November 2021 Volume 3

EQUIPMENT & TECHNOLOGY

Automotive-type anti-freeze solutions should never be used. They have corrosion inhibitors and pH buffers that are electrically conductive and not suitable for induction power supply equipment. A common misconception is that a cooling system that is not adequately protected against freezing can be safeguarded against ice damage by operating the circulating pump when the temperature is below the freezing point of the water/glycol solution. The idea is that moving water is not as likely to freeze, but this is a major fallacy. While it is true that the circulating water will not immediately freeze into one single mass because of movement and heat generated during pumping, an icy slurry can form and damage the pumping system and components. Having ice suspended in the cooling water is the near equivalent to having an abrasive suspended in the cooling water. This condition can lead to accelerated wear on the pump impeller, volute, and damage to components.

A 40°F temperature swing caused this hose to leak. Photo source: Integral Power Technologies

Too Cold for Comfort Cold circulating water can cause condensation to form on power components and conductors and leads to short circuiting of creepage paths (electrical spacing between conductors), reducing insulator resistance, increased leakage currents, and tracking1. The best practice is to avoid circulating the process cooling water through the cooling tower when the outside air temperature is below the dew point of the air inside the building or power supply enclosure.

Testing water/ethylene glycol solution: view through refractometer shows between 44% and 48% ethylene glycol. Photo source: Integral Power Technologies Water Leaks As temperatures drop, the rubber hoses in a cooling circuit may become hard and not effectively seal on hose barbs. It is often observed that leaks develop seemingly overnight. A recommended practice is to tighten all hose clamps every three months (quarterly preventative maintenance).

Arcing and corrosion on the ceramic insulator of these free-wheel diodes- caused by leaks and condensation. Photo source: Integral Power Technologies The freeze-up of a cooling system should be avoided at all costs. Cooling tower damage from freezing is estimated at several hundred thousand dollars. Power converter components such as capacitors and inductors (coils) are easily damaged and often scrapped after freezing. The cost of maintaining a glycol system is very minimal when compared to the cost of parts and labor associated with freeze damage.

FIA MAGAZINE | NOVEMBER 2021 12