The term "315 3" in a conveyor belt refers to the belt’s tensile strength and the number of plies. The number "315" represents the tensile strength of the belt in N/mm (newtons per millimeter) per ply. This means each ply can withstand a force of 315 N/mm. The "3" indicates that the conveyor belt has three plies. Thus, a 315 3 conveyor belt is a multi-ply belt with three layers of fabric, each capable of handling a tensile strength of 315 N/mm. This type of belt is suitable for heavy-duty applications where high strength and durability are essential, such as in mining, quarrying, and heavy industrial environments.