nitrogen vaporizer upgrade

Ted Berg tberg at stanford.edu
Mon Dec 10 06:21:14 PST 2007


Hello All,
    Yes today is the day we begin prep for the N2 upgrade. The gases 
will be put in bypass today , electrical will be disconnected tomorrow 
and Cranes will be in the corpyard on Wednesday to remove the old 
purifiers and begin work on upgrade. As Paul said we do not believe this 
will effect gas quality but you might be cautious of critical processes. 
We will be bringing in a temporary supply of N2 to keep us going next 
week as the upgrade progresses. Thank you in advance for your 
cooperation. Ted


Paul Rissman wrote:

> Dear Labmembers and CIS Lab Occupants:
>
> For the past few years, we have been working with Air Products on an 
> upgrade of our nitrogen vaporizer system.  As you may be aware, Air 
> Products supplies our bulk liquid gases and, to some extent, the 
> facilities for vaporizing them to gas form so that they can be used as 
> process gases in our labs in SNF and CISX.
>
> Collectively, we are now extracting anywhere between 3-4X the amount 
> of gaseous nitrogen that our vaporizers are rated for.  Needless to 
> say, this is not the best way to run.  Through a series of 
> negotiations, Air Products has generously agreed to donate equipment 
> and services to upgrade our vaporizers. In the current plan, Air 
> Products will use a tanker truck to provide a temporary N2 in order to 
> ensure continuous supply to the CIS and CISX buildings during this 
> transition.  The temporary supply will be hooked up on Tuesday, 
> December 18 and there should be no noticeable change in services.  
> From Wednesday, December 19 through Friday, December 21, the larger 
> vaporizer and new N2 purifiers will be installed.  Once the new system 
> is leak-checked and certified, it will go on-line and the temporary N2 
> supply will be removed.  During this time, metering systems will also 
> be installed in order to allow us to get a handle on nitrogen usage.  
> As you may be aware, liquid nitrogen is the largest single expense in 
> this building.  We have been looking forward for a long time for this 
> upgrade; this should facilitate a more reliable and cleaner supply of 
> N2 for the building.
>
> However, one aspect of this installation has the potential to affect 
> quality of gas delivered.  For staging the installation, the gas 
> purifiers for bulk O2 and ultra-high purity N2 will need to be 
> bypassed.  This is tentatively planned for Monday, December 10, 
> although we need to confirm this date.  Air Products' testing 
> indicates that the current N2 purifier system does not significantly 
> improve the quality of the delivered gas so bypassing this should not 
> have a noticeable effect.  However, the O2 purifier seems to be 
> somewhat effective at filtering particles (1357 particles >0.1 um at 
> the inlet versus undetectable amounts at the outlet.)  So, please be 
> aware that between December 10, when the O2 purifier is taken off-line 
> and December 21, when the new O2 filter is installed, that the quality 
> of the O2 may be somewhat compromised.  This is not anticipated to 
> affect most operations in SNF (namely, etches and depositions) but 
> critical operations, such as very thin gate oxides, may be 
> vulnerable.  Please be aware of this when planning your experiments.
>
> We apologize for the inconvenience these changes may cause.  But 
> please understand that these changes are necessary to ensure reliable 
> and continuous bulk gas supplies.  If you have any further questions 
> or concerns about this upgrade, please contact Ted Berg.
>
> Paul Rissman
>




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