Issue link: https://www.e-digitaleditions.com/i/1212417
60 / March 2020 powderbulk.com PBE SUPPLIERS' TIPS What maintenance steps should I take to ensure my vacuum pneumatic conveying system runs efficiently? B y their very nature, vacuum conveying systems must do a number of essential things to work efficiently, specifically: • Generate and hold a reliable differential pressure between the source of the material being con- veyed and the destination. • Provide a means of separating the transferred material from the generated airstream (a filter system). • Efficiently discharge the material from the vac- uum receiver to the process. You should always remember that with a vacuum system the maximum differential pressure possible is one atmosphere and, depending on the means of gener- ating the vacuum, in practice, however, the differential pressure achieved is less. Typically, a regenerative or side-channel vacuum pump will generate a maximum of 30 percent full vacuum, a roots-type positive-dis- placement vacuum pump will generate 50 percent, and a multiple venturi vacuum pump will generate 91 per- cent. The pumping device itself may be critical to perfor- mance but most modern pumps are extremely reliable. Therefore, any leaks in the system will seriously affect the conveyor performance. Leaks can occur in any part of the overall conveying system, and thus maintaining seals, hoses, and connection points is crucial. Similarly, the conveyor's discharge valve must hold the gener- ated vacuum, making valve maintenance an important aspect of pneumatic conveying. Filtration and separation of the transferred powder from the airstream are also critical to efficient opera- tion. Filters that are blocked or partially blocked result in a higher pressure drop across the system and, cor- respondingly, less available vacuum for conveying. Filter design, ease of cleaning, and the effectiveness of the in-process reverse-jet cleaning are all factors to consider as are the amount and pressure of any com- pressed-air supply. Most good manufacturers provide manuals with checklists concentrating on major maintenance items. Since maintenance is critical for equipment perfor- mance, conveying systems that allow quick and easy access to key parts will save you money. Some key fac- tors to look for in your system are: • common, nondirectional filters throughout the design • quick-release components that don't require adjustment or tools for disassembly • modular design elements • easy-clean construction, for example sanitary stainless steel, with minimal hang-up areas within the conveying system Nick Hayes, president, Volkmann, 609-265-0101 M aintaining your conveying system is very important for getting consistent product, avoiding production surprises, and achieving reliable productivity. One of the first maintenance steps is to make a plan and consistently execute it. For vacuum systems with filters, it's important to fre- quently monitor and record the pressure differential across the primary filter, which allows the operator to see performance trends. When the differential pres- sure exceeds the designed threshold, then it's time to change the filters. With the same process, monitoring the vacuum blower gives the same benefit. Many vacuum systems include a secondary safety filter just before the vac- uum blower. Frequently inspecting the secondary fil- ter is key to catching failures at the primary filter and proactively addressing them. Vacuum systems using cyclones as the primary receiver particularly need to have the secondary filter inspected. In addition, the vacuum blowers and feeding device need to be maintained. The blowers' assembly's bear- ings and seals need to be inspected for vibration, noise, and oil leaks along with the power transmission com- ponentry for wear. The feeding device needs to be checked for proper operation. Remember that preven- tive and consistent maintenance will ensure you get the most out of your system. Patrick Mahoney, systems process engineering manager, Coperion K-Tron, 785-825-1611