Vulcanization method of steel core conveyor belt joint

Vulcanization method of steel core conveyor belt joint

Jianyewudong building Zhengzhou, China

1 Overview

Steel wire rope core conveyor belt has been widely used in industrial production for its high tensile strength, low elongation, good grooving, bending fatigue resistance, stable operation, no damage to the supporting plate, superior impact resistance and long service life. Especially in the underground main transportation system of coal mine, steel wire rope core belt is mostly used in belt conveyors with high power, large transportation volume, long distance and high belt speed. However, due to the high cost of the belt, difficult laying, complex joint vulcanization process and long treatment time in case of failure, especially the quality of joint vulcanization is the key to determine the operation quality and service life of the conveyor belt, which is an important subject that needs to be carefully studied.

The installation of the whole conveyor belt goes through various working processes such as transportation, laying, joint stripping, joint vulcanization and belt tensioning. Here, the basic principles and operation methods of joint vulcanization are emphatically studied.

Joint vulcanization is the last important process to determine the quality of adhesive tape during installation. In this process, the chemical structure of rubber changes and improves the physical and mechanical properties. Accurately mastering its technical conditions is the key to ensure the strength and service life of the joint. The technical conditions of the vulcanization process are mainly the three elements of vulcanization, namely, vulcanization temperature, time and pressure. If the technical conditions of the vulcanization process are not controlled strictly or improperly, it will cause quality defects such as under sulfur, over sulfur, delamination, blistering, double skin, tape deviation and so on, which will bring adverse consequences to the operation and maintenance in the future.

1) Lap joints. There are four types of lap joint of steel wire rope core tape: Grade I, grade II, grade III and grade IV. The first two are suitable for tape with small number of steel wire ropes, small diameter and large gap, and the latter two are suitable for high and medium strength tape. The joint form shall be selected according to the belt type, belt strength, number of steel wire ropes, diameter of steel wire ropes, spacing of steel wire ropes and other factors. For improving the vulcanization quality of the joint, ensuring that there is no peeling and opening at both ends of the joint, and preventing water and impurities from penetrating into the joint to corrode the steel wire rope, the groove at the opening line is generally made into a ladder shape, so as to facilitate the firm bonding between the rubber and the master belt and ensure the strength and service life of the joint.

2) Curing time. After curing at a certain time at a certain temperature, the comprehensive physical and mechanical properties of the rubber material reach the highest, the longest service life, the degree of curing at this time is positive curing, curing time is too long (process is called sulfur) or too short (process is called sulfur), will make the rubber can not meet the performance requirements.

3) Vulcanization temperature. Curing temperature can accelerate curing speed and shorten curing time. The basic curing time can be shortened by half or prolonged by one time when the curing temperature increases or decreases by 100 ℃. The vulcanization temperature is generally 140 ~ 1 500℃, too high temperature will damage the core strength or lead to uneven vulcanization inside and outside the belt, too low time is needed or incomplete vulcanization.

4) Curing pressure. The effect of pressure is to make the adhesive material compact and fill the model and core fiber, so as to improve the adhesion of the wire rope, the tightness of the adhesive material and the flexural resistance of the joint. Generally 1.8mpa, pressure should be made on both sides of the pressure plate at the same time, to ensure that the rubber belt joint force balance.

5) In the selection of adhesive tape joints, generally speaking, should ensure to meet the following aspects: (1) Joint strength should meet the requirements, and reach more than 90% of the strength of adhesive tape; (2) The average effective distance of wire rope should be greater than 0.25 times of wire rope diameter; (3) Curing equipment should be able to meet the need of curing length, that is, the joint should be a curing molding; (4) At present, there are two kinds of joint forms: inclined mouth and vertical flat mouth. According to the production practice, we generally adopt the inclined mouth type, which can reduce the stress concentration during overwinding and prolong the life of the joint.

2 Operation Methods

Wire rope core rubber belt joint vulcanization mainly has the following processes: installation vulcanizer (operating platform). Clean the joint, find the middle, brush the glue, lay the glue, swing the rope, lay the glue, install the heating plate, fastening, heating, pressure, timing, molding, dressing.

2.1 Preparation before operation

1) Personnel requirements: familiar with the operation procedures and technological requirements before the shift, four-in-one, interconnection guarantee in place, and 3 to 5 skilled workers to check the operation.

2) Equipment preparation: water cooling belt vulcanizer (electrically heated and water-cooled flat vulcanizer).660 V and 220 V AC power supply, supporting vulcanization (automatic/manual) control switch, pressure pump, pressure pump control switch.

3) Material preparation: 1 500 mm x200 mm surface glue, 2 pieces of core glue, 5 kg of glue paste, 5 kg of 120 gasoline, 3 m of white cloth, 2 pieces of 1 500 mm x 3 000 mm heat-resistant interlining cloth, 4 pieces of 0.5 mm x200 mm x 1 400 mm white iron sheet.

4) Tools: 6 cutting knives, 2 clamping pliers, 2 adjustable wrenches, 4 ratchet torque wrenches, 1 electric wire brush, 4 brush, 1 cleaning brush, 2 wire scissors, 4 stripping pliers, 2 3 m steel measuring tape, 1 200 mm 1 square, 1 powder box, 6 thermometer, 1 bucket, 2 stainless steel basin, 6 rubber gloves, 2 scissors, 1 hair dryer, 2 dry powder fire extinguishers, etc.

5) Site requirements: flat, wide, clean, no dust, dry air, water supply, adequate lighting.

6) Staffing: 10-14 operators,1 electrician, four in one.

2.2 Operation

Carry the above-mentioned necessary tools and materials into the work place and start the operation.

1) Organize the operation site. (1) After entering the work place, observe whether there are safety risks in the surrounding environment of the site, and eliminate them; (2) Clean up and level the operation site to facilitate the movement and operation of personnel; (3) Tidy all switching equipment and cables to make them intact and tidy.

Main points: the operation site has hidden safety hazards, four-in-one is not in place, shall not start.

  • Install vulcanizer. (1) Equidistant horizontal stabilizer of the two I-beam bottom beam, placed width is less than the width of the vulcanizer (if it is bevel vulcanizer, bottom beam end according to the Angle of the vulcanizer placed at random); (2) The positioning platform at both ends of the bottom beam is fixed on the I-beam bottom beam, and the table should be flat with the vulcanized heating plate or slightly lower than the heating plate surface about 5 mm; (3) The aluminum alloy beam is evenly placed on the bottom beam according to the angle of the vulcanized plate, and the hydraulic plate is placed on the beam. Then heat insulation board is placed on the hydraulic pressure plate, and then down heat plate is placed on the heat insulation board.

Main points: (1) when installing vulcanizer, pay attention to each other to prevent injury to hands and feet; (2) The bottom beam should be placed flat and stable, the vulcanizer heating plate should be kept in the same horizontal plane, and the center line is basically the same as the center line of the belt machine; (3) Identify the upper and lower vulcanized plate to prevent mistakes; ④ There should be a space for easy operation around the vulcanizer.

3) Cut the rope and find it. (1) The two rubber belt joints to be vulcanized before and after having been stripped are neatly arranged on the vulcanized plate. (2) Find out the center rope, in accordance with the requirements of the lap size, cut marks on the placed wire rope, and then cut root by root with wire shear. Note: the outermost two wire ropes should be fully lap and cut as long as possible. (3) After the wire rope cutting is finished, start to find the center line of the tape. There are three people standing on both sides of the vulcanizer, two at both ends and one in the middle. First, find out two midpoints in the horizontal direction of the master tape joint, and then use the powder rope to tighten back and forth. After adjusting the tape so that the four midpoints of the two master tape ends are in the same straight line, fix the two master tape ends on the positioning platform at both ends of the vulcanizer according to the length required by the interface to prevent the tape from shifting.

Key points: (1) When intercepting the wire rope, the wire rope should be numbered one by one, carefully checked and strictly prevented from intercepting mistakes; (2) It is necessary to accurately measure and carefully adjust the tape to prevent deviation.

4) Dressing and shaving. (1) Trim wire burr and excess glue on the head of wire rope. When manually pulling the wire rope, the direction of force should be on the same level with the wire rope, and the force should be even to prevent the wire rope from twisting and looping. Use electric wire brush to remove residual glue on the joint step surface and hair, pay attention to avoid hazel shining or burning phenomenon. (2) Use two stainless steel basins, one for glue slurry and the other for gasoline, and scrub the steel wire rope head and joint groove with no. 120 gasoline soaked in white cloth. (3) After the gasoline volatilizes, brush the rope head and groove evenly with a brush dipped in glue slurry, generally brush two to three times as well. Each time to dry out before the next glue.

Main points: (1) Take care of each other when trimming the rope head with knives to prevent scratching yourself or others; (2) When grinding the wire rope, the Angle between the tool and the wire rope should be as small as possible to prevent the tool from damaging the wire rope; (3) Electric wire brush rotating front is strictly prohibited to stand, to prevent flying debris injury; (4) In the whole process, it is strictly prohibited to drip water, oil and other dirt on the wire rope and the interface slope rubber surface.

5) Glue and fit. (1) Choose a dry, clean and flat position, expand the covering glue and core glue, and clean the surface with gasoline respectively. ② Dip the brush in the glue slurry and brush it evenly for two to three times, and dry it. If necessary, use a hair dryer to speed up air drying. (3) After the glue solvent on the surface of covering glue and core glue volatilizes and dries, the two surfaces coated with glue are glued together for later use. During the laminating, both sides of the adhesive tape should be moderately consistent in tightness, center line alignment, and laminating from the middle to both sides to facilitate air escape from both sides. After laminating, the tape should be fully rolled to prevent the accumulation of bubbles. (4) if you need to increase the transverse reinforcement, the horizontal reinforcement on both sides of the wash slurry, and then fit between the covering glue and the core glue, and the size of the reinforcement is less than the interface size of 30 ~ 50 mm.

Points: (1) If there is water or other dirt on the laminating surface, it can be laminating after removal; (2) If the coating is dry or rolling is not solid, it will produce bubbles and bulges, resulting in reduced bonding performance or even vulcanization failure; (3) when laminating, the covering glue and core glue should be completely extended, without wrinkles, otherwise it is easy to produce bulges and bubbles.

6) With glue. (1) After dressing and gluing, clean the surface of the vulcanized plate, place a 200 mm ×0.5 mm copper skin or iron sheet at the joint of the heating plate, and then spread the temperature resistant lining cloth on the vulcanizer heating plate, and then spread the compound rubber on the vulcanized plate.(2) Cut the surface glue and the core glue according to the joint size requirements, its length should be equal to the distance between the two ends of the joint groove, the width should be equal to the width of the original tape. Use a hammer or wrench to hit the groove to make it reliably bonded to the compound adhesive. (3) When cutting, the two ends of the core glue should be 20 ~ 40 mm shorter than the covering glue. If it is too long, the rubber material will be extruded above the bevel of the master belt, making the joint uneven and easy to peel; Too short, will cause insufficient filler, joint density is not enough, not up to the required strength, affecting the joint quality. (4) after the glue laying is finished, scrub the core glue surface with gasoline, and then apply the glue twice. After the glue is fully volatilized and dried, the rope begins to swing.

Points: (1) check the joint position on the vulcanized plate, vulcanized joint should be in the middle position of the vulcanized plate, there should be a margin around; (2) Concentricity test: check the center line again before swinging the rope to ensure that the center lines of the two conveyor belts are in the same line; (3) If it is a new belt, it is necessary to identify whether the bearing surface is correct.

7) Placed the rope. (1) Check whether the center line of the lower interface is accurate with the pink rope and hit the center line on the core glue. After alignment, separate the two joint wire ropes from the middle. (2) find out the wire rope in the center of the joint and start swinging the rope according to the two-stage lap mode. When arranging and swinging rope, the staff should clean their hands or operate with rubber gloves. Swing from the center to the sides, to guard against wrong swing. (3) insert the wire rope into each other alternately, fill the wire rope and the butt end of the wire rope with vulcanized rubber strip, and fix the wire rope head firmly. The wire ropes must be arranged neatly and straight to avoid incorrect lap joints. And to straighten each root, no concave and convex, bending, no burr head phenomenon, adjacent wire rope spacing to uniform. (4) While swinging the rope, clean, glue and compound the covering glue and core glue according to the above method.

Main points :(1) The wire rope on both sides of the edge must be fully lap joint. In addition, the outermost rope head must be placed along the running direction of the tape, not reverse laying. (2) The vulcanization working face is strictly prohibited to drip into the water. Oil, ash and other impurities.

8) Cover glue,and cut glue. (1) The outermost part of the placed wire rope is filled with covering glue, and then the whole rope surface and groove is brushed with glue; (2) when the glue volatilizes, the composite core glue and the upper covering glue cover the wire rope; (3) The tightness on both sides of the tape should also be moderately consistent, the center line is right, and the tape should be fitted from the middle to both sides to facilitate the escape of air from both sides. After fitting, fully roll to prevent the accumulation of bubbles; (4) Cut off the excess glue material at the groove according to the required size, and cut off the excess glue at both sides of the interface according to the width of the tape. (5) Also use a craft knife or awl to draw or prick a number of pores above the covering glue to facilitate the discharge of water vapor and ensure the quality of vulcanization.

Main points :(1) The place without wire rope on both sides of the interface should be filled with adhesive material to reach the thickness of the original tape; (2) After cutting glue, the bevel and both sides must be brushed with glue; (3) Used gasoline and white cloth should be properly placed, not littering; (4) when covering compound adhesive, prevent the wire rope from warping or overlapping; (5) During the whole process, the vulcanizing surface must be kept clean and sanitary. It is strictly prohibited to drop water or oil on the vulcanizing surface.

9) Pressing plate and fastening. (1) Lay a layer of heat-resistant interlining cloth on the top of the covered rubber, place the iron on both sides, and fix the iron clamping tape with a pull rod; ② A 1400 mm x200 mm x 0.5 mm iron sheet is placed at the joint of the vulcanized plate, and then the upper vulcanized plate and the upper beam are successively placed; ③ Tighten the pull rod with a torque wrench in turn.

Key points: (1) When lifting vulcanized plate and beam, we must pay attention to personnel safety; (2) The upper and lower vulcanized plates should be aligned, and the number should be consistent; (3) The fastening degree of the tie rod should be uniform and appropriate; (4) Prevent the vulcanizing plate ring lifting, fastening screw, other things to interfere with the water injection hole of hydraulic plate or vulcanizing plate cooling hole pipeline connection; (5) It is strictly forbidden to leave any tools or other foreign bodies in the vulcanized joint.

10)Vulcanization (1) Check that the vulcanizer is installed correctly and the line is correct. Connect the temperature sensor (if necessary, plug in the metal thermometer at the same time), switch on the vulcanizer control switch power supply, start heating vulcanization. (2) Connect the pressure pump and hydraulic plate pipeline, start the pressure pump and gradually rise to the specified pressure. (3) The general curing pressure is kept at about 1.8mpa, the curing temperature is kept at 145℃, and the constant temperature is kept for 45 min.

Key points: (1) the curing link is the most critical, strictly in accordance with the specified parameters; (2) Temperature sensor should be seated, do not insert wrong; (3) there must be a person to continuously observe and monitor whether the vulcanization temperature is uniform and balanced, whether the pressure is balanced and appropriate, whether the vulcanization time is set to meet the requirements, whether the equipment runs normally, whether there is leakage, if the problem is found to deal with quickly, otherwise it will lead to the whole vulcanization failure; (4) When moving, avoid tripping, loosening or damaging the temperature sensor line, pressure pipe, cable, pressure gauge, thermometer, etc.

11) Molding and dressing. (1) When the timing is over, the curing switch will trip automatically; (2) After confirming everything is normal, you can lock the switch and remove the temperature sensor; (3) Connect the cooling water pipe and start to fill the heating plate with water for cooling; (4) When the temperature drops to below 80℃, the pressure can be removed, the vulcanization plate is removed, and the vulcanization is finished; (5) After removing the vulcanizing plate, check whether the vulcanizing quality of the joint meets the requirements, whether there are defects, and repair and repair immediately, so that the edges are neat and smooth, and there is no incomplete or redundant glue. If bulge is found, Pierce with an awl immediately to prevent bulge expansion.

Key points: (1) After confirming that there is no abnormal situation in the vulcanization process and everything goes well, cooling, pressure relief and mold lifting can be carried out; (2) When removing vulcanizer, take care of each other to prevent collision or damage to equipment;

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