[RASMB] (no subject)

Borries Demeler demeler at biochem.uthscsa.edu
Wed May 13 09:26:07 PDT 2009


> 
> Hello,
> 
> Recently a screw ring became stuck in a velocity housing used with our XL-A=
> . This is the second time this has happened in the last few months. It appe=
> ars that the screw ring becomes miss-threaded, one time after a 50,000rpm r=
> un, and a second during cell assembly prior to a run. In both instances the=
>  screw ring was threaded properly, gently tightened and loosened several ti=
> mes to further ensure proper threading, then at some point seizes such that=
>  the torque wrench and stand cannot loosen the cell assembly. (Our practice=
>  for assembling cells does not include Spin Coat due to the issues I have h=
> ad with contamination of the windows and such.)
> 
> That being said I have two questions. First, am I correct in thinking that =
> the seizing of the screw ring is likely due to deformation of the cell hous=
> ing? Second, we were able to use sturdier tools (compared to the torque wre=
> nch and stand) to separate the screw ring and housing in the first instance=
>  of this issue. However, no such luck in the second occurrence, does anyone=
>  have any suggestions for recovering at least the windows if not the window=
> s and the centerpiece from the housing?
> 
> Thank you in advance,
> Keith Connaghan

Is it possible that there was a small leak of a buffer, and some of the salts
may have crystallized in the screw ring, making it sticky? In that case, maybe
soaking overnight in a mild detergent could help, other than that I might try
rapid heating/cooling cycles to break the deadlock through expansion and 
contraction. Some torque wrenches have pins on which to set the cell housing,
rather than the friction type. If you can find one of those, you may be able to 
loosen it with the wrench.

-b.



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