 |
 |
|
|
| :: The
Quiet Corner |
Sponsorship:
Some trade banners space is available on the right hand side and affiliate
program banners can be replaced.
See
rate card.
Madness:
The Lord's Prayer contains 56 words, the Ten Commandments 297, the
American Declaration of Independence 1,300 - but the EU directive on duck
eggs contains
26,911...
Remember:
"The good you do comes back to you, sometimes when you need it most,
sometimes when you least expect it"
Communicate:
Promote yourself, your business and enhance your professional reputation
for FREE at:
DoubleGlazingWeb.Info
|
|
|
|
Glass:
Vacuum inside S/units
Do Sealed Units Have a Vacuum?
Double-glazed units don’t contain a vacuum, but many, possibly even most will have a negative pressure compared with our atmospheric pressure.
This is not deliberate, but purely an accidental result of part of the manufacturing process. There are a number of different types of edge seal materials and processes, and some are more likely to produce a greater negative pressure, sealed within the unit, than others. A high negative pressure is not a good thing, and under certain circumstances a unit can implode, although a slight negative pressure will in itself will not normally prove to be a problem, except under certain circumstances when the unit can implode. See
Why did my sealed unit explode?
| Look carefully at the glass and you will see the dished effect: |
 |
|
|
Here is one example
When it comes to larger sealed units there is an added reason why a
negative pressure can be accidentally sealed in. Imagine a sealed
unit for a patio door, probably 3ft to 4ft wide and around 6ft high
(90-120x180cm), laid horizontally on a flat work bench. The lower
pane is supported by the flat bench, the spacer is placed around the
perimeter and the other pane of glass is laid on top prior to
sealing up around the edge. The top pane will sag somewhat, and if
completely sealed like this it will have quite a high negative
pressure built in. Because manufacturers know this, they will
either:
|
| a) |
clamp a suction pad
in the middle of the top pane and pull out the sag until the
unit is completely sealed,
|
|
or |
| b) |
seal most of the
perimeter of the unit, then lift it off of the bench, stand it
vertically until the inside pressure has equalised with
atmospheric pressure and then seal the last little bit
|
For more information on this
subject see:
Sealed units - manufacturing techniques
All about 'misted-up' sealed units
Do sealed units have a vacuum?
Types of glass
About safety glass
Air gaps and insulation
Why did my sealed unit explode?
Brewster's Fringes
|
|
