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Technical problem in high vacuum coating plant

2005

Dear Sir,
We have a high vacuum coating plant , we are unable to get high vacuum in it.
We get low vacuum within few minutes .
Even when the Diffusion pump is separately tested we are not getting desired level of vacuum i.e -5.
The DP is cleaned properly and there is no leakage also.
What else can be wrong in the whole system which we need to check?
With what should one clean the DP?

[Ed. note: Our supporting advertisers will reply to the following proprietary question in private. We do not print public replies to commercial questions] --> Also please suggest a diffusion pump fluid which is not very expensive (other than santovac5 and DC 704)

Sonia Rathod
Coating - INDIA

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2005

You have not told us much about the system so how could we answer ? What size DP for what size chamber ? Air in India is very humid most places. What do you have in the system to pump down moisture (like a cold trap, LN2) ? Moisture without cold trap could hold the pressure in the low -4 s. Can you do helium leak check to make sure there are no leaks ?

Try this: keep pumping the system non-stop for two-three days and see if walls get dryer and pressure goes down (if the DP is adequate for the chamber).

Mandar Sunthankar
- Fort Collins, Colorado

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It could be the heaters on the DP. Have you checked the DP temperature? The heaters could be shorted or the thermal contact to the pump bottom could be damaged. Also, what is the foreline pressure in your system? DP performance is affected by foreline pressure.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover
San Diego, California
2005