Plows should be carefully located so that the material removed from the belt does not create a hazard as it falls or where it accumulates.
Just as it is important to have a roller above a secondary belt cleaner that provides downward pressure to keep the cleaner from pushing the belt up, it is important to have one or two pressure rollers below the pulley-protection plow installation. In this case, the mission is to prevent the plow from changing the belt line by pushing the belt down so that material can pass underneath the blade. Depending on the space available, this can be a single idler roller placed directly under the plow or a pair of return idlers, one installed before the plow and one after.
Like any other conveyor component that will be in contact with the belt, the installation of a pulley-protection device will increase the friction against the moving belt. Consequently, this drag will increase the conveyor’s drive power requirements.
In the sixth edition of Belt Conveyors for Bulk Materials, the Conveyor Equipment Manufacturers Association (CEMA) offers a recommended setting of 2 pounds-force per inch of belt width as the normal force for plow-to-belt pressure. (The metric equivalent is 0.35 newtons per millimeter of belt width.) this pressure can be converted into power consumption using formulas.
When specifying a pulley-protection device, there are a number of factors that should be considered.
A plow should: