Inspectioneering
Explore:

Infrared Inspection

Overview of Infrared Inspection

Infrared (IR) technology is widely used in the oil and gas industry as an inspection tool for condition monitoring and predictive maintenance. It is advantageous over traditional visual inspection and other tools because infrared technology does not have to be in contact with the equipment being monitored.

IR thermography is a form of nondestructive testing that measures temperature variances of a component as heat (i.e. thermal radiation) flows through, from, or to that component. IR thermography is also generically known as IR testing, thermal testing, thermal imaging, and IR thermometry.

Thermal radiation is directly related to changes in temperature. In other words, as a component changes temperature, the amount of radiation emitted changes. Since this type of radiation is a form of electromagnetic waves that cannot be seen with the human eye, components have to be analyzed using infrared cameras. Infrared cameras are able to detect and display emitted, reflected, and transmitted infrared energy from an component. The thermal image can then be analyzed to obtain a temperature reading for the component.

The purpose of mapping temperature levels and variances of a component is to detect any hot spots where equipment may weaken or fail. IR thermography is also capable of detecting corrosion damage, delaminations, voids, inclusions, and other flaws that affect heat transfer. However, in order to detect these anomalies, there must be sufficient temperature difference between the component and its surroundings.

Fundamental IR Thermography Concepts

Emissivity refers to a material’s ability to emit infrared energy. Emissivity is expressed as a value between 0 and 1 where 0 describes a perfect mirror surface and 1 describes a blackbody. For example, a material with an emissivity value of 0.95 absorbs and emits 95% of infrared radiation and reflects 5% of the surrounding radiation.

Reflectance refers to the amount of light reflected from the surface of a material.

Transmittance is a material’s ability to transmit thermal energy (i.e. heat) from a component being tested to an infrared camera. For example, plastics are transmissive while metals are opaque and are not transmissive.

Heat vs Temperature

These terms are commonly used interchangeably. Although they are related, they have very distinct meanings.

  • Heat is a measure of the total energy of molecular motion of an object and is dependant on the size of the object. Heat also describes how thermal energy transfers from one object to another or its surroundings.
  • Temperature refers to an object’s average energy of molecular motion and, unlike heat, can be measured directly. Temperature does not depend on the size of the object.

Heat Transfer describes the phenomenon of thermal energy transferring from a hotter temperature region to a colder temperature region.

Heat Transfer Mechanisms — Heat can transfer in three ways:

  1. Conduction is the transfer of heat between two solids.
  2. Convection is the transfer of heat through liquids and gases.
  3. Radiation is the transfer of heat through electromagnetic waves.

Thermography Considerations

Component Factors

In terms of equipment being tested, operators and inspectors should have working knowledge about the:

  • Equipment and process
  • Material type (e.g. steel, stainless steel, etc.)
  • Material properties (e.g. thermal diffusivity)
  • Thickness and geometry of the component
  • Emissivity of the material

Anomaly Factors

If infrared technology is being used to detect flaws, knowledge about the size, depth, and orientation of the anomaly must be known.

IR Camera Factors

Several instrumental factors to consider when performing IR testing include:

  • The distance between the component and the IR camera
  • Spatial resolution output (i.e. clarity of component)
  • Thermal resolution output (i.e. clarity of temperature differences)
  • Thermal range (i.e., ability to detect temperatures of the component being tested)

IR Testing Techniques

Several IR testing techniques exist and the decision on whether and which to use depends on the the considerations listed above.

Passive Thermography involves testing the component during or after operation. The primary advantages of this method are that it does not require an external energy source and equipment doesn’t have to be taken out of service.

Active Thermography requires an external energy source that produces thermal variances in the component. The component is monitored until it has reached thermal equilibrium. This technique is useful for determining how heat flows through, from, or to a component before it is placed in service. This method is also used to locate anomalies in equipment during service.

Flash Thermography measures the changes of surface temperature after a pulse of light energy is introduced to the component. This technique is used to locate voids, inclusions, and other deflects that obstruct heat flow into the component.

Vibrothermography is a technique that utilizes acoustic waves to find cracks in a material. The acoustic energy causes friction between the two sheared surfaces of a crack, which results in the production of heat. The frictional heat is then detected using an infrared camera.

Lock-in Thermography requires that an external source of energy (e.g. light, sound, etc.) be periodically applied to the surface of a component in order to reveal a subsurface anomaly. The depth, size, and orientation of the anomaly, as well as the properties of the material, must be known in order for the method to be highly accurate. This technique is much slower than flash thermography, however, it is capable of penetrating thicker-walled components.

Industry Applications

IR thermography is utilized in many industries and applications. In the oil and gas and chemical processing industries, for example, thermography can be used to detect piping insulation issues, fluid levels, or identify trouble spots where rotating equipment is experiencing too much friction. Furthermore, IR testing is commonly used to locate hot spots and anomalies such as voids and  inclusions. The benefits of IR testing include extended equipment life, decreased unscheduled shutdowns, reduced risk of equipment failure, and increased performance.

Is this definition incomplete? You can help by contributing to it.

Share this Topic

Related Topics

Acoustic Emission Testing (AET) Advanced Ultrasonic Backscatter Technique (AUBT) Eddy Current Array (ECA) Electro Magnetic Acoustic Transducers (EMAT) Guided Wave Ultrasonics (GWUT) Liquid Penetrant Examination (LPE) Magnetic Flux Leakage (MFL) Magnetic Particle Testing (MPT) Meandering Winding Magnetometer Array (MWMA) Pulse Reflectometry Pulsed Eddy Current (PEC) Radiography Remote Field Eddy Current (RFEC) Ultrasonic Testing (UT)
Articles about Infrared Inspection
  • July/August 2017 Inspectioneering Journal
    By Chris Leightell at Industrial SkyWorks

    The adoption of drones for use in industry is a trend that has grown rapidly over the past few years. As the technology increases in popularity, its capabilities continue to evolve beyond basic visual imaging, boosting the list of ever-growing applications.

  • September/October 2014 Inspectioneering Journal
    By Tim Hill at Quest Integrity Group

    For the past 30 years, infrared (IR) thermometry has been used to monitor tube metal temperatures in refining and chemical furnaces. Tracking temperature levels and variations determine performance capability limits and reliable tube life. However, the application of IR thermometry has often been characterized as highly operator dependent, which can result in less-than-optimal data accuracy as a consequence of poorly applied and interpreted results.

  • July/August 2009 Inspectioneering Journal
    By M.Z. Umar at Malaysian Nuclear Agency

    We have been introduced to Infrared Thermography (IRT) since World War I and over the last decade the application of this technique has gained impetus. Today, the IRT application is widely used and accepted by many industries such as power generation plants, oil & gas industries, manufacturing factories, medicine, agriculture and biology etc. The technique has been recognized as a reliable tool for technical diagnostics in particular to condition monitoring and predictive maintenance.

  • May/June 2008 Inspectioneering Journal
    By M.Z. Umar at Malaysian Nuclear Agency, A.R. Hamzah at Malaysian Nuclear Agency, V. Vavilov at Tomsk Polytechnic University, and W. Swiderski at Military Institute of Armament Technology

    The concept of pulsed thermal nondestructive testing including the simulation of finite-size defects in solid materials, optimization of test procedures and advanced data treatment has been proposed. The experimental results have been obtained on a bakelite reference sample which contains bottom-hole defect surrogates of different depth and thickness.

  • March/April 2004 Inspectioneering Journal
    By Mark Badrick at Bahrain Petroleum Company

    The title question is often asked and more often than not, impossible to answer. This paper follows on from a previous discussion (Inspectioneering Journal Volume 4 Issue 1 Jan/Feb 1998) relating to the difficulties arising whilst attempting to carry out temperature surveys of furnace tubes using a thermal imager. The issues discussed then i.e. calculation of emissivity and ambient temperatures, reflected heat etc, are still current concerns, but since the writing of that article, an additional equally important challenge has become apparent - "how do we measure the temperature of an externally scaled or fouled tube"? Where the external scale or some other external deposit, such as refractory dust etc. may mask the true tube temperature.

    Companies
    Videos related to Infrared Inspection
      White Papers related to Infrared Inspection
        Downloads & Resources related to Infrared Inspection
          Events related to Infrared Inspection
            News related to Infrared Inspection
              Interested in equipment reliability & integrity? Sign up for weekly updates.

              Inspectioneering Journal

              Explore over 20 years of articles written by our team of subject matter experts.

              Company Directory

              Find relevant products, services, and technologies.

              Job Postings

              Discover job opportunities that match your skillset.

              Case Studies

              Learn from the experience of others in the industry.

              Event Calendar

              Find upcoming conferences, training sessions, online events, and more.

              Industry News

              Stay up-to-date with the latest inspection and asset integrity management news.

              Blog

              Read short articles and insights authored by industry experts.

              Acronyms

              Commonly used asset integrity management and inspection acronyms.

              Asset Intelligence Reports

              Download brief primers on various asset integrity management topics.

              Videos

              Watch educational and informative videos directly related to your profession.

              Expert Interviews

              Inspectioneering's archive of interviews with industry subject matter experts.