Short "shelf life" of high pressure LN for SEM EDX system?
- From: waltd@xxxxxxxxx
- Date: Mon, 15 May 2006 07:34:59 -0400
I have had a LN cooled EDX system for 2-1/2 years and recently the time it takes for my storage bottle to evaporate has shrunken drastically. I get LN delivered in 306# tanks (approx 5 ft high x 2 ft dia). Pressure relief valve is always between 235 and 350 depending on the tank. Tank is different each time (supplier has many tanks).
For 2 years, I had gotten between 18 and 21 days out of a tank. The limit is mostly evaporative loss as I only draw about 15 liters a week to keep the EDX dewar filled. Starting about 4 months ago, I started getting 11 days from a full bottle (once), then 7 or 8 days ( a few times). Now I've had one fill that lasted 3 days and the latest 6 days. What life does anyone out there get from these bottles? I'm thinking the scale at the filling plant is defective or someone is punching in the wrong tare. At $100 per fill I'd like to get my meager 40 liters for my scope. All feedback greatly appreciated.
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