Thermal oil systems tend to be exceptionally smooth-running and trouble-free. It's not uncommon to hear of systems that have been operating quietly and efficiently for years with nary a hint of problems.

To keep your system "in the pink" there are some simple - and inexpensive - checks that you can perform in-house. These procedures can help you detect problems before they become real headaches.

Listening to the System
Like your car, each thermal oil system has its own sounds that tell you it's operating properly. But if you hear snapping, cracking and popping noises in the piping or tubing, it's highly likely water has gotten into the system. If the pump is making loud noises, it may be cavitating. This is a significant problem and should be dealt with immediately. If any part of the system is vibrating excessively, you'll want to know why.

Looking at the System
Hot fluid weeping from welds, flanges, instrument ports, valve stem packings or gaskets is certainly a housekeeping problem - and could become a burn hazard. Leaks of thermal fluid should be taken care of as soon as possible.

During each inspection include the pressure equalization line (vent). Steam coming from the vent can signal water in the system. If you see oil mist, it may mean that the heat transfer fluid is vaporizing at the heated surfaces. Both situations require immediate attention.

Closely inspect the catch-container. The container should be steel. It should be positioned so that overflows from relief, vent or overflow lines are safely contained. Do you see fluid in the container? If so, you'll want to know what the fluid is and why it's there. If it's heat transfer fluid, you'll want to determine what caused the relief valve to trip or the system to overflow. If it's water, oil, solvent or other liquid, it's a safety hazard and must be removed. The catch container should always be clean and dry.

Unusual Smells
Sniff the air in the heater room, and in the area near the heat user. If you detect a "varnishy," "burnt" or "acidy" pungent odor, the fluid is probably "bruised" and the odors may be escaping from the system. You'll want to find the source of the leak, and determine if repairs are necessary.

Observing the Fluid
With the heater off, start the circulating pump(s) in the morning and wait ten or fifteen minutes. Open a low-point valve, allowing a small amount of fluid and any accumulated grit to drain into a can. After the grit has cleared, place a clean water glass or beaker under the valve and fill about 3/4 full. Put the beaker on a bench and let it sit.

If liquid has "beaded" in the glass or if you see a phase separation (one fluid "floating" on top of the other), water has likely infiltrated the system. If you see particles on the bottom (or floating in the liquid), it could mean that the fluid is "coking" or that mill scale or other hard contamination is present. Either condition should be investigated before problems can escalate.

Gently tilt the beaker left then right. Does the used fluid look thicker than new fluid? Does the film appear thick or thin as it slides down the inside of the glass? If thick -- especially if it has visible suspended solid matter -- the fluid's viscosity may have substantially changed and it is probably bruised. A fluid analysis may be a good idea.

Sniff the fluid. If it smells burnt, "varnishy" or "acidy," the fluid is most likely bruised -- another reason to consider a formal fluid analysis.

If you check the system every week or two, these simple and inexpensive procedures will help you keep your system humming, and can reduce or eliminate nasty surprises.

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