Posted: Sat May 30, 2009 1:08 pmHi guys,
I built a bench to this design last weekend:
I've just been playing with my inclined manometer and I can't seem to get it to work correctly.
The manometer is 20" long, 10" rise.
0% at the top and 100% at bottom reading from left (top) to right (bottom).
I would expect the manometer to stay at 0% when the vacuum is applied and for it to move towards 100% when the test piece hole is covered. Is this correct?
My manometer moves away from 100% when the vacuum is applied when using a roughly cut 0.25" hole as the orifice plate (I'm just testing not looking for flow figures yet).
It will move only slightly towards 100% when the test piece hole is covered.
When using a ~2.5" hole (again just roughly cut to get a feeling for the bench, not flow figures) the manometer is even more lazy, and will hardly move towards 100% no matter what pressure I use, and how mush I cover the hole.
I recently painted the bench inside and out.
Before I painted the bench the manometer was working like I expected it too. If that is correct or not I'm not sure.
I think the painting has sealed the bench so well that when the test piece hole is covered the bench the bench is being crushed by the atmosphere. (It really is. I had the make braces for it as it imploded and I had to replace snapped screws. Even the 18mm MDF is bowing by an alarming amount)
I think the bench distorting is causing it to leak. Either to atmosphere or from the top plenum to the bottom plenum.
Either that or I've connected the manometer up the wrong way around.
Any ideas anyone?
I built a bench to this design last weekend:
I've just been playing with my inclined manometer and I can't seem to get it to work correctly.
The manometer is 20" long, 10" rise.
0% at the top and 100% at bottom reading from left (top) to right (bottom).
I would expect the manometer to stay at 0% when the vacuum is applied and for it to move towards 100% when the test piece hole is covered. Is this correct?
My manometer moves away from 100% when the vacuum is applied when using a roughly cut 0.25" hole as the orifice plate (I'm just testing not looking for flow figures yet).
It will move only slightly towards 100% when the test piece hole is covered.
When using a ~2.5" hole (again just roughly cut to get a feeling for the bench, not flow figures) the manometer is even more lazy, and will hardly move towards 100% no matter what pressure I use, and how mush I cover the hole.
I recently painted the bench inside and out.
Before I painted the bench the manometer was working like I expected it too. If that is correct or not I'm not sure.
I think the painting has sealed the bench so well that when the test piece hole is covered the bench the bench is being crushed by the atmosphere. (It really is. I had the make braces for it as it imploded and I had to replace snapped screws. Even the 18mm MDF is bowing by an alarming amount)
I think the bench distorting is causing it to leak. Either to atmosphere or from the top plenum to the bottom plenum.
Either that or I've connected the manometer up the wrong way around.
Any ideas anyone?