Guards at stationary grinding machines shall be able to retain high energy fragments in the work room after bursting of an abrasive product. Technical regulations and rules including the currently valid European Safety Standard EN 13218 neither contain practice-related information on how to achieve this safety objective nor a practice-oriented method for testing the guards.
In the project, the impact resistance of steel sheet and polycarbonate as typical materials for guards was determined by means of bursting tests with real abrasive products. A special test rig enabled aimed bursting of abrasive products at specified speeds. Subsequently, the resulting damages were documented and assigned to the different fragments on the basis of high speed video graphs.
The tests carried out showed that the abrasive product fragments resulting from the rupture may hit the guards in many different ways with their cross sectional areas, peripheral surfaces or bore sides. These different impact situations have an important influence on the impact resistance. Aside from this principle problem, practically usable reference values for the impact resistance of steel sheet and polycarbonate may be derived from the bursting tests. The bursting tests with real abrasive products confirm the tendency observed in the results of earlier impact tests with cylindrical projectiles of defined geometries made from different abrasive product ceramics. In these tests, an increase of the impact resistance was e. g. observed with decreasing projectile strength and increasing projectile diameter. A direct comparability between the results of a bursting test and an impact test is, however, not possible due to different kinematic and energetic conditions. According to the available results, the impact test partly furnishes impact resistance values, which are too high by far. Therefore, the design of guards at stationary grinding machines should be based on the results of bursting tests. This will be taken into account in the upcoming revision of EN13218.
-cross sectoral-Type of hazard:
Mechanische Gefährdungen, Gestaltung von Arbeit und TechnikCatchwords:
Maschinensicherheit, SicherheitstechnikDescription, key words:
guards, grinding machines, abrasive products