The deadliest threat to CT tubes is the arc, and now there is a way to reduce the danger. Tube oil processing. By removing contaminants from the oil that circulates through the tube housing, one hospital was able to double, even triple the life of inserts, and save tens of thousands of dollars. Too good to be true? Here is a story that is sure to spark interest.

f02a.jpg (8508 bytes)Reducing service costs is the cornerstone of an on-site radiology service program. There is a process, new to the radiology arena, that could double the life of CT tubes and save your hospital tens of thousands of dollars per year. Does this sound too good to be true? Read on.

The key to extending the life of a CT tube is to avoid electrical arcing inside the tube housing, and it is the tube’s insulating oil that prevents this arcing. The extreme heat and high voltage generated during normal tube use will cause insulating oil to break down and with this degradation, there is an increase in the level of contaminants in the oil. As contaminants increase, the tube becomes more and more likely to arc during an exposure. Eventually the contaminants rise to a level where the arcing becomes so frequent that normal CT scanning is impossible. Often the tube is physically damaged by arcs and this may render it permanently unusable. Through methods of processing the oil to reduce the contaminant levels, the likelihood of an arc can be decreased, extending tube life.

“Oil Processing”, as referred to in this article, is the reduction of moisture, gas and particle contaminants in the insulating oil. It can be performed with a system that consists of a vacuum pump, an airtight degassing chamber, a discharge pump and a particulate filter. The pulling action of the vacuum chamber, combined with the pushing action of the discharge pump, causes the oil to circulate through the processor. As the oil goes through the vacuum chamber, water and gases are drawn out. The discharge pump then moves the oil back to the CT tube assembly. Oil returning to the tube passes through a filter to remove particulate contaminants. (See illustration on page 25.)

Degassing can be demonstrated with an experiment: Draw 25cc of tap water into a 50cc syringe. Firmly place your thumb over the blunt syringe tip while drawing the plunger back with your other hand. You are pulling a vacuum on the water in the syringe and you will see air bubbles rising out of the tap water. The same thing occurs in the oil processor.

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