Service Note No: 11
To: Bay Voltex TCU users
Subject: Extending TCU (chiller) pump life
Problem: Bay Voltex temperature control units (a.k.a. chillers) utilize high flow turbine pumps to deliver proper coolant flow rates to the plasma systems. These pumps use brass in their construction and are subject to rapid corrosion when exposed to De-Ionized water. Since the electrodes in plasma systems require high resistivity water to be used, DI is sometimes used to fill TCU reservoirs. This leads to higher failure rates of the TCU's turbine pumps. Typical MTTF when using 18 megohm DI water is 18 months.
Solution: The manufacturer has recommended that pure DI water should NOT be used in the TCU's. Since high resistivity must be maintained to prevent RF losses, we now recommend using 500 k-ohm to 1 meg-ohm "rho water" (available from some DI systems - prior to going to final "polishing" tanks) or distilled water (available at most super-markets). Reported MTTF has been improved to 30 months by using the lower resistivity (and less corrosive) rho water.
Preventive maintenance: Check TCU's for proper operation and coolant loss every week. Replace coolant every 6 months or when resistivity falls below 250 k-ohm. Install and maintain filters, thermometers, and pressure gauges near system to verify and adjust TCU performance.
Note: on TCU's expected to be used below 15 degrees C: mix rho water with lab grade, high purity, ethylene glycol in a 1:1 ratio. Do not use automobile anti-freeze as it contains harmful additives.
Expert Tips: On channels dedicated to cooling turbo pumps and/or RF power supplies, you can use regular tap water instead of the rho/glycol mixture to economize.
Let us know at the AGS Support desk
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Last update made on: 6 September, 2002 by Webmaster