The production of non-bonded prestressing tendons generally adopts two kinds of extrusion coating process and coating molding process.
1. Extrusion coating process Extrusion coating process is mainly bondless tendons through the oiling device oiling, oiling bondless tendons through the plastic extruder coated with polyethylene or polypropylene plastic film, and then cooled by the cylinder mold molding plastic casing. This extrusion coating process is characterized by high efficiency, good quality, stable equipment performance, and wires, cables wrapped in plastic casing process is similar to the mass production of a single strand and 7 steel wire bundles. Extrusion coating flow process shown in Figure 1.
2. Coating and wrapping molding process Coating and wrapping molding process is unbonded tendons through the coating tank after the coating, and then through the bunch of rollers into a bunch and supplemental coating, coating thickness is generally 2mm, can be completed by hand within the coating of anticorrosive asphalt or anticorrosive grease, outsourcing of plastic sheeting. The coated non-bonded tendon is then automatically cross-wrapped with two layers of plastic sheeting through the cloth-wrapping drum, and then cut when it reaches the required length to become a complete non-bonded prestressing tendon, which can also be continuously operated on the paper-wrapping machine to complete the processes of bunching, oiling, upsetting, wrapping of plastic sheeting and cutting, etc. This coating and forming process is characterized by the fact that the thickness of the coating is generally 2mm. This kind of coating and wrapping molding process is characterized by good quality and strong adaptability. The working schematic diagram of the paper wrapping machine is shown in Figure 2. When making non-bonded prestressing tendons, the steel bar is put on the anti-wire plate, through the comb plate converged into a steel wire bundle, through the oil gun evenly coated with oil and threaded into the anchor ring with a cold upsetting machine cold upsetting the anchor head, with the anchor ring of the bunch of steel wire with a traction machine to pull forward, while driving the paper wrapping turntable equipped with plastic strips, steel wire bundles while moving forward to wrap the plastic sheeting work. When the wire bundle reaches the required length, it is cut off and becomes a complete unbonded prestressing tendon.
Figure 1 Extrusion coating process assembly line
1-Unwinding disk; 2-wire; 3-comb plate; 4-oil feeding device; 5-plastic extruder head; 6 -Air-cooling device; 7-Water-cooling device; 8-Tractor; 9-Positioning bracket; 10-Wire take-up reel.
Figure 2 Flow chart of paper wrapping process of unbonded prestressing tendons
1-Unwinding disk; 2-coiled steel wire; 3-comb plate; 4-oil gun; 5-plastic cloth roll; 6 -Cutting machine; 7-Roller table; 8-Traction device.