Interface - The Journal of Wheel/Rail Interaction

WHEEL/RAIL INTERFACE

Applying Quality Concepts to the Wheel/Rail Interface (continued)

So, how does the theory of constraints apply to the wheel/rail interface? There is only one factor or one interaction between factors from the groups of variables listed in Figure 4 that is the weakest link that limits the performance of the wheel/rail interface. The trick is to identify which factor is the weakest link. Bear in mind that the constraint may vary from line to line or from location to location on the same line. Also bear in mind that working on anything other than the weakest link does nothing to improve the strength of the whole chain.

NS did not use a theory of constraints approach to the wheel/rail interface when the six sigma grinding project described in the first part of this series of articles was initiated. We chose to work on a portion of the “repair” process instead of working on the cause of the damage. Quality professionals would accuse of us of attempting to “repair” quality rather than to build in quality. Although NS did not use the theory of constraints approach to select the six sigma grinding project, we did use a theory of constraints tool called a Current Reality Tree (CRT) to help identify the important variables (see Figure 5).

As mentioned earlier, quality professionals frequently have problems getting management to act upon their recommendations. This is typically a communication problem; neither side is using the same language. Quality professionals speak in terms of defects and nonconformities while management speaks in the language of money. Wheel/rail practitioners mostly speak in the language of lateral forces, but we need to speak in the language of money if we want management to take action.

So how do we begin to speak in the language of money? One possible method is by developing ways to identify where we waste train energy. If we can measure the horsepower required to move a specific train from point A to point B and if we can calculate the ideal amount of energy it should have taken to move the same train from point A to point B, then we have the wasted energy that (primarily) went into damaging the wheels and track structure. Because that energy came from the locomotive, we can calculate the cost to generate that wasted energy. Now we have a cost that even the Finance Department can accept because it is an expense that immediately affects the income statement. We can also use a wasted energy approach to identify constraints by location and to help determine which of the factors from Figure 4 needs to be attacked.

There are several quality principles that wheel/rail practitioners can adopt to make our jobs easier: Use the data that is available. Analyze the data correctly by verifying the analysis assumptions. Fix the real problem by finding the constraint. And communicate in the only language that management understands: the language of money.

Stephen S. Woody is Manager, Track Inspection & Development, Norfolk Southern

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