The inception of the dust collector has allowed companies to effectively capture airborne particulate from an air stream. This has become more important for several reasons. First, containing particulate — toxic or not — is necessary to provide a healthy and clean work environment. Second, increasing local and global awareness of air pollution, containment and the process dust in industrial applications has emphasized the importance of dust collectors. Finally, expanding regulations have pressured companies to properly design, install, operate and maintain dust collection equipment.
To ensure dust collector bags are functioning properly, you need to perform periodic inspections, as well as repair and replace damaged or malfunctioning equipment. A routine inspection and maintenance program will boost your equipment's performance and life. To maintain the health and effectiveness of your dust collector, follow our helpful list of procedures.
1. Create an inspection/maintenance program — A typical program consists of a schedule for periodic inspections that are performed on a daily, weekly, monthly, semi-annual and annual basis. Failing to periodically inspect the dust collector can hurt its performance. Subsequently, the dust collector may not meet EPA outlet emissions standards.
2. Don't exceed recommended pressure drop — Sometimes called differential pressure, it's the amount of static resistance across filters when operating a positive- or negative-pressure dust collector. Pressure drop, typically measured in inches of water column (in w.c.), is a good indicator of the amount of dust that has collected on the filter media and, if continually monitored, the condition of the filters.
New filters have the lowest pressure drop because of the inherent permeability of the media. As the bags develop a dust cake, some particulate embeds itself into the filter media, increasing pressure drop accordingly. The filtering of the airstream through this accumulated dust cake provides high-efficiency collection of fine particulate. In fact, the highest efficiency a dust collector can offer is just before the cleaning is initiated. However, high differential pressures can cause filter media bleed-through or blinding. Therefore, do not to exceed the manufacturer's recommended operating pressure drop.
3. Ensure cleaning system functions properly — Equipment use a variety of cleaning systems to dislodge accumulated dust cake from the filter media. Systems include reverse air, shaker or pulse clean. Regardless of the style of cleaning, it is imperative that this system function properly at all times. Without an effective cleaning system, dust will continue to build on the bags. The result will be an increased pressure drop and reduced volume of ventilation air at the pick-up points. Further, airstream velocities within the ductwork will decrease and cause dropout of dust in the ducts. This may choke the entire system and render it ineffective.
4. Watch for visible emissions — This includes any particulate that can be seen discharging from the exhaust stack. These emissions indicate a breach in a seal or a broken (torn) filter. In either case, you must find and correct the leak immediately. Not only will the emission cause a health concern and damage the property outside the plant, but it may also bring about monetary fines imposed by local, state and federal environmental agencies. Additionally, fans located downstream of the collector can be damaged from abrasion or become imbalanced if you don't correct this condition quickly.
Continually monitor exhaust from the dust collector. Besides visual inspections, consider incorporating a broken bag detector into the clean air ductwork. If a bag begins to fail, or there's a leak in the bag seal, you'll detect the particles that bypass the media. Typically, these detectors use triboelectric technology. These devices can be wired to an alarm horn, siren or PLC.
5. Select the right exhaust fan — Dust collection systems require an exhaust fan to accelerate ventilation air from the point of pick-up, through the ductwork and dust collector filter media and out the exhaust stack. Fans are selected to accommodate volume (SCFM) and pressure drop throughout the system. Calculate the pressure drop by evaluating the static resistance of the dust collector, ductwork and pick-up points/hoods.
6. Inspect the filter media — This is the most important item in a dust collector because it accumulates and supports a dust cake. This dust cake is what provides high filtering efficiencies during operation. Inspect the clean-air side of the dust collector for leaks and the bags for tears. If pressure-drop within a dust collector becomes extremely high relative to historical data, it may be caused by excessive dust cake or blinding of the filter bags.
Depending on the application, differential pressure may take a number of hours or even days to develop. It is essential that you keep filtering velocities low for new filter media. Reducing the volume decreases the airstream's velocity, thus protecting the bags from high-velocity impingement of dust. If you expose bags to the fan's full volume, fine particles may embed themselves into the bags' inner fibers and begin blinding. This can also reduce the life of the bags by damaging the fibers of the media. So make sure to season a collector's filter bags.
This is not an all-inclusive list. Each piece of equipment and application is different, and each has its own unique components and features. But these simple procedures can help you monitor and maintain your dust collector's heath, as well as prevent shutdowns due to inefficiencies, prolong filter life and prevent costly EPA fines.
Dust Filter Bag
The welding of the filter bag cage is not standardized. The unevenness of the welding frame of the filter bag cage or friction with the cabinet will cause the dust filter bag to be worn out during shaking. Generally, the uneven surface of the filter bag cage refers to burrs or edges at the welding place;
The dust bag installation is not standard. The dust filter bags are too loose when suspended, which may cause the dust filter bag to collide or friction with other components, resulting in damage to itself;
The disassembly and assembly of the dust filter bag is not standard. When the dust filter bag is disassembled or installed, it is likely to collide with metal edges and wear the cloth bag. This kind of injury is not easy to detect, but ash will appear during work;
The cleaning cycle is unreasonable. The dust removal cycle is too short and the dust removal method is wrong, which will increase the burden on the dust filter bag and cause the dust filter bag to be easily damaged;
Dust-containing gas properties. The temperature of the dusty gas is too high, the concentration is too high, and the wind speed is too high, etc., it will increase the burden of the dust filter bag and easily cause premature damage to the dust filter bag. In addition, if the dust filter bag used fails to match this working condition, it is easy to burn. On the contrary, if the temperature is too low and the wind speed is low, it is easy to cause condensation and dust removal of the dust filter bag. The high dust filter bag needs to be replaced.
Five Things You Should Know about Dust Collection Filter Media
#1: Most industrial dust collection manufacturers design filters or collectors. Few design both.
The customer wins when a manufacturer understands the behavior of both the filter media and the dust collector and designs both. When a supplier can optimize the interaction between the filter media’s performance and the collector’s performance as a single consolidated system, the customer benefits by a more stable and dependable operation and lower operating costs.
#2: Effective filter media designs may require thousands of computer simulations before initial lab samples are produced or final media grades are released to production.
Filter media development is very involved and includes the testing of raw materials and properties of filter media blends. Raw material testing and media development labs often evaluate media components using: high-performance liquid chromatography (HPLC), FTIR (Fourier Transform Infrared) Spectroscopy, TD-GC-MS (Thermogravimetric Analyzer - Gas Chromatography - Mass Spectrometry), and SEM (Scanning Electron Microscopy). These tools help ensure the optimal design and materials are being used to appropriately match the application conditions.
Development of Donaldson media grades includes computer modeling to predict tensile strength, stiffness, permeability, and a variety of other filtration and efficiency levels. This modeling helps ensure a thorough understanding of the potential physical properties of a media recipe before a test recipe is even produced in the lab. When a recipe shows promise, samples are produced in the lab so physical testing can confirm the predicted properties.
Donaldson considers filter media development one of its core competencies. Even so, with all our background and experience, new media recipes still go through thousands of computer and lab iterations to achieve the optimized characteristics before we begin production of a new media grade.
#3: There’s more to manufacturing filter media than meets the eye.
The general process of developing any filter media should begin by identifying the application requirements. Then specifications are determined for not only the finished media grade, but for the final filtration product in which the dust filter media grade will be incorporated (i.e. cartridge, panel, or filter pack).
Factors to be considered in media recipe formulation include: a cost level which makes sense for the market; minimum efficiency levels needed to achieve acceptable emissions; the type and amount of material being filtered from the fluid stream by the media filter; and the physical environment to which the media will be exposed. Other factors include: pressure, vibration, temperature, humidity, and chemical composition of contaminants.
Pressure drop, or the resistance necessary to cause fluid flow through the media, is considered critical to media design because this impacts the energy it takes to move fluid through the media and, therefore, the operating cost of the filter developed.
All of these variables are considered important, and they must be balanced against one another to formulate an optimized media grade for an application. For example, a formulation may use expensive materials and provide high efficiency, yet the very dense filter media might be expensive to operate in the collector because of the high pressure drop of the filter and its replacement costs. A dense filter media design might also compromise the performance of a cleaning system and could result in shorter overall filter life and increased maintenance material and labor costs.
On the other end of the spectrum, a filter media comprised of low cost materials with low pressure resistance may offer initial benefits. However, if the media does not handle the physical challenges of the operation or becomes quickly plugged, the operational disruption and maintenance downtime and expense make it a poor choice. Optimizing the various performance measures is essential to overall collector performance.
#4: Some manufacturers offer 300+ grades of filter media from which to choose.
Some manufacturers are so serious about providing exactly what the customer needs they offer hundreds of choices to the market, each tailored to meet specific challenges and requirements. If an appropriate media does not exist for an application, new media development may be undertaken.
#5: Evaluating dust collection manufacturers pays off.
When evaluating dust collection manufacturers, look for one that offers media grades optimized for your application and for the collector in which they will operate. This will help optimize your filter efficiency performance, extend your filter life, and lower your cost of ownership. Choose a company with a strong history of providing expertise and technical support.
If you’re employed by a global company, consider a global dust collection manufacturer that can provide excellent customer support around the world – including stock inventory of common filters and parts so they are ready to ship when you need them. A company like this will provide you exactly what you need.
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