Manual for the vulcanized conveyor belt splicing

A vulcanized splice is stronger than a conventional joint made with fasteners. In addition, vulcanized splices have the following advantages over mechanical fasteners:

1. Longer service life.

2. Greater protection against penetration of the belt carcass by moisture and fines.

3. Uninterrupted surfaces which do not score pulleys or idlers. This is due to their being flush with the top and bottom covers. Vulcanized splices will operate smoothly under belt cleaners and other conveyor parts with close clearance, such as skirt boards and deflectors.
4. Elimination of the hazard of damage to the belt which can result from partial fastener failure in a mechanical joint which can break or wear out from abrasion. Bent or broken fasteners can damage the belt by snagging conveyor parts with close clearance and in passing over pulleys and idlers.

5. Avoidance of the problem of fines sifting through to decking or return run.

6. Greater length of service uninterrupted by mechanical splice failure in belts carrying hot materials. Localized conduction of heat by the metal fastener into the belt carcass around the metal fasteners can result in splice failure due to excessive heat degradation of the belt fabric.

SPLICE PROCEDURE OVERVIEW

While varied methods are necessary in making vulcanized splices on specialized types of belting, the technique normally involves, but not limited to, the following basic steps:

1. Determine the proper belt for the service intended.
2. Determine the belt’s intended direction of travel (DOT). Most cases the bottom fill / keyway leads in the direction of travel. Finger splices and flex steel splices will have the outside fingers or cords pointing in the opposite direction of belt travel.
3. Determine the belt length required for the installation with the take-up in its recommended position for the type of belt.
4. Cut the belt ends allowing enough length for the splice.
5. Prepared the belt ends to match into a smooth, efficient joint.
6. Uncured cement and compounds, specified by the belt manufacturer, are applied to the prepared ends.
7. Cure the entire splice in a portable press under heat and pressure.

Storage of Hot Splicing Materials

When unvulcanized splice materials are stored under unfavorable conditions their physical and/or chemical characteristics change. Eventually these changes will render the unvulcanized splice materials unsuitable for use. These effects result in changes in the curing behavior and/or in the cured physical properties of the splice materials.

The harmful effects of these factors can be minimized by a careful choice of the following storage conditions. In case of doubt, consult the supplier of the conveyor belt splice material about the storage conditions.

1. Materials stored in non-refrigerated conditions will shorten shelf life. Materials stored in refrigerated conditions will increase shelf life Acceptable refrigerated storage temperature is at 55°F (12.8°C). Do not allow the materials to freeze.
   Allow refrigerated materials to warm before use and allow condensation to disappear.
2. The relative humidity should preferably be below 60% for long-term storage. Damp conditions should be avoided since long-term exposure to moisture can influence the curing and crosslinking behavior of the materials.
3. Sunlight and artificial light which has a substantial content of ultraviolet light can adversely affect the stability of unvulcanized rubber. Depending on the grade and the period of exposure, chain rupture and/or crosslinking may occur. Given this, exposure to light should be restricted to a minimum.
4. Where possible, unvulcanized rubber should be protected from excessive air circulation and should not be stored near electrical equipment (motors) that could be a source of ozone. For this reason, it is advisable to keep the splice material boxes closed and sealed.
5. Unvulcanized rubber should be stored in an area which meets the usual standards of cleanliness, even though the rolls are individually wrapped in polyethylene sheeting. Avoided direct contact with foreign materials of any kind. It is recommended that the material be kept in its original packaging until the moment it is used.
6. Splice materials should not be stored for any longer than the specific shelf life. It is therefore
   recommended that the FIFO (first in – first out) stock rotation system be used.

Tools and Equipment (Fabric Belt)

Instructions for the proper use of splicing tools may be part of a designed splice training program.

SPLICING CONDITIONS

Work Place

The quality and durability of a hot splice begins with a clean work place. The careful use and application of the splicing products are essential. Follow the approved safety practices for the locale in which the service is being conducted.

Conveyor Belt

The belt ends to be spliced must be dry and clean to ensure a reliable splice. If necessary, dry the belt using the pre-heated lower part of the vulcanizing press, before any further preparation work.

Ambient Conditions

The influence of humidity, e.g. formation of condensation water (due to temperature falling below the dew point), must be absolutely avoided. Avoid loss of heat due to wind.

Extreme cold may have a negative affect on splicing materials.  During extreme cold conditions a splicing tent with heating devices may be needed.

1. Set-up a tent to protect the working area against adverse ambient conditions (sunshine, cold, rain, wind, dust).

2. It is possible to warm-up the splice area of the belt using the pre-heated lower part of the vulcanizing press. Do not to allow the temperature to rise above 150°F (66°C).

Use of Thermocouples with Leads

Vulcanizing press temperatures should be verified with thermocouples allowing a minimum of one lead per heating zone (top and bottom platens). Thermocouples allow the control of the cure temperature during the cure cycle.

Documentation

During the splicing operation all irregularities and special conditions have to be recorded. During the actual cure cycle the curing temperature of each thermocouple and the curing pressure must be recorded at defined intervals. The heat-up and cool-down of the vulcanizing press is also recorded.

GENERAL PREPARATION

Center Lining the Belt Ends On both belt ends establish and mark

1. the belt center line;

2. the perpendicular square line;

3. the belt cover transition lines.

Establish and mark the centerline of the belt by measuring across the width of the belt at three points in length of each belt end at a distance of approximately 12 in (304 mm). At least three center markings on each belt end must be outside the splice area.