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What Is Bag House Filter 【How Does Bag Filter Work】

Views: 39     Author: Site Editor     Publish Time: 2021-10-10      Origin: Site


What is bag house filter


Bag filter is a kind of multi-purpose filter equipment with novel structure, small size, simple and flexible operation, energy saving, high efficiency, airtight work and strong applicability. Bag filter is a new type of filtration system. Inside the bag filter, the filter bag is supported by a metal mesh basket. The liquid flows in from the inlet and flows out from the outlet after being filtered by the filter bag. The impurities are intercepted in the filter bag and can be used continuously after replacing the filter bag.


Structure and working principle


The bag filter is a pressure filter device, which mainly consists of a filter cylinder, a filter cylinder cover, a quick opening mechanism, and a stainless steel filter bag reinforcement net. The filtrate flows into the filter bag from the side inlet pipe of the filter housing. The filter bag itself is installed in the reinforced mesh basket. The qualified filtrate can be obtained when the liquid penetrates the filter bag of the required fineness level, and the impurity particles are intercepted by the filter bag. This machine is very convenient to replace the filter bag, and the filter basically has no material consumption.


The bag filter has many advantages such as reasonable structure, good sealing, strong circulation ability, and easy operation. In particular, the probability of side leakage of the filter bag is small, the filter accuracy can be correctly guaranteed, and the filter bag can be quickly changed, which reduces the operating cost. The inner and outer surfaces of the filter are solved by mechanical sandblasting and polishing, which is average and easy to clean. We know that the filtering method adopted by the bag filter is a side-in-side-out method, or a side-in-bottom-out method. The filtered liquid medium is pressed or drawn into the bag filter barrel through the pressure in the pipeline. , The liquid medium to be filtered is filtered by the filter bag supported by the filter basket through the electro-polishing punching hole, and the changed solid and liquid reach the result of the liquid medium being filtered.


The structural design of the bag filter is that the top cover and the filter cartridge are sealed and locked by four sets of pendulum-type eye bolts, so that the filter can withstand extremely high filtration pressure and water hammer pressure impact. The bag filter is composed of a filter cartridge, a filter basket, and a filter bag. The structure is compact and simple; the liquid to be filtered enters through the inlet of the filter, flows into the filter bag, and flows out from the outlet of the filter after being intercepted by the filter bag . The inlet and outlet design of the bag filter generally adopts a side-in and bottom-out method, which is convenient for cleaning.


product category


There are several types of bag filters:single-bag filters, multi-bag filters, rocker-arm bag filters, high-precision bag filters, etc. The filter accuracy is in the range of 1-10 microns.


main advantage


1) The probability of side leakage of the filter bag is small, which effectively guarantees the filtering quality.

2) The bag filter can bear greater working pressure, with small pressure loss, low operating cost, and obvious energy saving effect.

3) The filter accuracy of the filter bag has been continuously improved and has reached 0.5μm.

4) The bag filter has large processing capacity, small volume and large dirt holding capacity.

5) Based on the working principle and structure of the bag filter system, it is convenient and quick to replace the filter bag, and the filter is free of cleaning, saving labor and time.

6) The filter bag can be used repeatedly after cleaning, saving cost.

7) The bag filter has a wide range of applications, flexible use and various installation methods.


Filter operation and precautions


The bag filter is easy to operate. When using, you only need to install the filter bag of the required fineness level in the filter cartridge, check whether the O-ring is intact, and then tighten the ring bolt of the filter cartridge cover, and then it can be put into work. After the pump is started, the pressure gauge on the filter rises slightly, and the initial pressure is about 0.05MPa. With the extension of use time, the filter residue in the cylinder gradually increases. When the pressure reaches 0.4MPa, the cylinder cover should be shut down and the filter bag should be checked for residue. In case, the filter bag can be replaced and used continuously (the filter bag can generally be reused by cleaning). The pressure of the filter is generally adjusted to 0.1-0.3MPa, which can be adjusted through the return line or the return valve on the pump. Excessive filtration pressure will damage the filter bag and the protection net, so special attention should be paid. Main uses: paint, beer, vegetable oil, medicine, chemicals, petroleum products, textile chemicals, photosensitive chemicals, electroplating solution, milk, mineral water, hot solvent, latex, industrial water, sugar water, resin, ink, industrial wastewater, fruit juice , Edible oil, wax, etc. There are many industrial chains in China, the industry’s low concentration of production, low R&D capabilities for high-end products, and low manufacturing technology in the bag filter industry still exist. The import and export trade deficit continues to expand. This high-speed shock is directly brought about The consequence is the expansion of the polarization in the brand camp.


1. Daily use


In the entire wire harness automation equipment industry, we need to know how to use these devices. For example, we need to know how to use the automatic computer wire stripping machine when stripping the wires, and how to use the automatic wire cutting stripping and crimping machine when processing the wire terminal.. The filter system at work needs to check the pressure difference between the inlet and outlet frequently. When the pressure difference reaches 0.05-0.1Mpa, the filter bag should be replaced in time to prevent the filter bag from rupturing and the support net from being damaged.


2. Correctly open the filter cover after filtering


Warning: Do not open the cover under pressure in the bag filter, otherwise the remaining liquid may spray out and cause liquid loss and personal injury.

Therefore, please operate strictly in the following order:

1) Close the input valve; when there is pressure at the outlet, close the output valve.

2) After confirming that the pipe connected to the exhaust valve has been connected to a safe place or the suction port (especially pay attention when filtering toxic and corrosive liquids), then open the exhaust valve to prevent the liquid from causing damage to the staff and the surrounding environment. Pollution.

3) Check the pressure gauge to make sure that the internal pressure is 0. At this time, the bag filter should have been separated from the pipeline system.

4) If there is a drain valve, confirm that the drained liquid is connected to the recovery point and open the drain valve; when the remaining liquid in the bag filter is drained through the drain valve, close the drain valve. This discharge can be completed with pressurization (please refer to the pressurized discharge process).

5) Unscrew the upper cover lifting cap, lift the upper cover, the multi-bag filter needs to be rotated through a certain angle.


Third, replace the filter bag


1) The high efficiency filter bag is made of fine fibers, and the hydrophilicity of these materials is relatively weak. The surface of the fiber will not be wetted by water, so like other filter elements that use the same material, they must be wetted with some other liquid with a lower surface tension before use. Before installation, you must immerse the filter bag in a pre-wet liquid that matches the filtered liquid for a few minutes.

2) Make sure to open the upper cover of the bag filter.

3) Put the upper cover firmly and take out the filter bag carefully.

4) Put in a new filter bag, please refer to the installation process.


Fourth, monitor the filtering quality


When the liquid input pressure is stable, the filtering quality is closely related to the pressure difference in the filter bag. If the pressure difference is too large, it means that the filter pore size of the filter bag has been blocked and the filtering speed has dropped. Therefore, we recommend that when the bag filter starts to work, the pressure difference should be checked regularly, and the time to replace the filter bag is determined by the pressure difference displayed by the front and rear pressure gauges. Generally, the filter bag can withstand a pressure of 0.5-1Kg/cm2 (0.05- 0.1Mpa). When the pressure difference reaches this range, the filter bag should be replaced in time to avoid the filter bag rupture and affect the filtering effect.

If the pressure difference drops suddenly, stop filtering immediately and check for leaks.


Five, pressurized discharge of residual liquid


When filtering high-viscosity liquids, compressed air can be introduced through the exhaust valve to accelerate the discharge of residual liquid and shorten the waiting time. Please note: The air used for pressurized discharge must be stable, and the pressure should not exceed the working pressure of the filter.


The operation steps are as follows:


1) Close the input valve.

2) Open the intake valve.

3) The gas is introduced into the bag filter, and the remaining liquid is drained under pressure.

4) Check the outlet pressure gauge to confirm that the gauge pressure is equal to the compressed air pressure; confirm that there is no liquid flowing out of the outlet.

5) Close the intake valve.

6) Open the exhaust valve slowly; residual liquid is sprayed from the outlet of the exhaust valve, which must be led to a safe place or the suction port of the filter.

7) After the compressed air is exhausted, close the exhaust valve. At this time, there should be no pressure inside the filter and the cover can be opened.


Six, cleaning bag filter


If the Shanghai Runhe bag filter continues to filter the same liquid, it does not need to be cleaned. But if you filter other types of liquid, you need to clean the machine before using it.


Seven, maintenance and replacement of O type sealing ring


Maintenance: When in use, the O-shaped sealing ring should be aligned with the O-shaped groove and put into it to avoid improper squeezing of the O-shaped sealing ring; when it is not filtered, the O-shaped sealing ring must be taken out and wiped clean, otherwise the residual liquid will adhere to it after solidification. The surface hardens and the sealing performance is deteriorated.

Replacement: If the O type sealing ring is aging or damaged, please replace it in time. When replacing, choose the same type of O type sealing ring.

Special statement:

1. Under normal use, the filter and support network are guaranteed for one year, if damage is caused by improper use, it is not covered by the warranty.

2. The maximum design pressure of the standard bag filter is 1.0Mpa, except for special specifications that the recommended maximum working pressure is 0.5Mpa.

3. The maximum design pressure inside the jacket of the bag-type jacket filter is 1.0Mpa, and the maximum recommended working pressure is 0.6Mpa.

4. The design pressure of the multi-bag filter is 1.0Mpa, and the maximum recommended working pressure is 0.6Mpa.




When installing, please follow the steps below:

1. Place the bag filter on the station to be filtered, and fix it after connecting the inlet and outlet flanges or pipe teeth; block the exhaust port, or configure an exhaust valve. Jacket type is connected to the heat preservation heat source.

2. Gently put the metal inner net into the bag filter so that the neck of the inner net matches the mouth of the bag filter.

3. Place the filter bag so that the ring opening of the filter bag coincides with the neck opening of the metal inner mesh.

4. Put the O-shaped sealing ring into the O-shaped groove, and the O-shaped sealing ring cannot be twisted or deformed. The multi-bag filter machine buckles the filter bag pressing ring.

5. Hold the handle of the upper cover with one hand and the other end of the upper cover with the other (turn the top handwheel of the multi-bag filter)

6. After the upper cover is aligned, tighten the two diagonal lifting caps at the same time, and tighten all the lifting caps one by one (insert a short stick into the lifting ring to tighten).

7. Close the exhaust valve installed on the top of the bag filter.

8. Please check whether the connecting pipes are firm; whether the working pressure is within the allowable range.

9. Open the output valve. When the heat source inlet valve is opened, the temperature of the filter rises to the specified temperature.

10. Open the input valve slowly and let the liquid slowly flow into and fill the filter to prevent the liquid from suddenly impacting the filter bag and causing rupture, and then observe whether there is any leakage. If there is no leakage, you can start filtering.


Common faults and solutions


The damage location of the filter bag at the bottom of the bag is mostly caused by the accumulation of material at the bottom of the equipment, and the accumulation of material is mostly caused by the failure of the equipment at the bottom of the bag filter. When the system equipment fails, timely process treatment should be made and the faulty equipment should be timely Overhaul, reduce the long-term accumulation of pulverized coal materials in the bag filter, minimize the damage of the cloth bag, and reduce the difficulty of replacing the cloth bag, ensuring that the maintenance is completed in the shortest time and the process production is restored as soon as possible.


Damaged location of the filter bag


The damage position of the filter bag occurs in the bag and the burning loss of the cloth bag with large bean grains is mostly caused by the problem of the material size and the material distribution method. There are high-temperature particles of different sizes in the filtered high-temperature flue gas. The temperature exceeds 400 degrees and cannot be detected by a general temperature detector. Most of them will settle in the gravity sedimentation chamber, and individual high-temperature particles will enter the bag filter through the flue gas duct at high speed with the airflow. If it is a polycondensation fiber such as polyester, polypropylene, PPS and other filter bags, when the surface of the filter bag is less dusty, the high-temperature particles will scald through the filter bag to form irregular round holes. When there is a lot of dust on the surface of the filter bag, the high-temperature particles will not burn through the filter bag and will form dark-colored baking marks on the filter bag. This requires operators to strictly control the relevant process indicators during the production process to ensure that the materials meet the relevant process requirements to ensure the stable operation of the equipment.


The damage position of the filter bag is mostly caused by the failure of the blowback system at the bag mouth. Excessive blowback pressure of the bag filter and the eccentricity of the nozzle will cause this situation. After this happens, the injection system of the bag filter should be inspected in time, and the injection pressure and angle of the injection port should be adjusted to ensure the stable operation of the bag filter.


Judgment method of filter bag shrinkage


Each bag filter material has its own special molecular composition, and its use temperature is also very different. When the temperature limit of the filter material is exceeded, the filter bag will shrink and cannot be filtered, and even the bag cage cannot be extracted. In general, there are the following types of shrinkage phenomenon of the filter bag:

(1) The bag cage in the dust collector is higher than the filter bag, sometimes on the top blow pipe, indicating that the filter bag shrinks;

(2) The bag cage in the filter bag cannot be taken out (except for the deformation of the filter bag), indicating that the filter bag is shrinking;

(3) The bottom of the filter bag is broken by the cage, indicating that the filter bag is shrinking;

(4) The color of the filter bag becomes darker (except for corrosion).


Filter bag clogging and its countermeasures


(1) The clogging of the filter bag is mainly due to the high filtering speed, the fine dust, the sticky dust, the poor cleaning of the filter bag, the sticking of the filter bag, condensation, and compaction. If the filter wind speed of the dust collector exceeds the design standard of the filter bag, it is very easy to cause the fine dust in the flue gas to enter the inside of the filter bag fiber, and the clogging resistance of the filter bag will increase. It is better to use coated filter material, coated filter material or pre-coating the surface of the filter bag. For dust with high viscosity, it is necessary to reduce the filtering wind speed, or increase the pressure of pulse spraying, or adopt the method of offline pulse dust cleaning filter bag, but the better way is to increase the filter area, reduce the filter wind speed, and extend the filter bag Service life.


(2) Poor cleaning of the filter bag mainly includes frequent cleaning times and too long cleaning time. Frequent cleaning times and excessive cleaning pressure will loosen the fiber structure of the filter bag and increase the fine dust in the flue gas to block the filter bag. If the cleaning time is too long, the initial powder layer on the surface of the filter bag will be washed away, resulting in a decrease in the filtering accuracy of the filter bag. If the dust removal time is too short, the dust on the surface of the filter bag is not completely cleaned, and then the filter will be started. The dust will gradually accumulate on the surface of the filter bag, which will cause the filter bag to block. To solve this problem, you can pass several times After the trial run, adjust the injection controller.


(3) Moisture is the biggest cause of clogging of the filter bag. The cause of moisture content is usually condensation at low temperature, especially when dealing with high-temperature flue gas. The following methods can be used to prevent this situation: avoid improper startup; avoid Turn on the dust collector when the resistance is large; turn on when it is below the dew point. The dust collector runs below the dew point, which is prone to problems. If the air intake is unevenly distributed, it is easy to cause local corrosion of the dust collector shell. Therefore, the dust collector should be avoided from working below the dew point. If it is unavoidable to start at low temperature, heat preservation devices should be used, such as steam heat preservation or electric heating heat preservation.


(4) Air infiltration. Air infiltration often occurs in the flange of the dust collector, the inspection door or the movable device of the dust collector. If the seal is not tight, the outside air enters the dust collector. When high temperature flue gas is processed, a low temperature area will be generated inside the dust collector, resulting in low temperature Condensation at the place, corrodes the dust collector, and causes paste or compaction of the filter bag.

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