Rotary feed through “O” ring type or “ferro fluid” type?
The ferro fluid type, although initially more expensive, will provide the best vacuum seal available, and requires no maintenance. Ferro fluid types are not subject to virtual leaks that “O” ring type seals demonstrate. “O” ring seal rotary feed through requires the addition of silicon grease to provide adequate sealing, and are prone to wear over time. A quality ferro fluid seal will provide 8-10 years life in a parylene coater, where as the rotary “O” ring type needs attention at least every six (6) months. Parylene coaters operate at medium vacuum and ferro fluid seals are designed for use in high vacuum equipment; thus the integrity of the seal is superior to the “O” ring type. Side by side tests demonstrate faster pump down rates and lower vacuum levels with the ferro fluid rotary seal.
