Page 27 - HUB-4 Magazine Issue 94

Material Recycling Facilities
Conveyor Skirtboard Design to
Control Dust and Spillage
R. Todd Swinderman, P.E. / President Emeritus / Martin Engineering
Whether the belt conveyor transfer chute is a dead drop, rock
box design, or sloped design, dust and spillage from dry bulk
material must be controlled. Fugitive material can limit access
to a system for maintenance, foul rolling components, add to
labor costs for cleanup, and reduce workplace safety.
material. The double skirting configuration is the most
effective in retaining a belt seal. Even if the belt profile
fluctuates, the secondary seal rides softly on the belt, retaining
the seal.
Figure 1 - This is an example of a fabricated curved skirtboard, which is
hard to maintain when replacing wear liners and skirting.
This article covers some of the common approaches to
skirtboard configuration that bulk handlers use to mitigate
dust and spillage to ensure a safe and compliant workplace
with a lower cost of operation. [Fig.1]
Configuring the Skirtboard
By far the most common configuration is the vertical
skirtboard.[Fig. 2] The height of the skirtboard is based on the
sealing system components and is commonly at least 300 mm
high. The double wall skirtboard is sometimes used with dust
extraction for very fine free flowing materials.
Figure 3
It is a common belief that the seal material must be softer
than the belt but the real property of concern is the abrasion
resistance of the seal should be less than the belt top cover.
The seal is sacrificial and designed for easy adjustment and
replacement without excessive sealing pressure.
Over-adjustment can cause excessive friction heat, leading to
belt damage and premature skirting wear.
The sealing pressure should be light. For the self-adjusting
seals, use 15 kPa contact pressure. CEMA proposes added belt
tension of about 4 kN/m per side without considering the seal
thickness.
Wearliner Configurations
The wearliner has two functions. First is to be a sacrificial
wear material protecting the skirtboard wall. The second is to
reduce the side pressure on the sealing system. Not all
systems require a liner. The most common liner is the internal
liner made of abrasion resistant material such as AR plate or
ceramic blocks. The liner often has some ability to adjust the
space between the bottom and the belt to adjust for wear.
[Fig. 4]
Figure 1
The perpendicular and angled configurations are used in some
industries. Angled skirtboards are designed to allow the load
to center. Perpendicular skirtboards relieve side pressure on
the skirtboard seal.
Skirt Sealing Configurations
Vertical seal with a rubber or elastomeric material is the most
common sealing system. [Fig. 3] The seal is held in place with
a series of clamps which can be loosened to adjust the seal
against the belt. The main drawback to the vertical seal is that
an undulating or vibrating belt can break the sealing contact
unless the belt is supported. The lay-in and lay-out seals are
self-adjusting depending on the elastic nature of the sealing
Figure 4
The deflector liner is a variation of the internal liner that is
used to center the load and reduce side pressure on the seal.
The canoe liner performs a similar centering effect with a
substantial volume of wear material and is often used in heavy
duty applications like hard rock mining.
The most important details for a liner are proper installation
and ease of replacement. The external liner was developed to
www.hub-4.com Sept/Oct - Issue 94
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