Overview
This test stand is designed to accurately measure the change
in volume and dimensions of a pressure vessel at different
pressures.
The test stand consists of a solid base that the bottle
stands on with a back support for the air inlet hose, and scale
measurement.
Test stand with bottle full of water standing on the
base.
Measuring change in length
A nozzle adaptor is fitted to the top of the
bottle to allow an air supply to be connected. Attached to the
nozzle adapter is a needle that extends out to one side. the
needle is adjusted to point at the scale attached to the stand.
As the bottle is pressurised the top of the
bottle stretches vertically and a reading can be taken from the
needle.
Measuring change in circumference
A strip of paper with a printed scale is
attached at one end with tape to the bottle. The other end
of the strip is wrapped once around the bottle.
The end of the strip is attached to a
hanging weight via a thread. This hanging weight provides
necessary tension on the strip as the bottle expands. The
end of the paper strip is reinforced with a piece of clear
tape.
A mark is placed on the inner part of the
strip section so that the scale can be read in relation to
it.
As the bottle is pressurised the
circumference will increase and the position of the mark
relative to the scale will move. The difference between the
two readings is the amount of circumference change under
pressure.
Measuring change in volume
The bottle is completely filled with water
all the way up to the neck. A zero mark is made at the
bottom of the meniscus. The bottle is then pressurised to
the desired level. The water level drops in proportion to
the pressure applied. A mark is then made for the new
meniscus level. The volume above the water level is volume
increase as a result of the bottle stretching.
When the bottle is depressurised enough water
is emptied until the meniscus lines up with the pressurised mark.
The bottled is placed on a scale and weighed. Water is then
added to the bottle until it reaches the unpressurised mark
and the bottle is weighed again.
The difference in weight in grams represents
the volume increase in mL.
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