HS-Group - Model OI-808 -Silicone Diffusion Pump Oil
HS-Group's Silicone Diffusion Pump Oil OI-808 serves as a high-performance fluid specifically designed for use in high vacuum and ultra-high vacuum applications. Known for its superior temperature and oxidation resistance, OI-808 is composed of a high-boiling fraction of phenylmethylsiloxanes, ensuring compatibility with materials such as aluminum, chromium, nickel, and steel. This oil enables ultimate vacuums of 10-6 to 10-7 mbar, with potential for even 10-10 mbar under optimal conditions using liquid nitrogen-cooled baffles. With a narrow molecular weight distribution, OI-808 minimizes oil backflow into high vacuum chambers, maintaining system integrity over extended operational periods. Unlike organic oils, it shows resilience against oxidation, especially in fast-vented systems. HS-Group's diffusion pump oil OI-808 is frequently used as a substitute for discontinued DC702, DC704, and DC705 oils, offering enhanced performance at competitive prices.
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The demands on working with diffusion pumps or to the pump fluids used in those pumps are constantly increasing Compared to purely organic oils (hydro-carbons, esters, etc.), silicone diffusion pump oils have the advantage that they can exhibit high temperature and oxidation resistance. HS-Group Silicone Diffusion Pump Oil (OI-808) has ideal properties and is therefore perfectly suited for use in terms of final vacuum, intake speed, pre-vacuum resistance and backflow rates.
The HS-Group silicone diffusion pump oil OI-808 is characterized in particular by the following properties:
- Suitable for all types of diffusion pumps
- Chemically inert, high thermal stability
- Oxidation resistance
- Radiation resistance
- Moisture resistance
- Steam resistance
- Excellent price/performance ratio
Another advantage is above all the low vapor pressure. In addition, the oil is chemically inert and thus compatible with the materials used in the diffusion pumps (aluminum, chromium, nickel and steel). A high-boiling fraction of phenylmethylsiloxanes forms the chemical structure of the HS-Group silicone diffusion pump oil OI-808. The properties of our oils can be found in the following table.
The HS-Group Silicone Diffusion Pump Oil OI-808 achieves ultimate vacuums of 10-6 to 10-7 mbar thanks to its low vapor pressure—provided it complies with the regulations of UHV technology (surface-treated parts and metal or Viton seals), and provides adequate heat output and sufficiently low pre-vacuum.
The following vacuum data are based on a test bench designed according to the rules of the UHV technology. The test set-up for the determination of the final vacuum is shown systematically in the adjacent figure. After the baffles and recipient are baked out over several hours, the resulting final pressure is evaluated. The test duration is 24 hours.
When using an ionization vacuum gauge, suitable for high vacuum measurements, the vacuum measurement is carried out. Depending on the design of the pump, the heating power and the method of measurement, the values for the final vacuum range from 10-6 to 10-7 mbar, unless the equipment is baked out and baffles are not used.
If the special baffles are cooled with liquid nitrogen, significantly better values (up to 10-10 mbar) can be achieved.
The upper limit of the vacuum system—that is to say, the maximum permissible vacuum pressure (counter pressure resistance)—which is still permissible for the operation of a diffusion pump is critical to the requirements. The pre-vacuum of the HS-Group silicone diffusion pump oil OI-808 should be in the range of 10-1 to 10-2 mbar.
In the figure opposite, the schematic setup for measuring the maximum the permissible vacuum pressure is shown. Here, the final pressure on the intake side of the diffusion pump is first measured.
With the aid of the gas metering valve, air is supplied to the pre-vacuum pressure until the high-vacuum collapses in the course of the falling motive steam flow inside the pump. As a rule, the measurements are carried out without gas load and with different heat outputs at the diffusion pump.
The diffusion pump oil backflow is that amount of oil which enters the high vacuum chamber under the same operating conditions in a certain time unit. Compared to hydrocarbons (organic oils), the HS-Group silicone diffusion pump oil OI-808 is remarkably favorable due to the very narrow molecular weight distribution.
It is remarkable that even after one week of operating the diffusion pump with diffusion pump oil OI-808 and by using a water-cooled baffle, no contaminated quantity could be detected.
The diagram on the right-hand side shows the setup for measuring oil backflow of the diffusion pump.