Airvate Blog

  Customer’s Problem The off-gases originate from a large paddle dryer that processes egg waste, along with other miscellaneous equipment such as material conveyors, two vessels, and two dumpsters. During the dehydration process, the egg waste releases odorous compounds—specifically ammonia (NH3) and hydrogen sulfide (H2S)—along with water vapor. Most of the water vapor is condensed before the remaining air streams combine and enter the scrubber system. Inlet Gas Conditions and Required Removal Efficiency Contaminants: NH3 and H2S Minimum Overall Removal Efficiency: 99% Desired Outlet Composition: H2S: <= 1 ppm NH3: <= 3 ppm Normal Gas Flow Rate: 5,000 ACFM (Air, H2O, H2S, and NH3) Normal Inlet Temperature: 84°F Inlet Pressure: –2.0 inches H2O Solution Provided To address the customer’s requirements, two packed tower scrubbers were supplied. The first stage uses sulfuric acid as a chemical reagent to remove NH3, while the second stage uses caustic and bleach to remove H2S. Th...

In the process of starting up a new baghouse dust collection system, we found this interesting pressure gauge on the PD blower; the blower was not turned on yet, but its pointer was sitting on the other side of the stop pin. Nobody knew how this happened and it had to be replaced.  If not carefully checked, the error was hard to spot. Figure 1 Pointer of the pressure gauge sits on the wrong side of the stop pin Leak Test, Air Balancing, Trouble-shooting, and System Evaluation services by Airvate Dye test for bag/cartridge leak  Dust collection system and industrial ventilation system Testing and Air Balancing Technical services: field survey and dust collection system audit / evaluation and trouble-shooting New system start-up Dust sample analysis Dust collector selection and sizing: baghouse, wet scrubber, cyclone, settling chamber, drop-out box, etc.

  When we inspect a dust collection system, we always work on the PD blower (positive displacement blower) if equipped with one. Figure 1 a PD blower with intake filter taken out Intake filter Nearly every time an intake filter was taken out,  it was dirty and covered with dust or dirt. Since the intake filter is normally shrouded inside of a cover, it is not visible and is forgotten or ignored easily by maintenance guys or other service contractors. If it is a paper or felt element, we will tell the customer when to replace it, or if it is a wire mesh element, we will clean it with lukewarm water, and if there is oil on it, we will wash it with mild detergent. Because of the tight clearances used in the design and manufacturing of the PD blowers, they require filtered intake air. Proper maintenance of the intake filter will help insure a long service life for the PD blower. Consequently, a clogged intake filter will cause poor performance and overheating of the PD blower. Her...

  One customer told us that their dust collection system had a very weak suction on the grinding process line, and we went to their workshop on-schedule to do troubleshooting.  Introduction of the dust collection system The dusty air from the plastic grinder first ran through a cyclone and the separated dust from the cyclone directly went back to the process; the airflow with fine particles from the cyclone went to a cartridge dust collector, and then the filtered air was released to outside of the building. Since the plastic dust is combustible, an explosion panel and a vent duct were installed on the dust collector, and a non-return valve on the ductwork just in front of the dust collector inlet. The cartridge dust collector was equipped with a pulse jet cleaning system controlled by a Photohelic pressure gauge. The Photohelic Gauge measures the Differential Pressure and provides the capability for “on-demand” cleaning in conjunction with a Timer Board. Troubleshooting proce...

  We were called in by a customer on one cold morning. Their dust collection system did not work when they turned on power as usual. First, we checked the ductwork to see if there was any dust accumulated inside from the sucking points, to the fan, then to the baghouse. It seemed the ductwork was not the problem. After being in the baghouse, the filtered air went back to the workshop. Then we opened the access door of the baghouse hopper, and what we saw showed us the problem: it was packed with wood dust (Figure 1).  Figure 1 baghouse hopper packed with wood dust  Later, the access door on the clean side of the baghouse was opened, and one bag was taken out, it was very clear that the dust even accumulated between bags (Figure 2). Figure 2 dust clogged up between bags After the dust was removed from the baghouse, the system was turned on. In the first 20 minutes, the baghouse was warmed up without dust loading.  When this happened, the daytime temperature outdoors w...

  In a periodic test of a baghouse dust collection system, the PD compressor’s belts were found almost worn out, though still running doggedly. The PD compressor supplies compressed air of about 8 psi to the low-pressure, high-volume pulse cleaning system of the baghouse. The belts had to be replaced. Per the model number on the old ones, the customer bought a pair of new ones, NAPA A38. Belt replacement for this PD compressor The alignment of the sheaves was checked first; it was good. The sheaves and their inner faces were cleaned up and inspected; they were fine. The motor base has a jacking bolt, so it is easy to adjust the position of the motor. The new belts were rotated by hand for a couple of rounds to make sure they sat in the groove properly. We then measured the span-length of the belt and the sheave diameter, read the motor RPM, and took the V-belt tension table by Browning as a reference to decide the deflection force of the belt as 6 pounds.  After the new belts ...

  In a periodic test of a baghouse dust collection system, dye test for leak detection was done to the baghouse by following the test procedure. The system collects wood dust, and the bags were installed 4 years ago. The air after the baghouse is recirculated back to the workshop to save energy, especially in winter. The dye test easily found glowing spots on some bags adjacent to the tubesheet with the help of a black light wand (Figure 1&2) . These spots were thought to be caused by the bleed-through of the green dye powder; they were not indicators of broken bags.  We put the dye test results in the comprehensive report for this periodic system test and explained our concerns to the customer.  Figure 1 Glowing spots under black light on bags, image 1 Figure 2 Glowing spots under black light, image 2 Leak Test, Air Balancing, Trouble-shooting, and System Evaluation services by Airvate Dye test for bag/cartridge leak  Dust collection system and industrial ventil...

  When we did a periodic test on a baghouse dust collection system, an abnormal noise from the airlock got our attention. The baghouse is equipped with a low-pressure, high-volume pulse cleaning mechanism.  After carefully studying, we found that the airlock’s rotation was interrupted each time the cleaning pulse was released, and consequently the airlock made noise.  We took off the chain cover, and a slack chain came into view (Figure 1 & 2). Apparently, the shaft of the gearbox reducer moved gradually closer to the airlock body shaft after years of operation because the mounting bolts of the reducer were not tight enough originally.  Because the airlock is a slow running device, we adjusted the gear reducer position and set the slack of the chain to 5% of the center to center distance of the shafts. After this was done, the airlock went back to normal.  Figure 1 Slack chain on the airlock, image 1 Figure 2 slack chain on the airlock, image 2 For compariso...

a magnehelic pressure gauge without a pointer When we audited a baghouse dust collection system, we saw this abandoned Magnehelic pressure gauge without a pointer in situ for the purpose of decoration only. Actually, it is very normal to see a malfunctional gauge on-site, for reasons such as mechanical vibration, pressure pulsation, elevated temperature, pressure differential out-of-range, connecting-hose clogging, mishandling and abuse, etc.  For a pressure gauge to lose its pointer is not uncommon either. Mechanical vibration is the major reason the connection of the pointer loosens and consequently drops to the bottom of the gauge housing.  The gauge in the above picture was installed on the support frame of the baghouse together with a differential pressure transmitter. We guess abnormal vibration caused by the baghouse operation on the whole support frame failed the gauge, or maybe the connection of the pointer was loose even before it was installed on-site. Magnehelic Di...

  When on-site, I happened to see a set of unused cyclones. Though rusted by wind and rain, they were still showing off their sturdiness under the clear sky.  Actually when travelling around from state to state, I saw some unused cyclones like this one too. I think they are a kind of relic preserved by the family and like a statue to signal the pride of the family. a set of unused cyclone under clear sky a set of unused cyclones, still looks sturdy

  We were called in to do a leak test on a cartridge collector. It had visible dust emission just out of the stack.  With the system running, fluorescent powder was added to the dirty side of the cartridge filter. The collector was then shut down, and access doors were opened. Broken gasket seals ( Figure 3 & 4 ) and one leaking cartridge with the help of black light ( Figure 5 ) clearly came into view. Figure 1 Dirty side of the collector Figure 2 Dirty side of the collector Figure 3 Broken and shrunk gasket Figure 4 Broken gasket Figure 5 Leak detected in a cartridge with the help of a black light After the leaky cartridge and the broken gaskets were replaced, the cartridge collector worked normally again.  Later, a dust detector paired with a tower light alarm was installed on the ductwork behind the dust collector. Any regular maintenance program for your baghouse/cartridge collector should include periodic Leak testing. This maintenance task helps to detect compr...

  When doing calculations, designing, and/or on-site work, we have to figure out which standard and code (federal, state, local) we will follow.   EPA and Permits EPA Title V Operating Permits (EPA) National Emission Standards for Hazardous Air Pollutants (NESHAP), Rule 6X for metalworking operations (EPA) Method 22: visual determination of fugitive emissions from material sources (EPA) Method 9: Visual determination of the opacity of emissions from stationary sources NAAQS (National Ambient Air Quality Standards)  On-site Measurement OSHA Technical Manual (OTM) Section II: Chapter 3, on-site Measurement (EPA) Method 22: visual determination of fugitive emissions from material sources (EPA) Method 9: Visual determination of the opacity of emissions from stationary sources Airborne Contaminants Cal/OSHA Title 8 Section 5155 - Airborne Contaminants OSHA (CFR, Title 29,1910) and Subpart Z - Toxic and Hazardous Substances OSHA 3348-05: Guidance for the Identification and...

  I happened to see a crushed filter cartridge when on-site. Normally, it is hard to see one, as they are always thrown into a Toter quickly and stealthily before someone notices. Though crushed, it still looks cool.  A crushed filter cartridge (1) A crushed filter cartridge (2)

This blog post consists of 4 sections 1. Brief on the Ferrous Sulfate Process (in a customer’s plant) 2. Introduction about Ferrous Sulfate and its hydrate state 3. Ferrous Sulfate in the product recovery system and problems it caused 4. Workplace exposure limit of Ferrous Sulfate Brief on the Ferrous Sulfate Process The Ferrous Sulfate heptahydrate bulk first goes through a dryer heated by hot air, then is lifted by a basket elevator to a cooling bed cooled by ambient air from the outside of the building. The exhaust airflows from the dryer and the cooling bed go to the same baghouse for product recovery . The old product recovery system was removed after years in duty and replaced, since the old one couldn’t meet the airflow requirement for the process. The old baghouse was made of carbon steel, while the new one was made of stainless steel which is more suitable for this moist and corrosive situation. Introduction about Ferrous Sulfate and its hydrate state Ferrous Sulfate,...

  Three sections in this blog: Push-pull ventilation system and its advantages Disadvantages of general ventilation and side exhaust systems Methods to design a push-pull ventilation system Push-pull ventilation system and its advantages Open surface tanks used in industrial processes often need ventilating to remove harmful pollutants (vapors, fumes or aerosols) from the working environment. One method of removing pollutants is the so-called side push-pull ventilation system, in which a jet of air is blown (or pushed) from one side of the tank and collected (or pulled) by an exhaust hood on the opposite parallel side. This system is particularly useful for large tanks where access requirements preclude the use of an overhead canopy, and the size of the tank makes side (or rim) exhaust systems prohibitively expensive. Most agree that a push-pull ventilation system can yield air savings of up to 50% compared to a side suction only hood. An illustration of a push-pull system for an o...