Before the advent of Silicone Diffusion Pump Oils
about 20-25 years ago. Hydrocarbon Diffusion Pump Oils ruled the Vacuum
Industry. These oils are prepared from base oil that has been distilled from
crude oil and purified by Dewaxing and Solvent extraction. This is further
purified by additional vacuum distillations. Famous hydrocarbon oils brands are
Supervac Hydrocarbon Diffusion Pump Oil(SV-DELTA), Apiezon C and Convoil 20. Silicone
Diffusion Pump Oils on the other hand are made by controlled hydrolysis of
Silanes, addition of Phenyl groups followed by Distillation. Famous Silicone
Diffusion Pump oil brands are Supervac Ultra high Vacuum Silicone
Diffusion Pump Oil (SV Sigma) and DC704.
SV-SIGMA
Table below gives the comparison of both these oils,
this will help user decide which particular oil is better for a particular
application.
Property
|
Hydrocarbon
Diffusion Pump Oil
|
Silicone
Diffusion Pump Oil
|
Ultimate Vacuum
|
1x 10 -6 Torr
|
1x 10 -8 Torr
|
Working Life
|
3-6 months
|
12 -18 months
|
Cost
|
Low
|
High
|
Pump Maintenance
|
Requires cleaning of Jets of Diffusion Pump every
time oil is changed
|
No jet cleaning required
|
Vacuum Time
|
Fast
|
Very fast
|
SV-DELTA
As it is clear from above that Hydrocarbon Diffusion
Pump Oil is suitable in following conditions------------
1)
Cost of operation
has to be kept very low.
2)
Operation
contaminates oil quickly.
3)
Equipment is very
old therefore working life of oil and vacuum level will remain low irrespective
of oil used.
For all other applications Silicone Diffusion Pump oil
is suitable. Supervac Industries manufactured Silicone Diffusion Pump oil SV-Sigma is one of the best
Silicone Diffusion Pump oils available in the world.
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