Infrared Thermal Imaging

Analysing mechanical systems using Infrared Thermography

Introduction

Infrared thermography is an excellent condition monitoring tool to assist in the reduction of maintenance costs on mechanical equipment. The technique allows for the monitoring of temperatures and thermal patterns while the equipment is online and running under full load. Most mechanical equipment has allowable operating temperature limits that can be used as guidelines. Unlike many other test methods, infrared can be used on a wide variety of equipment including pumps, motors, bearings, pulleys, fans, drives, conveyors etc. This section will explain the benefits of Infrared Thermography as a condition monitoring tool for plant mechanical systems.

We will highlight a few uses of infrared thermography when applied to analysis of mechanical equipment.

Infrared thermography is an electronic technique that quite literally allows us to see thermal energy. With this new capability plant maintenance personnel have recognized infrared thermography as one of the most versatile and effective condition monitoring tools available today. Thermal imaging enhances a company's ability to predict equipment failure and plan corrective action before a costly shutdown, equipment damage, or personal injury occurs

Why does Infrared work?

All mechanical systems generate thermal energy during normal operation which allows infrared thermography to evaluate their operating condition. One of the biggest problems in mechanical systems is excessive temperatures. This excessive heat can be generated by friction, cooling degradation, material loss or blockages. An excessive amount of friction can be caused by wear, misalignment, over or under lubrication and misuse.

Since most equipment or processes are designed to eliminate thermal energy under normal operation, simply identifying a thermal pattern does not mean a problem has been located. The thermographer must be familiar with the mechanical components being evaluated. Once a normal thermal signature is obtained and understood, any deviation from this normal signature will then provide evidence of a suspect problem developing.

In mechanical applications, thermography is more useful for locating a problem area than for indicating the root cause of the overheating. The heat is usually produced within a component that is not visible directly to the camera. That heat must conduct up through the material and present itself as a pattern on the surface of the object in order for the infrared camera to sense it. Other equipment such as vibration analysis, oil analysis, and ultrasound can be employed to further determine where the problem actually lies.

Let's take a look at some of the applications and the benefits derived from finding these with thermography.

Aplication	Conditions Detected
Drives/Conveyors, Pillow Blocks, Couplings, Gears, Power Transmission Belts, Pulleys, Shafts.	Overheated bearings or rollers, misalignment of shaft, pulley or coupling, lubrication failure uneven pressure.
Motors	Overheating of windings and bearings, blockages in cooling passages, friction, damping, material deformations, brush contact problems, rotors
Pumps/Compressors/Fans/Blowers	Overheated bearings, high compressor discharges temperature, high oil temperature, and broken or defective valve.
Internal Combustion Engines	Valve or injector malfunction, blocked radiator tubes and oil coolers. Thermal distribution, high radiator inlet or outlet temperature.
Heavy Duty Equipment - Tires, Bearings, Brakes, Hydraulics, Kilns, Ball Mills, Paper Machines	Overheating brakes, tires, bearings, pulleys, gears, gear or pulley misalignment, and blockages in hydraulics.
Mechanical DriveTurbines and Small TurbineGenerator Units, Gas Turbine, Exhaust Ducts	High lube oil temperature, high bearing temperatures, faulty stop/control valve operation, uneven metal temperature, leaking shaft seals, gas turbine firing conditions, including deterioration in firing chambers, cross firing tubes.
Ovens, Furnaces, Kilns, Pipes	Location and severity of damaged insulation, location of steam leaks in buried steam lines.
Valves: Shutoff Valves, Relief valves, steam traps	Leakage, Blockage.

Improve Troubleshooting

Thermography definitely should be one of the tools that are selected for motor and rotating equipment inspection. Thermographic examination can help technicians use the other tools, such as vibration analysis, more effectively. If a thermal anomaly is found, then the other tools can be employed to help isolate the cause of the problem.

-::- This site is designed and authored by David Stevens IEng MIIE(mech) F.I.Diag.E. -::-