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Re:Re: Re; diffusion pumps
Ted and Don: ask my girlfriend who is the most gulible person in the world.
The reason that I have/had believed that metal diff pumps could not be
through-pumped comes (mainly) from the following: reps from Edwards and Cook
that have been in my shop (Transco sells both), and things like reading
"Modern Vacuum Practice" by Nigel Harris (available through Edwards) where
they say things about screwing up the oil by exposing it to atmosphre. I had
believed that metal pumps were different in tha they ran hotter than glass
pumps (but now that I think about it, the temp to boil the same oil should be
the same temperature), and that they used less oil than glass pumps (my glass
pump uses twice the amount of oil as my metal pump). I have always defended
the position of through-pumping glass pumps mainly on how well they have
worked in my shop, and on EXTENSIVE oil annalysis on 4, 6, and 8 month old
oil to check for degridation (It has shown some contamination past the 6
month check) even though there are people who say that you can't through-pump
a glass diff pump. I would love to know that I've been lied to about the
metal pumps. When you say they have worked well (Ted) are you basing that on
vacuum gauge readings? How low does your gauge read? Have you done oil
annalysis on old (changed) oil? How often do you change oil? Do you leave
your pumps on/diff pump heater on all the time? Any other tips would be
greatly appreciated. Thank you in advance. Morgan