Greiner caps popping off in centrifuge

[SMILLER 863]

We are in the process of switching our specimen collection tubes to Greiner Vacutte (previously we used BD).    For some reason, with one of our STAT fuges, the stoppers keep coming off while being spun.  Not all the time but enough to be annoying. 

The centrifuge in question is a Hitteck EBA200.  The vendor has recommended a certain insert for these Greiner tubes, but they still keep popping off at random.  The stoppers are slightly different from the BD tubes, but we cannot see what is causing this.

If anyone has any ideas for fixing this they would be appreciated.  We are trying to see if Greiner has any ideas.

Scott

[A. DeRossett 1]

We had to use tube lifters in some of our centrifuges to prevent the tubes from sinking down into the holders.  If we didn't use the tube lifters, the cap of the tube would hit the lip of the holder and pop the cap off.  Once we used the lifters, we stopped having caps pop off.

[Jennifer G 1]

We are switching to Greiner tubes from BD. We are a small transfusion service averaging about 150 RBC transfusions per month. We use Ortho gel for ABSC and ABID and tube testing for everything else with Immucor reagents. What would be considered an adequate number of specimens for a parallel study? Would every test we perform have to be done? Can the number of specimens vary with the type of test? When we rarely use tube testing for ABSC or ABID and when we do comparisons every six months, we have to change the 0.8% cells to 3% which is time consuming. I want to adequately check the Greiner tubes without going insane. SMiller, what did you do? Thanks for your help!