We use cookies to enhance your experience. By continuing to browse this site you agree to our use of cookies. More info.

Heat transfer fluids can get degraded in two ways:

Degradation of a heat transfer fluid can be effectively checked by performing an annual fluid analysis that includes a distillation range, or boiling point, test for measuring the amount of cracked molecules, i.e. low boilers, and an acid number test for measuring oxidation. As soon as the issue is recognized, the causes and cures are quite straightforward.

Oxidation takes place only in the expansion tank, or the reservoir. The tank normally turns hot during the system start-up due to the expansion of the fluid into it. As soon as the system attains the operating temperature, the tank must be cooled such that one can place a hand on it; a temperature of about 140°F is the threshold of pain for most of the people. A popping sound from the inner side and smoke emanating from the vent indicate that the tank is very hot.

Care must be taken to ensure that all the boilout/warmup lines reaching the tank are valved off once the temperature of the heater outlet reaches 250°F. During normal operation, only one line must connect the tank to the main loop. If a combination deaerator/expansion tank is integrated into the system, the manufacturer’s instructions concerning the part to be insulated should be thoroughly followed. If all the measures fail, then a nitrogen blanket should be installed on the tank head space.

A prevalent source of overheating is flame impingment. In the majority of fired heaters, the area of the radiant zone, i.e. the coil surface actually facing the flame, is less than 30% of the area of the total heated surface but it contributes to about 50%-70% of the total heat transfer. The high heat-to-surface-area ratio is the reason for the high film temperature in the heater. In the case of a corroded flame disperser or a mis-aligned burner, the flame may directly impinge onto the surface of the coil, resulting in extremely high film temperature that can surpass the recommended maximum film temperature for the fluid. If this issue is not fixed promptly, it may lead to heater tube failure.

Another reason for overheating is the decrease in flow rate through the heater. The transfer of heat from the heater tube wall, i.e. the electric element surface, is affected by low flow in the following two ways:

Yet other common reasons for low flow are improperly set or malfunctioning bypass valves and plugged Y-strainers.

Invariably, thermal fluid system contamination is mostly self-inflicted. It occurs when a fluid of poor thermal stability, i.e. hydraulic fluid and glycol that are usually stored in drums in the same area, is added mistakenly. An instantaneous consequence may be a “geyser” emanating from the expansion tank vent or pump cavitation. However, mostly the increase in the quantity of carbon solids in the fluid is the only indication for contamination to have taken place.

This information has been sourced, reviewed and adapted from materials provided by Paratherm.

For more information on this source, please visit Paratherm.

Please use one of the following formats to cite this article in your essay, paper or report:

Paratherm. (2022, May 19). Causes and Cures of Fluid Degradation. AZoM. Retrieved on June 18, 2022 from https://www.azom.com/article.aspx?ArticleID=12866.

Paratherm. "Causes and Cures of Fluid Degradation". AZoM. 18 June 2022. <https://www.azom.com/article.aspx?ArticleID=12866>.

Paratherm. "Causes and Cures of Fluid Degradation". AZoM. https://www.azom.com/article.aspx?ArticleID=12866. (accessed June 18, 2022).

Paratherm. 2022. Causes and Cures of Fluid Degradation. AZoM, viewed 18 June 2022, https://www.azom.com/article.aspx?ArticleID=12866.

Do you have a question you'd like to ask regarding this article?

AZoM speaks with Joseph Toombs, a Ph.D. student at the University of California, Berkeley, about his research that has developed a new 3D printing process for the manufacture of small glass objects.

In this interview, AZoM talks to Jeanette Madigan from Mai Dubai about their water analysis, services and how Metrohm instruments impact their work.

James Tour & Kevin Wyss

AZoM spoke with Professor James Tour and Ph.D. candidate Kevin Wyss from Rice University about their research that has looked at upcycling disused car parts into high-quality turbostratic graphene.

This product profile outlines the MAX-iR FTIR Gas Analyzer from Thermo Fisher Scientific.

Learn more about the JAM-5200EBM E-Beam Metal Additive Manufacturing System for 3D Printing.

This product profile outlines the features and benefits of the Contour X - 500 3D Optical Profilometer.

AZoM.com - An AZoNetwork Site

Owned and operated by AZoNetwork, © 2000-2022