We have two Parr 1108 bomb systems at Wittenberg that we use annually for two or three weeks for about 50 firings during that period. Parr's service department and documentation are excellent and it is good to rely on them for advice. As the Davis report
states: "With proper maintenance, these particular calorimeters can operate safely and accurately for decades." Unfortunately we had to learn "proper maintenance" the hard way. Because of the low duty cycle, we were not vigilant about replacing seals and
had an incident like the one at Davis about 3 years ago. The bomb head itself was scrap, but there was little other damage and no injuries. We use electronic thermometry, so mercury was not an issue.
We now have a socket and torque wrench stored with the bomb that allow us to properly torque the packing nut (#27)
every week during use. We replace seals annually before the cycle of labs.
In teaching labs, another problem is instructional. Many people don't like to read details and think they can outguess the equipment. This is not good bomb technique. Our lab manual used to include excerpts from the Parr documentation
on data handling during a run, but not enough about the 1108 bomb itself. We have now included the 1108 manual with the lab instructions. The firing buttons have a note: " If you have not read the Parr 1108 instruction manual, do not push this button".
The other bomb mishap we had was a case where students had trouble seating the bomb head in the bomb body. They decided that the screw cap would seat it sufficiently. The escaping flame welded the bomb shut forever.
THe bomb head MUST seat into the bomb body so that the top of the bomb head is flush with the lip of the body, else it WILL leak.
Students also like to exceed the recommended sample size, so that, too, needs to be watched. I make myself annoyingly present during the bomb labs so that neither students nor faculty cut corners. This equipment is very well designed,
but needs to be apprached with respect and awe.
Coordinator of Chemistry Labs
From: DCHAS-L Discussion List [dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of Dan Crowl [crowl**At_Symbol_Here**MTU.EDU]
Sent: Wednesday, February 15, 2012 8:19 PM
Subject: Re: [DCHAS-L] A lesson learned about oxygen bomb calorimetry
Thanks for the interesting case history.
NASA has some good technical reports on oxygen service - regular cleaning is essential.
Your report identifies the immediate cause, but does not state anything about the root causes. I bet you could come up with a number of root causes.
Thanks for sharing.
"Debbie M. Decker" <dmdecker**At_Symbol_Here**UCDAVIS.EDU> wrote:
I've posted my report of this incident at
http://ucih.ucdavis.edu/docs/ll_CalorimeterFailure.pdf for your reviewing pleasure. The listserv chokes on embedded images.
This was a very near miss and thankfully, no one was injured. If your chemistry/chemical engineering/materials science folks use this technique (and it's a pretty classic one), it would be
good to follow up with them about routine maintenance on the bomb vessel. Don't forget undergraduate teaching, where it's taught in p-chem lab.
Ya'll be safe out there,
Debbie M. Decker, Campus Chemical Safety Officer
Environmental Health and Safety
University of California, Davis
1 Shields Ave.
Davis, CA 95616
Co-Conspirator to Make the World A
Better Place -- Visit www.HeroicStories.com and join the conspiracy