Alumina sphere crush test

Case study

Alumina sphere crush close up and samples

Single pellet crush test with upper and lower self-levelling compression plate fixtures

Solution

MultiTest 2.5-xt software-controlled test stand
Self-levelling compression plates for stable force application

Benefits

Reliable and repeatable test on very small test sample
Capture of all relevent eveents in crush and fracture behaviour

Our customer’s quality laboratory decided to upgrade their equipment and contacted G.T. Michelli Co. to provide them with a new system. Initially we evaluated a Mecmesin competitor’s system, and it failed to meet the standards required. We had recently sold a Mecmesin torque tester to another customer and so were aware of the force test stands the company manufactures. I contacted Mecmesin’s technical sales engineers and supplied some samples and within days a complete solution was developed and demonstrated. This system now performs our customer’s tests seamlessly, with higher accuracy and less uncertainty than ever before. The system is so easy to use and the software so intuitive that the operator needed very little assistance!

Patrick Jester, Quality Assurance, Safety & Training
G.T. Michelli Co.

Requirement

G.T. Michelli Co. serves a wide variety of industries and markets from petrochemical manufacturing to biomedical facilities. The company supplies products and systems in the field of force measurement plus the support services to maintain those applications.

A customer needed a new solution to improve both the accuracy and repeatability of measuring the compressive crush force for its alumina sphere products. Used in the chemical industry as efficiency-improving catalysts or in peptization processes, these high-purity spheres of only 0.7 mm in diameter must perform consistently under extreme conditions. The manufacturer has pre-determined specifications for the crush failure characteristics that must be met, and the existing manually-operated stand and gauge system was not providing the required level of confidence.

Solution

Mecmesin tested samples of the alumina product, and produced video footage of the process with a detailed report of the measured force characteristics output from the proposed computer-controlled system. Based on this information, G.T. Michelli’s end customer adopted the solution. A single-column Mecmesin test stand and 2.5 kN intelligent loadcell with a self-levelling 70 mm diameter base compression plate and 50 mm upper plate exerts a top load on a single sphere until it cracks. The force on the sphere under load is displayed as a real-time graph and the first-peak failure value captured as the critical data.

The product testing is carried out under laboratory conditions and the connected PC running Emperor™ software automates the whole process via the bespoke test program written by Mecmesin engineers. The elimination of human error or variability afforded by the software control is of particular value to the manufacturer. Additional benefits over the previous system are that the test stand’s fixed compression plates require no adjustment, and the crosshead’s upper and lower travel limit switches protect the loadcell from overload damage.

The ASTM D4179 test standard "Single Pellet Crush Strength of Formed Catalysts and Catalyst Carriers," specifies the method for compressive 'side crush strength' (SCS) of individual pellets in regular forms such as spheres, short cylinders, or tablets. It allows for testing as a radial or axial crush. The procedure requires the application of a uniform force to the pellet specimen until it crushes or collapses, recording the maximum crush force at the point of initial collapse, to calculate a strength value.

This solution would now be implemented by an OmniTest universal tester and VectorPro software.