When properly maintained, most thermal fluids will provide reliable performance for many decades. Unfortunately, many organizations lack proper stewardship of their fluid and do not monitor or maintain the health of their fluid.
Annual fluid testing is the key to identifying and correcting ordinary age-related fluid degradation issues. However, when routine testing and annual maintenance recommendations are deferred, degradation of the fluid will be compounded until the point where the fluid can no longer be rehabilitated. At this point, the entire charge of thermal fluid in the system must be replaced.
Unfortunately, dealing with severely degraded fluid is not just as simple as draining out the old fluid and refilling with new. Degraded fluid typically has a large amount of contamination, such as undissolved solids. Most of these particles will simply fall to the bottom of the pipes when the fluid is drained. When the new fluid is filled into the system, it will not only pick up this residual contamination, but it will also act as a solvent and begin to dissolve harder coke deposits from the wall of the piping. The result being that your brand-new fluid will be immediately contaminated.
To overcome this situation, HEAT has developed a specialized fluid cleaning procedure to eliminate this recontamination phenomenon during fluid replacement. The following is a sample procedure provided to illustrate some of the potential complexities of fluid replacement. Actual procedures are developed based on the fluid sample test results prior to draining the contaminated fluid from the system.
SAMPLE THERMAL FLUID REPLACEMENT PROCEDURE
1. Hot Draining of Fluid: First, the HEAT team will install a high velocity flushing and filtration skid into the system piping. This equipment will be used to rapidly drain and remove as much of the existing fluid from the system as possible. In the next step, the bulk fluid temperature is cooled down to approximately 150°F before initiating the hot draining process. The high velocity pump is used to pull as many solids in suspension as possible during the draining process. Pressurized air or nitrogen may also be used to push the fluid from sections that do not have adequate drainage. Any low piping runs that do not have drains will require the breaking of flange connections to allow trapped fluid to drain into catch basins for transfer to the disposal containers. In some cases, the fluid manufacturer will agree to accept this contaminated fluid back for reconditioning and credit against the purchase of new fluid. Otherwise, this contaminated fluid must be disposed of by the customer.
2. Refill with Virgin Fluid: The system is now re-filled with the new heat transfer fluid. After circulation of the virgin fluid has been achieved, a sample should be taken for testing. The testing will show how much the new fluid has picked up contamination, particulates and moisture left in the piping system.
3. Flushing & Filtration: The flushing and filtration skid will now be used to re-circulate the new fluid at high velocity through the system. The filter housing on this skid will be used to catch and remove most of the heavy sludges and particulates that are dissolved and become suspended in the new fluid while at ambient temperature. The flushing skid also includes an onboard electric heater that is then used to raise the fluid temperature up to a maximum of 225°F. We have found that some contaminates are more easily dissolved and removed at low temperatures and other contaminants are more easily dissolved and removed at higher temperatures.
4. Polish Filtration: Once the majority of the contaminants have been removed from the fluid, the final polish filtration of the fluid will be done using beta 1000 filter cartridges. This step will ensure that both the system and the fluid are in “like-new” condition before being returned into service.
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