Advantages of Vulcanization
Even though a vulcanized splice is more expensive and time-consuming to preform, it is usually an excellent investment. It provides a strong joint able to withstand high levels of belt tension. Splices performed by reputable firms will feature high-quality materials and workmanship and are typically guaranteed. Since a vulcanized splice chemically bonds the belt into an endless piece with no possibility of material sifting through the splice, From the standpoint of control fugitive material, vulcanization is the splice of choice. A properly-performed vulcanized splice will not interfere with rubber skirting, idler rolls, belt-support structures or belt cleaners.
Cold vulcanization offers some advantages over hot vulcanization. There is no heating source nor press required, the equipment is easier to transport, and no special electricity is required. Therefore, cold vulcanized splices can be performed even at remote sites where access is difficult and power is unavailable. Only small hand tools are required, so the cost to purchase and maintain the splicing equipment is low.
Hot and cold vulcanized splices take roughly the same amount of time to prepare the belt and complete the joining process; however, the cold splice may require more downtime than hot vulcanization due to the long cure time of the adhesive bond.
The finger splice can provide the best mix of splice strength and dynamic life in applications on high-tension belting. This system keeps all the factory belt plies in place, without any steps cut into the belt. A finger splice can be cut square or on a bias across the belt.
Disadvantages of Vulcanized Splices
The disadvantages of vulcanization that must be considered are the higher initial cost and the length of time required to preform the splice when compared to a mechanical splice. The peeling back of layers of belting to prepare for both hot vulcanization and cold chemical bonding can be difficult. It can take over 24 hours to return a conveyor to service by the time the splice is prepared, heated, and cooled sufficiently to allow the finished joint to the handled, or even longer for the cold chemical bond to cure.
This added time to complete a vulcanized splice will be particularly troubling (and expensive) in cases where an emergency repair is required to allow the resumption of operations. In this case, the delay required for hiring and bringing on-site an outside crew and equipment increases the cost of downtime by extending the outage and adding “emergency response” surcharges.
Due to time and cost pressures, vulcanized belt splices cannot be justified in applications where frequent extensions or retractions of the conveyor length are required. The same is cure where the takeup allowance does not allow enough belting for a vulcanized splice, and a short section of belting, often called a saddle, must be added, requiring two splices.
Vulcanizing can be more difficult and less reliable on older, worn belts. In applications on conveyors that are utilized in the process of transporting hot materials, it is important that all material be discharged from the belt prior to stopping the belt. Hot material left on a stopped belt can “bake” a splice and reduce its life.
Installation of a vulcanized splice can consume a considerable length of belting, as much as 2.4 to 3 meters (8 to 10 feet) in some cases, particularly when a bias splice is used on a wide belt. This installation may require a longer belt to be purchased or a new section of belt, or saddle, to be added.
When designing new conveyor systems that will incorporate vulcanized belts, it is wise to include a take-up pulley mechanism, designed to take up slack in the belt. The take-up pulley should have sufficient movement to account for belt stretch, thus avoiding the need to shorten the belt with a time-consuming new splice.
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