Yeah I hear what you're saying about ebay...but sadly they don't sell this sort of thing at BnQ,.... but I'll look for a more reputable supplier.
You've raised some interesting points there about the hoses...thanks...that's the reason I'm throwing this out there.
As regards the vacuum line hose and valves, I was considering that the whole unit would be suitable for use under sustained vacuum not just the metal section at the end...after all it does say vacuum line not just vacuum valve.
So I've been looking around the web at other vacuum line hose and valve assemblies......I've found many described as vacuum line with shut off valves that have rubber hose sections on both sides of the valves.....so I think that having metal on the one side and rubber on the other is just a peculiarity of that particular assembly and not necessary for safe function.
But I do take your point that it may not be best practice to leave a rubber hose under constant load....those hoses will actually only be under compressive load when the unit is in operation and not 24/7....most of the time they will be under no net pressure either compressive or expansive.
I don't intend to thread and connect any of hoses into the chamber...they will simply be fixed via adhesive.....they are under no more load than the cables which penetrate the chamber wall and i see no reason they should be secured in a stronger fashion.
With the rubber hoses I will however bond them to the chamber via their terminal metal fittings.....if I just used the rubber to seal to the chamber wall then pressure compressing/squashing the rubber could tend to break apart the adhesive joining the rubber to the chamber wall.....any such deformation would obviously not occur with the terminal metal fittings.
Originally Posted by RnRollie
As for the stainless hoses... AFAIK these are "regular rubber" hoses with a braided SS shield. THe SS shielding being there to protect the rubber hose and to prevent rupture in case of overpressure.
I assume you are going to drill and tap and use real hose connectors/fittings on the chamber walls? As running braided SS through the wall will give you the same problems as you have with the wires.
I'm not sure you've had a good look at those they are not just normal rubber hoses with stainless steel braiding to reinforce them, they actually have an internal flexible SS tube running through the center as well as the outer SS braiding.
As they claim that there is no extraction of plasticizer from the rubber then the inner SS tube must be a completely sealed tube in itself just being reinforced with the outer rubber and SS braiding.
Again my original intention was not to use threaded fittings but just to pass the SS hose through the chamber wall sealing further along its length so that the end would be right at the bottom of the chamber sump.......but yes have doubts that the braiding may compromise the chamber integrity.
Its difficult to know how the end is sealed in this respect and is something I'm going to have to suck and see as it were although it does say in the pdf the ends are welded but that is no guarantee the outer casing is air tight....it may be necessary to butcher the end and so terminate the braiding outside the chamber and continue the inner SS tube inside to the chamber sump...but I'd need the inner SS Tube to be completely intact as it will be drawing the liquid out by suction so needs to be a completely sealed tube in itself...or if the central SS tube is not a completely sealed tube I may need to just extend the SS inner tube with a short length of pvc tube running into the sump...this is something I'm going to have to play by ear until I have the items in hand.
PS.....In fact Rollie your comments about the SS braiding have made me think further about the rubber hose....if you look at a cross section of hvac rubber tubing you will see that they are also reinforced with a layer of some type of cord...this again could be an issue and these hoses were not designed to form a seal with the outer layer of the hose but with the inner layer...so it may be neither of them will prevent atmospheric air from entering the chamber in my usage scenario.
This again is something I'm going to have to test when I get them.....it may be that I'll have to terminate the hoses with some type of metal spigot fitting which is sealed into the chamber wall.....but tbh....looking around at the various fittings I can get...this problem should be easily overcome.Edited by technogiant - 8/16/13 at 12:54am