How to make belt hot vulcanized joints?

Joint vulcanization is a very important and complex process, which is related to the strength of the entire conveyor belt. Every step and link of vulcanization has rules to follow, and must strictly implement the vulcanization process rules that meet international standards.

Selection of vulcanization site

The location of the vulcanization joint should be selected in a spacious and flat chamber (roadway), convenient transportation, low wind speed, low humidity in the air, low temperature and less coal dust. Before the vulcanization joint, the roadway 20 meters before and after the vulcanization point should generally be washed without dust, and a shelter should be built above the vulcanization point if possible. It is strictly forbidden to carry out vulcanized joint construction in places where the roof is broken, water sprayed, coal dust is large, wind speed is high, and humidity is high.

Fix the belt and build the workbench

If the conveyor belt in use is re-joined, it should be moved to the vulcanization site, first use a belt clamp to fix one side of the conveyor belt head, and then drag the conveyor belt to make sure that there is enough extra belt for splice. Finally, the other side of the conveyor belt is also fixed, and the conveyor belt clamp that fixes the conveyor belt must have sufficient strength and tightness to ensure that the belt does not slip. After the two conveyor belt heads are fixed, the idler on the vulcanization point conveyor can be removed, a workbench can be built, and the bottom beams of the vulcanizer and the lower heating plate can be placed on the workbench.

 Marking the center line

In order to prevent the conveyor belt from inclining, the center line must be accurately found.

Can use The three-point connection method on site to confirm the middle point. Details as next, selecting a complete place near the joint end of the conveyor belt to find three transverse midpoints perpendicular to the conveying direction of the conveyor belt (the distance between the two points should be greater than 1 meter) and connect them into a straight line. Use a rubber marker to mark to prevent erasing.

Carry out the stripping treatment of the conveyor belt

In the process of stripping, it is necessary to avoid rolling of the wire rope, and the less rubber left on the wire rope, the better. This process is the most time-consuming and labor-intensive, and we have professional tools to simplify the workload of this process and improve work efficiency. When stripping the rubber on the steel wire rope, it is strictly forbidden to damage the coating of the steel wire rope, and it is strictly forbidden to use electrician pliers to clamp the end of the wire rope and pull the steel wire out of the rubber.

To ensure good adhesion between the galvanized layer and the rubber. Use coarse emery cloth to roughen and peel off the wire rope one by one, and remove the residual rubber attached to the surface of the wire rope to the maximum extent without damaging the wire rope. The rubber at the root of the wire rope, the slope surface and the covering surface of the adjacent slope surface (about 30mm in width) are carefully ground into a rough surface with a grinder.

After grinding, remove the rubber powder left by the head and wire rope after grinding, and clean the vulcanizer and workbench. In order to protect the galvanized layer on the surface of the wire rope, it is best to keep the residual rubber on the surface of the wire rope with a thickness of 1mm.

 Cut the wire rope

Determine the length of each wire rope according to the selected lap method and lap length, draw a line to make a mark, and use a wire breaker to cut the wire rope to the required length as to the mark.

Clean the wire rope

Use a clean brush dipped in SK353 cleaning agent to clean each wire rope and the polished rubber surface (slope). After the cleaning agent is completely dry, brush one hot splicing cement evenly 2-3 times. The cement must be applied after the previous brush dry. If the underground air humidity is high and it is difficult to dry, use a hot air blower to help it drying.

The following process is the same. After the wire rope is dry, fill the gap of the wire rope with the same dried uncured core materials noodle shape that has been cleaned with cleaning agent and coated with hot splicing cement, or lay it flat on the fabric core and press it firmly. When laminating, the end of the core rubber is also cut according to the lower edge of the slope. The end of the uncured core rubber and the end of the uncured cover rubber should be staggered in parallel to maintain a certain distance, generally about 20mm, to ensure mutual bonding and avoid bubbles.

Start the conveyor belt vulcanizer

After the lap joint process at the joint is completed, use an electric pressure pump to pressurize the vulcanizer for 5 minutes, during this process you can be lifted and lowered 1 to 2 times to help remove the air from the joint part. Then release the pressure and turn on the hot plate to check whether there is a lack of uncured rubber materials, bubbles, etc. If there is, repair it and use a needle rollerto pierce the hole to release the air. Then close the heating plate, install the upper conveyor beam to the joint, align it with the equipment parts below, tighten the screws and pressurize. During the vulcanization process, the pressure will continue to drop due to the complementary unevenness of the rubber after the rubber softens and the water seepage of the pressurized package. Therefore, the pressure must be constantly replenished to keep the pressure constant.

 Start vulcanization

Switch on power, heat the vulcanization, preheat at low pressure for 3 minutes and then increase the pressure, and start calculating the time when the temperature reaches the standard temperature (145 ℃). During vulcanization, pay attention to the pressure change and keep the pressure constant. Vulcanization temperature: 145±2℃ (equivalent to the temperature of 45 psi saturated steam), vulcanization pressure: 1.8-2.8MPa. During the vulcanization process, the vulcanization temperature should be reached quickly within 50 minutes, otherwise the uncured rubber materials may be aged at high temperature and affect the quality of the joint.

The three elements of the vulcanization process, which are pressure, temperature and time, should be strictly controlled when make splicing operation. Too low pressure will affect the density and strength of the vulcanized joint, and too high pressure will deform the joint and the vulcanizer beam. Therefore, it is necessary to control the matching of vulcanization temperature, pressure and time.

When the temperature is low, the raw rubber cannot become mature rubber, and the joint cannot meet the strength requirements. When the temperature is high, the rubber may be aged and the strength will be reduced. Insufficient or too long vulcanization time also cannot achieve the required strength of the joint so time is also important.

Cooling stage

After vulcanization, there must be a cooling and stable stage, and the vulcanization equipment can be dismantled when the natural cooling is below 80 degrees. You can also choose our vulcanizer with water cooling device, which greatly reduces the cooling time and improves the work efficiency. It is professionally prepared for the construction team with a large workload.

Testing of joint hardness

Use a durometer to test the hardness of the surface of the cover rubber. When the durometer acts vertically on the surface of the covering rubber, slowly apply a pressure of 1Kg to record the relative scale of the durometer. See if the joint is close to the hardness of other working surfaces.

The measurement points shall be no less than 3 points, and the average value shall be taken.

In short, the vulcanization connection of the steel cord core tape must control the quality of each steps and strictly abide by the vulcanization process regulationsStrict compliance with the vulcanization process regulations can ensure the joint strength requirements, meet the joint surface quality, and lay a solid foundation for the safe running of the conveyor belt.