Temperature-Indicating Coatings: Visual Detection of Hot Spots in Industrial Equipment
Dampney Thurmalox 884 Technology | Visual Overtemperature Monitoring | Asset Integrity
Temperature-Indicating Coatings: Visual Detection of Hot Spots in Industrial Equipment
In refineries, petrochemical plants, and power generation facilities, an abnormal rise in temperature may indicate deterioration in critical equipment.
In vessels and furnaces with refractory linings, a loss of insulating capacity can cause localized temperature increases on the external metal surface, known as hot spots.
These conditions can compromise the material’s mechanical properties and, depending on their magnitude and duration, affect equipment integrity.
How can abnormal temperature exposure be identified when the event is no longer occurring at the time of inspection?
Temperature-indicating coatings offer a passive visual monitoring alternative through irreversible color changes, making it possible to identify certain thermal exposures without the need for permanent electronic instrumentation across the entire surface.
A Technology That Turns Temperature Exposure into Visual Evidence
The U.S.-based company Dampney Company, Inc, through its Thurmalox 884 line, has developed temperature-indicating coatings formulated with modified silicone resins and heat-sensitive pigment systems.
These coatings undergo color changes when the surface reaches specific thermal conditions.
Their most significant feature is that the color change is irreversible, so the visual evidence remains after the surface cools down.
This makes it possible to identify areas that may have experienced overtemperature conditions during operation and guide their subsequent evaluation.
The Thurmalox 884 family includes formulations with one or two color-change stages, which can be selected according to normal operating temperatures and the exposure levels to be identified.
How Does Thurmalox 884 Work?
Its operation can be illustrated using the Thurmalox 884-083 product, designed to provide two irreversible color changes.
| Specified Thermal Condition | Visual Response |
|---|---|
| Continuous service up to 177 °C | Green, no change expected |
| Exposure between 218 and 246 °C | Green to brown |
| Exposure between 304 and 327 °C | Brown to red |
These ranges are based on the product data sheet. The transition depends on variables such as temperature, exposure time, and metal thickness; it does not provide an instantaneous or exact measurement.
Other products in the family offer different indication temperatures and color combinations, including changes from green to white, blue to white, or red to pink.
Selection should be based on the equipment’s normal operating temperature and the level of thermal exposure to be identified.
.png)
Industrial Applications
Temperature-indicating coatings can support the inspection of:
This technology is particularly useful for accessible external surfaces that can be viewed during inspection rounds. |
Benefits for Asset Integrity Management
The main contribution of these coatings is that they provide a visual indication of thermal exposure that can remain visible after the event.
This feature makes it possible to:
- Identify areas requiring technical evaluation.
- Complement inspections using thermography and direct measurements.
- Include evidence of thermal exposure in inspection records.
- Support maintenance decisions based on equipment condition.
Their value lies in complementing existing inspection tools, particularly when a transient overtemperature condition may no longer be present when a measurement is taken.
A color change does not, by itself, confirm an internal failure, but it is an indication that should be investigated.
Limitations and Technical Application Criteria
Like any monitoring technology, temperature-indicating coatings have limitations that must be considered during specification.
- They are not measuring instruments. The color change does not provide an exact maximum temperature or indicate the time or duration of the thermal event.
- The response depends on exposure conditions. Temperature, exposure time, and the thermal characteristics of the surface can influence the color change.
- They do not replace monitoring systems. They are not a substitute for thermocouples, thermography, process alarms, or safety instrumented protection devices.
- They have service restrictions. The Thurmalox 884-083 technical data sheet does not recommend use in immersion, on surfaces beneath insulation, or on certain internal surfaces of ducts and gas-handling equipment.
- They require maintenance. Dampney notes that certain formulations may need recoating after 18 to 24 months, depending on operating conditions.
- They must be applied according to specification. Surface preparation, primer compatibility, film thickness, curing conditions, and application procedures must comply with the manufacturer’s recommendations.
For these reasons, an indicating coating should be integrated into an inspection strategy and should not be used as the sole safeguard against overtemperature conditions.
Aplika: Technology Applied to Asset Integrity
At APLIKA CONTROL CORROSIÓN S.A.S. we promote specialized technologies that provide new capabilities for the assessment, maintenance, and protection of industrial assets.
Dampney Thurmalox 884 temperature-indicating coatings offer an option for incorporating visual evidence of thermal exposure into inspection programs for equipment operating under demanding conditions.
Our approach is to assess operating conditions, deterioration mechanisms, inspection requirements, and the compatibility of available technologies.
Asset integrity begins with the timely identification of conditions that may compromise equipment performance.
Are your assets at risk of overtemperature conditions or refractory lining deterioration?
Contact our technical team to assess the application of temperature-indicating coatings and their integration into inspection and maintenance programs.
APLIKA CONTROL CORROSIÓN S.A.S.
Phone: +57 310 209 8850
Email: gerenciatecnica@aplika.com.co
www.aplika.com.co
Engineering Applied to Asset Integrity.
