Just like any equipment, heat transfer systems require maintenance to operate reliably. While the fluids in these systems are often considered low maintenance, regular monitoring and servicing are still necessary—and eventually, a fluid change will be required.

In our previous post, we shared tips for small system maintenance. Now let’s look at some important considerations for larger systems.

Large systems are usually designed and coordinated by engineering firms. They’re typically powered by gas- or oil-fired boilers and are assembled from multiple components: one vendor may supply the boiler, another the pump, and yet another may provide user-side equipment such as kettles, laminators, or reactors.

Routine fluid analysis is one of the best maintenance tools available. For most large systems, a yearly sample is sufficient, though you should work with your fluid provider to set the right schedule for your operation.

In addition, regular system inspections are essential. Check for leaks, monitor accessible areas, and keep an eye on pressure gauges, flow meters, and other instruments. Record this data carefully and watch for trends—sudden changes in pressure or flow could signal potential issues that may lead to fluid degradation.

Boilers and furnaces should also be inspected regularly, with periodic tune-ups to maintain efficiency and ensure smooth operation.

Strainers and filters should be checked as well. The presence of carbon deposits is often a sign of thermal degradation, while sludge is a common indicator of oxidation. Unexpected foreign matter could point to a process-side breach.

Large systems usually employ expansion tanks with inert gas blankets—commonly nitrogen—to minimize oxidation. Be sure to check valves, gauges, and controls, and verify that enough buffer gas is available. The expansion tank should also be monitored for temperature: ideally, it should remain below 200°F to help reduce oxidation.

When it’s time to replace the fluid, thoroughness is critical. Make sure that degraded oil is drained as completely as possible (at least 95%). Many fluid suppliers also provide flushing fluids that can help achieve a cleaner system before refilling.

Above all, consistency matters. Staying on top of maintenance tasks and adhering to your analysis schedule will extend the life of your fluid and keep your equipment clean and efficient.