An Elephant in the Classroom

As part of our scattershot marketing effort, I was given the opportunity to teach EVERYTHING ABOUT VACUUM TECHNOLOGY  to a bunch of employees at a plant largely involved in metallurgical vacuum, that is furnaces and heat treatment.   I hadn’t been up against a blackboard or its equivalent in a long time, so this got me thinking about how arcane and fractionated the world of vacuum technology is.   I started with units, of course, and realized that the practical mess caused by all of our non-SI, weird units involving mercury columns, inches of water, pieces of a standard atmosphere etc., could not be explained in a few minutes.   Explaining gauges and measurement without resorting to any physics proved also to be problematical, so I moved on to pumps and pumping.   Here, I was on more solid ground, as there are good analogies to things like compressors, turbines, engines and so forth. 

Save Your Pump Oil, Boys!

Users with only a few vacuum pumps, or those not in constant use, don’t think about pump oil very much.  On our small deposition systems, I’ve heard from customers about decades of running without an oil change.  However, oil gets dirty, changes chemically, and often just leaves the pump one way or the other.  We can only assume that the hydrocarbon versions at least, are going to get expensive along with everything else oily.

Let’s keep these costs down!

If you’re pumping something particularly reactive, like pure oxygen, effluent from a plasma reactor, CVD tool, etc, you already know how fast oil can get degraded.  The mechanisms are chemical change, usually in the direction of increasing viscosity,  corrosive additions,  accumulation of abrasive particles, and just plain dirt.   A rotary vane pump running hydrocarbon oil may fail in just a few hours, and a Fomblin or other inert oil pump may fail surprisingly soon as well, especially because the impurities will not mix with the oil, form a supernatant film, and rot through the pump.  A bathtub ring of the nasty kind!