Other Causes of Baghouse Filter Failure

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An image of dust collection filters completely covered in build-up from moisture

The four main reasons why baghouse filters fail prematurely are abrasion, exceeding the maximum operating temperature, chemical attack and fire. All of these can dramatically shorten the the life of a baghouse filter as well as cause serious damage to the baghouse system*. However there are other lesser known causes that can cause premature dust collector filter failure. Let’s review them.

“If the filter system is undersized, then the filters will suffer increased wear…”

Undersized Dust Collector for CFM

It is essential that an industrial baghouse system be carefully engineered and sized to handle the right amount of air flow (CFM) for the application. If the filter system is undersized, then the filters will suffer increased wear.  Additionally, an undersized system will eventually lead to inadequate air flow, poor venting that can damage equipment, higher emissions, loss of reclaimed product and a hazardous work environment.

A dust collector can be undersized in two main ways: (1) by not having enough filters for the airflow, and (2) by having too much airflow through too small of a unit, thus creating high internal can/interstitial velocity.

Sadly, many less reputable sales reps and even some dust collector OEMs often undersize systems in order to undercut their competition on price. Other times, plants have tried to increase system capacity without consulting with an experienced dust collector manufacturer and even up overloading their units.

Wrong Filter Media or Style of Filter  

The choice of baghouse filter media depends on a number of factors, such as temperature, resistance to chemicals, target dust size, physical characteristics, collection efficiency and price. If the choice of fabric is unsuitable for the application required, this can have a dramatic reduction in the lifespan of the filter.

For example, trying to use a low temperature filter fabric such as polyester (max temp 250F – 275F) in a high temperature (300F – 500F) baghouse system will quickly result in filter failure. 

Often, operators must consider more than just the maximum temperature as the mix of temperature, humidity and chemical makeup in the gas stream can cause failures if not accounted for when selecting the media. For example, in many gypsum applications the temperature is not normally very high (under 200F) so polyester media might seem to be a good choice. However, the combination of elevated temperatures and high humidity can cause the gypsum to react with the polyester and cause hydrolysis, which leads to the bag becoming hard and brittle. For this reason many gypsum applications used aramid filters even though the temperature normally would allow for cheaper polyester bags.  

Finally, many suffer problems due to using cartridge filters where a bag filter is more appropriate. Man applications can make good use of cartridge collectors to improve operation and reduce the overall cost of a system. However, we often see people try to use cartridges in applications ill-suited for them such those with irregular-shaped material, sticky materials, or high temps.


An image of a baghouse filter that has hardened from hydrolysis
Picking the right fabric for the right temperature isn’t everything. This is the effect of hydrolysis on an improperly selected baghouse filter.

Bent and Damaged Cages

During regular maintenance or when stored improperly, cages can be bent, damaged, warped and or even corroded. Using baghouse filter cages in this condition will lead to the filters failing prematurely. When a cage is bent or damaged, sharp points can form from broken wires and cracked welds that can physically damage the filter creating tears and holes.  If rust or corrosion is present on the cage, this creates abrasion and leads to tears and holes in the filter. Additionally, bent cages will cause the bags to hit each other or the sides of the housing when they are pulsed creating localized wear spots.

An image of a PTFE filter with two small holes in its fabric
Have you reused rusted or bent baghouse filter cages and then seen holes in your filters like these?

Poor Installation

Improper installation of filter bags can also result in early bag failure and loss of cleaning effectiveness. For top load pulse jets, the most common install errors involve not seating the snap band properly. For a bottom load unit the bag not being folded over the top of the cage properly, poor clamp placement and tightening the clamp too much or too little are all common. 

Additionally, duct design, turning vanes and deflection plates all contribute to uniform gas distribution to all filters. However poor installation of these elements can result in high airflow regions that will abrade the filter bags.  Rough handling such as bending or stepping on the bags during installation or improper tensioning can also cause holes or tears in the bag filters reducing their strength and durability.

Moisture

An image of dust collection filters completely covered in build-up from moisture
Please tell us that you check your baghouse filters enough before letting moisture build up this badly.

Common sources of condensation and moisture in a baghouse are leaking gaskets around the doors and airlocks or upset conditions in the process.  Moisture can weaken the filter media, causing filter leaks or failures, and allow dust to bypass the filters. It can also alter the adhesion characteristics of the dust creating hard-to-clean mud and blinding of the filter. Moisture can also create chemical issues within the baghouse. For example, acid gases mixed with high moisture can cause an acid flash. This is where the acids condense out of the gas stream and damage the filters and housing. 

As discussed in this and the previous article, there are a number of reasons why industrial baghouse filters fail prematurely. Baghouse.com has experience helping many with these and other problems find solutions to get their systems back to peak performance. For more information and to arrange a quote for all your baghouse requirements, please contact us at Baghouse.com

* See article “Top 4 reasons why baghouse filters fail”

Need Help Ordering Baghouse Filters?

Whether you know exactly what you want or could use some help getting the right dust collection filter, we’ll put together a free quote with the perfect filter for you.

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Top 4 Reasons Why Baghouse Filters Fail

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An image of a baghouse filter that's been damaged by fire.
An image of the worn-out cuff of a baghouse filter

The regular operational life of a baghouse filter can be shortened by a number of factors. In this article we will discuss the top 4 reasons:

  1. Abrasion
  2. Exceeding Maximum Operating Temperature
  3. Chemical Attack
  4. Fire

1. Abrasion

The deterioration of filter bags through abrasion can be a result of a number of causes.  It can be caused by bags physically rubbing against each other, from the type of cleaning mechanism used or from where the dust enters the bag and impacts the fabric. The most common is caused by excessive particulate loads in the gas stream. Poor inlet design may lead to particulate laden air striking the filters in certain spots more than others such as near the bottom cuff, or strike the filters closest to the dirty-air inlet. In shaker baghouses, bags can deteriorate prematurely due to vigorous shaking particularly at points where the bags are attached. In pulse jet baghouses  the repeated rubbing of the bags against the support cages (especially if the cages are bent or rusty) can considerably shorten the working life of the baghouse filter. This is usually the case when the filters are not sized properly to the cage (otherwise known as the correct amount of “pinch”). 

“A properly designed, installed and maintained system can go a long way in preventing premature baghouse filter failure…”

2. Exceeding Maximum Operating Temperature

An image of dust that's collecting inside of a baghouse
Is your baghouse building up dust?

Baghouse filters are manufactured using various materials depending on the application they are being used for. These materials have different thermal durability, that is the upper temperature limit of the fabric. Thermal durability may also be a potential cause of early failure. When operating temperatures rise above the designed limits of the fabric, whether for short spikes or longer overages, filters will begin to degrade and eventually fail. This may be a sudden failure such as the filters melting or catching fire or it could result in less obvious damage that causes the bags to become brittle. Changes in the plant process, fuel source, maintenance shutdowns of other systems, etc., may result in temperature spikes that will irreparably damage the filters. 

3. Chemical Attack

Baghouse filter failure can also occur from a chemical attack. In its simplest form, this can be caused by using the wrong fabric for the chemical makeup of the gas stream. If gas stream characteristics are not taken into consideration when selecting the filter fabric and/or treatments/finishes, chemical attack can cause considerable damage to the baghouse filter.  Other times unexpected changes occur in the gas stream that can cause changes in the composition of the gas. For example, operating temperatures may drop below the dew point allowing chemicals in the gas stream to condense on the filters. This can have a dramatic effect on the life span of a baghouse filter, therefore proper fabric selection and maintain tight control over the process operating conditions and procedures can help eliminate bag deterioration caused by chemical attack.

4. Fire

An image of a baghouse filter that's been damaged by fire.
A dust collection filter damaged from fire.

Premature baghouse filter failure can also be caused by fire. This could range from a relatively mild occurrence to a far more serious event. A minor event could be caused by an ember or a spark entering the baghouse system. The ignition source can then be drawn through baghouse system and make make its way to the surface of the filter causing a hole to be burnt in the bag or for it to catch fire.

Additionally, if the dust collection system is not working properly dust accumulations may form that can then provide fuel for a potential fire or explosion. If then a spark or ember enters the system this built up dust can ignite causing a fire, which can then be dragged through the entire system causing a serious or even catastrophic conflagration. This often happens when a system is choked off with high pressure drop (differential pressure) across the filters or when the dust discharge system (baghouse airlock and any connected screw/pneumatic conveyors downstream) do not remove the dust from the baghouse quickly enough.

Prevention

A properly designed, installed and maintained system can go a long way in preventing premature baghouse filter failure. Following a regular preventative maintenance provided by a reputable dust collector OEM like Baghouse.com can keep your system in good working order. At times a dye leak test among other things can help technicians identify the exact cause of early filter failure.

Further Information 

For further information on baghouse filter failures, please see additional article on lesser known reasons of baghouse filter failures.

Need Help Ordering Baghouse Filters?

Whether you know exactly what you want or could use some help getting the right dust collection filter, we’ll put together a free quote with the perfect filter for you.

Contact Us Today!
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The 3 Most Overlooked Baghouse Preventative Maintenance Tasks

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Baghouse maintenance from Baghouse.com personnel
Read more
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How to Avoid Undersizing a Baghouse Dust Collection System

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Large backdraft workstation vented to dust collector by ductwork

Dust collector OEMs constantly try to come in with bids lower than competitors. In an attempt to do so, some baghouse manufacturers offer undersized systems. This article discusses what customers can do to avoid accepting a bid for an inadequately-sized baghouse dust collection system.

By Dominick DalSanto
Dust Collection Expert & Sales Director
Baghouse.com

”I’m sorry, but the other supplier came in lower than you. We went with their proposal over yours.”

I think there are few things I hate hearing more than those words in my position in baghouse sales. I can respect a client who has found a better deal on a comparable system. But I am upset when I hear that my competition came in with a bid lower than mine by recommending a grossly undersized system. As a sales professional, this particularly exasperates me as I feel these OEMs abuse the level of trust placed in them by the customer by offering something they know will not work properly — and because I know how big a problem it is in our industry.

Many sales reps apparently believe in the viability of their plans, and, thus, offer them in good faith, but others have — and will — propose systems that are smaller than customers require knowing that it will not perform adequately. The end result is that vital baghouse systems do not operate adequately, and customers, workers, and the community end up paying the price in the form of higher operating costs, safety hazards, and more pollutants.

The situation can present a major problem for customers as most of them rely on the experience and expertise of baghouse manufacturers or environmental technology experts to recommend a properly sized system. Lacking knowledge on dust collection engineering and industry best practice, customers must rely on others without being able to independently verify their figures.

The question this arises, how can customers prevent this from happening?

Baghouse Case Study at Silver Mine Lab

View of entire testing area equipped with a dust collection system

View of entire testing area including the various hoods and backdraft table connected to a dust collection system.

A few years ago, a silver mining operation contacted us and requested a technical inspection of one of the mine’s baghouse dust collection systems. The task was to examine a small 5,000 cfm system used for venting an onsite testing lab. In the lab, plant personnel conducted daily tests of ore samples taken from various locations in the mine to ascertain which areas had the highest concentrations of silver ore. The process for conducting these tests involved the use of several extremely harmful substances, chiefly lead and cyanide.The main concern was that during some recent evaluations for safety purposes, lead dust had been found on windowsills and in nearby rooms. Additionally, the amount of lead dust found on the clothing of workers in these areas — specifically lab technicians — was found to be several times higher than allowable under MSA standards, leading to one worker requesting a transfer to a different department. In addition, the system itself appeared to function at a very low level of efficiency and “did not seem to run properly,” according to staff.

Problem — An Undersized Baghouse System

Large backdraft workstation vented to dust collector by ductwork

Backdraft workstation – Draft (i.e. suction) on the table was so weak it could hardly contain any dust generated on the table

After conducting an inspection and reviewing several elements of the system, I immediately realized it was grossly undersized. It was “designed” to ventilate the testing lab using a series of venting hoods and vented workstations. There were five pickup points in the system that were connected directly to the baghouse, which was located just outside the exterior wall. The first drop point was a large backdraft workstation (Picture  #2), 72 in. x 36 in., for mixing the lead and other compounds together with the ore samples. There were three small furnaces — used to heat samples — with venting hoods of 32 in. x 39 in. above them. And there was one tall, ducted workstation, 32 in. x 39 in., used as a back-up for the other mixing station. Venting for everything went straight up through the ceiling to the main trunk (Picture #3), which then ran directly out through the exterior wall and into the baghouse. The main trunk was 12 in. in diameter, tapering to 10 in. then 8 in. then 6 in. The main workstation was connected using a 10 in. duct, and all others used a 5-in. duct (Picture #4) to connect the hoods to the main trunk.

Dust collection system ductwork above the ceiling of the testing room

The ductwork above the ceiling of the testing room. The size of the individual branches and the way they connect to each other was not designed according to industry best practice

According to the supplier-provided specifications, the baghouse had (49) 5.5 in. x 10 in. bags, and the system fan was rated for 5,043 cfm at approximately 10 in. w.g. of pressure. In this arrangement, the system should have resulted in an air-to-cloth ratio of approximately 7.15:1.

After manually taking airflow readings, I found that the system cfm actually was 3,969. Additionally, when we physically removed a sample bag and measured it, we found it to be 5 in. in diameter, not 5.5 in. as the spec sheet listed. After crunching the numbers, we determined that the air velocity was, at times, below 79 ft./m. This was less than one-50th of the minimum recommend air velocity for this application.

Venting hood connected to a dust collection system

One of the hoods over a test furnace. Notice the lack of curtains and small diameter duct going up out of the hood.

Poor ductwork design, a grossly undersized baghouse, and an equally underpowered fan combined to make this system almost worthless to the facility. (they neglected to size the fan based on the relative elevation and in doing reduced the output of the already undersized fan by another 30%) The effective pull from the system was so weak that one could place a hand directly under the intake on any of the stations and feel almost no noticeable suction — even when the system was running at full power. It was so weak it could hardly lift a piece of paper out of my hand! Obviously, this led to the excessive contamination of the workers and surrounding area.

Why So Small?

The system was designed by in-house personnel, who had no air-handling engineering experience, and a testing lab consulting company. The consultant procured the system from a sales rep organization, which, in turn, procured it from another independent sales rep that worked with the manufacturer. The final cost of the system was more than $75,000 for the baghouse, fan, ductwork, and hoods — much of that being mark-up for all the parties involved. The system was undersized from the start, so while cheaper for the customer, it ended up virtually useless for that customer.

Using even rough calculations, with a minimum conveying velocity of 250 ft./m in the hoods — and that really should have been even higher — the system would have required at least 12,000 cfm to function at an adequate level. Heavy dusts such as lead require high conveying velocities between 4,000 ft/min or more to prevent product drop out. This would mean a much larger system fan, (adjusted to the 4,400-foot geographic elevation of the plant), a baghouse with either triple the amount of bag filters or the use of pleated filter elements to increase filter area, and a completely redesigned ductwork system with a larger trunk and branches, along with better hood design and a damper system to further increase collection efficiency.

Solution — How to Avoid Being Sold an Undersized System

Some may feel that this case study serves only as a horror story to scare potential buyers on the pitfalls of trusting unscrupulous salespeople. I agree that part of the reason for telling this story is to advise you that implicitly trusting any vendor trying to sell you something as large and expensive as a dust collection system is not wise. The main moral of the story, however, is to help you make sure you get the best dust collection system for your needs. In the previously outlined case study, the following steps may have helped prevent this disaster:

1) The first step is to do your homework before you call for quotes. While becoming an expert on every piece of industrial equipment before contacting vendors isn’t feasible, gaining as much knowledge as possible goes a long way to ensuring you get what you need. Knowledge provides you with leverage during the sales process. Since, in this case, company personnel went in completely ignorant of how a dust collection system operates, they were at the mercy of whatever their vendor was going to tell them. This meant they had no idea of air-to-cloth ratios, air conveying velocities, ductwork design, etc.Additionally, where possible, deal directly with a baghouse dust collector manufacture (such as Baghouse.com) as opposed to sales rep organizations, that often have little to no practice experience engineering dust collection solutions.

2) Second, verify vendor calculations. While at times you may be able to determine exactly what size a system you need on your own, you may require assistance. This is especially true with regard to new installations and new processes. There is nothing wrong with asking vendors to assist you, but make sure to review their numbers afterward. This may require a bit of research or even hiring an outside consultant to verify the engineering. In the case study, had plant personnel taken the time to review system specifications proposed by the vendor, people would have found that the figures were far off from accepted industry standards. (See the American Council of Governmental Industrial Hygienists (ACGIH) Manual for standards on minimum air-conveying speeds and system design standards.) This would have exposed that the system was grossly undersized and allowed staff either to correct the problem or to seek a different vendor.

3) Third, seek alternative proposals. Had the company solicited alternative bids, personnel likely would have noticed the obvious discrepancies between them. Additional proposals likely would have shown a large difference in price, owing to the vendor’s undersizing of the system. Other vendors (likely) would have submitted more realistic proposals. Instead of believing that any one supplier somehow may have managed to undercut the competition by such a large margin — while offering an adequate product — the wise course would be to investigate why one bid would come in so much lower than the others and correct any mistakes that may have been made.

Conclusion

Yes, this story is meant to raise concerns over the buying process, but that is a good thing for potential buyers. If they keep in mind the points outlined here, they can avoid the pitfalls of an installing an undersized dust collection system and avoid the complications that can come with it.

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Baghouse Differential Pressure – How To Troubleshoot False Readings

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Baghouse differential pressure air lines

For baghouses to run efficiently, trustworthy differential pressure readings are required. How can you tell if your DP readings are accurate? What can you do if you suspect you are receiving false readings? This second article in our series on baghouse differential pressure will answer that question. 

By Dominick DalSanto
Baghouse Technology Expert and Sales Director
Baghouse.com

Why Worry About False Differential Pressure Readings?

As we mentioned in our previous article in this series, having accurate differential pressure readings is essential to operating your baghouse correctly, and efficiently. Operators base almost all of their operational decisions on baghouse DP. If they are given incorrect readings it could result in damage to the system, increase emissions, or even fire and combustible dust hazards.

For example, assume that a unit is giving readings that are lower than they actually are, 3″ w.g. when it really is running at 8″. Because the operator sees such a low reading, he could now make several incorrect operating choices that could have very severe consequences. He may take this low DP reading to mean that his filters are in good condition and do not need to be replaced. With blinded bags, he could begin seeing decreased system performance. Or perhaps his bags could begin producing higher emissions levels thus causing the plant to exceed its air permits, potentially leading to heavy fines and sanctions.

While we cannot detail every possible problem that could arise from this, the point is clear. So what can and maintenance personnel do if they they are receiving incorrect DP readings?

How To Troubleshoot Differential Pressure

Maintenance personnel should examine the DP instruments and determine if there is any obvious problem. Lose connections, backwards connections, and obviously broken gauges are common enough that they should be expected.  Other times, maintenance personnel will need to troubleshoot the instruments to diagnose and remedy less conspicuous issues.

Maintenance personnel will need to determine whether the individual pressure gauges are faulty, or simply have blocked lines coming into them. We recommend the following troubleshooting procedure:

  1. Disconnect all gauges, controller boards, etc., from air lines coming from the collector.
  2. Using compressed air, clean all air lines thoroughly, making sure to blow back into collector.
  3. Using a handheld DP gauge (a normal manometer with flex tube connectors will suffice), hook up the air lines from the collector to obtain the operating DP.
  4. Reconnect the newly-cleaned air lines to the controller board and/or pressure gauge.
    1. If the controller board/pressure gauge reads the same as the handheld gauge did after cleaning the lines, then the controller board pressure sensor and/or pressure gauge is working properly
    2. If the controller board/pressure gauge reads the differently than the handheld gauge did after cleaning the lines, then the controller board pressure sensor and/or pressure gauge is not working
      1. (For the baghouse-mounted DP gauge) Replace with new gauge.
      2. (For controller board) Contact manufacturer about possibility of replacing only the board’s pressure sensor.
        1. If not possible, replace entire board with new controller board.
  5. Remove all unnecessary line splitters, additional lines, and long runs, ensuring all gauges are located as close as possible to the air taps (within 10’ – 15’)

Baghouse differential pressure air lines

Avoid the example here. Avoid splitters and crooked lines.

NOTE: When connecting the new gauge to the clean and dirty side lines, make sure to connect them to the correct ports on the gauge. They should be marked “HIGH” and “LOW”. Just remember, that if hooked up backwards, the needle will pull backwards, instead of giving a positive reading.

How To Prevent False DP Readings

It is important to remember that just because you fixed this problem once, it likely will come back again and again over the life of the baghouse. Inspecting and cleaning/repairing the DP gauges and air lines should be a regularly scheduled maintenance task for all baghouses.Industry best practices should be followed when installing the gauges and air taps to reduce the likelihood of fouling.

Notice in the picture to the right how the maze of lines coming in and out this DP gauge. Best practice is to have just one line from each side of the baghouse coming into the gauge. The lines should run in the most direct and shortest path possible. For this reason, avoid locating the gauges exceedingly far from the unit, such as in other rooms or other floors. Further, to avoid buildup in lines themselves, place the taps near the top corners in each side of the unit.

Baghouse Differential Pressure - Good air lines

A better example of how lines should be run.

Also, using copper line as opposed to plastic or rubber tubing is preferable and we facilitate easy cleaning and is far more durable.

Once You Have Accurate Readings

With your now trustworthy readings in hand you can now begin consider what these readings in conjunction with other available information is telling your about your baghouse.Our next article in this series will examine how to understand your baghouse DP readings and use it to make wise operating decisions.

 

 

| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in dust collection systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Sales Director at Baghouse.com. His articles have been published not only on Baghouse.com , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.

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Baghouse Differential Pressure – Why Important?

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Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Accurate differential pressure readings are essential for efficient baghouse operation. This article outlines the importace of baghouse differential pressure and what baghouse problems it can be used to diagnose. 

By Dominick DalSanto
Baghouse Technology Expert and Sales Director
Baghouse.com

Baghouse Differential Pressure – Why Important?

Within a baghouse a number of factors must be controlled to ensure the efficient operation of the system at all times. Of these, the most important variable to control is the system differential pressure. This measurement is the key indicator of how the baghouse is operating and the most important factor to consider when diagnosing and troubleshooting issues with the baghouse system.

Over time more and more dirt will penetrate deep into the fibers of a bag being harder to remove. When this happens the bags become blinded or are unable to be adequately cleaned. This causes massive differential pressure increases.

Over time more and more dirt will penetrate deep into the fibers of a bag being harder to remove. When this happens the bags become blinded or are unable to be adequately cleaned. This causes massive differential pressure increases.

Differential pressure (also known as pressure drop or Delta-P) is the difference in pressure between the dirty-air side of the baghouse and the clean-air side. As in the incoming air is pulled through the filter media (i.e. filter bags) vacuum is lost, resulting in the air entering the baghouse having a weaker vacuum than the air exiting the baghouse. For example, let’s say that the system fan is pulling 10″ w.g* of vacuum pressure. When the dirty air comes into the baghouse the pressure is at 3.5″ w.g.* of vacuum, but after entering into the baghouse and passing through the filters the pressure rises to 10″ w.g.. This means the pressure drop across the baghouse is 6.5″ w.g. (Note: This example assumes a clean-air side fan or negative pressure system)

Differential pressure readings are used to determine a number of things about the operation of a baghouse system, such as filter bag condition,  and structural problems with the unit, (airlock and conveying system condition and door seals condition among other things). Furthermore, a high system differential pressure usually indicates that the system is not running efficiently and therefore is incurring higher operating costs than it should under optimal circumstances. The following problems can be diagnosed from observing the system differential pressure:

Filter Bag Condition

  1. Bags are blinded off
    • Dirty bags will become more resistant to airflow thus causing the force to push the air through them to rise.
  2. Bags have holes in them
    • This will create a path of less resistance for the air to flow through leading to lower pressure drop
  3. Bags are not installed properly
    • See above

Structural and Sealing Issues

  1. Leaks within the structure
    • Common leak areas include airlocks, welds, joints (especially panelized construction units), and door seals
  2. Airlock leaks
    • Common around flaps,rotars, gaskets and connection points.
  3. Conveying system leaks
    • Common at connection point to hopper/airlock, holes in ductwork structure, etc.
  4. Doors and hatch sealing
    • Gaskets on all doors and hatches, including viewports. Also includes making sure all doors have sufficient fasteners (i.e. bolts) to secure the door/hatch securely to form a tight seal.

Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Diagram of how to install a magnehelic differential pressure gauge on a baghouse dust collector.

Why High Differential Pressure Means Higher Operating Costs

Controlling your baghouse differential pressure is required to get the maximum performance and efficiency from your system. If your system is running at a high differential pressure it will inevitably cost more to operate, have lower performance and experience more downtime. High DP means the system fan needs to work harder to pull the same amount of airflow throughout the system. IF DP starts to rise above the recommended levels,  maintaining the same level of draft (i.e. suction) at all of the systems pickup points will prove difficult. This will lead to much higher energy costs to run the system fan at high speed and can if over taxed lead to premature fan/motor failure. If the system fan is not adjusted to compensate for the higher differential pressure, the system will lose draft at all of its pickup points. This will mean less performance from your system and inescapably cause problems for your facility process whatever it maybe, especially so for certain industries that are more dependent on the dust collection system as part of the process such as cement, powdered metals, chemical processing, etc. In the end, this will result in the process being shutdown or even a shutdown of parts or the entire facility until the system is running again.

Conclusion

Clearly, it is of vital importance for maintenance staff and operators to keep close watch on dust collection system differential pressure. If system DP is higher than recommended it can be a indicator of several potentially serious issues, ranging from blinded bags, to holes in the structure to poor seals, etc. Accordingly, obtaining accurate differential pressure readings is vital to have an accurate picture of what is going on within your baghouse system. But what can you do if your equipment is giving you suspicious or even false readings? How can you determine when your DP gauges and controls are sending false readings? These questions will be in the following article in the series: Baghouse Differential Pressure – How To Troubleshoot False Readings

Footnotes:

* “w.g. stands for inches of water gauge, that is vacuum pressure as measured in inches of water (sometimes mercury) as in a magnehelic gauge.

 

| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in Dust Collection Systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Sales Director at Baghouse.com. His articles have been published not only on Baghouse.com , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.
Baghouse.com Corp

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Dust Collector Systems: A Holistic Maintenance Strategy

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Systemic View of Dust Collector Systems Maintenance

By Dominick DalSanto
Baghouse Technologies Expert & Author
http://www.Baghouse.com

When examining the performance of any component of your facility’s dust collection systems, it is vital to take into consideration the interaction between the various elements of the entire system. Problems such as bag failure, may be a symptom of a intake problem earlier in the system. Only by understanding the impact various parts of dust collection systems have on each other, can you effectively troubleshoot problems as they arise.

Let’s look at just a few common situations that may at first glance confound and confuse due to a lack of apparent causes within the specific component.

Baghouse Corrosion

Problem: The Baghouse is experiencing is corroding rapidly without any clear cause.

At first, the most likely cause might appear to be a design/installation problem leading to increased exposure to the elements. Indeed this very often is the leading cause of dust collector erosion. However what if you determine there exists no major flaws in the installation and setup of your Baghouse? Taking a more holistic view of your system often will lead you to the cause and eventual solution to your problem.

Systemic erosion can occur within dust collector systems when gas stream conditions change to include more corrosive elements. For instance, at a coal-fired power plant, has the plant switched to a different coal mixture that produces higher amount of sulfides that in turn can lead to higher concentrations of highly corrosive sulfuric acid within the dust collector? Treatment systems before the Baghouse, such as a air scrubber, could be malfunctioning leading to increased amounts of corrosive compounds being transported to other parts of the dust collector system. Or perhaps maintenance has been performed on the pulse-jet cleaning system, such as installing new lines, valves, etc…and due to improper installation and/or calibration they are condensing water leading causing your moisture source.

Premature Bag Failure

Problem: Filter bags are failing without any apparent reason.

Early or premature bag failure is often a good indicator that any of your dust collector systems are not being operated correctly, within recommended parameters. Regrettably many times inferior bag manufacturing methods on the part of shady bag suppliers/manufacturers lead to substandard products being used, that can not endure the riggers of everyday use in an industrial setting.

However should these theories not be proved true, other causes must be examined. Particulate loads may have increased substantially (increased production rates, change of process/fuel, malfunction of pre-filters [e.g. cyclones], etc…), or cleaning cycle frequency/efficiency might have changed/been affected, leading to increased strain on your dust collector system. Additionally, to meet new mercury emission regulations technology such as activated carbon sprayers located upstream of  your Baghouse may be having a larger impact than calculated. Or changes in maintenance procedures may have unexpected consequences on the service life of the filters.

Holistic Approach Needed for your Dust Collector Systems

In both of the proceeding examples, while initially the most obvious cause of a problem should be investigated first, often times, a taking a wider look at all of the ways in which your dust collector systems interact with each other is needed in order to located the root cause of your problem. Problems in one part of your system will often lead to systemic issues. To ensure this does not happen, maintenance personnel must remain vigilante to even seemingly insignificant fluctuations in operating parameters as these can cause maintenance issues in other parts of the system.

 

 

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Dust Collector Troubleshooting Guide

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Introduction to Dust Collector Troubleshooting

Operating and maintaining an equipment system as complex as an Industrial Dust Collector can be a challenge. Here at Baghouse.com we pride ourselves on being experts in our field, with decades of experience designing, installing, maintaining and servicing every kind of Dust Collect design available. We have prepared this short troubleshooting guide in order to help you solve some of the more commonly encountered issues involving Dust Collectors.

Table of Contents

  1. Blower (Fan) & Ductwork Issues
  2. Common Baghouse Issues (All Designs: Shaker, Reverse Air, & Pulse Jet)
  3. Baghouse Design Specific Problems
    1. Shaker
    2. Reverse-Air
    3. Plenum Pulse-Jet
    4. Pulse-Jet

Blower (Fan) & Ductwork Issues

Many Baghouse difficulties originate as problems with the main Blower, or Fan and the supply and exhaust Ductwork.

Problem: Insufficient Airflow Rate coming from the Blower, or Ductwork System

  • Is your Blower (System Fan) powering on and operating properly?
  • Action: Check electrical connections and turn on the Blower.

Addition Questions

  • Is the motor pulling the specified proper amount of Amps?
  • Action: Check wiring
  • Is the fan turning in the right direction?
  • Action: Make sure that motor leads are attached to the proper terminals.
  • Is there excessive vibration?
  • Action: Ensure that there is no excess build up of material on the fan blade, or Blower housing.

Are you getting the proper amount of Air Flow (Cubic Feet per Min) from the Blower?

  • Is the Fan Dampener Open?
  • Action: Close Dampener.
  • Is the air volume at fan rated capacity?
  • Action: See Below.
  • (If your Blower output is normal) Has the Ductwork System been inspected for obstructions, leaks or design flaws that increase static resistance?
  • Action: Redesign Ductwork System to have lower resistance.

Addition Questions

  • Are there elbows, or other directional changing Ductwork immediately preceding the Blower Inlet?
  • Action: Redesign Ductwork to remove any Elbows, or similar configurations near the Blower.
  • Is there an obstruction near the outlet of the Ductwork?
  • Action: Removed any obstruction and try again.

Problem: Excessive Airflow Rate

  • Is the Blower set to the proper speed?
  • Action: Check setting and adjust.
  • Is the Ductwork System oversized?
  • Action: Evaluate the Ductwork System and consider redesigning if needed.
  • Are there any access ports on the Ductwork that are open?
  • Action: Close all ports, and ensure they are sealed properly.

Problem: You have High Static Pressure and a low Airflow Rate

  • Are there any obstructions in the Ductwork System?
  • Action: See above
  • Is the Ductwork System to restrictive?
  • Action: See above

Common Baghouse (All Designs: Shaker, Reverse Air, & Pulse Jet) Issues

Many of these issues can be resolved with a simple maintenance procedure; others may require a qualified service technician to implement a solution a particular problem.

Problem: There is a higher than anticipated Pressure Drop in the Baghouse

  • Have all gauges and pressures sensors been checked for accuracy?
  • Action: Clean all pressure taps, check houses for leaks, for proper fluid level in Manometer, and diaphragm in gauge.
  • Is the Baghouse the undersized for the application?
  • Action: Consider upgrading to a larger unit.
  • Is the cleaning mechanism adjusted to the proper settings?

Addition Questions

  • Is the cleaning timer working properly?
  • Action: Reset the timer. Check wiring, and replace if needed.
  • Is the dust not able to be removed from the Filter Bags by the cleaning mechanism?
  • Action: Check for condensation on Bags. Dry clean bags, or replace them. Take dust samples and send them to the manufacturer for analysis.
  • Is there excessive reentrainment of dust on the Filter Bags?
  • Action: Empty Hopper continuously.

Problem: Dirty discharge at stack

  • Are the Bags leaking from either the clamps, or are from being too porous?
  • Action: Replace Bags, isolate leaking compartment or module. Allow sufficient filter cake to form. Check and tighten clamps. Change to a different Filter Bag; smooth out Bag before clamping.
  • Are the seals between the different compartments  (Dirty Air, and Clean Air Compartments) of the Baghouse leaking?
  • Action: Repair by caulking or welding seams.

Problem: Moisture in the Baghouse

  • Is the Baghouse temperature below the dew point?
  • Action: Raise gas temperature; insulate unit.

Additional Questions

  • Are there any cold spots where pipes or other components connect?
  • Action: Eliminate direct metal line through insulation.
  • Has the Baghouse been sufficiently preheated (Certain applications only)?
  • Action: Run system with hot air only before process gas is introduced.
  • Is the system purged properly after each shutdown?
  • Action: Run fan for an additional 10 min after processing is shut down.

Problem: Material is bridging in the Hopper, thus preventing proper operating of the Baghouse

  • Is there excess moisture in the Baghouse?
  • Action: (See previous solutions)
  • Does the Hopper retain too much material, or is it cleaned on a regular basis?
  • Action: Clean Hopper on a regular schedule.
  • Is the Hopper slope sufficient to allow for the collected material to fall?
  • Action: Redesign and replace.
  • Is the opening for the Screw Conveyor (Or similar device) of adequate size?
  • Action: Redesign and replace.

Problem: The Bags fail prematurely, or wear or faster than they should

  • Is the Baffle Plate worn out?
  • Action: Replace with a new Baffle Plate; Determine whether the Gas stream is striking the Baffle Plate correctly, if it is not, consult with the manufacturer, redesign and replace.
  • Is the dust load to high for the particular Baghouse, or Bags?
  • Action: Install a Primary Dust Collector (Pre-Filter) to reduce dust loads to the Baghouse.
  • Are the Bags being cleaned at the proper intervals?
  • Action: Clean less often.

Baghouse Design Specific Problems

The most common variations in Baghouse design regard the cleaning mechanism.  The three most common are Shaker, Reverse Air, & Pulse Jet. While the proceeding information applies to all Baghouse designs, the following covers specific design related problems.

Shaker Baghouse Type Specific Issues

Problem: Cleaning Mechanism Does Not Function Properly

  • Does Shaking action take place, as it should?
  • Action: Check pins, Keys, Bearings, Etc and repair if necessary.
  • Is the Shaking action strong enough?
  • Action: Increase Shaking rate.
  • Have the Filter Bags been checked to have proper tension?
  • Action: Tension Bags to proper rate.
  • Are any other Baghouse functions affected when Shaking process begins (Fan, or Isolation Dampener, etc)?
  • Action: Repair Isolation Damper, or stop Fan.
  • Are the different compartmental isolation dampener valves functioning properly?
  • Action: Check linkage, Valve Seals, and Air supply of the Pneumatic Operators.
  • Is the cleaning cycle set to the proper interval?
  • Action: Set to the shortest interval possible between compartments.
  • Is the Air to Cloth Ratio at least 3:1?
  • Action: Add Bags; Consider installing a larger unit.

Problem: Filter Bags fail prematurely

  • Is the shaking mechanism set too high?
  • Action: Slow down shaking mechanism.

Reverse Air Baghouse Type Specific Issues

Problem: Cleaning Mechanism Does Not Function Properly

  • Are the different compartmental Isolation Dampener valves functioning properly?
  • Action: Repair if necessary.
  • Do the Bags have the proper amount of tension?
  • Action: See above.
  • Is the Reverse Air Fan powering up/running properly?
  • Action: Run Fan and check differential pressure.
  • Does the Reverse Air Fan spin in the correct direction?
  • Action: See section:  Blower (Fan) & Ductwork Issues
  • Is the Air to Cloth Ratio at least 3:1?
  • Action: Consider acquiring a larger Baghouse.

Plenum Pulse Jet Baghouse Type Specific Issues

Problem: Cleaning Mechanism Does Not Function Properly

  • Is the air pressure at the Pulse Valves within the recommended levels and are all Solenoids and Diaphragms operating properly?
  • Action: Check for leaking solenoids and pulse valves; check compressed air source and check differential pressure.
  • Are the cleaning pulses at set to the correct duration (0.1 sec)?
  • Action: Reset to 0.1 sec.
  • Is cleaning interval at the lowest setting the will allow air manifold pressure to rebuild?
  • Action: Change setting, and check the differential pressure.
  • Do all poppet valves seal properly?
  • Action: Adjust and/or repair all valves and check differential pressure.
  • Is the Air to Cloth Ratio at least 4:1?
  • Action: Switch to pleated media; Consider installing a larger unit.

Pulse Jet Baghouse Type Specific Issues

Problem: Cleaning Mechanism Does Not Function Properly.

  • Is the manifold pressure within the manufacturer’s suggested range?
  • Action: Check for leaks at the solenoids and pulse valves; Check compressed air source and then check differential pressure.
  • Are the cleaning pulses at set to the correct duration (0.1 – .015 sec)?
  • Action: Set to 0.1 – 0.15 duration.
  • Is cleaning interval at the lowest setting the will allow air manifold pressure to rebuild?
  • Action: Change setting and check differential pressure.
  • Is the compressed air pressure at the proper level?
  • Action: Check for leaks; Increase pressure.
  • Is the Air to Cloth Ratio at least 6:1?
  • Action: Switch to pleated media; Consider installing a larger unit.

 

 
About the Author

| Dominick DalSanto is an Author & Environmental Technologies Expert, specializing in Dust Collection Systems. With nearly a decade of hands-on working experience in the industry, Dominick’s knowledge of the industry goes beyond a mere classroom education. He is currently serving as Online Marketing Director & Content Manager at Baghouse.com. His articles have been published not only on Baghouse.com , but also on other industry related blogs and sites. In his spare time, Dominick writes about travel and life abroad for various travel sites and blogs.

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