淫乱社区 Engineers Explain the Importance of Baghouse Leak Detection Testing

Transcript

Who needs to do a baghouse leak detection test?

Anyone who owns or operates a dry-type dust collector, such as a baghouse or cartridge collector, needs to do a baghouse leak detection test.

How often do you need to do a leak detection test?

Leak detection tests should be done every time you do a filter change. Some regulatory requirements dictate that leak detections need to be done on an annual basis, or a six-month basis, and then also any time you suspect a leak in your system, a leak test is good to help diagnose where that leak is coming from.

What are the risks of not doing a leak detection test?

Filter changes are a fairly expensive operation, so not doing a leak detection test could mean all the money you spent on that filter change is thrown out because of an improper installation.

Additional reasons to conduct these tests, and reasons to mitigate the risk by doing them, is because a hole in your filter could mean a failure to comply with regulatory requirements.

Step by step: The baghouse leak detection system

Before conducting the test, you鈥檙e going to want to consult your safety department to ensure that all lockout, tagout and confined space procedures are followed for this procedure.

Step one is we are going to be inserting the dye into the system. In this case, we鈥檙e going to insert the dye (or baghouse leak detection powder) into the hopper here. [In your system, dye may need to be inserted into the collection ductwork.]

Now that our dyes have been added, we鈥檝e ensured that our filters are evenly coated, we are going to do an inspection of the clean-air side of our bags to ensure that none of the dye made it through or around the filters and ensure we have a nice, good installation.

Now we鈥檙e up on the clean-air section of the baghouse. Because this thing is so small, we can actually lift off the entire roof of it. So first I鈥檓 going to do a quick initial inspection to see if I see any dye. Usually, if there鈥檚 a major leak, you鈥檒l see it instantaneously. But now that we don鈥檛 see any, we鈥檙e going to actually do the blacklight portion and turn off the lights and see what we can see.

All right. Since in our test we didn鈥檛 see any leaks, we wanted to show you we scattered some dye around here and wanted to show you what it would look like if there was a leak and how vividly that shows up.

Whether you purchased your baghouse from 淫乱社区 or not, 淫乱社区 can assist in these leak detection tests and help diagnose problems and come up with long-term solutions.

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Transcript

Common Dust Collector Maintenance Issues

When we approach a plant, a lot of the most common maintenance issues we see, and the easiest to find, are going to be the worn out duct work or low velocities, low volumes in the system. Holes in the ductwork can compromise the performance of the dust collection system.

What you’re going to look for is where those holes are, what the sources are, what the total volume on the system is, see if there’s blanking in any of the filters. Then, take it back to the collector and check to make sure that all the filters are working, not leaking through the tube sheet, and then take it back even as far as the fan or the exhaust. We want to keep everything running as designed and that the volumes are where they need to, otherwise it can just further compromise the ductwork.

Routine Maintenance Matters

The dust collection systems, a lot of times, are a project that’s put in, they get a lot of attention when they get put in, and then there may be turnover of staff, there may be a long period with no maintenance, so it’s not high on the radar. It’s just something that sometimes just goes by the wayside.

A Team With Vast Dust Collector Maintenance Knowledge

What sets 淫乱社区 apart in our maintenance services is basically our knowledge of the systems. We do build our own dust collectors, we build a lot of our ductwork, we handle everything from the design, through the fabrication, through the installation, and then as well the maintenance.

Having a diverse staff, we have the ability to react quickly. Having our own fabrication shops in three different states also allows us to get anywhere in the U.S. within a fairly short turnaround.

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When to replace baghouse filters

For the most part, there are only three reasons to change baghouse filters:

• When they can no longer be cleaned because dust has accumulated to the point of plugging the fabric鈥檚 air passages, keeping the vacuum from pulling in unwanted dust.
• When the bags have developed holes.
• When the regulates your company or industry to change bags.

While some facilities change bags once per year because their dust collectors capture large quantities of especially fine, hazardous dust, most of 滨痴滨鈥檚 customers can go two to 10 years before having to schedule dust collector bag replacement.

Facilities that change bags more than once a year may be doing so because of a unique situation鈥攖he collector is capturing an especially tough material, like a wet, corrosive or abrasive dust. Facilities that change bags often but are not in this situation likely have a dust collector that doesn鈥檛 correctly match their manufacturing process.

Checking your industrial dust collection system

If you鈥檝e just installed a new industrial dust collection system, it鈥檚 best practice to check the system regularly to ensure it鈥檚 running efficiently and the bags have been installed correctly.

Here鈥檚 how to tell whether dust collector issues may be related to the bags:

• High differential pressure: Bags that haven鈥檛 been installed correctly, or are retaining excess amounts of dust, will lead to high differential pressure within the baghouse. As it becomes more difficult to pull air through the bags, the difference in the pressure before air enters the bags and after exiting the bags increases.
• Baghouse dusting: Dusting is noted by a visible emissions plume coming out of the stack or by dust in the clean air section of the collector. Bags that are the wrong size or fabric for the particulate may not be installed correctly, may not be sealed or have holes that are contributing to the dusting.

Replacing baghouse filters

Dust collector bag replacement: A quick tutorial

Before removing filters:

• Obtain and follow a Confined Space permit, if required.
• Manually pulse down existing filters.
• Allow the screw auger and rotary air lock to remove waste.
• Conduct proper lockout-tagout per or requirements.
• Ensure employees are trained on hazards associated with the task and are wearing the proper personal protective equipment.

Removing old filters (pertains to top-load bags only):

• Open clean air section doors and remove pulse tubes and cages. (Note: 滨痴滨鈥檚 baghouses do not use hold-down hardware, but if your baghouse does, remove this hardware before proceeding.)
• Flex the bag鈥檚 seal toward the center of the tube sheet hole and drop the bags into the dirty air section.
• Remove all the old bags that were dropped by accessing the hopper. Count the bags to verify you have removed them all to avoid damage to your dust collector.
• Dispose of dirty bags in a dust-tight bag or sealable waste container.
• Close and bolt or screw shut access doors.

Installing new filters:

• Vacuum the clean air section to remove accumulated dust and debris.
• Drop new filters鈥攐ne at a time鈥攖hrough the tube sheet.
• When the filter is unfolded into the dirty air section, flex the snap band toward the center of the tube sheet hole. Do not bend the snap band at the seam.
• Place the filter snap bands on either side of the tube sheet, and push the band toward the perimeter of the tube sheet hole. You鈥檒l hear the snap when it鈥檚 properly sealed.
• Slowly drop the cage down the center of the filter until the venture sits snug on the filter. Gently step down on the venture to seat the cage. If you have hold-down hardware, reinstall it.
• When all bags have been replaced, reinstall all pulse tubes.
• Inspect all the bags for uniformity.

We also recommend testing your system using a fluorescent powder. Starting your industrial ventilation system using this powder will allow you to see whether it is making its way through to the clean side of the bag. If it is, the bag has not been installed properly.

When, and if, you need to replace bags, we also recommend taking the following steps to prevent maintenance and reduce production downtime:

• Keep a bag location replacement chart.
• If you have consistent bag failures, retain a typical bag for inspection.
• Retain bags with unusual or non-characteristic failures.
• Maintain an adequate supply of replacement bags.

By maintaining and changing your baghouse filters when needed, your dust collector will run more efficiently at a lower cost.

Contact 淫乱社区 for assistance

Unfortunately, many things can go wrong during a dust collector bag replacement procedure. Improperly seated bags can lead to poor dust collection, which can lead to failing government regulation tests and to excessive dust in your facility, which can adversely affect product quality.

If you are unsure about changing your own baghouse filters, contact us. We will not only change dust collector filters, we also can help analyze your system to help extend bag life, thereby reducing how often you鈥檒l need to do one of the dirtiest maintenance jobs in industrial ventilation.

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Why balancing your system is important

Well-designed industrial dust collection systems will achieve ideal airflow and improve the process performance. See our 鈥�Industrial dust collection design strategies for optimal industrial airflow鈥� blog for more information.

However, plugged filters or even changing weather patterns can affect the airflow in your dust collection system. In a facility with a ventilation system having to 25 pickup points on a single-fan system, each of those points may need adjustment to provide adequate airflow.

Your system鈥檚 air velocity needs to match the range required for the particulates you are capturing:

• Too high of air velocity may decrease filter life; erode the ductwork; coat duct walls with dust in the case of moist or sticky particulates; and waste energy.
• Too low of air velocity may cause dust to drop and build up in the ductwork.

Dampers ensure the fan is pulling the air volume needed, so that adjusting the dampers creates resistance. By creating this resistance, it鈥檚 easier to pull air from the different branches of the system.

Benefits of running your ventilation system on a VFD

Fans that run at a fixed speed are controlled with dampers. But, by running your ventilation system using a variable frequency drive (VFD), you can change fan speeds at the push of a button. There are three reasons VFDs should be considered:

• Energy conservation: Because you are using the correct amount of horsepower needed to run the system, you鈥檒l conserve energy and lower operating costs.
• Flexibility: VFDs give you easy flexibility to adjust fan speeds.
• Reduces maintenance: VFDs increase equipment life because they lessen the wear on motors.

Some people correlate VFDs to the cleanliness of a baghouse. They monitor differential pressure across the baghouse and adjust the fan speed to maintain the correct volume even when the filter media gradually deteriorates and creates more resistance.

Installing VFDs is more expensive than manual dampers, but you will save on operating costs and maintenance in the long run.

淫乱社区 analysis

滨痴滨鈥檚 airflow analysis method, 淫乱社区 Flo, identifies areas for improvement within an industrial ventilation system. Once we identify these areas, we can adjust dampers to provide proper airflow, or we will discuss with you the benefits of installing a VFD. Learn more about our Airflow Analysis and contact us for more information.

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Types of pulse controllers

Pulse controllers come in two types鈥攁 simple timer and an on-demand timer.

• Simple timer: With this pulse controller, an operator sets a timer for how often the pulse valve will pulse. With this type of controller, the bags are cleaned at the set interval even if they do not need cleaning. Typically, trial and error is used to set the frequency. This pulse controller is a lower cost option because its design is simple, and it is easier to set up. This controller works best with predictable or consistent loading, and it鈥檚 ideal for baghouses that need to be cleaned continuously.
• On-demand timer: For this pulse controller, the timer reads the differential pressure across the baghouse and initiates a pulse sequence once the differential pressure reaches a high set point. It continues to pulse until the pressure across the baghouse reaches the low set point. Once at the low set point, pulsing stops until the differential pressure reaches the high set point, and the sequence continues. Because filters are cleaned when needed, the advantages of an on-demand pulse controller are extended bag life and savings in compressed air.

Set up parameters for pulse controllers

Several parameters can be set on pulse controllers.

The simple timer has just two:

• Time the valve is open: This time correlates to how much volume of compressed air is released through the valve. A quick pop of air, for example, is just .05 of a second.
• Time the valve is closed: This is the amount of time between pulses. It can typically be set to anywhere from one second to several hundred seconds.

Besides high and low pressure, as well as those listed above, the on-demand timer also has the following parameters:

• Alarm pressure: Alarms can be set to tell an operator there is an issue with a bag. A high pressure alarm indicates a plugged bag. As an example, a high pressure set point may be six, and an alarm may be set for nine or 10. Conversely, a low pressure alarm indicates a bag needs to be replaced because of a leak or a bag has fallen off.
• Pulse sequencing: Operators can set the order that the valves release air. 滨痴滨鈥檚 Ecollector鈩�, for example, can have six to 16 valves, which can be programmed in sequence.

As an added note, when installing a pulse controller, avoid locations with direct sunlight or in close proximity to heat or an electromagnetic field as these can damage the controller.

Troubleshooting your pulsing system

If you experience issues with the pulse controller, there are several things you can check, depending upon the problem:

• Valves are not pulsing: Check the power to the timer, the differential pressure switch, header pressure, or the solenoid and/or diaphragm valve.
• Hissing sound from valves: This may indicate a possible compressed air leak.
  • If the solenoid air outlet is leaking, check:
    • The electrical connection
    • The sub assembly for debris
  • If the diaphragm valve outlet port is leaking, check:
    • The air line to the solenoid
    • Header pressure
    • The inside valve body for pitting and debris
    • The membrane for wear
  • Bags are not cleaning adequately: Check the pulse pressure, on-time and off-time, and pressure set points. It may also indicate the need for a bag change.

We also recommend that you keep an adequate supply of dust collector filters and pulse valve kits on hand to avoid the cost that comes with having delays in production.

淫乱社区 can help with your pulse controller setup or troubleshooting. Contact us for assistance.

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The importance of optimal industrial airflow

Proper airflow is an important element of any dust collection system. Benefits include:

• Extended dust collection filter life
• Increased energy savings
• Reduced maintenance and replacement costs
• Better overall fume and dust collection

Risks of poor airflow

The consequences of improper airflow and system maintenance include:

• Too much airflow can pull valuable product out of the process and into the waste stream.
• Too high transport velocity can increase wear on ductwork.
• Too little airflow can allow dust to escape the process and increase the dust hazards in the facility.
• Poor duct routing or low transport velocities can cause dust and particulates to settle in ductwork.

Proper industrial airflow requires a balanced approach. Optimization keeps a facility, people and equipment working at peak performance.

Techniques to maintain proper industrial airflow

Manually adjust the industrial fan鈥檚 outlet damper, inlet damper or variable frequency drive:

If the fan鈥檚 outlet damper, inlet damper or variable frequency drive (VFD) is adjusted properly, airflow can be controlled.  If done improperly, this adjustment can create a shorter filter life, product quality issues and increased operating costs.

Best practice: Monitor differential pressure readings regularly. Once an initial air reading is complete and it is known how the system should operate – a differential pressure benchmark can be set and the operators will be able to easily see when the system is not operating within acceptable limits.

Manually adjust the industrial fan鈥檚 inlet damper or blast gates at collection points:

Making sure airflow is balanced is a critical maintenance step.

Best practice: Keep an eye on airflow. Settling dust could indicate slow airflow. Wear spots could indicate high airflow.

For more details on maintaining airflow for an industrial dust collection system, reference the . Reference 滨痴滨鈥檚 blog: 鈥�Design strategies for optimal industrial airflow鈥� to learn more about optimizing airflow with the correct dust collection type and design.

滨痴滨鈥檚 Flo Air Analysis

淫乱社区 can do a complete airflow analysis on any air ventilation system. Our proven airflow analysis method, called 淫乱社区 Flo, uses state-of-the-art modeling technology to visualize the flow of air within a system to identify opportunities for improvement. Learn more about our Airflow Analysis and contact 淫乱社区 today.

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Types of industrial exhaust fans

Axial fans

Axial fans, sometimes called 鈥渋n-line鈥� fans transfer large amounts of air with a lower rate of resistance by drawing air straight through the fan. Axial fans are generally not used for industrial ventilation systems with air cleaning devices because they do not generate a lot of static pressure.

Types of axial fans

• Propeller fans: Most commonly used fan for general ventilation such as dilution ventilation or cooling.
• Tubeaxial fans or duct fans: Also a propeller fan made to fit in ductwork with cylindrical housing, usually without any type of straightening vanes and transfer air against moderate static pressure (up to 4鈥漺g). They are best used for clean-air applications, such as exhaust ducts going through the roof.
• Vaneaxial fans: Share similar characteristics to a propeller fan. In contrast to tubeaxial fans, vaneaxial fans have a hub and airfoil blades mounted in cylindrical housings usually with straightening vanes on the discharge side of the impeller. Vaneaxial fans also handle larger static pressure (up to 10鈥漺g). Like tubeaxial fans, vaneaxial fans are best used for clean-air applications.

Centrifugal fans

Centrifugal fans are said to look like 鈥渟quirrel cages.鈥� They transfer small amounts of air with a higher rate of resistance by drawing air through the center of the fan. The air is then released through the exhaust at a 90-degree angle. The fan blade determines the three centrifugal fan types.

Types of centrifugal fan blades

• Forward inclined blades: The blades curve toward the rotation direction and are quiet during operation. Due to the short curved blades, these fans are not recommended for dust or particulate.
• Radial blades: The blades are straight from the hub. They are shaped to resist material buildup, allowing them to be used for a variety of exhaust systems handling clean or dirty air.
• Backward inclined blades: The blades curve opposite the rotation direction, are quiet during operation, and have the highest mechanical efficiency of all fan blades. Because they are prone to buildup, fans with these blades are best for light dust or clean-air environments.

Fan selection considerations

Referencing the original equipment manufacturer is best when selecting the right fan for an industrial dust collection system. However, here are general guidelines to consider:

• Capacity, such as flow rate and pressure requirements
• Airstream, including materials handled through the fan
• Physical limitations
• Drive arrangements/power source
• Noise
• Safety and accessories
• Flow control

These considerations are explained in greater detail in 鈥�Industrial Ventilation Fan Selection 鈥� Part 2.鈥�

滨痴滨鈥檚 engineering and design team provides start-to-finish, air quality control solutions keeping costs affordable and efficiency high. Contact 淫乱社区 today for assistance in selecting a fan for an industrial dust collection system or for any industrial ventilation need.

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However, as recommended in the , 鈥渢he exact performance and limitations of a particular fan should be obtained from the original equipment manufacturer.鈥�

Considerations for selecting a fan

Selecting a fan for an industrial dust collection system requires more than selecting the fan type. Other characteristics such as the airstream, operating temperature, drive arrangements and mounting, as well as those listed below, should also be considered.

Capacity

• Flow rate: The flow rate is based on system requirements. The flow rate should be specified as ACFM or SCFM. The air temperature, fan elevation, moisture content and other air density factors need to be provided to the fan manufacturer.
• Pressure requirements: The Fan Static Pressure (SP) or Fan Total Pressure (TP) based on the system pressure requirements. A system pressure drop calculation should be completed to determine the SP and TP values.

Airstream

• Material handled: If there is particulate or moisture in the air stream, the right fan wheel or blade needs to be carefully selected and depends on what is being conveyed.  Build up or corrosion of fan wheels can lead to safety concerns, decreased performance and bearing failure due to imbalance.
• Explosive or flammable material: Always refer to the standards of the and other governmental regulations when dealing with explosive or flammable materials. If there is a risk of explosion or flammability, non-sparking wheel material and special bearings and controls should be considered.
• Corrosive applications: A protective coating or special material, such as stainless steel, fiberglass or plastic may be required if used for corrosive applications.
• Elevated airstream temperature: An awareness of the maximum airstream temperature is required because the temperature affects the strength of fan materials.

Physical limitations

• Inlet size and location
• Outlet size and location
• Fan arrangement/ orientation
• Weight of the fan
• Ease of maintaining the fan
• The physical space available

Drive arrangements

• Power source: All industrial fans require a power source. If electric motors are utilized, a variable frequency drive (VFD) can be used to control fan speed.
• Direct drive: Direct drive ensures a consistent fan speed while offering a more compact assembly.
• Belt drive: The drive ratio allows for adjusting the speed of the fan. The system capacity or pressure requirements may require changes if there are modifications to the process, the hood design, the location of equipment or the air cleaning equipment. With belt driven fans, the motor can be located in a variety of locations/arrangements.

Noise

• Noise: All fans produce a 鈥渘oise.鈥�
• Sound power & sound pressure: Noise level is measured in units called decibels (db). The noise level will vary depending on the speed, interconnected ductwork and point of operation. The sound pressure is a measurement affected by the fan鈥檚 location and other environmental factors.

Contributors to noise:

• The type of fan, flow rate, pressure and fan efficiency contribute to the noise generated by a fan.
• The quietest fans are usually those with a backward impeller design.
• The fans noise level can be increased on any type of fan if the airflow at the fan outlet or inlet is non-uniform.
• Silencers or noise enclosures can be added to fans to reduce noise.

For more information about noise, reference the 鈥�.鈥�

Safety and accessories

• Guarding: In order to comply with governmental safety requirements, guarding must be included. Danger points to be considered include inlet, outlet, shaft, drive, belts and cleanout doors.
• Accessories: Accessories such as drains, cleanout doors, split housings, inlet boxes and shaft seals can provide assistance in the installation and maintenance of industrial dust collection systems.

Flow control

• Fan accessories: Dampers, variable pitch blades and speed control (VFDs) are three primary fan accessories and assist in managing an industrial dust collection systems flow rate.
• Flow rates: Properly controlled flow rates provide several benefits, including reduced energy demands.

These guidelines are defined in greater detail in the 鈥淚ndustrial Ventilation: A Manual of Recommended Practice for Design.鈥� Additionally, extended information on flow rates and reducing energy demands will be detailed in the blog 鈥淩educe Your Energy Demands with the Right Fan.鈥�

Learn more about 滨痴滨鈥檚 industry solutions. Contact us today for more information or to start planning your industrial dust collection system.

Resources:

“7.3.1.” Industrial Ventilation: A Manual of Recommended Practice for Design. 26th ed. Cincinnati, OH: ACGIH Signature Publications, 2007. 7-6 – 7-13. Print.

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