Airvate Blog

  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...

  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...

  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...

  Introduction Most baghouse users are confused why their baghouses suffer moisture condensation problems in winter. This blog post tabulates the dew-point temperatures of the airflows with different Relative Humidity (RH) at three different airflow temperatures of 68 o F, 120 o F and 250 o F to show why moisture problems in baghouses or cartridge collectors occur   in winter. Definitions of dew-point and Relative Humidity Dew-poin t is defined as the temperature at which condensation begins when the air is cooled at constant pressure. Relative Humidity (RH) expresses the moisture content of air as a percent of what it can hold when the air is saturated. The temperature of the airflow from a process will likely remain fairly constant and warm year round. However, a temperature differential (approximately 15 o F or more) between the dust collection point and the dust collector may indicate a potential condensation risk. Condensation in a baghouse causes problems When wate...

This post includes 3 sections: One pressure gauge reading is high but the baghouse works fine One pressure gauge reading is high and indicates baghouse problem Explanation about 2 types of differential pressures

  We did a Dye test for a customer in a newly installed baghouse. In this standard dye test procedure, green fluorescent dye powder was applied. No leaks were found in the clean plenum of the baghouse. All the bags were properly installed and no breach between the clean air and dirty air plenums was found either. View of Clean Plenum after Dye applied Per the request of our customer, we also got inside the dirty side of the baghouse through the inspection door on the hopper and visually checked dye powder distribution on the bags. From the picture below, it is apparent that the dye powder evenly distributed on all the bags, which means that the airflow was evenly distributed too. Customer was very happy about this visual check. Bottom View of Bags after Dye Applied

  There are four groups of variables that influence dust collector performance. They are variables regarding: 1.       dust, 2.       fluid, 3.       operation, 4.       Dust Collector. Variables regarding dust are size, shape, density of dust particles, and agglomerating tendency Variables regarding fluid are density and viscosity. These are functions of air or gas composition, temperature, and barometric pressure. The effect of dust and fluid variables can be simplified by using the terminal velocity theory. Terminal settling velocity, commonly called terminal velocity or "settling velocity”, is the velocity of a particle, falling in still air or another fluid, after it stops accelerating. So it is clearly determined by dust and fluid’s properties. Variables regarding operation are gas velocity through the collector, or capacity in cubic feet per minute, and dust loading, generally...