Compressed Air Best Practices - May 2008 - (Page 18)

| 05/08 Compressed Air Industry AUTOMOTIVE ASSEMBLY | How to AVOID the Most Common Bus/Coach Kneeling FAILURES By Paxton Augustine, Product Marketing Manager, Parker Hannifin Corporation, Pneumatic Division Overview Kneeling modules are quickly becoming the centerpiece of accessible vehicle equipment. This trend began with passage of the Americans with Disabilities Act (ADA) in 1991. Prior to the ADA, about 40% of all transportation vehicles were accessible to persons with disabilities. Today, over 50% of a fleet owner’s vehicles (e.g., public transit authorities and school districts) must be compliant with Title II of the Act, which explains the extent to which public transportation services are affected and how the Department of Transportation (DOT) will regulate requirements. By 2012, 100% of the vehicles in these provider’s fleets must be accessible to persons with disabilities (except providers that meet the small business definition). For this reason, bus OEMs require that these modules are durable, compact and lightweight while withstanding harsh elements. Functionally, the modules must be able to deflate air bags on demand and lower the bus quickly to ease passenger entry. Conversely, the module must then inflate the air bags at a similar pace, enabling the bus to resume its scheduled route. Kneeling modules are designed for OEM installation on new vehicles and to retrofit older model vehicles. Extensive testing must be performed to ensure that kneeling modules are reliable and durable enough to meet the demands of the Bus & Coach Industry. A typical bus kneeling application could see a module mounted to the exposed underside of a NYC transit bus where hundreds of stops are made per day in wintry conditions with temperatures reaching extreme negative degrees. If the kneeling module fails to perform as required, needless time delays result and passengers endure unnecessary difficulties in entering/exiting the bus. If the circumstances are severe enough, passengers may be denied entry on the bus due to their physical limitations that require the kneeling. This white paper addresses the most common types of failure modes regarding bus kneeling, along with the causes for these failures, and therefore what design considerations need to be incorporated into a kneeling module to prevent these failures from occurring. Extensive testing illustrates how these design criteria ensure optimum performance in a variety of harsh conditions while maintaining the durability and reliability of the module by minimizing component failure. Failure Modes and Causes What is a failure? If a product or system does not meet or exceed a customer’s expectations in regard to performance, service, and/ or quality, then a product failure results. The two most common failure modes for kneeling modules are life cycle failures and leakage failures. A Life Cycle Failure is when the product does not perform as promised. This is the most extreme failure mode. Many transit authorities and fleets will disable the vehicle’s kneeling function as a result of continual inconsistent performance. This failure mode can occur for various reasons, from solenoid failure, to poppet or spool valves not shifting, to spring breakage. In the case of Leakage Failures, the product continues to perform, but excess air is wasted because of system leakage. This is considered a secondary failure Figure 1: Pneumatic Circuit for a Kneeling Module – Integrated valves in a singular kneeling module provide a compact unit with less tubing and fittings. 18 www.airbestpractices.com http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices - May 2008

Compressed Air Best Practices - May 2008 Contents From the Editor Utility-Air News The Compressed Air Audit of the Month Pneumatics Real World Best Practices Delta Industries: Doing What is Right for Customers Delta Industries: Six Truths You Need to Know about Really Putting the Customer First Power Supply Industries Resources for Energy Engineers Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - May 2008

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