Compressed Air Best Practices - April 2008 - (Page 36)

| 04/08 Compressed Air Industry PLASTICS BLOW-MOLDING | Are you taking full advantage BY CHRIS LANDIS Put advancements in pneumatic valves to work for your organization Pneumatic valves have come a long way since the development of the compressor over a century ago. Starting with large manual and mechanical valves, they migrated to individually wired electric solenoids and ultimately ended up with plug-into-the-base electronics allowing for a single multi-pin connector or fieldbus installation. Today’s valves are smaller, faster and more advanced than their predecessors and offer many advantages that can be easily overlooked. With advancements in ISO valve standardization, collective wiring solutions and diagnostic capabilities, both end users and original equipment manufacturers (OEMs) are seeing significant cost reductions resulting from multivendor support, wiring simplification and decreased machine downtime. The International Organization for Standardization (ISO) specifications 15407 and 5599 offer valve users protection against ever changing business conditions and product obsolescence, which are often the cause of vendor issues. These industry standards dictate the size and location of the valve porting, base porting and mounting screws, as well as the electrical connector location, size and wiring, if utilized. By migrating away from proprietary valve mounting patterns to a completely standard and interchangeable pneumatic and electrical ISO pattern, companies are able to ensure multi-vendor support on a global scale. Gone are the days of regionally based vendors undercutting prices at OEMs with hopes of high MRO prices at the end user facility. ISO interchangeability and consistent cost structure ensure consistent pricing levels. Collective wiring solutions, especially when integrated with a fieldbus solution, provide an elegant mechanism to consolidate solenoid wiring into a single “collective” connection on the valve manifold. This methodology offers significantly reduced cost and complexity of the machine. Industrially rugged electrical connections, combined with advanced sealing technology, allow the valve manifold to be moved out of the control cabinet to point-of-use application located near the pneumatic process. This eliminates long tubing runs and corresponding delayed responses in pneumatic operations. When integrating a fieldbus solution, there is a sharp reduction in the number of components on the bill of material as terminal strip laden junction boxes and control cabinets are reduced to simple connections. Now, two cables — one communication and one power — can handle the work-load of hundreds while eliminating home-run wiring and long conduit runs. Large machines can be broken down for shipment and reassembled with an absolute minimum of labor since the wiring is bus connected with only two cables. Finally, diagnostic tools like short circuit detection, confirmation of signal and status LED lights offer advancements in troubleshooting and maintenance. When combined with an integrated fieldbus solution, status bits from advanced valve driver modules are able to quickly alert an industrial PLC when a short circuit is detected on any valve solenoid, which is the most common failure mode of an electric solenoid. With user programming, the status bit change can be turned into a detailed error message stating, “Valve Number four Must Be Replaced with a Two-Position Double Solenoid ISO 15407-2 Valve.” Also available from advanced valve driver cards is a status bit indicating that the current has been sent to the solenoid. This functionality acts as a double check to confirm the PLC program issued by the command, that the fieldbus network communicated the request and that the valve driver module had the correct working voltage and applied it to the solenoid. This is a way to confirm the command was executed by all components in the system, as expected. Status LED lights offer a fast, visual indication of the component status. Malfunctions in the power source, fieldbus status and modules can be detected without queries to the PLC. With some upfront programming, these types of feedback will alert the user to a potential issue and offer a way to stop production before bad parts are made, improving both scrap rate and machine downtime costs. 36 www.airbestpractices.com http://www.airbestpractices.com

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Compressed Air Best Practices - April 2008 Contents From the Editor Utility-Air News The Compressed Air Audit of the Month: Minimizing Blow-Molding Pressure Fluctuations AF Compressors: Focused on 40 Bar, Oil-Free Air for the PET Industry Real World Best Practices: PET Plants Using Boosters for High-Pressure Air Guaranteeing Audit ROI for Blow-Molders Managing Vacuum Pressure Differential Are You Taking Full Advantage of Pneumatic Valve Technology? Are You Strategic? Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - April 2008

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