Overview
The carton bursting strength tester is a special device used to evaluate the uniform increasing pressure of corrugated cardboard or box cardboard on a unit area until the maximum pressure at the time of rupture. This assay is crucial for quality control of packaging materials and is widely used in industries such as packaging, printing, logistics, and consumer goods production. Its working principle is based on a hydraulic or pneumatic system, which applies continuous pressure to the specimen through a rubber diaphragm, and the instrument accurately records the peak pressure at the moment of rupture, which is the bursting strength value, usually expressed in kilopascals (kPa) or pound-force per square inch (psi).
Preparation before operation
Ensure that the instrument is placed on a stable, level bench and away from vibration sources and direct light before operation. Check whether the power connection and air supply or hydraulic system are normal, and confirm that the instrument has passed periodic calibration and is within the validity period. Specimens should be cut from the flat part of the carton in accordance with relevant standards (such as GB/T 6545, ISO 2758, etc.), and the size should not be less than 100mm×100mm, and there should be no wrinkles, cracks or obvious defects. Specimens should be balanced under standard temperature and humidity conditions (e.g., 23±1°C, 50±2%RH) for at least 4 hours to ensure comparability of test results.
Procedure:
Turn on the power of the instrument and warm it up to a stable state. Place the balanced specimen in the center of the lower clamp ring, ensuring that it completely covers the test area. Tighten the clamping ring so that the specimen is evenly clamped without slipping or wrinkling. Set the test parameters, such as pressurization rate, unit system, etc., and usually control the pressurization rate at 170±15kPa/min or 95±10mL/min hydraulic pressure growth rate. Start the test program, the instrument automatically pressurizes until the specimen breaks, and records the peak pressure. After the test is completed, the clamp ring is released, the broken specimen is taken out, and the instrument pressure system is automatically reset. It is recommended to test at least 5 valid specimens per sample, and take the arithmetic average as the final result after eliminating outliers.
Notes:
When clamping the specimen, the clamping ring pressure should be uniform and moderate, too tight may cause premature damage to the specimen, and too loose will cause sliding. During the testing process, the rubber diaphragm should be checked regularly, and if there is aging, deformation or damage, it needs to be replaced in time to avoid affecting the accuracy of pressure transmission. After each test, the clamping ring should be cleaned to prevent residual paper scraps from interfering with subsequent tests. If the test results fluctuate abnormally, check whether the specimen is underrepresentative, whether the instrument is leaking, or whether the calibration status is invalid. Operators should avoid touching specimens or clamping areas during testing to ensure safety.
The result is calculated
The bursting strength results are read directly by the instrument in kPa or psi. To calculate the average, the formula is as follows:
\[ P = \frac{\sum_{i=1}^{n} P_i}{n} \]
where P represents the average bursting strength, PiIndicates the value of a single test, and n represents the number of valid tests. Standard deviation assesses the degree of data discreteness:
\[ s = \sqrt{\frac{\sum_{i=1}^{n} (P_i - P)^2}{n-1}} \]
The test report should include the average, standard deviation, test conditions, number of specimens, and a description of the abnormal situation.
Routine maintenance
Routine maintenance includes cleaning instrument surfaces, inspecting line connections, and changing hydraulic fluid or filter elements regularly. Calibration should be performed according to standard procedures, usually using standard weights or standard pressure modules to verify instrument accuracy, and it is recommended to perform a full calibration every 12 months or after every 5,000 tests. Calibration records should be kept properly to ensure traceability of test results. If the instrument is idle for a long time, the system pressure should be released and covered to prevent dust.
FAQs
| Problem phenomenon | Possible causes and suggestions |
| The test results are low | the specimen is not adequately balanced; insufficient clamping pressure; Diaphragm aging. Check the temperature and humidity conditions, adjust the clamping force, and replace the diaphragm. |
| The specimen slides during the test | contamination or wear of the clamping surface; The sample is too small. Clean or repair the clamp torus to ensure specimen size compliance. |
| The pressure cannot rise | insufficient hydraulic oil; System leaks. Refill the hydraulic fluid, check the seals and tighten the connections. |
| The readings show instability | power interference; Faulty sensor. Ensure a stable power supply and contact a technician to access the sensor. |
References
GB/T 6545-1998 Determination method of breaking strength of corrugated cardboard
ISO 2758:2014 Determination of paper breaking strength
ASTM D774/D774M-97 Standard Test Method for Bursting Strength of Paper and Paperboard
Instrument Operating Manuals and Calibration Specifications (General Technical Documentation)