Update 12/23/09 Illinois EPA wants action taken against NDK for plant explosion
CSB was recently deployed to the NDK America explosion in Illinois. The six year old facility grows quartz used in frequency-control devices in which NDK is the world's largest manufacturer.
Eight 50 ft high/75 ton autoclaves are on site are used in the production process which generate internal temperatures of up to 700 F and pressure in excess of 20,000 psi. Pressure vessels such as these are inspected every three years by the Illinois State Fire Marshall Office. Last year the office conducted over 45,000 inspection on boilers and pressure vessels throughout the state.
Interesting problems with autoclave vessel seal failure prior between the lid and 75 ton autoclave in a situation that Ingenium Technologies solved for a client. Could this be a clue to the NDK America explosion that CSB is investigating?
Autoclave Vessel:
• vessel weighs 75 ton
• vessel lid weighs 5 ton (10,000 lbs)
• clamps that secure the lid to the vessel weigh 5 ton
• 50’ tall
• 3.5’ diameter
CSB claims the explosion was so strong it threw a 10,000-pound piece of metal 400 feet into another building. Could this of been the 5 ton lid from the top of the autoclave?
Process of making high quality single quartz crystal using silica glass nutrient
Crucial growth parameters, pressure, temperature, and fill:
Fill
"Fill is the most important parameter determining the average autoclave pressure. A ten percent change in fill will increase the pressure more than two fold at 350° C. The fill for quartz has been varied from 65 to 88 percent corresponding to pressures of 150 to 3000 atmospheres. Most present commercial growth processes use up to 1500 atmospheres pressure."
Temperature
"Catastrophic failures have occurred even at commercial establishments. For alpha-quartz the growth, the growth T g near the seeds, can be varied from 200° to 573° C. At 200° the reaction is very slow but above 573° C. undesirable beta quartz is formed. Typical growth temperatures vary from 340° to 375° C."
Resources:
Google Map Satellite View
Kajima Builds NDK America's First U.S. Plant
Illinois State Fire Marshall Office.
Quartz Crystal Basics:From Raw Materials to Oscillators"
Posts
John:
ReplyDeleteThank you for posting this very valuable news item. A few comments:
1.) The apparently unknown "piece" that was found blown away indeed could have been the 5 ton lid, it could also have been the same-weight clamping system mentioned in your other reference source. Odd that CSB investigators seem so stumped at what this piece could possibly be..albeit it is a bit early in the investigation phase. Yet still...people like us find it in the public domain this quickly !
2.) Interesting that the process is so sensitive to fill...a small extra amount promotes such disproportionately higher operating pressures. Without getting ahead of ourselves this may prove to be a crucial fact.
3.) From other public domain sources it appears that other installations (as a "best-practice") may bury their 50 foot tall vessels almost completely underground, to limit the potential shrapnel distance if something like this should occur. Apparently NDK was allowed to build above-ground using a blast wall building construction around it.
Another point...as we continue on the journey, I would suggest that each of us as posters be very careful and precise in quoting operating parameters. I believe the pressures for operations like this go as high as 29,000 psig. Temperatures reach 570 degC (= 1058 degF), although other sources quote 700 degF as reasonable max.
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