To test at what pressure a Robinson coupling will fail.
Experiment Setup
The standard hydrostatic burst test procedure was used to carry
out these tests. (See above).
These tests were carried out under water about
40-50cm below the waterline to contain debris and for sound
suppression.
Results
We submerged the bottles under test to
contain the noise..
Two 2L Robinson coupled bottles failed at
165psi.
Preparing to test a 2L bottle.
A typical 2 L bottle failure. Splits down
the side.
The coupling still retained some of the
plastic from the failed bottle.
Stress fractures in the base of a 2L bottle
after being subjected to 140psi.
A 2L bottle as above and a 2.25L bottle
were coupled base to base using our standard 8mm
Robinson coupling with three thick hard rubber washers.
It appears the bottle burst again on its side and the
crack propagated to the coupling hole. From there the
cracks fanned out from the hole. There was significant
damage all around the coupling. The 2.25L bottle was
stretched but otherwise undamaged.
A standard 2L bottle again but this time
without the central ridge on the flat section. We
pressurised this bottle to 140psi. We stopped the
pressurisation and held it for 40 seconds. During this
time the bottle continued expanding and air having
entered it it started floating to the surface. We
aborted the test and let the pressure out. The bottle
was stretched considerably. Normally the bottle has a
2280ml capacity, but after stretching it held 2360ml
unpressurised.
Same bottle as above. We pressurised it
to 130psi and held it at that pressure for 3 minutes. No
visible continued inflation could be seen. Then we
slowly increased the pressure and the bottle failed at
150psi.
