Understanding Inward Skirtboard Sealing Systems in Conveyor Applications
Some sealing systems are clamped onto the outside of the chute, with the elastomer strip curled back under the steel. In these systems, the seal is formed inside the skirtboard. Due to this inward placement, the wear liner needs to be positioned sufficiently above the belt to allow for some vertical movement of the seal. These inward systems have shown success in handling conveyors that carry light, fluffy materials and fine, non-abrasive substances like carbon black. They also serve as a temporary solution on belts with limited edge-sealing distance, where space outside the skirtboard steel is restricted for applying a sealing system.These systems are particularly useful in areas with high internal chute pressure, such as under a rail car dump, where the material loaded on the seal aids in sealing effectively. However, it's important to note that seals in this configuration may wear out faster, and material trapped underneath can prematurely wear the belt's top cover.
Some sealing systems are clamped on the outside of the chute with the sealing strip curled back under the steel to form a seal on the inside of the chutewall. Because the seal lies inward, the wear liner must be spaced far enough above the belt to allow for some free vertical movement of the seal.
Inward sealing is sometimes applied due to a belt with mistracking issues, because the belt is less likely to move out from under this type of system. However, solving mistracking problems at their source is preferable to relying solely on sealing solutions.
The protective benefit of installing wear liners can be neutralized when the sealing system extends beneath the skirtboard, placing the sealing strip inside the wear liner. This setup can lead to abrasion of the sealing strip by the material load and easier entrapment of material against the belt.
The main advantages of inward skirtboard sealing systems include:
- Self-adjusting
- Handle light, fluffy materials and fine, non-abrasive materials
- Require limited edge distance (free-belt distance)
- Handle high internal chute pressure
- Handle severely mistracking belts
Principal disadvantages of inward skirtboard seals are:
- Shorter life of the seal due to being in the material flow
- Prone to material entrapment under the sealing strip lading to premature belt wear
- Reduced load-carrying area of the belt due to the "rainbow" effect
A hybrid approach combines elements of these systems with a floating vertical-sealing system described previously. This hybrid utilizes an "L"-shaped rubber strip where the foot extends inward under the skirtboard steel and wear liner towards the bulk materials. This integrated sealing system functions both as a material (lump) seal and a dust seal, enhancing resistance to side pressure from belt cargo and expanding the range of belt mistracking the system can tolerate.
Such systems are particularly beneficial at transfer points where the wear liner is positioned 25 millimeters (1 in.) or more above the belt, safeguarding the belt from damage caused by contact with the wear liner. This practice is common in industries like coal mining and aggregate production where conveyor conditions are less than ideal.
The hybrid system allows the seal to float on the belt, adjusting with belt movements including splice passages. The low application pressure helps reduce wear on both the belt and sealing strip.