Infrared Thermography Testing - Going Beyond The Electrical Connection

Executive summary

Sandy Sanor, HSB Thermography Services, Hartford Steam Boiler

Most people think of infrared thermography as a tool that is used to detect problems with electrical connections. But that represents only part of the array of applications and potential benefits when this technology is properly conducted by qualified personnel.

Many Applications

In addition to electrical inspections, infrared thermography has many other uses, such as the discovery of moisture entrapment in flat roofs, refractory/insulation degradation in boilers and ovens, and bearing problems in mechanical equipment. Infrared imaging has even been used in veterinary medicine to detect damage in the legs of horses.

Finding the "Hot Spots"

 Infrared thermography is a non-destructive technique for detecting temperature differentials that may indicate problems such as loose electrical connections or excessive friction in machinery and mechanical systems. A camera-like device views a large area at a time, senses infrared emissions and converts the emissions into a visual display. The equipment remains in operation, so production is not interrupted. “Hot spots” can be pinpointed quickly, saving labor and cost, and targeting plant maintenance where it is needed.

Three Common Uses

This article will touch upon three of the most common applications of infrared thermography:

  • Electrical — using infrared thermography a technician can help detect faulty connections in early stages, so possible breakdowns can be avoided.
  • Mechanical — excessive friction can cause breakdowns if equipment is not lubricated properly. Infrared thermography can help detect problem areas in motor bearings, gears, couplings, pulleys, conveyors and chain drive systems.
  • Refractory/Insulation — this application addresses hidden losses of heat that can drain performance and increases costs. Experienced thermographers can evaluate thermal images of walls, ceilings and roofs for signs of heat either escaping from those areas or entering the insulated space.  

Making It Work For You

The key to a successful program is to choose a qualified thermographer. Hartford Steam Boiler’s HSB Thermography Services (www.hsb.com/infrared) has been conducting infrared thermography surveys since the mid-1980s in locations from office buildings to paper mills, both in the United States and around the world. Both the client and the thermographer should understand what results are expected and how success will be measured. And you must accept the thermographer’s recommendations about repairing equipment and follow up to make sure the work is properly completed.

About the Author

Sandy Sanor is the director of HSB Thermography Services, which provides infrared thermography at facilities around the world. He holds a Bachelor’s degree in Business from St. Louis University and is a member of the International Society of Optical Engineering. Sandy joined Hartford Steam Boiler in 1974.

The full article

Infrared Thermography Testing - Going Beyond The Electrical Connection

Introduction

Most people today think of infrared thermography as a tool that is used to detect problems with electrical connections. But that represents only one segment of the array of applications and potential benefits when this technology is properly conducted by qualified personnel. This article offers some basic information about infrared thermography and several advantages that can provide a good return on investment.

Finding the "Hot Spots"

Infrared thermography is a non-destructive technique for detecting “hot spots,” which are temperature differentials that may indicate problems such as loose electrical connections or excessive friction in machinery and mechanical systems. Other uses for this technique include finding defective or leaky steam traps and clogged steamed lines, as well as many other conditions which can lead to failure or energy loss.

Infrared thermography utilizes a camera-like device which views a large area at a time, senses infrared emissions and converts the emissions into a visual display. Large quantities of equipment are scanned while in operation, so production need not be interrupted. Trouble spots can be pinpointed quickly, saving labor and cost and targeting plant maintenance resources where they are needed.

How Does the Camera "See" Heat?

All objects (even cold ones) radiate heat in the form of infrared energy. As an object heats up, it radiates more energy, and the wavelength gets shorter. Infrared radiation, visible light and ultraviolet light are all forms of energy in the electromagnetic spectrum. The only difference is their wavelength.

inspectrum 

The human eye can only see a small range of colors in the electromagnetic spectrum. These light waves range in length from 0.4 to 0.7 microns. If an object gets hot enough, the energy will reach the visible range and the object will be “glowing” red, like the burner on an electric stove. Fortunately, infrared imaging systems can detect infrared energy long before it reaches the visible stage.

The camera-like device then converts these invisible light waves into a graphic image that is displayed on a monitor. Modern infrared cameras also provide actual temperature readings, and store the data, so that the information can be later used to produce a report. However, gathering the information is the easy part. The real work — and value — is what the thermographer can do with the data that is gathered. As in any form of nondestructive testing, the interpretation of the finding takes both education and experience.

Most Useful Applications

In addition to electrical inspections, there are many other applications for infrared thermography, such as the discovery of moisture entrapment in flat roofs, refractory/insulation degradation in boilers and ovens, and bearing problems in mechanical equipment. Infrared imaging has even been used in veterinary medicine to detect damage in the legs of horses.

This article will touch upon three of the most common applications of infrared thermography — electrical, mechanical and refractory/insulation.

Electrical terminal points to components such as fuse blocks, control circuits, circuit breakers, transformer bushings and main disconnects can all develop faulty connections. Infrared thermography allows a technician to test and help detect faulty connections in early stages, so that repairs may prevent possible future breakdowns that would be very costly.

Thermal image of an electric motor 

 inredgen 

Mechanical equipment can face an inherent problem with excessive friction, if not lubricated properly. As one example, a motor is spinning at nearly 3,600 rpm and its rotor is in near contact with a bearing surface, of which there is but a thin film of lubricant separating the two surfaces. But if the lubrication breaks down, or misalignment takes place, or excessive loads are applied, there will be elevations in the amount of heat generated. Infrared thermography can be used to help detect these conditions. Of course thermography is not limited to just motor bearings. It can also detect problems in gears, couplings, pulleys, conveyors and chain drive systems.  

Refractory/Insulation is an application that is considered as a cost savings. It addresses a problem that is often hidden from the daily view of predictive and preventive maintenance, although it can result in an expensive drain on plant performance. The refractory and/or insulation of boilers, heat treat ovens, refrigerated spaces, driers, ovens and buildings all represent places where the slow and undetected loss of a desired control to the atmosphere can increase operational costs.

Thermal image of a boiler   

ST-FS-9 

Those areas that have less insulation will allow greater amounts of heat to escape than those areas that have the thicker insulation. If a hot-spot is detected in a wall or ceiling, some owners might think that additional insulation is needed. Not so in all cases. The problem may be that the insulation is not where it is supposed to be, and it creates a chimney effect that actually draws in cold air from the outside. Trained and experienced thermographers are able to evaluate thermal images of walls, ceilings and roofs for signs of heat either escaping from those areas or entering the insulated space.  

Table 1, Applications of Infrared Thermography  

Key Equipment    

Conditions Found  

Potential Impact  

Electrical Equipment  

Electrical Distribution Equipment      Loose connections or poor contacts, unbalanced loads, overloading, overheating.   Arcing, short circuiting, burning, fire.  Average main switchboard repair: $10,000 - $50,000.  Replacement:  $80,000 - $100,000. Several weeks lost.  
Transformers Loose connections, overheated bushings, poor contacts, overloading, blocked /restricted cooling passages  Arcing, turn-to-turn faults, fire.  Repair /rewind (5,000kVA): $40,000 - $60,000.  Replacement: $60,000 - $80,000.  Several months lost.  
Motors Overheated bearings, unbalanced loads, overheating /overloading, blocked cooling passages.  Defective bearings causing damage to iron and/or windings.  Motor rewind (1,000 hp): $15,000 - $20,000.  Replacement: $50,000 -  $60,000.  Several weeks lost.  
Boilers and Steam Systems 
Boilers Refractory /insulation breakdown, hot gas leaks.  Wasted energy.  
Steam Systems Valve or joint leakage, insulation effectiveness, underground system leakage, restricted or blocked condensate return lines.  Loss of steam /wasted energy.  Annual cost of steam leaks:  $10,000 or more, depending on size and pressure.  Also damage to surrounding equipment, as a result of leaks.  
Steam Traps Trap malfunction, backup from malfunctioning downstream of the trap.  Trap failed to open, loss of steam, wasted energy.  Annual cost of steam leaks:  $10,000 or more, depending on size and pressure.  
Mechanical Equipment 
Internal Combustion Engines Blocked radiator tubes and oil coolers.  Overheating, valve breakage, damage to piston, rods or shaft.  Repair: $5,000 - $50,000, depending on size of engine.  
Refrigeration Systems Air leaks, clogged condenser /heat exchanger tubes.  Inefficient operation and wasted energy.  
Pumps, Compressors, Fans and Blowers Overheated bearings, high discharge temperatures, high oil temperatures, broken or defective valves.  Loss of bearings, damage to shaft and internal parts.  
Kilns Insulation breakdown, high bearing temperatures, high gear temperatures.  Wasted energy, overheating and warping of shell, loss of bearings, gears, or both.  Repair: $20,000 - $100,000.  Replacement: $1 million.  
Other Applications 
Process Industry Dryer Rolls Condensate buildup, high bearing temperatures.  Bearing damage causing breakage of trunion, dripping of roll and damage to other rolls.  Repairs: $10,000 to $2million  
Storage Tanks Determination of liquid levels, inadequate insulation.  Wasted energy.  
Ovens and Furnaces Insulation breakdown.  Wasted energy, overheating and warping of structure. 

 

Table 1 lists the major uses of infrared testing, as applied to key mechanical, electrical and pressure equipment. As shown in Table 1, infrared thermography is an appropriate predictive/preventive maintenance tool for many different industries. But thermography is not limited to industrial facilities. Commercial properties, such as apartment buildings, office buildings, hotels and retail malls also have preventive maintenance applications.  

Specific Applications

Roofs – Moisture entrapment in flat roofs or vertical walls has been the target of thermography for several decades. In principle, it is quite easy to detect moisture that has found its way into these surfaces. For example, when water penetrates a flat roof it will often travel along a path created by the layers of roofing material. But knowing where the water comes out of the roof does not tell anyone where the water came in, or how much of the roofing material may now be waterlogged.

The area affected by the leak can usually, under proper conditions, be found with the use of thermography. Because the water will absorb heat during the day, the damp areas will cool slower than the dry material of the roof after the sun goes down. A thermographer located on the roof can help detect these wet areas as being warmer than the dry ones several hours after sunset. While further testing using other methods is often used to confirm the damaged area, thermography can greatly assist in defining the problem area.

Dairy Plant – In another application, an infrared scan helped a dairy owner to improve the temperature of the milk that was stored in two tanks on the premises.  The milk being discharged from the South tank was one to two degrees warmer than the milk discharged from the North tank. The average temperature of the milk was approximately 32 F. After the infrared scan, the owner was informed that the milk entering the South tank was one or two degrees warmer due to heat loss from the pipeline that fills the tank.

 ST-FS-10In addition, the milk was then heating up an additional 5 to 6 degrees in each tank between filling and discharge times. Many environmental ambient parameters can affect the external skin temperature of the tanks, which in turn will affect the internal temperature of the milk. On a clear sunny day, the surface of the tanks measured in excess of 160 F. These tanks are coated with a dark paint, which tends to absorb infrared radiation from the sun. Changing the color of the tanks reduced the heat absorbed from the sun.

Infrared scan of dairy tanks 

ST-FS-11 ST-FS-15 

 

Formal Criteria

Whether the facility is a commercial building or an industrial plant, the client should know why they need an infrared survey, how to distribute reports and what they plan to do in the future. The client should also know that the person surveying the location was properly trained, and what can be expected as a return on investment. An effective way to answer these questions is with a written practice program. A formal written practice program is not expensive to create and it can prove invaluable in assuring that the right people do the right things, and for the right reasons. A formal program should have, as a minimum:

  • Criteria for thermographers training, experience and certification as outlined in the American Society for Nondestructive Testing Inc. (www.asnt.org)  publication, “Recommended Practice SNT-TC-1A.”
  • Report format, content and distribution.
  • Reconciliation of findings.
  • Cost-to-benefit tracking.

Don’t confuse having a formal program with the need to have thermographers on staff. That can be very costly and is not recommended, unless there is enough work to maintain the efficiency levels of the staff. But it can be just as expensive, or even more so, to retain an infrared firm to conduct an infrared survey that doesn’t have properly trained personnel and a formal protocol to demonstrate that their Thermographers are Level I or II.

HSB Can Help

Hartford Steam Boiler’s HSB Thermography Services (www.hsb.com/infrared) has been conducting infrared thermography surveys since the mid-1980s in locations from office buildings to paper mills, both in the United States and around the world. We take our own advice, in that we have a formal written practices program, in addition to best practices. This means that there is a good chance that we have had experience with your type of business and we can assist you in writing a formal program and in conducting infrared surveys. Should you decide to train your own personnel, we can assist in their development.

It Takes Planning, Commitment to Succeed

Infrared thermography can be a valuable tool to detect adverse conditions and help avoid equipment breakdowns due to electrical, mechanical and insulation/refractory problems. The key is to choose a qualified thermographer. Both the client and the thermographer should understand what results are expected and how success will be measured. And you must have the commitment to accept recommendations about repairing equipment and following up to make sure the work is properly completed.

About the Author

Sandy Sanor is the director of HSB Thermography Services, which provides infrared thermography at facilities around the world. He holds a Bachelor’s degree in Business from St. Louis University and is a member of the International Society of Optical Engineering. Sandy joined Hartford Steam Boiler in 1974.
Disclaimer statement:

All recommendations are general guidelines and are not intended to be exhaustive or complete, nor are they designed to replace information or instructions from the manufacturer of your equipment. Contact your equipment service representative or manufacturer with specific questions.

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