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BASICS




Thermography

is a predictive maintenance thechnique that can be used to monitor the condition of plant machinery, structures, and systems. It uses instrumentation designed to monitor the emission of infrared energy to determine operating condition. By detection thermal anomalies, an experienced surveyor can locate and define incipient problems within the plant.


Infrared scanning procedures

The purpose of an infrared inspection is to identify and document problems in an electrical or mechanical system. The information provided by an inspection is presented in an easily and understandable form. A high percentage of problems occur in termination and connections, especially in copper-to-aluminum connections. A splice or a lug connector should not look warmer than its conductors if it has been sized properly. All problem connections should be dismantled, cleaned, reassembled, or replaced as necessary.


Types of infrared problems

There are three basic types of thermal problems:
(1)Mechanical looseness

A loose connection will result in thermal stress fatigue from overuse. Fuse clips are a good example because the constant heatup and cooldown creates a poor connection.

(2)Load problems

(3)Component failure

Understanding the nomenclature of the problem can identify component failure. Specifically, the actual component will be the heat source.


Common problems found and what to scan

(1)Motor control and distribution centers

Have the switchgear panel covers opened or removed by qualified personnel before inspection. Scan cable, cable connections, fuse holders, fuse circuit breakers,and bus.

(2)Main secondary switchgear

(3)Circuit breaker distriution panels

Covers on small circuit breaker panels do not have to be removed for scanning. Circuit breakers and conductors are very close to the metal covers.

(4)Bus Duct

Electrical conductors are very close to the metal "skin" of the duct. Defective joints are usually detectable by the heating of the cover in the vicinity of the problem.

(5)Motor

Do not scan motors less than 25 horsepower unless they are critical to production.

(6)Transformer-oil Filled

On all transformers, the oil level should be inspected during the survey. During the infrared survey, if a transformer appears exceptianally warm, the cooling radiators are near ambient temperature, and the transformer is above 50 percent of full load, the oil level is too low to circulate the oil and cooling is not taking place.

(7)Transformers-Dry-Type

Compare all windings. If temperatures are over a winding, but there is a difference in temperature of two windings, there may be an unbalanced load. A hot spot on a winding may point to s shorted trun.


Answer

1. What is Infrared? Return
Infrared is a form of energy and is part of the electromagnetic spectrum. Infrared is similar in many ways to the visible spectrum yet it is not visible our eyes!


2. What is Thermography? Return
Infrared thermography is a non-contact, non-destructive test method that utilizes a thermal imager to detect, display and record thermal patterns and temperatures across the surface of an object. Infrared thermography may be applied to any situation where knowledge of thermal profiles and temperatures will provide meaningful data about a system, object or process. Thermography is widely used in industry for predictive maintenance, condition assessment, quality assurance, and forensic investigations of electrical, mechanical and structural systems.


3. Why have an Infrared Scan? Return
     SAVES MONEY
         • Reduces unexpected failures
         • Insurance Discounts
         • Less expense for repairs
         • Reduce costly unscheduled downtime or outages
     SAVES TIME
         • Easily identifies areas needing repair
         • Reduces Emergency calls
     INCREASES SAFETY
         • Decreases risk of Fire
         • Decreases Electrical and Mechanical catastrophic failure
     ENERGY SAVINGS
         • Building heat losses
         • Electrical System efficiency
         • Mechanical System efficiency
     MORE REASONS
         • Extremely Reliable
         • Identify problems immediately
         • Follow analysis for future problems


4. What Types of Equipment and Processes Can Be Surveyed? Return
The following is just a small selection of the types of equipment and processes which can be surveyed by our fully trained and experienced engineers:
         • Motor winding problems
         • Bearing failures
         • Misalignments in couplings
         • Refractory lining inspections
         • Pipe wall thickness variations
         • Lagging damage
         • Locate Leaks
         • Damage to tanks, pipe work or ductwork
         • Corrosion under insulation (CUI) inspections


5. The equipment we have is new, there is no reason to check it. Return
Unfortunately, age has no relationship to hot connections. Poor initial installation has been the cause of many failures.


6. Do I need to shut down my equipment in order to have an infrared inspection? Return
No.1 Infrared Thermography is a non-invasive tool, so there is no need to switch any plant room equipment off. In fact, thermography produces the best results when the system under review is either fully operational or under load.


7. Why one might see a hot spot within an IR image? Return
About seven reasons refer to :
(1). Increased Isolated Resistance Increated resistance usually occurs at an electrical connection and is an actual problem. The heat is generated at the point of resistance change and is conducted away by the surrounding metal and air.
(2). Loading The heat generated in a conductor is proportional to the square of the current passing through it. Therefore, a small change in current flow can result in considerable heat differences.
(3). Reflectance Reflections from surrounding temperature sources generally appear as well defined thermal anomalies. The method of diagnosing reflection is to change the IR imaging position. If the hot spot moves or changes intensity, then it is a reflection; if it remains stationary, it is a true electrical anomaly.
(4). Solar Loading Solar loading will appear as a hot spot through IR imagery and is truly a hot area. Looking at the component from the shaded side can sometimes be of help.
(5). Emissivity Differences It is necessary to be well acquainted with the operational systems and their differing materials and emissivity values. Emissivity differences can be identified if the observed qualitative temperature change is not characteristic of an electrical fault.
(6). Eddy Current Inductive heating Induced electrical heating is characterized by hot areas on components of adjacent equipment, that are not established electrical current carrying circuits. This generally occurs when the distance between current and ground is not adequate to the ground source for the current carrying conductor.
(7). Tacking heat or (leaking) voltage This is a reaction not easily detected by IR. Most likely there is a very slight heat rise compared to the conductor temperature. Detecting such a reaction of thermal differentials requires infrared equipment with high thermal and pictorial resolution and a knowledgeable thermographer trained to recognize where and how this can occur.


8. Do I have to prepare for your Predictive Maintenance visits? Return
Usually identifying which machines you want checked, is all the preperation that will be needed. Our technicians quickly learn where your equipment is and go about their business without interfering with maintenance or production schedules.