Lubricants Lubrication Oil Analysis Reliability & Maintenance Center

Analyze Your Thermal Fluids

EP Editorial Staff | June 1, 2023

Thermal-fluid analysis should be done regularly and involve 11 tests, not the traditional seven.

Leaving pipework unmonitored can lead to unexpected downtime and safety issues, particularly when working with thermal fluids.

Instead of reacting to issues, regular thermal-fluid sampling and analysis enables manufacturers to proactively monitor fluid condition and intervene before issues affect production, extending thermal oil lifespan and reducing maintenance costs. These steps should be part of any analysis.  

• Effectively monitoring heat-transfer-oil condition requires engineers to regularly send samples to a specialist for analysis. Analysts should conduct 11, not the traditional seven, tests to generate results that best reflect what’s happening inside the system.

• Once the sample arrives at the test lab, a chemist will visually assess the color and look for any particulates in the fluid. Color can range from the clear, bright appearance of newer fluids; to hazy, a sign of high-water levels; to dark, which indicates carbon buildup in the system.

• Testing oil water content is vital to regulatory compliance. Water will convert to steam and expand, increasing system pressure.  

• The next step is to test viscosity and assess the impact the fluid has on the system pumps. If a fluid is too thick, flow rate will reduce, increasing pressure on the pumps. Reduced flow rate can create hot spots in the system, leading to inconsistent heating or cooling that results in waste products, increased system damage, and rising maintenance costs.

• The level of carbon in the system indicates the degree of system fouling. As carbon deposits and hardens in the pipes, it becomes an insulator. This degrades heat-transfer efficiency, requiring more energy to heat the system. Carbon build-up also creates hot spots that accelerate pipe wear and increase the risk of leaks.

• Analytical chemists will then test the total acid number (TAN). High acid levels lead to increased corrosion and accelerated carbon creation. By measuring this parameter, manufacturers can slow degradation and reduce the frequency of scheduled maintenance. 

• Particulate quantity and iron tests highlight the degradation of system components. Both tests indicate wear in the system. 

• Also look at the results of the Pensky-Martens Closed Cup flash point, Cleveland Open Cup flash point, and fire point tests to reduce health and safety risks. The closed flash point of a fluid cannot be less than 100 C, because it means the fluid could ignite at lower temperatures. 

• Once analysis is completed, the thermal-fluid expert delivers a report to the plant manager, organizing points into cautions, actions, or serious findings. Use this information to establish a proactive maintenance plan.  

Maintaining an efficient heat-transfer system is integral to productivity and a key factor is effectively monitoring the system’s fluid. Thermal fluid testing can be complex, so manufacturers should work with experts to ensure they obtain an accurate representation of what’s happening inside the system. —Clive Jones, Managing Director, Global Heat Transfer, Chicago EP

To learn more about the thermal fluid testing and the company’s Thermocare program, visit the Global Heat Transfer website:


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