[Ocp-europe] RuggedPOD v2 sealing feedbacks and improvements

Jean-Marie Verdun jean-marie.verdun at splitted-desktop.com
Sun Jul 5 20:32:57 UTC 2015


Hi Folks,

I spent some time drawing the concept of the top sealing that we used 
for RuggedPOD v2.

The sealing concept is quite easy to understand. We roughly used a 3D 
torus joint which is standing at the top of the edge of the tank. This 
joint is placed under pressure from the top cover which is bolted to the 
tank using threaded rod which have been pre-assembled into the tank.

This principle is currently not working efficiently and we must find the 
root cause of the issue. The first thing we observed is that most of the 
theaded rod are getting bent or unlocked from the tank. They are 
currently based on stainless steel a strong material with a 3 mm diameter.

We used also specific glue to lock them down into the hole which was 
threaded.
The top surface of the tank edge has been post processed to be flatened 
as much as we could.

Roughly the assembly process is the following one:-

- Solder the tank side to each other
- Solder the bottom
- Post process the edge of the top surface of the tanke to flaten it
- use CNC to create 3D torus joint placement area
- Put the thread rod in place
- Run the whole assembly

Looking at some math, when we put the tank under vacuum, I believe that 
the pressure on the top cover is slightly moving to 1kg/square cm as the 
pressure inside the tank is going to 0.007 bar, which means about 1.4 
tons for the whole cover. This pressure is transferred in some way to 
the tank edges, and stainless steel elasticity is exercising a strong 
force on the threaded rod which are breaking there glue link and create 
some small leakage.

I might be totally wrong, and this is where I need your help !

We urgently need to have a look to this issue, as I would like to 
upgrade asap this design flow. The following options might be explored 
and will be discussed with some of our manufacturing partners this week 
like:

- Embedding the threaded rod during the panel manufacturing process 
rather than gluing them
- Use higher diameter and longer threaded rod
- Put one at each corner (currently there is none, and most of the 
leakage are observed in that place)
- Put them in a Z shape around the 3D torus joint instead of a standard 
aligned position
- Increase the number of Threaded rod
- Use bolt with wide pressure area (we are using standard 3mm bolt, 
perhaps using 3mm hole bolt but 6mm contact diameter surface might be 
better)
- We could also increase the thickness of the top cover, but what will 
be the right one ?

I like to avoid increasing the thickness of the tank panel (which will 
increase the contact surface with the top cover), as it will lower heat 
exchange capacity.

Feel free to jump into the discussion ! JJ will try to run some static 
mechanical simulation tomorrow with solidworks as to understand how much 
pressure each threaded rod have to address. But we are not expert in 
mechanical simulation and if you have some options to help us feel free !

Jm


-- 

  Jean-Marie Verdun
 *Splitted-Desktop Systems*
  President
  Batiment Aristote
  Parc des Algorithmes
  Route de l'orme des merisiers
  91190 Saint Aubin FRANCE

 jean-marie.verdun at splitted-desktop.com

Â
	Splitted-Desktop Systems is a proud member of the Open Compute Foundation
and a Gold member till July '15. We can provide you consulting and 
engineering
services related to any OCP hardware. We also drive RuggedPOD and Daap Open
Hardware projects





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