What Is a Burst Test? A Guide to Internal Pressure Testing of Containers
A burst test measures the internal pressure a container can withstand before it deforms or breaks. The bottle, can or keg is filled with water, sealed, and the pressure inside is raised until a set value is reached or until the container fails. Burst testers are standard instruments for manufacturers and users of PET bottles, glass bottles, aerosol cans and beverage cans.
How does a burst tester work?
The container is filled with water and sealed on a clamping head. Water is used rather than air because it is almost incompressible: when the container fails, very little stored energy is released, which makes the test much safer.
The tester then raises the pressure and records it throughout the test. Two types of test are common:
Pass test: the pressure is raised to a predefined value and held for a given time. The container passes if it does not leak or break.
Test to destruction: the pressure keeps rising until the container bursts, and the burst pressure is recorded.
For glass containers, ISO 7458:2004 specifies two methods: Method A applies a uniform internal pressure for a predetermined period, and Method B applies an internal pressure that increases at a predetermined constant rate.
Main applications
PET bottles for carbonated drinks: the bottle must hold the pressure of the CO2 during filling, transport and storage without bursting or expanding too much.
Glass bottles: checking the internal pressure resistance of glass containers according to ISO 7458.
Aerosol cans: measuring the pressure at which the cone and the dome deform, then the burst pressure.
Beverage cans and can ends: measuring the pressure resistance of the can dome and of the ends.
Kegs: testing kegs of up to 20 L with the keg version of the PBBT-2 (PBBT-2-K).
Key concepts: burst pressure, expansion and ramp rate
Burst pressure is the pressure at which the container fails. It is the most common result, but not the only one.
Volume expansion: under pressure, a PET bottle stretches before it bursts. The AT2E PBBT-2 displays the pressure and volume expansion curves during the test, which shows how much the bottle grows before it fails.
Ramp rate: the speed at which the pressure rises changes the result, because PET slowly deforms under a constant load. In the fill ramp mode of the PBBT-2, the bottle is pressurized quickly to an initial pressure and held for a given time (for example 13 seconds), as on a filling line. The pressure then rises at a set speed, such as 0.7 bar (10 psi) per second, until the bottle bursts or reaches the maximum pressure or volume.
Range and resolution depend on the container. The PBBT-2 measures 0 to 20 bar (0 to 290 psi) with a resolution of 0.01 bar, while glass bottle burst testers go up to 60 bar (870 psi) with a resolution of 0.1 bar.
A carbonated drink is a small pressure vessel
The CO2 dissolved in a drink creates a pressure inside the bottle, and this pressure rises with temperature: a bottle left in a hot truck is under much more stress than one in a refrigerator. A burst test checks that the container keeps a safety margin above the pressures it will meet in real life, including during filling, when the pressure rises very quickly.
PET and glass fail in very different ways. Like a balloon, a PET bottle first grows, then fails at its weakest point. Glass does not stretch: a glass bottle breaks suddenly, often from a small defect or scratch on its surface. This is why glass burst testers have safety doors and bins that collect the fragments.
Calibration of a burst tester
The pressure sensor is checked against a precision reference gauge:
Connect a precision pressure gauge to the test circuit.
Apply several pressures across the measuring range and compare the two readings.
On testers that measure volume expansion, check the volume with a graduated calibration flask.
The optional calibration pack of the PBBT-2 includes the precision pressure gauge, the graduated calibration flask and a spacer. If the deviations exceed the acceptable limit, the tester must be adjusted before it is used again.
AT2E burst testers
AT2E burst testers cover PET, glass and metal containers:
PBBT-2: PET bottle burst tester, 0 to 20 bar (0 to 290 psi), fill ramp, burst and custom modes, bottles up to 3 L.
PBBT-ECO: PET bottle burst tester that needs no electricity, 0 to 20 bar.
GBBT-1 and GBBT-2: glass bottle burst testers, 0 to 60 bar (0 to 870 psi), single or dual station, according to ISO 7458.
GBBT-AUTO: automated glass bottle burst tester for unattended testing.
ACBT-1: aerosol can burst tester, 0 to 40 bar (0 to 580 psi); cone, dome and burst pressures are recorded automatically.
CEBT-1: can and end buckle tester, 0 to 10 bar (0 to 145 psi).
Conclusion
A burst test answers a simple question: how much pressure can the container take before it fails? The answer depends on the material, on the test mode and on the speed of pressurization. Choosing a method that reflects real filling and storage conditions, and keeping the pressure sensor calibrated, makes the results meaningful for production.
Request a quote
AT2E is an ISO 9001 certified company (AFNOR Certification).
Request a quote: info@at2e.com
Comments