Rubber or PVC? ■

Rubber belt not PVC.I do not think mechanical splices are for the plaster forming belt as the board will have the impression of the splice.It must be a either cold or hot splice with micron finish to avoid splice impression on the board. ■

I agree you'd best refer to the supplier/manufacturer of the belt. A rubber forming belt is usually spliced in a normal fashion, but as the compounds are especially suitable for grinding/buffing, these must be retrieved from the manufacturer.

In a nutshell it is performing a regular splice, but very tidy, and buffing the filler strips to smoothen the belt. It's not a novice job...

So in general, the procedure looks like this:

With the belt installed on the conveyor structure install the bottom half of the splice press. The belt is clamped using full width belt clamps with full width pads placed between the clamps and the belt.

Support the belt on either side of the vulcanising press ensuring the levels are the same. This is to ensure no press end deformation occurs through curing.

Cut both ends of the belt in line with regular splicing methods for step-splice, eg. 250mm steps. You must ensure that through cutting no plies are “nicked”, this will reduce the strength within the spliced area.

Scratch all cover chamfers and remove any debris from the spliced area. Coat both sides of the splice with solution and allow to dry completely.

Lay Skim rubber over the entire area of the splice and coat with solution. If you see any gaps between the corresponding plies fill these with skim rubber. This will ensure that once the splice is complete no voids will be present in the top and bottom covers. Bring the two ends of the belt together making sure that all plies are in correct alignment and that the jointed area is straight.

The joint straightness can be checked using a string line.

Once aligned remove the foil that protects the skim rubber and bring the two ends together. Roll down using wide bodied roller.

Both chamfers must be cleaned and buffed. Lay in the skim and brattice cloth and roll down. Lay skim compound over this ensuring that the skim is taken over the chamfers.

Cut the cover compound ensuring the interface angles between the infill and the belt are the same. Roll down and trim off excess.

Place release cloth under the belt and over the top surface of the spliced area.

Place edge irons at both sides of the belt ensuring that they are at least 0.5mm smaller than the belt gauge, hold in position using sash clamps.

Assemble the top half of the press and prepare to vulcanize.

The pressure during vulcanisation must be approx. 8 bar, or 120 psi.

The vulcanisation temperature is between 150ºC and 155ºC.

The vulcanisation time starts when a temperature of 150ºC is reached, approx. 35 min. needed.

After Splicing & Vulcanising, buffing of the jointed area must be undertaken with extreme caution using a flat bed sander. The whole spliced area must be supported flat and preferably under some tension.

A fine black line on either side of the filler will be evident, this is normal and acceptable with no effect on the end product.

Check the flatness of the splice after buffing using a straight edge and feeler gauge.

Clean the entire area to remove all debris and trim edges of belt. ■

Perfectly smooth and dent free cooling/dispersion plates for the vulcaniser are very important to obtain a smooth finish on the splice. ■