How to Splice a Steel Cord Conveyor Belt Correctly?

Why ST Belt Splicing Is More Demanding Than EP

Steel cord (ST) belt splices require greater precision and skill than fabric belt splices. The steel cords cannot tolerate any kinking, misalignment, or contamination during preparation —?defects that are not visible externally can lead to cord pullout under tension. On a major mine conveyor, a failed ST belt splice can cause complete belt destruction and weeks of lost production. There is no shortcut to correct ST splicing.

Tools and Materials Required

• Angle grinder with thin cutting disc (1mm) —?for cover removal
• Rubber buffers and solvent (MEK or toluene) —?for surface preparation
• Splice vulcanizing press with precise temperature and pressure control
• Calibrated thermometer —?verify actual platen temperature (not just controller reading)
• Pressure gauge —?verify actual press pressure
• Manufacturer-supplied splice kit: bonding rubber sheets, cover rubber, cord-to-cord bonding compound
• Steel ruler, chalk line, mitre square —?for geometric accuracy

Step-by-Step Procedure

Step 1: Cut Belt Ends Square

Both belt ends must be cut perfectly perpendicular to the belt centreline. Even 2mm off-square creates a skewed splice that causes tracking problems. Use a mitre square or laser guide. Mark and cut with angle grinder.

Step 2: Expose Cords to Splice Length

Remove top and bottom cover rubber to the full splice length specified in the manufacturer's splice table. Splice length varies by ST rating —?typical values:

Step 3: Arrange Cords per Splice Pattern

The cord arrangement in the splice is critical. Cords from opposite belt ends must be interleaved in a specific pattern that distributes tension evenly across all cords. Follow the manufacturer's splice pattern drawing exactly —?do not improvise. Cords must not cross or contact each other.

Step 4: Clean and Prepare Surfaces

All rubber surfaces in the splice zone must be buffed with a mechanical buffer to remove the surface skin and expose fresh rubber. Immediately apply bonding cement to all buffed surfaces. Allow solvent to flash off before applying splice rubber sheets.

Step 5: Apply Bonding Rubber and Close Splice

Apply bonding rubber sheets between and over the cord layers per the splice kit instructions. Apply cover rubber to both top and bottom. Ensure no air pockets are trapped —?roll firmly with a stitching roller.

Step 6: Vulcanize

• Temperature: 145—?55°C (verify with calibrated thermocouple)
• Pressure: 0.7—?.0 MPa (100—?50 PSI)
• Cure time: per manufacturer table, typically 25—?5 minutes at 150°C depending on cover thickness
• Allow splice to cool under pressure to below 60°C before releasing press