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Best Practices For Used Heat Transfer Fluid Sampling

Relatherm Heat Transfer Fluids offers a complete suite of cradle-to-grave life cycle services designed to ensure the optimal operation of your heat transfer system. Besides our industry leading extended fluid life technology, we also offer a complimentary, no-charge fluid testing and analysis program. This program is popular with many of our customers because it helps them to adopt a preventative maintenance approach with their heat transfer systems. By keeping a pulse on important parameters, lessons can be quickly learnt on optimal operating procedures and potential causes of fluid degradation that would not otherwise be evident without a laboratory analysis. We see this as an integral part of our commitment to end-users in diverse industrial sectors to maintain a safe, efficient, clean, cost-effective, and trouble-free equipment operation. In the sections below, we discuss best practices for used fluid sampling.

Frequency of Sampling and Analytical Testing

How often should you draw sample of heat transfer fluid? The answer to this all-important question is dependent on the type of heat transfer system that you have and whether or not you are at the start of the thermal fluid life (newly commissioned system or recently added virgin fluid) or you’ve had the fluid running in your heat transfer system for some time (meaning that the fluid is used). For a new system or one in which virgin thermal fluids was recently introduced, we recommend taking a sample of the fluid for baseline laboratory testing. It is also best practice to analyze a sample from a batch of heat transfer fluid that is to be discarded.  The results will serve as a foundational boundary for understanding and interpreting the results of future fluid tests.

The sampling and testing frequency of used thermal fluids is a bit more intricate due to the multiplicity of factors at play. In Table 1 presented below, we attempt to simplify these with an easily understandable chart. On the vertical column to the left, the size of the system is noted (small, medium and large). The horizontal top row details the system type (open and closed) and whether or not a Nitrogen blanket is present.  To use the chart, you should select the recommendation that corresponds with the intersection of your selection on the horizontal row and vertical column.

 

Open  System*

Closed System without Nitrogen Blanketing

Closed System with Nitrogen Blanketing

Small System (Containing less than 110 gallons/416 liters)

Quarterly/ four times a year

Semi-annually/ twice a year**

Once every two years***

Medium Size System (Containing between 110 gallons and 440 gallons/1666 liters)

Quarterly/ four times a year

Once a year (if operation is steady and continuous), otherwise test twice a year

Once every two years***

Large System  (Containing more than 440 gallons/1666 liters)

Quarterly/ four times a year

Once a year (if operation is steady and continuous), otherwise test twice a year

Once every two years***

Table 1: Recommended Sampling & Testing Frequency for Used Heat Transfer Fluids

* This classification is for open systems where a mineral-oil based is used. If you are using a dedicated open bath fluid like Relatherm S-1 or Relatherm PAG, longer sampling frequencies (semi-annual testing) may apply.

** Most Temperature Control Units fall under this category. They are subject to frequent starts and stops. The tank lids are often opened as well necessitating a more frequent testing schedule.  

*** If process upsets, seal leaks or other unusual trends are common with your equipment/process, consider testing annually.

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