Coming Undone

It is not news to the railroad industry that air hose separations are one of the most common causes for undesired emergency braking (UDEs). Nor is it groundbreaking to consider the costs, both direct and indirect, related to such unplanned stoppages – expenses connected to the delays caused to the subject train while engineers walk the train, locate and reconnect separated hoses and wait while rebuilding brake system pressure. Indirect costs come in the form of additional train delays ahead of and behind the stopped train, potential damage to railcars during emergency braking and the associated repairs and maintenance that results, and of course the potential for damage to freight during emergency braking.

Not Accepting the Status Quo

Unfortunately such incidents, while unwanted, are all too common in the railroad industry to the point of being accepted as a potential setback on any train run. Pennsy engineers didn’t think this had to be the case. Working collaboratively with railroad industry engineers and professionals, Pennsy embarked on a research effort surrounding common causes for air hose separations and their research pointed to failures in air hose support straps as the leasing cause. But why were the supports straps failing?

There were two root causes uncovered. The leading culprit was found the be the metallic spring wire clips used for attaching the supports to the bottom of the coupler and to the air hose gladhands. Engineers observed that as the supports cycled between slack and tensioned states during coupler buff and draft movements, these oblong clips were susceptible to rotating sideways within the gladhand hole. Once rotated sideways, the clips defromed easily under re-loading leaving the hose unsupported.

Second to the clip failures were failures in the strap material itself. It was noted that the strap portion on the majority of the currently available air brake hose supports were manufactured from rubber. A known problem with using rubber material for these parts is that, while fairly inexpensive, the rubber stretvhes out of shape under loading and does not regain its original length when the load is released. This necessitates frequent hose height adjustments in the yard, with each adjustment costing the car owner up to 3 times the cost of the support itself. This stretching ultimately leads to an increased potential for strap failure. The affects of U/V exposure on the rubber only accelerates the material's degradation further shortening its useful life.

Attempts at alternative straps made from braided steel cable did not offer significant advantages as the cable typically frayed at the attachment points creating an immediate safety hazard for workers and again leading ultimately to the support failure.

An Innovative Twist on the Standard

The first generation solution from Pennsy tackled the issues with the strap material by using an advanced polymer in place of rubber or braided cable. The material was chosen for its ability to last longer under the environmental conditions and physical demands, and offer sufficient flex without permanantly stretching out of shape. A combination of in-house and field testing showed the polymer material did not degrade or break down in the environment, and it did not stretch as far or exhibit the permanent elongation of its rubber predecessors.

When the AAR announced its initial criteria for revising the specification S-4006-03 to improve hose support performance, the new Pennsy support was the only product able to meet the requirements. The AAR's criteria were eventually lowered in the final revision of the specification but the design of the Pennsy engineers had already proven its superiority.

The bottom line - the engoineering effort was viewed as a success. The oberservance of fewer support replacements and hose height adjustments by field maintenance personnel means that this new product would reduce expenses for the railroad over time. In the broader view, the greater reliability of the new support translated into fewer train stoppages and overall operational improvements.

Getting Pennsy Involved on Your Project

For over two decades Pennsy Corporation has designed and marketed innovative products to meet the specialized needs of the railroad industry. Our team of engineers has a combined service of over 120 years in the locomotive, freight and transit segments of the railroad industry. Pennsy excels in solving engineering problems using innovative thinking together with the latest technologies and in-house testing facilities for validation of new products. Our four-step R&D, Design, Testing and Manufacturing process enables us to collaborate closely and effectively with engineering divisions of major railroads, freight car builders and shippers to deliver the right solution.

This process ensures our customers the lowest total cost design solutions by providing quality products and reducing the overall application and maintenance cost of customer equipment.

To get the Pennsy team involved in addressing your railroad specific needs, contact Pennsy at questions@Pennsy.com.