Spark Arresters and Coolers

Important Factors in Spark Arrester Selection
(1) Pressure drop across QUENCHER style of unit is a function of the Reynolds number which is proportional to the density for air. This means that a unit can be sized smaller if operating at a higher temperature. For instance a suppressor operating at 440 degrees F is 2/3 the size of the typical unit applied at 70 degrees F and the pressure drop will be designed the same. This lowers the cost of the suppressor. The density is also affected by the water vapor in the gas stream. It has little effect at temperatures below 125 degrees F but can be a major factor when operating at higher temperatures.
(2) If the gas steam has dust that might drop out in the duct at the velocities in the blender style or QUENCHER suppressor, a booster must be provided to periodically remove this accumulation. If this unit is not kept clean it might pose a threat by putting an extra load on the duct-work. Without an Automatic Booster System, the suppressor might require periodic manual cleaning.
(3) The booster design is also temperature sensitive and must be altered to accommodate changing gas steam conditions. Most suppliers do not have the capability to modify these booster designs.

There are several approaches to the issue of extinguishing sparks in a gas stream.

Cyclone Dust Collectors
Contrary to common belief Cyclones are not an effective spark arrestor. For a spark arrestor/cooler to work, there must be turbulence to be effective. If you have turbulence in a cyclone pressure drop is very high. They are designed to avoid turbulence. Many bag house fires occur in systems with cyclone pre-cleaners. Amazingly the inlet baffles on the bag-house are more effective as spark arrestors, however they are not foolproof.

Static Baffle-Box Spark Arrestor
Many dust collector suppliers offer this type. It consists of air entering at one end of a baffle box running over a baffle plate which drops out the sparks and much of the dust collected. The air exits at the other end, and then travels to the dust collector. The big drawback is that a hopper and flexible or solid hose connection to a collection barrel is required. Also, these devices do not eliminate all of the sparks. There is not enough turbulence generated to ensure hundred percent spark arrestance. Sparks may ignite the contents of the collection bin

Mesh Filters
This is a common stop-gap measure where the filter is placed at the exhaust duct of hoods or installed in the duct-work. When clean, the mesh filter will stop at best 80% of sparks. These filters do not produce enough pressure drop to be fully effective. It only takes one spark to ignite dust in the duct or set a dust collector on fire. The only thing these filters do is clog up and add to your maintenance.

Blender Type Air Mixers
A number of these air blender/mixers have been applied successfully as spark coolers and suppressors. Over the last 5-6 years standard air mixers have been adapted and applied between the spark generating process and dust collector. They were applied in processes where fires in the dust collectors had previously occurred. One supplier hired a consultant to develop a market for these air blender/mixers as a spark arrestor/cooler. This blender design was an outgrowth of mixing two gas streams of different temperatures to insure a uniform temperature after the static mixer. It was deduced that the gas stream produced turbulent flow as it passed through the blades and this was the reason it could be adapted to spark cooling. However, these are air mixers first and spark arrestors second. There are performance limitations because not enough turbulence is imparted to the spark ember.

Improved Spark Arrestors
QAM developed the QUENCHER, which is a variation of the blender/mixer design. Employing a 60 year old spin vane mist eliminator technology developed by Sly Manufacturing in the early 1960’s, led QAM to vary the blade designs to have the most effective performance, inducing maximum turbulence to the gas stream, and lowering the cost. Maximum turbulence is the key to spark arrestance. After several tests it was found that the air blender/mixer design did not impart enough turbulence and some sparks got through, especially at low gas stream velocities. Eventually, there was a specific design which imparted the most effective swirling and turbulence thereby extinguishing the sparks quickly and most effectively. In fact, during testing of the QUENCHER, the arrestor cell would light up as a ball of fire, however, one inch past the cell nothing was left in the gas stream. These designs were incorporated into the QUENCHER. QAM has developed special application data in which the blade angles are adjusted to produce minimum pressure drop for different temperatures and gas densities. To our knowledge, no one else accounts for the gas density effects on spark arrestors. In truth, due to the advanced design, even applying the incorrect parameters to a QUENCHER may not result in a failure to put out sparks. Since the pressure drop across the blender and mixer are a function of the velocity through the device, the development of a pneumatically operated booster was introduced to prevent dust dropout accumulating in the static blender/mixer. It also blows out accumulations on the blades.
Read more: Quencher Spark Arrestor


Liquid Spray Systems.
For many years these systems were the only available systems to prevent fires caused by sparks. The system consists of electronic detectors that detect sparks and react to their presence. When a spark is detected liquid sprays are actuated and water sprayed into the duct. The sprays actually cool the gas stream below the dew point. However, in dust collection systems, the water then wets the filter bags or cartridges. This prevents fires but the gas flow is interrupted and the bags must be either replaced or dried out before the process can resume. The detector sensitivity can be lowered to prevent excessive actuations, but, this reduces the reliability of the systems. The detector missing a spark is an ever present danger and a fire may occur. Bag or cartridge replacement is definitely required.

Static Blade Spark Suppressor (Tri Pass)
These were developed in Japan to replace multiple cyclones in Coal fired boilers. They found that the multiple cyclones did not stop sparks from entering the dust collectors. The first ones were installed in the early 70’s. They ran at 1.5 inches of pressure drop and were fabricated from structure angles to resist the wear of the abrasive ashes in the coal that they fired. There are several of these applications installed in the USA designed by one of our colleagues.

We trust that the above information will enable you to evaluate and select the most suitable method and supplier for your application. Buying our QUENCHER/BOOSTER combination will give you a risk free unit, fine tuned for each application. 

More on... Dust Collection and Spark Arrestors

Spark Arresters Prevent Fires

Transport of sparks through ducts; Referring to the sketch below, there is a glowing ember (red particle) surrounded by some hot air (yellow envelop)) which gives the spark buoyancy. This spark (at approx 1400degF) and the hot gas (at approx 800degF) associated with it can travel hundreds of feet in a duct. The ductwork is designed to give laminar (smooth ) flow. This is illustrated on the left of the QUENCHER spark arrestor. Spark suppressors are placed in the duct to change the flow to turbulent (coarse) flow, as shown on the right of the QUENCHER spark arrestor. This agitation or turbulence strips the air from around the ember thereby removing the fuel (oxygen) and breaking up the envelop of hot air, therefore extinguishing and cooling the spark below ignition temperature (pink particle).
Prevention depends on eliminating the causes of ignition. Spark traps can change laminar to turbulent flow and extinguish any sparks in a duct. Design duct systems for dust transport velocities. Install a pneumatic actuated duct booster to flush dust into the dust collector. Use air jets to remove electrostatic charges on duct surfaces. 
Read more about... QUENCHER Spark Arrestors
Read more about... Booster - Duct Cleaner

View a video on the QUENCHER

Furnace and Dust Collector Fire Hazards

Fires in brass furnaces have always been a danger.

First let us review the process; as the material is fed into the furnace it has many metals including zinc, tin etc. Some of these actually go to vapor and then condense and turn into solids.

The key is that these metals are very fine with very large area to weight ratios. The exhaust is generally cooled by mixing with ambient air so the metals are not appreciably oxidized. The dusts collect, with the other dusts, in the dust filter cake.

When the collector is shut down the metals start to oxidize and the effect is like catalytic combustion. The oxidation produces heat. The dust is usually a good heat insulator and "hot spots" occur. Sometimes the temperature is high enough to start a fire when the flow was stopped. More often, when the collector is turned on, the initial flow fans the sparks and when conditions are optimum for combustion, a fire will start. Most of the time small holes or scorching can be noticed on the bags before a fire.

Sparks may occur as scrap is added to the molten metal. This is common when the scrap is oily.  The usual time to add scrap into the furnace is at the end of the shift when the collector is especially vulnerable to fires.

The approach to prevent fires is to extinguish sparks if they are present and to cool the hot spots when air is not flowing through the system.

To extinguish sparks the flow before the collector must be changed from laminar to turbulent flow. This is accomplished by installing a QUENCHER spark arrestor in the air conduit to the dust collector.

To keep the "hot spots" cool, my suggestion is to pulse the collector off line every thirty minutes or so for one complete cycle to cool the "hot spots". If the off-line cleaning is too frequent, the cake will be destroyed or damaged, so, the cleaning must be controlled.

When selecting a fabric pulse jet collector, high-ratio technology designs can operate at filter ratios of 16:1.  Cartridge collectors are not a good selection as the pleats may promote formation of the hotspots described above.

We first used this technique at St Joe Mineral, which was near Pittsburgh, 30 years ago, on their zinc oxide furnaces. We were informed that they were venting through an AAF pulse jet collectors. AAF has managed to put out some of the worst pulse jet collector designs in the Industry. From the description it sounds like a AAF FabriPulse. That collector if it is top access design has these venturies that wedge in the top of the bag. Using the American vernacular, it sucks. The purpose of the venturi is to seal the top of the bag with the cleaning jet. There are openings around the top of the bag below the wide part of the venturi. This, in effect, allows the jet to grow until the growth is stopped by the walls of the bag. That is an over simplification of the process, but it is a fact that it sucks. The net result is that the collector cleans poorly and there is a lot of dust that is forced into the surface and subsurface filter cake.

On any kind of brass furnace it is best to keep the dust cake porous and thin. As I explained previously, in a brass and other process, the zinc goes from vapor to liquid to solid and forms zinc fume. This zinc fume because of its large surface area to weight ratio can burn or explode quite easily.

We were involved in a legal action where the customer hired a man to change bags on a MikroPul collector venting a zinc dipping operation where they were coating pipes. The young man, after he was half finished (inside removal) sat on the temporary grate and decided to light up a cigarette. The collector exploded and then burned down. He was blown out the access door with the explosion and the sprinkler heads went on after the fire started and water poured over him as he was lying on the ground.

Since we were told that the fires started when the process flow continued we need to look at the source of ignition. If the ignition is caused by sparks, the best way to suppress sparks is by going from laminar to turbulent flow in the dust before reaching the collector, with a good in-line spark arrestor. The next source of ignition might be through the cleaning jet. The cleaning jet can supply oxygen from the compressed air and when it reaches the cake maybe sufficient to cause some sparks similar to small explosions to occur in the cake. This may ignite the rest of the fine fume fuel to start a fire. This would be very pronounced, if the collector was running at a high pressure drop with a dense thick cake and frequent pulsing.

We can attack the symptoms or the causes. One way to attack the symptoms is to limit the thickness of the cake. This can be accomplished by installing PTFE membrane laminated bags. Another way to attack the symptoms is to clean the collector with compressed nitrogen instead of compressed air.

One cause may be because of the atrocious design of the cleaning system. The way to remedy the poor design is to modify the cleaning system design. To implement the change we need to throw away the venturies and modify the pulse pipes so they can run without venturies. We can get the pulse pipes modified so they will induce more cleaning air per unit of compressed air, possibly lowering the formation of sparks on the bag surface. It would allow the collector to run at a lower pressure drop with less frequent pulsing.

I always like to look at how the operation of the collector interacts in the process of venting the furnace. 

Read More...  About assistance with dust collection applications.

Welding Fumes

Venting welding fume operations poses some difficult application decisions. Welding is different now than it was even five years ago. Welding is welding, the difference primarily is the coating or lack of it on the metal to be deposited. Anti-spatter is putting the coating on the welding rod from the bottom.

In fact, many suppliers refuse to bid fabric or cartridge collectors for this application.

Electrostatic Precipitators:

Years ago, the preferred method of collecting weld fume was with two stage electrostatic precipitator dust collectors. These had several advantages, they were relatively compact and were generally very effective on general ventilation applications. They could handle relatively large gas volumes through the collectors and generally were located near the roofs of buildings. The collection efficiency was variable depending on the velocity going through the collection plates. The same unit could run at 98%, 90% or 80% collection efficiency at volumes that would vary as much as a ratio of 3:1. The higher the volume would produce the lowest efficiency. On general ventilation lower the efficiency did not cause any problems. The cleaning of the precipitators was accomplished by a detergent wash system. The loading for general ventilation units were from 0.5 to 1 grain per thousand cubic feet per minute. The washing frequency was typically once a week or once every two weeks. The presence of condensed hydrocarbons along with the fume was not a problem. Generally these would be oxidized into solids by time that they were collected. These collectors were generally the same ones that were applied in HVAC systems. The washing mechanisms were designed for 1000 cycle life which would translate to over ten years of life under these general ventilation loading conditions. As the welding operations generated heavier loads, especially in high production facilities, the trend was to hood the welding operations. This venting of the hoods had some pronounced effects on the application of these precipitators:

Effects of hooded systems

1. The load to the precipitators was increased to levels that varied from 5 to 20 grains per 1000 cfm. This was 10 to 40 times as high as the general ventilation requirements.
2. The distribution of air across the intake of the precipitators became critical.
3. Lower efficiencies; The precipitators, because of competitive pressures, were sized for the higher volumes and lower efficiencies

The increased loading meant that the life of the washer systems became 1/10 to 1/40 of that of the general ventilation units. The translated into washer units that had less than six months service life. These HVAC service designs also had problems with coatings building up on the high voltage insulators so they required replacing at about the same frequency as the washers.

The gas distribution across the collection plates radically affected the collection efficiency. If we had a gas stream that averaged 100 fpm that would be designed to operate at 95% collection efficiency and the real velocities entering the plates varied from 50 to 150 fpm, the section at 50 fpm might have a collection efficiency of 98% and the section at 150 fpm would be running at 80%. This would mean that the overall efficiency might operate at close to 85%. Lower efficiency caused by running at higher average velocities were common. In the example above, the collector might be selected to run at 125 fpm and an average efficiency of 85%.

The electrostatic precipitator ionizes the gas molecules and in the process places a charge on all of the dust particles. The charge attracts the dust to the grounded plates. Later these collecting plates are cleaned to remove the dust from the unit.

Running the collectors at these higher loads and decreased efficiency allowed some dust to pass through the precipitator while the dust still retains its charge. As the exhaust gas mixes with the ambient air the dust usually loses its charge and the gas stream loses it’s ionization. The length of time required to lose its charge depends on the dust loading in the exit gas stream as well as the humidity of the ambient air. Dry air will allow the charge to be retained longer. Under certain conditions of low humidity and higher dust concentrations, the dust will hold the charge indefinitely. Suddenly the whole room will be ionized and the charged dust will be attracted to all the neutral surfaces in the room including walls, eyeglasses worn by personnel, windows and even light bulbs. This phenomenon is known as “plating”. There have been occasions where a newly painted plant was coated with black soot within minutes. It is because of these circumstances that welding fume collection was changed to pulse cleaned dust collectors.

Cartridge Dust Collectors:

There are thousands of cartridge collectors in service on these applications

However, there were big differences in power requirements, cartridge life and penetration of dust through the collectors: These were due to the following :

1. Cleaning controls: The much used pressure drop actuated cleaning control has some serious flaws. It is impossible to predict the pressure drop at which the most effective filter cake is formed. It is likely, that this pressure drop may be just slightly higher than the initial pressure drop. If the cartridges are not cleaned early enough the result is that the dust will bridge across the pleats and a large percentage of the filter media in the cartridge (that which is below the bridge) will be unclean able. Initially, the collector should be cleaned by a timer control until the pressure drop stabilizes. The control can be extended until the pressure drop starts to rise and then the timing speeded up slightly. Alternatively, the pressure control can be set slightly above the stabilization point. The best operation occurs when the collector runs at the lowest possible pressure drop. Penetration of dust, cleaning frequency and cartridge replacement time, increase with pressure drop, usually related to the square of the increase in pressure drop.
2. The filter area of the cartridge can be and often is excessive. The media that can be cleaned by the cleaning system is the only media that is useful. Often, suppliers cram more media into a given size cartridge by inserting closely spaced pleats. This cramming of media provides useless media and causes operational and structural defects. If pleats are close together, the adhesive that holds the cartridge together will not wet the media and a strong bond cannot be developed between the end caps and the filter media. A poor bond may allow leakage between the media and the adhesive. If the filter cake is deeper than the open distance between the pleats the cartridge will bridge. Typically cartridge filtering ratios should be no less than 3 FPM, and generally will operate at 4-7 FPM. Most systems operate at lower filter ratios where pressure actuated controls do initiate frequently enough to clean the cartridges effectively. Conventional cleaning systems may not allow for recommended filter ratios of 4-7 FPM. Advanced technology collectors will run at even higher filter ratios and clean the media more effectively, promoting higher efficiency and longer cartridge life.
3. The cartridge shape should be flat and cylindrical. Truncated cone bottoms, formed into the closed end cap, causes damage to the filter cake allowing excessive penetration through the dust collector. The cone develops more cleaning pressure near the bottom than in the rest of the cartridge. Premium construction cartridges are often necessary to develop maximum cartridge life and improved collection efficiency.

Oil-Smoke:

The above applies to welding of clean parts. Recently, there has been a trend to vent from welding operations where the parts are coated with a light film of oil.

A mixture oil and powder can produce oil based paint. This oil/powder mixture can progressively blind the cartridges and produce premature cartridge failure. When you collect oil on the cellulose cartridge, it acts like a blotter and the media swells, permeability and available collection media is reduced. This latter phenomenon is in at edition to the painting action. With some hydro/oleo phobic media, that is specially coated, the oil will not wet the fibers and the media will not swell. Some of these cartridges can be recovered by washing them in detergent, but over a period of time the oil starts to dry and a solid is formed which cannot be washed. Typically after two or three washings the cartridges must be replaced, as there will a creeping higher initial pressure drop.

Usually, the welding fume load is extremely light and with the special fibers, the cartridges can last for several months before they need to be washed or replaced. Actually even cellulose based fibers can be washed successfully two or three times, but the time between washing goes down for each wash as the residual permeability decreases after each washing.

There is some promise in using a precoat (filter aid) of some dust on the media to blot some of the oil so a paint will not form. There are some commercially available coatings that are promising. The choice will be empirical.

Stainless Steel

This is one of the most deceptive applications we can deal with. Most of the time, you will believe that the material has not been pickled with oil or another preservative. The metal looks perfectly dry. Some manufacturing processes will prewash the stainless, thinking they are removing any residue that may be there. When you well donned the material, to everyone's surprise, a residue appears at the dust collector filter elements. A way to determine this is to soak the filter elements in a tank and observe a film of oil form on the surface of the water. Another test would be to take a folded piece of tissue paper and squeeze it between the pleats of the filter element for 24 hours. Automatic pre-coating, or seeding, of the filter elements is a solution to this problem.

Weld-aid (anti-spatter)

Welders often use “weld aid” type of substance to prevent spatter from adhering to the work piece. It is mostly water with a 15% fatty substance. It is usually sprayed on the work piece before welding. This is a very greasy substance that is difficult to remove from the cartridge media and fills in the pores. You should have a washable media, such as polyester spun bond, preferably with a non-stick surface. All paper, cellulose formulations are unacceptable media selections because water gets absorbed and the media swells. Do not use exotic medias that have low permeability. It is recommended to install an automatic filter-aid feeder, such as the one designed and sold by QAM. You also should consult a welding expert to change the welding process, which will eliminate the necessity of using weld-aids or change to a powdered version.

Automatic seeding system

With a special design and a seeding system, it can last indefinitely. A layer of inert absorbent dust is fed into the collector. The collectors not pulsed except twice a day. The inert layer blots up the oil fume and the oxides from the welding are also mixed on the surface. There is an airlock, usually the smallest kind available which feeds the dust back into the bags after the collector is restarted or even pulsing is done while the collector is operating. The ULTRA-FLOW bag-house can run at 18:1 ratio and is probably less costly than the cartridge collector for the application.

Read more on ... Ultra-Flow Baghouse dust collectors

SPARKS & FIRES

Sparks are a very common occurrence in the welding process. These sparks are swept up into the collection hood or device and are transported to the collector. Fires can occur in exhaust ducts as well as inside dust collectors. Requirements of fires or any combustion process are: a) Fuel, in gas, liquid or solid form. b) Oxygen (Atmosphere consists of 20 per cent oxygen) c) Fuel must be raised to the ignition temperature to start burning.

Transport of sparks through ducts.

There is a glowing ember surrounded by some hot air which gives the sparks buoyancy. This spark and the hot gas associated with the spark can travel hundreds of feet in a duct. The ductwork is designed to give laminar (smooth) flow. Spark suppressors are placed in the duct to change the flow to turbulent (coarse) flow. This agitation or turbulence strips the air from around the ember removes the fuel (oxygen), therefore extinguishing and cooling the spark below ignition temperature.

Read more about ... Spark Arresters and Coolers

Prevention depends on eliminating the causes of ignition. Spark traps can change laminar to turbulent flow and extinguish any sparks in a duct. Design for proper dust transport velocities. Install pneumatic actuated duct booster to flush dust into dust collector. Use air jets to remove electrostatic charges on the duct surfaces.

View and print... fires and explosions

Fires - Smelting Process

First we must be careful to find out if the fires are a result of ignitions by a spark. All these acids mixed with carbon can spontaneously ignite, especially if the precious metals include catalysts, such as vanadium, like they use in catalytic converters. Or, they get fires when they are in the ten hour mode? My calculations indicate that during the ten hour precious metal mode they are basically diluting the exhaust to meet discharge requirements into the atmosphere.  To discharge from the hood at 125 degrees they either need a lot of dilution air or water vapor. For 30 hours a week, they use it as a trash burner. Here again they seem to be trying to hide the true nature of the operation. In the trash burning 30 hours they probably have wild swings in emissions which might ignite poorly combusted components and would be ignited by sparks in the baghouse. I would hate to live downwind during either operation. You need to find out the following.

1.  Do the fires occur while operating?
2. Do fires occur when they are shut down?
3. What are the temperatures in the ducts over a 60 hour period?
4. If they run 8 hours a day do they run 2 hours on smelting mode and six hours trash mode?
5. Do they insulate the duct?
6. What is the charge to the smelter? Coins? scrap gold, scrap silver? perhaps catalytic converters?.
7. It seems like they would have a severe corrosion problem and preheating of ducts should be considered.

We can put out sparks with Quencher^tm spark arrester but we cannot remedy poor control.

The ten hour mode is the ten hours per week when they are smelting. The 30 hour mode is when they are trash burning. Get a piece of bag to examine. It will be obvious if it has been chemically attacked. You should be able to tear or burst a piece with pliers and a vise. 

For more on spark arresters, see  QUENCHER spark arrestor

MINI-QUENCHER Spark Arrestor for Small Vacuum lines

QAM is pleased to announce the MINI-QUENCHER spark arrestor for use in 1", 2", 3" and 4" dust collection vacuum lines. This is the latest extension of of our incredible QUENCHER in-line spark arrester line.

The Q-1, Q-2, Q-3 and Q-4 spark arrestors answer a demand for spark protection in these smaller applications. Until now nothing has been available on the market for vacuum dust collection applications.

The MINI-QUENCHER:

• needed for welding, grinding, cutting operations
• extinguishes and cools sparks and embers that set fire to dust collectors and duct work
• in-line device, that is easily inserted in the duct work or vacuum tubing
• no maintenance, no additional drop out collection point required
• no moving parts, static device, no power required

More on... The Mini-Quencher

Spark Arrestors and Booster - Duct Cleaners

Service Reports:

Chambly, QC: The installation was at a microbrewery. This is a problem common to all breweries that recycle their boxes. In the process, they have an automated machine including a band saw which cuts up the boxes and then bundles the cardboard for recycling. A good deal of paper dust is generated by the process and needs to be collected through an extraction duct from the saw to a dust collector.
The problem is that these boxes may still have staples and bottle caps in them. When the saw hits the staple or bottle cap a spark is generated which is drawn into the extraction system and produces a fire in the duct and in the dust collector itself by igniting the cardboard dust.
Our proposal was to install an LC series high ratio dust collector providing the maximum filtration efficiency and making the system the most compact possible. Floor space was an issue. However, to protect both the duct system and dust collector from ignition, a QUENCHER in-line spark arrestor/cooler was installed in the ductwork at the outlet of the extraction hood for the band saw.

Read more about ... Quencher Spark Arrestor

The installation has been running since June 2005. The maintenance supervisor indicated that the system should have caught fire within a maximum of two months of operation, which was the experience they've had until then on the other systems in the plant. There have been no incidents to date. He also stated that there was no light dust accumulation around the dust collector outlet which was typical in the other systems that they had. This is an indication that the dust collector is operating at a high level of efficiency and that there has been no sparks which would have burned holes in the filter material.

London, ON: This is a metalworking shop which does a good deal of welding and grinding. The dust and fumes are extracted to a central dust collector through source capture articulated arms and downdraft tables. These processes produce a lot of sparks which get drawn into the dust collection system.
In one system, the main duct line is oversized and the dust is dropping out into the duct work prior to reaching the dust collector. As a result, the sparks that are transported through the duct will ignite this volatile dust in the duct causing a fire to be drawn into the dust collector.
We recommended that they. install a "booster duct cleaner" which would blow this settled dust down the duct and to the dust collector before it could be ignited by the sparks We also recommended that they install a QUENCHER in-line spark arrestor/cooler to quench the sparks and prevent them from going down the duct work. The client has yet to install the booster which means that he has not solved the dust settling problem but they did install the QUENCHER. Since the installation of the QUENCHER, there has been no further ignition of the dust in the ductwork or in the dust collector.

Read more about ... Booster-Duct Cleaner

Quencher (spark arrestor) with Plasma/Laser Cutting

Some people have used Quenchers, and other style spark arrestors in plasma and laser cutting applications but still experienced fires in their dust collectors. In the majority of cases, the Quencher alone is sufficient to control dust collector fires. However, in some isolated cases, sparks are only one issue to deal with these applications. A good spark arrestor is definitely needed to stop sparks and embers, but, it is no guarantee against fires in the dust collector.

The problem:
1.    The operator may have to reset the heat setting of the plasma head. It could be generating too much atomic static particles. This causes a "painting" effect on the cartridge media, eventually clogging it.
2.    Large heavy particles of molten metal can be generated in the process.
3.    You should use spun bond wide pleat cartridges, to ensure proper clean out of the cartridges. That way the dust will spread over a large surface of media, instead of on the outer surface only.
4.    Current cartridges that are clogging over time (can vary from hours to weeks, depending on loading). When clogging occurs, the air flow drops and sparks can slip through any spark arrestor (not just the Quencher). This sets fire to the combustible dust accumulated on the surface of the cartridges.

Normally, plasma cutters have different characteristics depending on the settings of the cutter torch. The quantity of dust produced is relatively small. At some torch settings the dust is reactive by initiating an atomic bond between the dust and the surface of the cartridge, forming a hard durable impervious coating which totally or partially plugs the filter media. This mechanism is an inherent part of the plasma coating process to put wear resistant coatings on shafts, turbine blades etc. that allow the parts to receive very long lives. In the plasma coating machinery, the key to collecting the overspray in cartridge or fabric collectors is to allow the atomic bond to dissipate. This is accomplished by extending the time that particles travel from the torch to the filter media elements. In plasma coating systems at this time, depending on torch settings will vary from 0.5 to 0.8 seconds depending on the metals being sprayed.

In plasma cutting applications often the dust being emitted from the torch does not require any special considerations. In fact, collectors can operate for many months quite well with moderate pressure drops. Then the torch settings are changed because of various factors such as the composition or thickness of the pieces that are cut. As the settings of the gun or the speed of the cut is changed, the dust can act as a plasma coating torch and the cartridges start plugging. Sparks are often produced. If the dust is combustible the sparks may ignite the coating on the cartridges. Normally the fuel on the cartridge surface is not very heavy so the fires do not damage the housing of the collector. The cartridges are then usually replaced. The QUENCHER spark arresters are sometimes applied to limit the risk of fires and extend cartridge life. In the tandem horizontal type collectors, the cartridges are usually tight spaced, so, as the pressure drop rises, the pleats are pinched in the valleys so the pressure drop goes up. Combustible dusts can put pounds of dust to be stored in the cartridges to fuel a fire in the collectors. However, the squeezing of the pleats also causes pressure drop to increase and slow the flow through the dust collector. This often allows dust to be released into the work area.

Although spark arrestors will protect the system from sparks, pieces of molten metal go through the spark arrestor unaffected. These heavy, hot particles lodge on the surface of the cartridge and ignite the combustible dust coating. The heavy molten particles need to be dropped out of the system prior to the spark arrestor and collected safely, so as not to cause a fire in that collection device. Cyclones and drop out boxes are sometimes used for this. However, be aware that these devices have little effect on sparks / embers which are light buoyant particles and slip through to the dust collector.

An excellent example of these effects was the experience of the Day division of Donaldson who supplies this design. In cutting the filter mounting plates for their design they plasma cut holes in a 1/4 inch thick plate. They found that the filters plugged quickly in the after filters. They added distance in the filters venting the operations. This experience occurred 20 years ago and we do not know how this operation is now performing.

Our recommendation is to replace the current cartridges with a wide spaced stiffened spun bond media carried and pre-coat the cartridges with a 1/64 inch thick coating of inert pre-coat material.

We suggest you send each job application data (layouts & pictures) to QAM technical support at gary@qamanage.com and/or call 800-267-5585. We’ve dealt with plasma cutting applications for decades and feel that yours would be a common problem. If you contact us, we'll be happy to work with you on this.

More about... Spark Arrestor applications with plasma/laser cutters (PDF)

Coal Dust and Quenchers

First let us review the facts on explosions.

Explosive dusts have lower and upper explosive concentrations. An explosion can only occur if the following is true. Assuming we have outside air with 20% oxygen being used to ventilate the mill, it is probable that the outlet from the hammer-mill will be between the upper and lower explosive limit concentrations. Between these limits if there is enough energy in the spark that ignites the dust, an explosive flame front will be triggered and move along the duct toward the ventilation outlet and presumably toward a dust collector, and, we are assuming this is to be a fabric (baghouse) collector. Determining the upper concentration limit is very difficult. The lower explosion limit is around 30 grains per SCFM for combustible dusts like coal. Once an explosive flame front is ignited the normal procedure is to put explosion vents in the ducts and collectors.

The action of Quencher spark arrestor.

Our Quencher spark suppressor works by changing the flow in the duct to turbulent flow. During laminar flow the spark can be carried for extremely long distance as the spark travels with a layer of air which insulates it. When turbulent flow is induced, the spark is immediately cooled so it lacks sufficient energy to start a fire or trigger an explosive front. Most insurance underwriters require explosion venting of the duct systems and dust collectors. The way of achieving this conversion from laminar to turbulent flow is by slowing the air down to lower the power consumption of the conversion device. The conversion device thoroughly mixes the dust laden gas stream with propeller type fixed vanes to extinguish the spark(s). To rid the potential low velocity build up of coal dust in the spark arrestor, it is periodically boosted in air stream speed to sweep the dust into the collector. This uses a compressed air propelled stream identical in design to that of a reverse pulse jet collector with time durations similar to that in those dust collectors. This the “Booster - Duct Cleaner” option is offered with the Quencher spark arrester.

Read more about ... Quencher Spark Arrestor

QUENCHER Application to Various Processes

This is an overview of the potential for the QUENCHER spark arrestor in the ventilation market. It may seem detailed but the terms had to be defined as well as recent approaches. This can be exciting for all of us.

FOREWORD
Many gas steam processes, especially in powder collection systems, are candidates for the application of low cost gas mixing products as the Quencher supplied by Quality Air Management.
Note that embers & sparks get extinguished in the Quencher cell itself. Combusting material, such as paper or wood shavings, must be completely consumed within 4 duct diameters past the Quencher (where there is still enough turbulence) and taken the form of embers to be extinguished.

1) SPARK COOLING
Prevention of Sparks entering Solids separator (dust collector) equipment and starting fires
Definition:  First we must define a spark. A spark is a piece of solid particulate which is completely oxidized and is at a temperature of 600 degrees F or over and which is above the ignition temperature of the powder being collected or above the ignition temperature of the filter elements.
Effects of sparks: Sparks can be carried along in the exhaust gas stream in laminar flow and will not cool off since cooling requires a difference in velocity between the gas and the spark being transported. Therefore, the spark will be carried into the solids separator and deposited on the filter element surface where it has a possibility of igniting the surface. If ignition occurs, the fire may spread and cause damage and produce harmful gases.
Response by the QUENCHER to sparks occurring in exhaust stream: The static blender converts the laminar flow to turbulent flow by thoroughly mixing the solid sparks with the gas stream, reducing the temperature of the sparks below the ignition temperatures of the filter media and the powder transported through the system.

2) HIGH TEMPERATURE COATING AND CUTTING PROCESSES
Originally a lot of these operations were performed by cutting with an acetylene torch to cut metal and with flame spray equipment which fed a wire into the flame of a gas torch to produce coating on various metallic and non-metallic surfaces.
The torch cuts were very coarse and had to be ground or put into other cold forming devices to make the parts usable. Often these cutting torches were applied to cutting up and reclaiming scrap. Most venting systems for torch cutting were vented into general ventilation and HVAC systems.
The flame spray equipment was limited to certain thicknesses and uniformity was such that on many parts subsequent grinding and smoothing operations were necessary. The coating produced was relatively coarse and the overspray was easily collected by low pressure drop wet powder collection devices. This avoided any requirements for mixing equipment.
The Advent of high temperature technologies was developed in the 1980-90’s decade; Lasers, plasma, and arc tools have been applied to the processes long dominated by gas torches and sprays. These new technology systems are much more intense, quicker, more accurate and more efficient than the old gas flame units. The temperatures developed in the devices are sufficient to vaporize metals and actually increase the temperature above this value. These systems can take sharp cuts and make intricate cuts, cut fine round holes replacing shears, drill with little or no need for grinding or finishing. They can process thick plate or light gauge sheet metal with the same machinery. They are guided by CNC controls for maximum flexibility. Applying these processes to spray systems is also very effective. The spray process must be explained prior to treating the ventilation of the high temperature cutting devices. These are the fastest growing fabrication processes in the world.
Spray systems; These systems were vented into relatively large gas and powder over spray collection hoods. They produced particles with a very strong attraction to the parts being coated. Some have theorized that the bonding is at the molecular level. When it strikes the surface to be coated it bonds to the surface as if the coating was integral with the object that is in the path of the spraying device. The coating is either fed into the device as a powder or a wire.  The particulate overspray is relatively light in dust loading and the hood is vented to a dust powder collector. The wet collectors are not sufficiently effective to collect this much finer overspray. To develop sufficient collection efficiency, the overspray is vented to fabric or cartridge collecting device. The overspray is still attracted to any solid it gets near and will form a hard impermeable coating which can seal the surfaces of filter collection elements. These overspray particles though much finer than the sparks described above are carried along in ducts which have laminar flow. They must lose their attractive ability before they reach the dust collector / powder separator. If the powder spray is given sufficient time in flowing through the duct work, it will lose its coating ability. Typically the residence time of the dust flowing in the duct, is designed for about one second and sometimes up to 1.5 seconds. For a system running at 2400 feet per minute at least forty feet of duct work would be required between the hood and the collector. Most plants do not have the room for these long ducts. We theorize that a QUENCHER element could allow the reduction of this residence time by as much as 90% and be more predictable than the residence time especially as newer spray compounds are being developed.
Venting High Temperature Cutting Systems; Although the dust venting from the cutting processes do not have as high an attraction as the coating guns, the dust has the same problem. Residence times are often in the 0.5 to 0.7 seconds. Because the dust loadings are so low and the customer often removes the coated filter elements and vents outside, the emissions will be lower than most air pollution codes. However, if the dust could be collected and neutralized, the savings in heating and cooling costs could pay for a QUENCHER device in a month or so.

3) GAS MIXING IN POWDER SEPARATORS
QUENCHER gas mixing cooling of gas  streams; Usually all gas streams are designed for the lowest pressure drop to save on power consumption in moving the gas from one point to another. This is accomplished by moving the gas in a flow pattern called “laminar flow”. In effect the gas stream is divided into cylinders that flow parallel in the duct work so that little or no mixing occurs between these cylinders within the walls of the ductwork. The other flow in a duct occurs when “turbulent flow” occurs. This is a violent mixing that occurs and will quadruple the pressure drop if it occurs in a length of duct. The gas follows the path of least resistance and naturally wants to revert to “laminar flow” when the disturbance or duct element, which produces the turbulent flow is removed. Both laminar and turbulent flow pressure drops are a function of the average velocity through the ducts. If we mix two gas streams flowing through well designed transitions that maintain laminar flow in the total stream, the resultant is that the gas streams will continue in the duct with little or no mixing of the combined gas streams. For instance if a gas stream at 300 degrees F is mixed with one at 100 degrees F, the resultant gas stream will be stratified and continue through the system with part of the flow at 100 degrees and part at 300 degrees. There might be a very narrow layer of the flow that mixes.
The proprietary QUENCHER design is such that the whole cross section of the duct produces an effective mixing with a minimum penalty of pressure drop by producing turbulent flow through the mixing element. 
Temperature Lowering Processes for Solids Separation; Some powder collection gas streams use various means to cool the powder laden gas streams by mixing ambient outside air to reduce the gas temperature (and associated powder temperatures) to a level where a fabric media powder collector can separate the powder and gas for subsequent collection of the solids. A typical operation of this type is on a clinker cooler system in a cement plant. The gas temperature may vary from 200 to 900 degrees F. For operation of the powder separator collector, the temperature entering the collector must be lowered to less than 500 degrees, usually 475 degrees. This can be accomplished by blending the ambient gas stream with process gas. When this mixture is designed, the resultant gas streams often remain stratified with low and high temperature streams entering the powder separator collector. In the past there were various schemes to mix these streams such as special duct fittings. However with these schemes, the air was mixed at high velocities which produced wear on the high velocity mixing components. Placing a QUENCHER in the gas streams achieves the cooling and mixing at minimal wear because of their low velocity designs. This application combines the most difficult circumstances that are likely to be faced in this type of circumstance.

4) FIRES IN POWDER SEPARATING SYSTEMS, CAUSES OTHER THAN SPARKS
There can be solids and liquids in exhaust systems that can cause fires in powder separation equipment.
Solids that are still burning when they enter the exhaust system; These can possibly develop into an explosion front entering the exhaust system. However more likely they will have the appearance of a spark in the exhaust system. A good example of this phenomenon is the collection of burning particles of paper usually strips. The paper provides both the oxygen and fuel to continue the burning process. The mixing process in the QUENCHER element may not cool the burning debris to lower it below the ignition temperature of the powder or filter media. The solution is to completely oxidize the solids before it enters the collection device (dust collector) and associated spark cooler. In that case multiple QUENCHERs may speed up the oxidation and may be a field for future consideration in expanding the QUENCHER market. Another approach might be to install sprays of water prior to the blender and to modify the blender to separate droplets from the cooled gas stream. We can modify the blender designs to make them water droplet separators. (This was the approach taken at Mueller Brass. That service report confirms the efficacy of this approach.)
Spontaneous Combustion; Some metallic and other compounds will oxidize when mixed at room temperatures. This process is well documented when we hear of fires that are smoldering after a fire that suddenly break out into a full scale fire. Catalytic combustion where oxidation takes place between 120 and 300 degrees F is another example of this phenomenon. These fires can be prevented with a combination of QUENCHER and control changes to the powder dust collector operating and will be covered in a separate report in the future.
Explosions; Explosions in the exhaust system can and do trigger fires in collectors. The combustion produces a sustainable conflagration which travels through the ducts at very high speeds. While a QUENCHER mixer can reduce the effect of this flame front by lowering the intensity, the QUENCHER cannot be an approach to prevent explosions.

5) QUENCHER AS PART OF EVAPORATIVE COOLING SYSTEM FOR WET AND DRY POWDER SEPARATORS (DUST COLLECTORS)
In venting furnaces for metallurgical processes; Typically, these furnaces will exhaust at temperatures between 900 and 1800 degrees F. They are vented to either wet collection equipment or through fabric filter element powder collection equipment. As the gas stream enters
Wet Collectors; Wet collection equipment are called air washers or gas scrubbers. These collectors are most effective if the exhaust stream entering the collection device is close to 100% relative humidity, typically 120 to 160 degrees. The temperature is usually reduced by coarse water sprays. The humidification efficiency is usually 80 to 85 percent. The efficiency of the humidifier has a drastic effect on the collection efficiency of the wet collector. The addition of a QUENCHER will increase this humidification efficiency to over 95 per cent. This simple addition might improve collection efficiency to meeting the existing air pollution codes.
Dry Collectors; Many Industrial Processes such as insulation processes or making Mineral, fiberglass insulation, perlite processes develop the process in a furnace. Then the exhaust stream from the furnaces, containing the insulating batts or powder, must be separated from the exhaust stream. The separation device is a dry powder/dust collector. Collecting in a wet form will not produce a usable type of product. Normally the method of cooling is with an evaporate cooling tower that forms a wet cyclonic action from top to bottom. The purpose is to cool the dust laden gas stream to a temperature below 400 degrees F and with dew point temperatures that avoid condensing on the cooling tower walls, as the process temperature rises and falls. The humidifying is controlled to maintain the  proper relationship of wet and dry bulb as determined by system operating parameters.. Fogging nozzles and the control of the water spray rates is used to control the outlet temperature and humidification. The controls are complex because of the relatively low velocity of gases in the tower.
QUENCHER adaptation; The cooling tower would be replaced by a spray mounted in the high temperature ductwork. The QUENCHER would cause the water to evaporate completely and the spray would be increased by the temperature measured at the entrance to the powder collector. This would be more effective and reliable than the big bulky cooling towers which try to control the residence time of the droplets as they evaporate.

CONCLUSION
Every metal working, foundry, Metal processing, Cement and woodworking plant is a candidate for QUENCHER Technology.

Read more about ... Quencher spark arrestors

Plasma Cutting & Cartridges

This is the result from using our cartridge and fabric filter element inspection service.

1) It was not the cartridge that was normally supplied to clients.
2) It had an inverted cone reinforcement in the bottom closed end cap. We always recommend a flat closed end cap for maximum life. The pleat spacing was optimum for this kind of application.
3) The seals (gasket) were resilient which insures effective sealing between the clean air and dirty air compartments. The cartridge exhibited no evidence of improper installation or handling.
4) You could expect indefinite life on this filter element on all suitable applications with an advanced technology pulse jet cleaning system like ULTRA-FLOW.

This plasma cutting operation is quite common and we see many cartridges with problems from these operations. The dust generated is extremely fine and problems with seals and installation account for a big majority of problems. The other problem, that we see is that the settings on the cutting head are such that the dust can be prone to plasma coat the filter elements. The solution of the coating problem is to give the dust time to lose its reactivity before it reaches the filter media. None of these usual problems were evident on this filter element.

A) My first observation was the color of the coating on the filter. In cutting ferrous metal with a plasma arc cutter, the dust is black and coated with fine easily removed powder. In handling of these filter elements, we usually wear a mask because of the fine dust generated in the inspection process. In this case there was no dust generated in the procedure. The color of the coating was brown.

B) My second observation was that there was hard inflexible crust covering the dirty side of the pleats as if the element had been painted. It had the same strength as baked on auto finish.

C) The only time I previously observed this kind of coating on a cutting operation was when the plates were covered with some kind of coolant, cutting oil or pickled. On some cutters they use compressed air at the head. I would suggest checking the air line lubricant as a possible source of the binder that is creating this paint like coating.

Finally, a continuous coating of filter aid could be maintained on the surface of the filter media. The dust load is usually quite light and the coating might be about a 64th thick. The surface coating would be painted instead of the media. When the collector pulses the inert filter aid, coated with the paint, would be ejected into the collection hopper. How often to clean would be a judgment call. I would expect the cleaning and re coating every 2- 4 hours would be appropriate.

Read more ... Retrofit Service for Cartridge Dust Collectors
Find out about ... Most Advanced Technology Dust Collectors

Compare Spark Arrestors

Spark Arrestors; and Spark Coolers

(A comparison of different methods)

There are several approaches to the issue of extinguishing sparks in a gas stream.

Important Factors in Spark Arrestor Selection

1. There is no such thing as an efficiency rating for spark arrestors. They either work or they don’t. Remember, it takes only one spark/ember getting through the device to cause a fire or explosion.
2. Maximum turbulence is the key to effective spark arresting and in the selection of a spark arresting device. Some devices do not impart enough turbulence (and/or pressure drop) to be 100% effective. The recommended pressure drop for an in-line device (one that is installed in a section of the ductwork) is between 0.75 and 1.5 inches WC. Anything less is highly risky. This is a basic law of physics.
3. Pressure drop across a QUENCHER style of spark arrestor is a function of the Reynolds number which is proportional to the density for air. This means that a unit can be sized smaller if operating at a higher temperature. For instance a spark arrestor operating at 440 degrees F is 2/3 the size of the typical unit applied at 70 degrees F and the pressure drop will be designed the same. This lowers the cost of the spark arrestor and ensures its effectiveness. The density is also affected by the water vapor in the gas stream. It has little effect at temperatures below 125oF but can be a major factor when operating at higher temperatures.
4. If the gas stream has dust that might drop out in the duct at the velocities in the blender style or QUENCHER spark arrestor, a booster must be provided to periodically remove this accumulation. If this unit is not kept clean, it might pose a threat by putting an extra load on the ductwork. Without an automatic duct cleaner-booster system, the spark arrestor would require periodic manual cleaning.
5. The duct cleaner - booster design is also temperature sensitive and must be altered to accommodate changing gas stream conditions.
6. Most suppliers do not have the capability to modify the designs as referred to in item (3), (4), (5) above.

Blender Type Air Mixers

A number of these air blender/mixers have been applied with varied success as in-line spark coolers, arrestors and suppressors. Over the last several years standard air mixers have been adapted and applied between the spark generating process and dust collector. They were applied in processes where fires in the dust collectors had previously occurred. One supplier hired a consultant to develop a market for these air blender/mixers as a spark arrestor/cooler. This air blending or mixer style design was an outgrowth of mixing two gas streams of different temperatures to insure a uniform temperature after the static mixer. It was deduced that the gas stream produced turbulent flow as it passed through the blades and this was the reason it could be adapted to spark cooling. However, these are air mixers first and spark arrestors second. They are marketed as having low pressure drop (maximum 0.5 inch WC) through them. There are performance limitations because not enough turbulence (and related pressure drop) is imparted to the spark/ember. To achieve spark suppression, we need to go from laminar to highly turbulent flow in the duct which strips away the hot air envelope around the spark/ember thereby cooling it and starving it of fuel (oxygen). For air blending this is not a requirement. Also, these devices have large gaps between the mixing blades, when looking through the inlet and downstream of the device. These gaps can allow a percentage of sparks/embers to slip through and cause a fire or even an explosion in the dust collector.

Improved In-Line Spark Arrestors

QAM developed the QUENCHER, which is a variation of the blender/mixer design. It is also an in-line spark arrestor. Employing a 60 year old spin vane mist eliminator technology developed by Sly Manufacturing in the early 1960’s, led QAM to vary the blade designs to have the most effective performance, inducing maximum turbulence to the gas stream, and lowering the cost. Maximum turbulence (and the pressure drop that results from it) is the key to spark arresting. After several tests it was found that the air blending/mixer design did not impart enough turbulence and some sparks got through, especially at low gas stream velocities. Eventually, there was a specific design which imparted the most effective swirling and turbulence thereby extinguishing the sparks quickly and most effectively. In fact, during testing of the QUENCHER, the arrestor cell would light up as a ball of fire, however, one inch past the cell nothing was left in the gas stream. These designs were incorporated into the QUENCHER. QAM has developed special application data in which the blade angles are adjusted to produce minimum effective pressure drop for different temperatures and gas densities. To our knowledge, no one else accounts for the gas density effects on spark arrestors. In truth, due to the advanced design, even applying the incorrect parameters to a QUENCHER may not result in a failure to put out sparks. Since the pressure drop across the device are a function of the velocity through it, the development of a pneumatically operated booster was introduced to prevent dust dropout accumulating in the static arresting cell. It also blows out accumulations on the blades.

Find out more ... Quencher spark arrestor

Liquid Spray Systems
For many years these systems were the only method to prevent fires caused by sparks. The system consists of electronic detectors that detect sparks and react to their presence. When a spark is detected liquid sprays are actuated and water sprayed into the duct. The sprays actually cool the gas stream below the dew point. However, in dust collection systems, the water then wets the filter bags or cartridges. This prevents fires but the gas flow is interrupted and the bags must be either replaced or dried out before the process can resume. It takes a whole day or two to dry out the bags or even to prevent blinding and replacement. The detector sensitivity can be lowered to prevent excessive actuations, but, this reduces the reliability of the systems. The detector missing a spark is an ever present danger and a fire may occur. Bag or cartridge replacement is definitely required.

Cyclone Dust Collectors
Contrary to common belief cyclones are not effective spark arrestors. For a spark arrestor / cooler to work, there must be high turbulence in the air stream. If you have turbulence in a cyclone the pressure drop is very high. Cyclones are designed to avoid turbulence. Many bag house fires occur in systems with cyclone pre-cleaners. Amazingly the inlet baffles on the baghouse are more effective as spark arrestors, however they are not foolproof.

Static Blade Spark Suppressor (Tri Pass)
These were developed in Japan to replace multiple cyclones in coal fired boilers. They found that the multiple cyclones did not stop sparks from entering the dust collectors. The first ones were installed in the early 1970’s. They ran at 1.5 inches of pressure drop and were fabricated from structural angles to resist the wear of the abrasive ashes in the coal that they fired. There are several of these applications installed in the USA and Canada designed by one of our colleagues.

Static Baffle-Box Spark Arrestor
Many dust collector suppliers offer this type of device as a spark arrestor. It consists of air entering at one end of a baffle box running over a baffle plate which drops out the sparks and much of the dust collected. The air exits at the other end, and then travels to the dust collector. The big drawback is that a hopper and flexible or solid hose connection to a collection barrel is required. Also, these devices do not eliminate all of the sparks. There is not enough turbulence generated to ensure 100% spark arresting. Sparks may also ignite the contents of the collection bin under it.

Mesh Filters
This is a common stop-gap measure where the filter is placed at the exhaust duct of hoods or installed in the ductwork. When clean, the mesh filter will stop at best 80% of sparks. These filters do not produce enough pressure drop to be fully effective. It only takes one spark to ignite dust in the duct or set a dust collector on fire. The only thing these filters do is clog up and add to your maintenance.

We trust that the above information will enable you to evaluate and select the most suitable method and supplier for your application. Buying our QUENCHER/BOOSTER spark arrestor combination will give you a risk free unit, fine tuned for each application.

See our engineering bulletin ... "Compare Spark Arresting Methods" (PDF)