Water In Thermal Fluid Systems -- Part 2 of 3 -- Removal

There are laboratory procedures that can measure water in thermal fluids. However, such lab tests are really only useful for fluid that hasn't been charged into the system. Water in a running hot-oil system is relatively easy to detect.

Small water infiltrations (less than 300- 400 ppm) can show up as pump pressure fluctuations. These fluctuations most always produce pump noise and dancing pressure-gauge needles. While significant pump noise can mean a bad gauge or loose coupling, it almost always points towards water.

It may be easy to ignore or misinterpret the fluctuations considering that fluid temperature at the heater outlet is so much above water's atmospheric boiling point. However, the lowest fluid temperature -- and pressure -- in the system is at pump suction. That temperature and pressure determines whether the water will be liquid or gas at that point in the system. So if the fluctuations or cavitations start suddenly while the system is heating up, you know there are low levels of water in the fluid.

High levels of water (like the free water visible at the bottom of a decanted sample of fluid) are pretty difficult to misinterpret. Once the water residing at a system low-point reaches its boiling temperature, its volume increases suddenly -- by up to 1600 times, depending on the fluid temperature and pressure at that point -- as it flashes to steam. The displaced fluid is quickly forced up into the expansion tank and out the vent. Hot fluid and steam spurting out of a vent is hard to ignore. Serious injury -- and possibly fire -- can occur. This danger is aggravated if an open drum is used as the catch tank.

Be on the lookout for any sudden change in your system, be it pump cavitation, increased expansion tank volume, unusual sounds or increased pressures -- especially during start-up. It can often mean you've got water in the system.