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— by Julie Sneider, associate editor
If continuous-welded rail (CWR) buckles, bends or breaks during extreme weather conditions, a derailment could occur. So, preventing abnormalities in the rail is vital.
Prevention typically involves a couple of steps: First, CWR must be properly "de-stressed" to avoid malformations; and second, workers responsible for installing and maintaining CWR need to be properly trained on the rail's characteristics.
The Federal Railroad Administration (FRA) requires all railroads that employ CWR to craft an FRA-approved plan covering procedures for installing, adjusting, inspecting and maintaining the rail, which generally is welded together to form uninterrupted lengths stretching several miles long.
A number of consultants and suppliers offer products and services to help railroads manage CWR. For example, Track Guy Consultants increasingly is contacted by railroads to train their workers to properly install and maintain CWR, including rail de-stressing techniques, says John Zuspan, the company's president. Track Guy Consultants provides track inspection, project management and various other consulting services.
Prior to de-stressing CWR, a railroad needs to determine the correct rail-neutral temperature (RNT) based on a track's geographic location. The neutral temperature is a point at which the rail is neither expanding nor contracting, or the temperature at which the rail experiences zero longitudinal force.
"The rail neutral temperature is what a lot of people like to call 'happy rail,'" says Zuspan.
The RNT should not be set too low or high based on a region's air temperature. The American Railway Engineering and Maintenance-of-Way Association (AREMA) offers a formula to determine a desired RNT. The temperature needs to be monitored to accurately determine if CWR is at risk of buckling or bending.
There are several ways to de-stress CWR, such as through the use of rail heaters and pullers. Railroads determine their preferred method and outline the process in their FRA-required de-stressing plan, says Bob Rolf, vice president and general manager of RailWorks Track System Inc.'s South Division based in Houston.
CWR can exceed 400 feet in length, and anything that long requires de-stressing, says Rolf, who currently serves on an AREMA committee that's trying to update a portion of the association's manual pertaining to de-stressing.
Once the desired RNT is determined, the rail is unclipped, heated to the proper temperature and vibrated to get it to reach the desired length.
"You want the rail to uniformly grow and de-stress along the entire particular piece of rail," says Rolf, adding that crews need to reapply clips to keep the rail from moving and weld the rail at the end of the installation process.
Before de-stressing any existing CWR, track workers need to be well informed of the hazards of working with the rail in order to prevent injuries, Rolf advises.
"It needs to be understood that the existing track could have stored energy," he says. "It could be in a situation in which [the track] wants to buckle if it's a hot day. So, you have to train your employees not to simply go down the track and [remove spikes] on a bunch of rail because it could spike out and seriously injure someone."
Balfour Beatty Rail Inc. also helps train railroad workers who install and maintain CWR. The company offers a number of qualified employees who are trained and certified in CWR management and de-stressing operations according to FRA track safety standards, said Balfour Beatty Rail Vice President Mark Snailham in an email.
The company's CWR management services include VORTOK International's VERSE® (Vertical Rail Stiffness Equipment) testing machine that's designed to mechanically measure rail temperature to help ensure a railroad achieves the correct RNT. VERSE was first used in the United Kingdom in 1998, then introduced in the United States in 1999. CN began using it in 2002.
Using VERSE machines, Balfour Beatty Rail has performed numerous tests on track operated by Class Is and short lines to help them manage CWR programs and prevent kinks and buckles, said Snailham. The company works with the railroads "to make sure the track has the correct profile, especially in curved track, to prevent creep at the bottom of the slope or gradient," he added.
Maintaining appropriate ballast levels in the cribs between, on the shoulders of and underneath ties also is a vital part of proper CWR maintenance.
"The No. 1 restraint is the ballast," says Track Guy Consultants' Zuspan. "When a buckle happens, a lot of times the ballast is missing on the shoulder."
According to a research report on track buckling issued by the Volpe National Transportation Systems Center in November 2013, maintaining ballast levels in CWR helps ensure a "stress-free" state. A full ballast section is important, especially on curves, the report stated. Adequate ballast in the high side in curves should reach 12 to 18 inches to provide adequate lateral strength.
"Ballast on the low side is important because inward (pulling-in) movement in cold weather could lead to line defects and lowering of neutral temperature, which could lead to a buckle when higher temperature rises occur in early spring," the report stated.
Monitoring rail temperature and stress conditions can go a long way toward preventing track buckles, according to L.B. Foster Co.'s Salient Systems Inc. To that end, the company offers the RailStress Monitor™, a strain-gage system that is micro-welded directly to the rail in order to measure longitudinal stress and rail temperature.
The strain gage contains a sensor that gathers real-time information and reports it to L.B. Foster's IntelliTrack® Navigator wayside reader. Under normal conditions, the data is collected at various points throughout the day. But if the data indicates the rail is at a "state of alarm" — or at risk of buckling or breaking — the system transmits that information immediately so that corrective action can be taken, says Walt Spicker, Salient Systems' principal engineer.
Introduced in 2006, the RailStress Monitor has been installed by railroads across the globe, according to the company. In some cases, railroads install the monitor in potential problem areas or to determine if conditions are right for a rail buckle in a particular location, says Phil Huebner, Salient Systems' technical sales director.
Huebner expects demand for the RailStress Monitor to grow as railroads assess and address the impact of unusual or extreme weather conditions on their rail networks. For example, record-high heat in parts of North America two summers ago prompted a rash of emails to Salient Systems from railroads seeking better ways to detect rail-buckle conditions, Huebner says.
Monitorization and detection are the primary goals of a system developed by ProTran Technology and QinetiQ North America in 2012. The companies teamed up to craft the Intelligent Rail Integrity System™ (IRIS), a real-time network of remote sensors that can test and evaluate CWR.
The system is designed to continuously monitor changes in rail temperature, stress and rail neutral temperature. If buckles or breaks in the CWR are detected, IRIS alerts the operator to the event's location through an emergency notification system.
Each of IRIS' six- to eight-inch wireless sensors fit in the web of a rail. The sensors can detect if the rail has experienced any major change that would indicate the situation is right for a rail kink, buckle or break, says ProTran President Peter Bartek, adding that the system can be installed on existing or new rail.
So far, the system has been deployed by eight major railroads and transit agencies, he says. Transit agencies that have deployed IRIS are relying on the system to monitor CWR condition in potentially troublesome areas, Bartek adds.
In April, ProTran announced it received a grant from the Transportation Research Board to further develop IRIS so the system can provide advance warning of buckles and breaks along curves and at abutments, he says. The grant proceeds also will be used to extend the wireless sensor's battery life longer than one year.
As ProTran continues to develop IRIS, the system likely will become more widely adopted, Bartek believes.
"In the next five years, I suspect every railroad — Class Is and transits — will be using this technology," he says.