Tube sticking on FACSCalibur

Hi everyone. I’m having a problem with the loader on a FACSCalibur,  
and I would appreciate any suggestions. My apologies for the length.

Basic problem: When running racks using the loader, tubes keep  
sticking, hanging from the SIP after the arm drops. This interrupts  
the run and requires constant monitoring of the machine. This is not  
a “vertical motion” error, but rather, a “tube stuck” error.

Some important background:
	     I have been using this machine, with this style of  
loader, for over 6 years. We had the loader replaced last year, and  
the problem started about 6 weeks after that. It was intermittent at  
first, but has become worse. I am using the same types of sample  
tubes (Falcon), the same type of loader seal (BD 19-66379-03), and  
the same basic procedures that I always have. I have had occasional  
problems with tubes sticking in the past, and I have always been able  
to resolve them by cleaning or replacing the loader seal, and by  
stressing to users the importance of keeping the tops of the tubes  
clean. These standard “fixes” are not helping in this case. I have  
replaced the seal, which has resulted in a temporary improvement,  
only to have the problem recur after a couple of days. If anything, I  
am being more careful than usual about keeping the tops of the tubes  
clean.

What’s been tried:
	     When we had a BD technician in to do a 6 month  
maintenance, he suggested using a different type of loader seal. I  
don’t know the product number offhand, but it was a combination of a  
thin, flat orange seal and a black conical one. I tried this for a  
while, but the problem recurred. The next time I contacted BD they  
suggested that I adjust the loader settings, reducing the “high”,  
“low” and “final low” settings by one (from 9 to 8, 8 to 7, and 7 to  
6, respectively). I tried this, with the old style of seal (the one I  
had used for the last 6 years), and it worked for 4 days. After that,  
it became rapidly worse, until after a couple of more days, every  
tube was sticking.

Theories:
	     It seems too coincidental that after years of use, this  
problem started after a new loader was put in. The fact that there is  
a temporary reduction in the problem when I change the seal suggests  
that the seal is becoming damaged in some way, causing the tubes to  
stick, but this is happening at an accelerated rate. I thought that  
the loader might simply be “pushing too hard”, creating too much  
pressure on the seal, but changing the loader settings hasn’t fixed  
this.  Is it possible that some kind of alignment problem (i.e. the  
loader arm relative to the SIP) could cause this to happen?
	     I would be especially interested in any ideas about  
possible causes of this problem. The suggestions we have received so  
far from BD have been of the “what to try” kind, rather than the  
“what’s causing it” kind.

A comment on BD technical help:
	     We have generally been very happy with the support we  
receive from BD. We have had some very skilled, very thorough  
technicians working on this machine in the past. Unfortunately, the  
cost of anything but the most basic service contract is out of our  
reach right now, and we would obviously prefer to avoid a costly  
repair visit.

Thanks for your help!



Paul Kron
Dept. of Integrative Biology
University of Guelph
Guelph, Ontario, Canada
pkron@uoguelph.ca