MATERIALS HANDLING
centreline of the conveyor. Idlers that are not closely spaced under the skirtboard enclosure will make a bumpy belt path that leaves gaps between the skirt and the belt for dust and fi nes to escape. To produce a fully sealed environment, the belt should be supported with closely spaced idlers or an impact slide bar system. T e infl ection point created at the fi rst fully troughed idler creates an entrapment point for abrasive particles. T erefore, loading must only start after the belt is fully troughed to control fugitive material release and belt damage.
SKIRTBOARD WIDTH T ere are various historical ratios for the spacing of skirtboards. T ey are usually based on belt width such as the Conveyor Equipment Manufacturers Association (CEMA) standard is two/three times or ½ times belt width for very free fl owing material or multiple loading points. Another approach states three times the size of the largest average lump. T e standard edge distance is an
allowance to prevent material from falling from the belt as the edges sag between carrying idlers after the load zone. T e mistracking allowance is the expected deviation of the belt path from the central axis of the conveyor. CEMA Misalignment Guide is based on the dimensions of standard CEMA idlers and pulleys and considers three categories of mistracking: allowable, actionable and critical. T e International Organization for Standardization (ISO) misalignment allowance is +/-40mm for belts up to and
Skirtboard structure can be unique to the operation and the
application and should be determined by an experienced engineer
SKIRTBOARD SYSTEM T e system includes the belt, tail pulley, loading chute, skirtboards, skirtboard covers, dust curtains belt support, sealing system and wear liners. It is recommended that the belt be in reasonably good condition without existing skirtboard grooves, otherwise, the system may not seal the belt eff ectively. If dust is an issue, consider replacing enclosure covers after maintenance. T e material should be centre-loaded and the skirtboards aligned parallel to the
including 800mm or +/-5% (+/-75mm max.) of the belt width for widths over 800mm. T e free belt edge should be based on the thickness of the sealing system, skirtboards and wear liners added together and measured along the troughed belt surface. T is distance will determine the maximum skirtboard spacing. With a BW of 1,200mm, Bc of 452mm, trough angle of 35°, standard edge distance of 60mm, a mistracking allowance of 100mm and a sealing system 50mm thick the skirtboard width inside the wear liners would be 757mm. Note that this is the distance between skirtboards, not the distance between the wear liners, but wear liner thickness should be included.
SKIRTBOARD HEIGHT T e minimum skirtboard height is based on the maximum expected cross-sectional area contained between the skirtboards, so the belt’s full edge-to-edge area should be used to determine the height of material rubbing on wear liners and to make sure the skirtboards are tall enough for a completely full belt. . Use the loose bulk density – material before it settles on the conveyor – to represent the bulk density. T e reason for this is the loose bulk density can be up to 40% less than the settled (vibrated) bulk density, requiring the material cross-sectional area to be 40% greater at the point of impact before settling.
When a conveyor is purchased on price
the skirtboards will typically be 300mm tall to accommodate a basic vertical slab
Skirtboard width: actual requirements versus a generic rule
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