WEAR DEPENDS ON HANDLED BULK MATERIAL
The amount of wear strongly depends on the abrasiveness of the handled bulk material. The harder the material, the higher the wear on the grab scales. The scales of a grab handling coal or fertilizer will have a much longer lifetime than a grab handling clinker or iron ore.
Verstegen uses the best possible steels for building their grabs, but also Verstegen grabs wear when handling abrasive materials. Depending on the hardness and shape of the material, iron ore grabs can require maintenance already after 25.000 cycles. Maintenance and/or repair can take between a few days up to a number of weeks. Good planning and organisation (getting spare parts, make sure a spare grab is available) is extremely important.
NOT ALL SCALE PLATES WEAR EVENLY
Further the wear depends on the path of the scale plate moving through the material. The lower knives, knife corners and lower part of the side knives are pushed through the bulk material for a long distance and therefore the wear on these areas is the highest. Other critical points are the front edges of the internal strengthening plates.
GRAB DIVIDED INTO WEAR AREAS
From a wear point of view the grab scales can be divided in a number of wear areas.
Strong wear (yellow):
- Cutting edges (lower knives);
- Knife corners;
- Lower part of the side knives;
- Lower part of the internal strengthening plates (from lower knives to ± 500 mm upwards).
Medium wear (red):
- Side scale plates;
- Lower part of the scale plates (from lower knives to 800-1000 mm upwards).
Little wear (blue):
- Upper part of the side knives;
- Upper part of the internal strengthening plates;
- Upper part of the scale plates.
The above areas determine the required maintenance on the various scale parts.
The “strong wear” areas (yellow parts) normally require 2-3 times more maintenance than the “medium wear” areas (red parts).
HOW TO DEAL WITH WEAR
Wear is inevitable, but of course there are possible solutions. Below the most common solutions are described.
- Periodic repair of heavy wear areas
- Using heavier (thicker) plates for the heavy wear areas;
- Using harder material for the heavy wear areas;
- Applying hardface welding on the heavy wear areas
Each of above options have advantages and disadvantages. Please contact us for more information.