From: John Philo <jphilo@mailway.com>
  To  : Sandy Go <sandygo@uhnres.utoronto.ca>
  Date: Tue, 27 Mar 2001 15:51:56 -0800

RE: broken windows

I and many others have used the housings, window holders etc. for many years
without problems.

Have you checked for dirt/particulate build-up at the bottom of the aluminum
cell housing (assuming you are talking about 2-channel cells). Any such
thing down there will keep the window holders from lying flat and could
potentially cause this problem.

Is it possible that your torque wrench is bad? Do you have the style with an
actual dial-type gauge, or the ones where you set the torque by turning part
of the handle? With the dial-type gauges you can accidentally rotate the
dial so it no longer reads zero at zero torque. I'm not aware of problems or
issues with the other style (though I note that Beckman no longer sells
them), but one could imagine, for example, that if some contaminant got into
the mechanism it might throw the calibration way off.

John Philo


-----Original Message-----
From: Sandy Go [sandygo@uhnres.utoronto.ca]">mailto:sandygo@uhnres.utoronto.ca]
Sent: Tuesday, March 27, 2001 11:35 AM
To: rasmb@alpha.bbri.org
Subject: broken windows


    Has anyone had any problems with broken windows?  Lately I have been
having some problems with frequent window breakages.  I have lowered the
torquing pressure to about 90 in-lb, so I know it is not an over
torquing problem.  Breaking or cracking of the windows usually happen
just after I take out the cell from the torque stand.  I wonder if
frequent use eventually leads to the centerpiece warping so it does not
lie flat anymore.  Do these parts i.e., the cell housing, centerpiece,
quartz windows, and window holders, have a certain lifespan?  We have
had the instrument for three years now and we run about 125 cells worth
of samples per year.  We typically run samples between 20k to 48k rpm.
We have never replaced any of the parts except for the windows and the
disposables (window liners and gaskets and a few screw rings).  Please
help ASAP.  Thanks.

Sandy Go
Research Technician
OCI/Princess Margaret Hospital
University of Toronto