and amplitude; When the bearing is worn, the abnormal noise and
vibration increase during the operation of the equipment, affecting the
stability of the screen; Deformation of the screen frame will affect the
installation accuracy of the screen and reduce the screening accuracy.
Troubleshooting method: regularly check the appearance of each component of
the equipment, such as whether the vibration motor housing is overheated,
discolored or cracked, and whether the bearing is obviously worn or the
clearance is too large; Listen to the running sound of the equipment with a
stethoscope. If there is abnormal noise, the parts may be worn; Measure the
current and voltage of vibration motor and compare with the initial value of
equipment to judge whether the motor performance declines.
Solution: establish equipment maintenance plan, conduct comprehensive
inspection and maintenance on the equipment regularly (e.g. quarterly), and
replace aging and seriously worn parts in time. For example, after 2-3 years of
use of vibration motor, if the performance declines significantly, replace the
motor in time; Regularly add lubricating grease (high temperature and high load
resistant lubricating grease) to the bearing, and replace the bearing in case of
serious wear; When the screen frame is slightly deformed, mechanical correction
can be adopted; In case of serious deformation, replace with a new screen frame
to ensure stable operation of the equipment.
Control system failure: "command failure" upset
Problem performance: the automatic control system is faulty, such as the
sensor is damaged, the material flow and equipment vibration parameters cannot
be accurately detected, and the control system cannot adjust the feeding speed
and vibration parameters according to the actual situation; PLC controller
program error, equipment operation logic disorder, such as feeder and screening
equipment start and stop asynchronously, affecting production continuity and
screening accuracy.
Troubleshooting method: check the sensor data through the control system
operation interface. If the data is abnormal (such as 0 or far beyond the normal
range), the sensor fault can be determined; Check the fault indicator of PLC
controller. If the indicator is on, check the fault code inside the controller
and analyze the cause of program error.
Solution: replace the damaged sensor in time, select the sensor with reliable
quality and high accuracy, and calibrate it after installation; Contact the
technical personnel of the equipment manufacturer to check, repair or upgrade
the PLC controller program to ensure the stable operation of the control system;
Meanwhile, the control system shall be backed up regularly to prevent data loss.
In case of failure, it can be recovered quickly.
Impact of ambient temperature and humidity: "climate change" precision
disturbance
Problem performance: Under high temperature environment (> 35 ℃),
equipment parts (such as rubber screen and sealing elements) are easy to age and
deform, affecting screen tension and equipment tightness; Under low temperature
environment (< 0 ℃), the material mobility becomes worse, which is easy to
agglomerate, and the viscosity of equipment lubricating oil increases, affecting
the operation of bearing and other parts; When the humidity is high (> 70%),
the materials are easy to absorb moisture, the cohesiveness is enhanced, and the
screening is difficult; When the humidity is lower (<30%), the electrostatic
effect will be aggravated, which will also affect the screening accuracy.
Troubleshooting method: install temperature and humidity sensor in the
production workshop to monitor the environment temperature and humidity in real
time; Observe the operation status of equipment parts under different
environments, such as whether the screen is loose at high temperature, whether
the materials are caked at low temperature, and whether the screening effect
fluctuates when the humidity changes.
Solution: control the environment of the production workshop, install air
conditioners, dehumidifiers, humidifiers and other equipment, and control the
temperature within 15 ℃ - 30 ℃ and humidity within 40% - 60%; For equipment
design, materials resistant to high temperature, low temperature and moisture
shall be selected to make components, for example, metal screen shall be used to
replace rubber screen in high temperature environment; In the low temperature
environment, the equipment shall be insulated (such as wrapped with insulation
cotton), and the lubricating oil shall be heated or replaced with the
lubricating oil with good low temperature mobility; For humidity changes,
moisture removal or static elimination devices can be installed in the screening
equipment to improve the screening conditions.
As a professional quartz sand production equipment manufacturer, we not only
provide excellent quality screening equipment, but also provide customers with
full-cycle technical support. If your screening equipment fails to meet the
grading accuracy or other faults, please contact our 24-hour technical service
team at any time. We will help you quickly solve the problems and resume
production through remote diagnosis, on-site guidance, etc. At the same time, we
can provide personalized equipment upgrading and transformation scheme according
to your production needs and equipment operation conditions, further improve the
screening accuracy and production efficiency, and help you to stand out in the
quartz sand market competition.