Matzan Reliability Solutions2187 North Washington St., Rochester, NY 14625

http://www.matzanreliability.com ematzan1@rochester.rr.com

Acoustical Wheel Defect Detection

Railroad Car Wheel Related Problems;

• Prevention• Detection

For more information contact:

Eugene Matzanematzan1@rochester.rr.comPhone 585 387 8921

Fig 1 Fig 2 Fig 3

Dragging Brakes Have Devastating Consequences: When Brakes are applied they can be fully engaged, partially engage, or no brake at all. This leads to wheel and bearing failure and can result in derailment.

Observations: The assumption is that the 12 PSI air pressure application is constant. Signal analysis and infrared conformation shows that 60% of the brakes do 90% of the stopping. Two cars, (5%) on a 40 car train do not come on at all.

These are Infrared images of a wheels with the brake applied. The farther up the red scale the hotter the wheel and the more brake pressure is indicated.

Dragging Brakes have Consequences:

What Causes Wheels & Bearings to Fail?

Why Equipment FailsASLE Bearing Workshop M.I.T. Study

Rabinowicz, 1981

Equipment FailsBecause

Obsolete15%

Surface Degrade70%

Corrosion20%

Caused byWater in oil, degraded oil,Process contamination,

Coolant, condensation…

Wear50%

Fatigue WearDamage resulting from

Micro-cracks loading

Caused byMisalignment, imbalance,Improper fit / assembly,

Secondary damage

Abrasive WearDamage resulting from

Abrasive particles between

Two moving surfaces

Caused byAbrasive particles in oil,

Dirt, secondary wear,Process contamination

Adhesive WearDamage resulting from Metal surfaces dragging

Over each other

Caused byInadequate lubricationLow visc, no oil, high

temp,Excess load, slow speed..

Accident15%

The typical grease used in these railroad car wheel bearings is Lithium based grease with a mineral base oil. The recommended temperature range is 180°F. The chart below shows the temperature range of a nominal Lithium based grease.

Figure 1 shows the thermal range of a typical rolling element bearing used in Railcars. The green zone represents the sweet spot for bearing and lubrication temperature; operating in the yellow zone reduces lubricant and bearing life; and if your bearings are in the red zone, expect both the bearing and the lubricant to be destroyed rapidly. For every 25°F increase in temperature above 160°F, the lubricant life is more than halved and there is a negative effect on bearing life. Any mineral oil operating at a temperature above 190°F will have a greatly diminished life. In no case should bearing temperature ever exceed the maximum rating of either the bearing or the lubricant.

Bearing Temperature °F

SKF high load, extreme pressure (EP) bearing grease

LGEP 2

LGEP 2 is mineral oil based lithium soap thickened grease with extreme pressure additives. This grease provides good lubrication in operating temperatures ranging from –20 °C (–4 °F) up to 110 °C (230 °F).

Premium Rail Grease

Timken Premium Railroad Grease has an operating temperature range of -40°C to +121°C (-40°F to +250°F) once in the application. CAUTION: Follow equipment manufacturer’s recommendations concerning lubrication frequencies. Failure to follow correct lubrication practices can result in premature equipment failure.

Viscosity @ 100°C, ASTM D 445, Centistokes 15.5

Viscosity @ 40°C, ASTM D 445, Centistokes 163

Viscosity Index 96

Base Fluid Properties:

Adhesive Wear

Hot Box Detectors are Limited

•Heat is a very late indicator of bearing problems. By the time they are hot enough to detect, damage has hit an irreversible stage.

•The inner bearings can not be scanned at all reducing the Hot Box detector to an effectiveness of 50%

•Reflected light, load, speed, weather, and distance all affect wheel and bearing temperature.

Wayside Ultrasonic Systems are Limited

•The inner bearings can not be scanned at all reducing the Sonic System by an effectiveness of 50%

•Wind, weather, load, background noise and speed all affect the sound signal using Microphones along the track.

New TechnologyTrack Isolated Ultrasonic System

• Detects and Locates Problems before the train leaves the yard• Mechanical Brakes engaged• Malfunctioning Air Valve• Broken Wheel• Wheel Flats• Wheel Hunting

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Theory of Operation:

Metal surfaces will vibrate if excited by a force, (gong ringing a bell), or friction, (sound made from squealing brakes). The Amplitude or size of these sound waves is generally proportional to the force applied. Hence steel rails generate a sound at the wheel – rail interface caused by the normal vibration in the wheel. Dragging brakes, wheel flats, and defective wheel bearings will generate a higher level of vibration than a “Normal” wheel because of the greater amplitude of force generated by these conditions.

A drawback or hindrance to the analysis of these signals is that signals from different wheels interfere and mix with each other and make identifying a faulty wheel difficult to pin down. In fact, a train can be “heard” or monitored a ½ mile away under normal conditions.

In our approach to resolving the problem of cross talk between wheels we have developed and patented a technique that isolates the sound generated from each wheel so that individual wheels can be analyzed. The methodology is to clamp rubber bumpers to the rail in a sandwich type of arrangement on either side of a transducer. The transducer acts as a microphone and records the sound generated by the wheel. The rubber composite material acts as an acoustical insulator that absorbs the vibration on either side of the transducer limiting the sound waves to only those generated by the wheel as it passes over the transducer.

Equipment Layout The system installs in hours, can detect several wheel failures; stuck brakes, air leaks, brakes that fail to actuate when applied, wheel flats, wheel spalling, and truck warp are some of the inspection capabilities of this equipment.

The system is composed of Ultrasonic Transducers mounted to the track. Sections of Railseal are used to isolate the ultrasonic vibrations, Wheel Sensors that detect the location of the wheel, and a Control Panel that houses amplifiers and electronics.

Method of Isolation

Sections of Rubber Rail Seal are sandwiched in the web of the track and held in place by clamps inserted under the rail or to the railroad tie. The ultrasonic transducer is located between the dampened sections of rail.

Urethane Rubber isolators

Ultrasonic Transducer and Rail ClampThis unit clamps to the track at the base of the trackand fits into the track web leaving only a small portionof the transducer exposed. No electrical contact to the track is present and this has been approved and tested at TTCI and other railroads.