How to deal with severe wear and tear on the bottom of the cloth bag?

The wear of the bottom of the bag is a high-frequency problem of bag filter bag failure in bag filters.The core causes are concentrated in four categories:airflow erosion,dust impact,mechanical friction,and improper installation/working conditions.After wear,it not only leads to dust leakage and a decrease in dust removal efficiency,but also causes a sudden increase in the load on surrounding filter bags due to single bag damage,leading to a chain reaction of increased resistance and bag damage.The handling should follow the principle of"temporary sealing to ensure operation,precise investigation of wear and tear causes,and finally targeted repair/replacement+long-term protection".The full process solutions that can be implemented on site are as follows:bag filters suitable for various industrial conditions:

1、Emergency handling:Temporary sealing to prevent a large amount of dust leakage

If there are small cracks or wear at the bottom of the filter bag that have not penetrated,and there is no spare filter bag replacement available,temporary sealing can be used to ensure short-term operation of the equipment(recommended not to exceed 48 hours,only for emergency use):

Offline shutdown of the filter chamber where the worn filter bag is located,close the corresponding inlet valve/lift valve,and cut off the airflow;

Cut the filter material from the same material as the filter bag into patches,and use a special adhesive that is resistant to high temperature and dust to stick it on the worn area(one layer on each side,compact and wait for the adhesive layer to solidify);

If the rupture is small,high-temperature resistant zip ties can also be used to wrap and seal it(wrap 3-5 times to ensure sealing and prevent airflow from passing through the rupture);

When put into operation after emergency response,focus on monitoring the pressure difference of the filter chamber.If there is a sudden drop or ash emission from the outlet,immediately go offline again for further processing.

2、Accurate investigation:Identify the core cause of bottom wear(easy to determine on site)

The bottom wear of the bag can be divided into three forms:uniform wear,local wear,and edge tearing.Different forms correspond to different causes.Combined with on-site inspection,it can be quickly located.The following are 90%of the core fault points that occur on site:

1.Airflow erosion wear(most common,mostly uniform thinning of the bottom/annular wear)

After the flue gas enters the dust collector,if the airflow distribution is uneven,the high-speed airflow will directly rush to the bottom of the filter bag.Long term flushing will cause the filter material to gradually become thin and perforated.Common causes include:

The air inlet method of the dust collector is unreasonable:the air inlet is directly facing the filter bag area,without a guide plate or airflow distribution plate,and the high-speed airflow directly impacts the bottom of the filter bag without buffering;

Handling air flow exceeding the design value during operation:If the surface wind speed of the filter bag is too high,the bottom airflow scouring force will suddenly increase,especially fine dust will form a"sandblasting effect",accelerating wear;

Excessive accumulation of ash in the ash hopper:Failure of the ash discharge valve and blockage of the ash hopper bridge have caused dust to bury more than 1/3 of the bottom of the filter bag.The airflow passes through the surface of the dust,forming a local high-speed airflow that flushes the parts of the filter bag in contact with the dust.

2.Mechanical friction and wear(mostly caused by local holes or wire drawing at the bottom)

The bottom of the filter bag is in direct contact with the surrounding components,and the vibration and airflow disturbance during equipment operation can cause continuous friction between the filter bag and the components,resulting in the abrasion of the filter material.Common causes include:

Deformation,open welding,and burrs at the bottom of the cage bone:The cage bone bottom ring is bent,the welding point falls off,or the cutting part is not polished and has sharp corners.When the filter bag shakes with the airflow,the bottom continues to rub against the hard points of the cage bone;

Filter bag installation too long/too loose:The length of the filter bag exceeds the design value,or it is not tightened during installation.During operation,the bottom of the filter bag shakes and collides and rubs against the ash unloading device,guide plate,and ash hopper wall inside the ash hopper;

Excessive vibration of the dust collector casing:The connection between the fan,motor,and dust collector has not been shock-absorbed,resulting in overall vibration during equipment operation,which drives friction between the bottom of the filter bag and surrounding components.

3.Dust impact abrasion(mostly in the direction of the bottom air inlet)

The front-end pre dust removal equipment fails,and coarse particles and heavy dust(such as ore and sand particles)directly enter the bag filter,hitting the bottom of the filter bag at high speed,forming an"impact pit"type wear.Common causes include:

The efficiency of the front-end cyclone dust collector and settling chamber decreases:the inner cylinder is damaged,the guide plate falls off,and the coarse dust is not separated and directly enters the bag filter;

Raw material crushing and inadequate sealing during transportation:A large amount of coarse dust particles enter the flue gas system unorganized,increasing the impact load on the bottom of the filter bag.

4.Installation/filter material itself issues(auxiliary causes,accelerated wear)

Improper selection of filter material:The working condition is coarse dust and high erosion environment,but thin and low wear resistant filter material is selected(such as ordinary polyester filter material,without thickening and wear-resistant treatment);

Poor sewing process at the bottom of the filter bag:the stitches are too dense,the stitches are loose,or there is no wear-resistant bottom ring installed,which makes the filter material easy to crack and wear from the stitches;

The offline valve of the multi chamber dust collector is not tightly closed:during dust cleaning or offline,high-speed airflow from adjacent filter chambers enters and flushes the bottom of the offline filter bag.

3、Symptomatic treatment:specific solutions for different causes

Based on the wear pattern and investigation results,we will start from eliminating the wear source,repairing/replacing the filter bag,and optimizing the equipment structure to thoroughly solve the problem of bottom wear.The specific steps are as follows:

1.Solve the problem of airflow erosion and wear(core)

Install airflow distribution device:weld a guide plate and airflow distribution plate at the inlet of the dust collector,or set up a baffle in front of the bottom of the filter bag to buffer high-speed airflow and avoid direct impact on the filter bag;

Control air flow:Reduce the operating air flow to the design value.If the actual operating air flow is too high,it can be solved by increasing the number of filter bags and expanding the filter chamber to avoid operating at excessive air speeds;

Thoroughly clear the accumulated ash in the ash hopper:turn on the ash hopper air cannon and vibrator to remove the bridge accumulated ash,repair/replace the faulty ash discharge valve,ensure that the ash hopper material level is always more than 30cm below the bottom of the filter bag,and arrange a dedicated person to regularly check the ash discharge situation.

2.Solve mechanical friction and wear

Repair/replace the problematic cage bone:correct the deformed cage bone bottom ring,weld open the welding points,and polish all sharp corners and burrs of the cage bone;For severely worn cage bones,replace them directly and prioritize using cage bones with bottom welded wear-resistant rings and overall galvanized/sprayed to reduce friction;

Re adjust the installation size of the filter bag:cut the filter bag to the design length,and tighten it moderately during installation(the filter bag is in contact with the cage bone without looseness or shaking),ensuring a safe distance of 10-20cm between the bottom of the filter bag and the internal parts of the ash hopper;

Add shock-absorbing measures:Install shock-absorbing pads and soft connections at the connection between the fan,motor,and dust collector,reinforce the dust collector housing,and reduce overall equipment vibration.

3.Solve the problem of dust impact and wear

Repair the front-end pre dust removal equipment:replace the damaged inner cylinder of the cyclone dust collector,re fix the guide plate,clean the dust accumulation in the settling chamber,ensure that the coarse dust separation efficiency is restored to the design value,and control the dust particle size entering the bag filter to be≤100μm;

Sealing raw material conveying process:Seal the air leakage points of crushing,belt conveying and other equipment,install dust covers,and reduce the unorganized entry of coarse dust particles.

4.Solve installation/filter material issues

Replace wear-resistant filter bag:Based on the working conditions,select a new type of filter bag.For coarse dust and high erosion environments,prioritize thick film coated polyester(thickness≥0.8mm)and PPS thick filter material.The filter bag manufacturer is required to install a wear-resistant bottom ring(rubber/polytetrafluoroethylene material)and double stitching reinforcement needle feet at the bottom to improve the bottom wear resistance performance;

Maintenance of offline valves/inlet valves:replace valve gaskets,calibrate valve plates,ensure tight closure,and prevent airflow from entering;

Wear resistant reinforcement for slightly worn filter bags:sew a circle of wear-resistant filter material patch on the outer side of the bottom of the filter bag,or cover it with a detachable wear-resistant rubber ring to extend its service life.

4、Long term protection:Starting from selection,installation,and maintenance,avoid repeated bottom wear and tear

The wear on the bottom of the bag is mostly a"preventable fault".Through standardized selection,installation,and regular maintenance,the probability of wear can be significantly reduced.The core measures are as follows:

Standardization of filter bag selection:Determine the wear resistance requirements for the bottom of the filter bag according to the working conditions.For coarse dust and high airflow scouring conditions,filter materials with wear-resistant bottom rings,thickened and high wear resistance must be selected,and ordinary filter bags without wear-resistant treatment are rejected;

Standardization of installation process:

Before installing the cage bone,check it one by one to ensure that there is no deformation,burrs,or open welding.The filter bag should be matched and adhered to the cage bone without looseness;

Maintain a safe distance between the bottom of the filter bag and all metal components inside the ash hopper to avoid contact;

The air inlet must be equipped with an airflow distribution plate/guide plate,which is a mandatory requirement to prevent bottom airflow erosion.

Establish a control mechanism for ash hopper unloading:

Inspect the material level of the ash hopper and the operation status of the ash discharge valve every day,regularly clean up the accumulated ash in the ash hopper,and strictly prohibit the ash hopper from being filled with ash and burying the bottom of the filter bag;

Install a level gauge and a blockage alarm device on the ash hopper,which will automatically sound an alarm when the ash accumulation exceeds the limit and be promptly dealt with.

Regular inspection of potential wear and tear hazards:

Offline inspection of the bottom condition of the filter bag every week,with a focus on checking for thinning,wire drawing,and small breaks.If any problems are found,they should be repaired/replaced in a timely manner to prevent small wear from developing into major damage;

Monthly inspection of cage bones,airflow distribution devices,and offline valve status,polishing of cage bone burrs,and reinforcement of loose guide plates.

Optimize operating parameters:

To avoid long-term operation of the dust collector with excessive air volume and concentration,control the surface air speed of the filter bag within the design range(conventional 0.8-1.2m/min);

During dust cleaning,control the compressed air pressure to be≤0.5MPa to avoid severe shaking of the filter bag caused by high-pressure spraying and friction with surrounding components.

5、On site operation taboos:These behaviors will aggravate the wear and tear of the bottom,absolutely avoid them

It is strictly prohibited to continue operating in a state where the ash hopper is too full of ash,as this is the primary cause of scouring and wear at the bottom of the filter bag;

It is strictly prohibited to use cage bones with burrs,deformations,or open welds.Forcefully installing them will directly wear the bottom of the filter bag,and the wear rate will be extremely fast;

It is strictly prohibited to omit the installation of inlet and outlet air flow distribution plates/deflectors for the sake of"saving trouble".High speed airflow will thin the bottom of the filter bag in a short period of time;

It is strictly prohibited to operate beyond the designed air volume.Simply increasing the fan frequency to increase the air volume will significantly enhance the airflow scouring force and accelerate bottom wear;

It is strictly prohibited to use ordinary zip ties or non high temperature resistant adhesives for long-term sealing.After emergency sealing,new filter bags should be replaced as soon as possible to avoid cracking and leakage at the sealing site.

KASPER G,KURTZ O,LÖFFLER F.Investigation of Filter Bag Wear and Service Life Extension in Pulse-Jet Baghouses[J].Filtration&Separation,2016,53(7):32-37.

MLA 9th

Kasper,Gerhard,et al."Investigation of Filter Bag Wear and Service Life Extension in Pulse-Jet Baghouses."Filtration&Separation,vol.53,no.7,2016,pp.32–37.

APA 7th

Kasper,G.,Kurtz,O.,&Löffler,F.(2016).Investigation of filter bag wear and service life extension in pulse-jet baghouses.Filtration&Separation,53(7),32–37.