 Tim Milburn Wm. W. Meyer & Sons Engineering Manager Visit Website |
Tim Milburn, Engineering Manager, Wm. W. Meyer & Sons (www.wmwmeyer.com), has 30 years experience in the successful design, manufacture and operation of industrial process equipment and production plant systems (e.g. cement, power, coal, limestone, food, grain, pharmaceutical, wallboard, fertilizer, catalyst, plastics, chemical, and waste treatment).
He has spent the last 3 years at Wm. W. Meyer & Sons developing new products for process material and air handling equipment (e.g. rotary airlocks, flap-gate valves, solids screw pumps, slide gates, fans, vacuums and other industrial material handling equipment). Prior, he spent 20 years engineering and managing the design and manufacture of process equipment for pulverizing, particle size separation, calcining, drying and incineration at CE Raymond (later ABB Raymond/Air Preheater), applying to a wide array of process materials and including integrated gas, material and environmental management technologies. He has a BS Mechanical Engineering from the Illinois Institute of Technology and a BA in Biology from the University of Illinois.
Wm. W. Meyer & Sons is a leading supplier of powder and bulk material handling equipment to a wide variety of industries.
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Valves, Gates & Airlocks Q&A
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I have two bins side-by-side that feed into a negative pressure pneumatic convey system. Both have the same size airlock at the bottom of the bin to control the feed into the pneumatic conveyor. When conveying out of one of the bins, we get an overpressure alarm when feeding at the same rate as from the other bin, so we have to slow the airlock down. I have noticed that the airlock under this bin is very close (6-12 in.) to the convey line, while the other airlock is about 10 ft above the convey line. Could this be causing the issue or are there other potential causes?Answered February 10th, 2010 by Expert:The symptoms you describe could be caused by a number of factors. However, based on direct conversation with the person who submitted the question, the difference in lengths between the airlocks and the convey line does not appear to be the main cause, although in some instances this could contribute to performance differences due to flow and dispersion characteristics of the material below the airlocks and ease of pickup in the convey line.
We learned the system has two bins and airlocks in series (sharing a common convey line), with the airlock above the longer chute being closest to a vacuum receiver feeding packaging line, with a third airlock underneath this receiver, and positive displacement blower as the prime mover, pulling system vacuum upstream of the receiver.
Based on this additional information, the most likely cause is insufficient conveying air flow when operating the bin or airlock directly connected (short) above the convey line:
a. If one or more of the 3 system airlock(s) is (are) leaking (worn) excessively, this can cause insufficient flow in the convey line. Most likely, the airlock with the 10 ft line may be leaking, leading to insufficient convey pick-up velocity in the other airlock discharge point, causing capacity limits.
b. Dirty filters, leaks in piping, connection, gates, or flanges could cause or contribute to consuming available convey energy.
c. The blower capacity could be less than the system is requiring, due to a slow speed or increased blowers slip (loss in efficiency) due to wear or damage, or possibly an undersized blower.
d. A combination of the above, with the cumulative effect resulting in a system capacity limit.Ideas for resolution:
1. The ideas presented could be tested by isolating the various components (e.g., bypassing or blocking off suspected leaks) and seeing if capacity improvements occur. External leaks may be heard, felt, or tested.
2. Check all airlocks for wear and maintain as required.
3. Check conveying lines for material buildup. Clean out as required.
4. Thoroughly check system for leaks and repair as required
5. Check filters for plugging, and clean out as required.