[Solid_hgc] [EXTERNAL] SoLID HGC Vessel update

[Garth Huber]

Hi,

To give a brief update, the vessel was leak tested for a 4th time yesterday 
afternoon.  We suffered a bit of a setback, as leaks which were previously 
sealed with RTV started leaking again.

In addition, the thin aluminum front window had some leakage issues past the 
O-ring.  Close inspection of the window indicated pulling on one side, as the 
bolt holes on that side were stretched.  The other side appeared fine.  I'm 
surprised this happened, as we never experienced this with the same window 
material on the SHMS HGC.  We think this happened during the window pressure 
tests, where the bolts were tightened more tightly on one side than the other. 
We will switch to the spare aluminum window for now.  If the problem continues, 
I will have to get more windows made with the remaining aluminum from the SHMS HGC.

LESSON: It is very important that the bolts on the thin window are tightened 
uniformly.  Only one torque wrench should be used, as the settings between one 
wrench and the other are not very accurate.  It's okay if more than one person 
tighten the bolts, but one person should be designated to check every bolt 
afterwards to ensure uniformity.

THE PLAN: Danny is going to try to fix up some of the problem areas with new RTV 
today, and then let it cure.  Assuming all goes well, we will do a 5th leak test 
on Thursday at 14:00.  We will need a couple of volunteers.

The Thursday afternoon test will be very important.  If we continue to have 
problems with the RTV, we will have to discuss our options.  One option being 
considered is to disassemble part of the vessel, apply epoxy between the joints, 
and put the pieces back in place before the epoxy cures.  Maybe we will apply 
RTV too, that is not yet decided.  This means we will most likely need a second 
set of volunteers on Friday, to assist Danny with whatever next step we decide 
on Thursday afternoon.

Thanks everyone for your hard work.  As a reminder, we need some volunteers for 
both Thursday afternoon and Friday (either morning or afternoon).

Garth

-- 
Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.
tel: 1-306-585-4240. fax: 1-306-585-5659.