Analysis of typical problems of heat vulcanization bonding of nylon conveyor belt
In the coal-fired power plant coal conveying system and mining material handling machinery, belt conveyor is widely used. The quality of the belt bonding interface is the key factor in the safety of the belt conveyor. The existing belt bonding technology has some non-standardities, which makes the bonding process of the belt poor and affects the service life of the belt interface, resulting in the decrease of the belt reliability. Increase coal transportation maintenance costs. At the same time, failure of the belt interface can cause the coal handling system to be relieved of standby, which in severe cases will result in the shutdown of coal-fired power plants and mines. Through the improvement of the belt bonding process, can effectively improve the safety of the belt interface and its service life.
1 thermal vulcanization bonding process characteristics of the three elements of adhesive is the basic factor in adhesive selection, joint production is an important factor, the curing process is the key factor.
Adhesives used in hot-melt belts are now divided into three types.
(1) Sealant (plastic surface). The neoprene mass fraction is 48%. Consistent with the formula of the working face of the conveyor belt and the non-working face, the neoprene is used as a vulcanized material at the upper and lower sides of the belt, with a thickness of 2 mm and 5 mm.
(2) pulp film. Neoprene 70% by mass, vulcanized material of belt core plastic high tensile strength. Films and gasoline (volume ratio) 1: 3 ~ 4 Stir into a paste.
(3) Shop plastic (rubber lining). The vulcanized material of the belt core, uniform in thickness, ensures the vulcanization strength at a thickness of 0.5 mm.
1.2 belt head production
(1) Belt connector design principles. As much as possible to make the joint shear stress, as much as possible to avoid the role of peel force, the interface and the edge should be defect-free, as much as possible to increase the bonding area.
(2) the type and form of the belt connector. Both ends of the joint are cut into a step-shaped bevel shape, so that the intertwined laps are overlapped so as to improve the stress concentration and reduce the strength, accelerate the aging and prolong the service life of the joint. The counterpart of the joint is beveled.
(3) step size. Step size includes the number of steps, step length and the number of layers of canvas. Step length is generally 150 ~ 250 mm, the number of steps is 3 to 5, the general level of a core step, the core more, there is a layer and two core steps, the upper and lower belt must ensure that with the core Can be used as a step, and strictly ensure that the two ends of the connector corresponding to the same level of the core layer.
1.3 vulcanization process
(1) The three elements of vulcanization process are temperature, pressure and time, indispensable. Vulcanization reaction is the solvent through the solvent evaporation, polycondensation, cross-linking and other chemical reactions and physical effects, the adhesive becomes solid, and has a certain intensity of the process, only fully cured, the vulcanization effect to meet the strength requirements.
(2) the surface of the belt connector. Belt joints should reach clean, dry, fresh, active surface requirements, surface treatment should be promptly bonded.
(3) glue. Uniform thickness, dry glue need to remove the volatile, no bubbles so far; buckle should be aligned once the location, and flatten the connector to discharge air, sealing, sealing edge processing.
(4) vulcanization. The pressure is 1.2 ~ 1.5 MPa and the temperature of 140 ℃ under the conditions, holding 40 min, can eliminate the internal stress and improve the bonding strength, vulcanization inspection is strictly prohibited with peel force for dressing. Curing machine layout installation, shown in Figure 1. Figure 1 vulcanizing machine installation and installation diagram 2 belt bonding problems and solutions (1) interface alignment. When the belt joint is made, problems such as large interface angle deviation and large belt skew on the timing belt are prone to occur. The following methods can be used to solve the above problems when manufacturing the belt interface working face and the non-working face. Take the upper headband over the lower headband, and after aligning the two centerlines of the belt, draw 3 straight lines parallel to the edge of the belt for future reference alignment, take 2 points in common position on both sides of the belt, The angle between the connecting line and the belt edge is the same as that of the heating plate of the vulcanizing machine, and the two belts are separated. Two points are taken as the reference of the belt joint angle line to eliminate the shape error of the belt joint. Figure 2 shows. Figure 2, the size of the interface belt drawing line requirements Drawings should be confirmed before the tape face and non-face, conveyor belt should be run above the head of the interface to tear non-face, the mouth of the mouth tear the face (under the conveyor belt running above the head Tear the face, the lower mouth tear non-face), belt interface production selection requirements shown in Figure 3. Press the 3 connector buckle head baseline test buckle correction, belt interface alignment process requirements shown in Figure 4. Figure 3 belt interface making the selection requirements Figure 4 belt interface alignment process requirements (2) belt interface sealing process. The non-cutting surface connector seal, in accordance with the provisions of the slope and size of the work surface and non-working surface of the surface of the plastic strip processing, the production of the belt interface sealing requirements, the tape interface sealing tape requirements and the adhesive interface belt processing requirements As shown in Figure 5, Figure 6, Figure 7. Figure 5, the production requirements of the belt interface sealing Figure 6 tape interface sealing tape requirements (3) the old belt bonding, encountered side baffle slot wear, the vulcanization of the belt vulcanized to form drum kits, can be used Figure 8 Show measures to solve. Figure 7 coal seam tank side wear measures to address the 3 quality standards for belt bonding requirements (1) adhesive tape ladder unequal distribution of not more than 1 mm. Figure 8 belt face wear treatment (2) cut the surface should be smooth, no rupture, the depth of the accidental damage to the lower layer of canvas joints less than the thickness of the core layer, the length of each step should not exceed the full error Long 1/10. (3) steel wire wheel cleaning float, the core of the accidental injury does not exceed the thickness of 1/4. (4) plastic deterioration, shall not be used. (5) The edge of the tape joint should be a straight line, its straightness should be less than 0.3%. (6) Belt joints without deviation phenomenon. (7) joint quality should be guaranteed to use more than 2 years, in this period may not occur when the interface opened, Alice edge and so on.