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(1) Anti-loosening method of threaded connection Commonly used nuts, spring washers, stop washers, cotter pins and other connectors on the valve prevent the nut from loosening. Figure 4.1 shows the five methods of loosening the nut. Stem and closing pieces of the connecting structure often used to stop the gasket chucking method and winged card chucking method to prevent loose, the effect is better. In addition, the valve is used to prevent loose methods are the riding screw (riding screw) fixation and point riveting method, both methods are used in occasions disassembled. Point riveting method is the nut and bolt meshing with Yang Yan point riveting two or more positions, so that the screw at each other squeeze deformation to achieve the purpose of anti-loose. If the nut loose with the above method is difficult to solve, can be used adhesive method. Identification of left-hand thread and right-hand thread Correctly identify the thread is left-handed or right-handed, is the most basic knowledge of the valve assembly and disassembly. So, how can we find out whether the thread is left-handed or right-handed? It can be determined by the internal thread or external thread on the valve. Under normal circumstances, they become a positive and negative thread structure, to prevent loosening of the thread. Such as the stem, the stem nut thread connection: the stem nut on the tight circle is left-handed, the handwheel thread is right-hand, stem nut trapezoidal thread left-handed. In addition, the thread's angle of elevation is to the left of the thread is called left-handed; the other hand, right-handed, as shown in Figure 4.2. (3) How to dismount the bolts Bolt removal and assembly methods are usually related to the connection type, damage, and the degree of rusting. Described below the stud bolt disassembly; rusty bolt nut disassembly; decapitation bolt disassembly method. ①How to Remove and Attach the Studs The method of removing and assembling the stud bolts together with the two nuts together is shown in Figure 4.3a. When removing the stud, the upper wrench tightens the upper nut against the lower nut, and the lower wrench forces the nut anticlockwise and the bolt is unscrewed. If the stud is anti-wire (left-handed), then tighten the nut on the upper wrench, the lower wrench to force the nut clockwise to unscrew the bolt; when the stud is to be fitted to the valve, the lower wrench presses the lower nut on Wrench clockwise force on the nut, you can tighten the stud on the valve body. If the stud is anti-wire, lower the wrench to tighten the lower nut and the upper wrench counterclockwise to rotate the upper nut to tighten the stud. Another way to tighten studs is shown in Figure 4.3b. A special nut is used, with a screw on it, which plays the role of a double-headed bolt. The internal thread of the nut is the same as that of the stud bolt. Use the stud bolt into the nut and tighten the screw, and then turn the nut, you can twist the stud. ② rust dead bolt nut removal method rust and corrosion of the bolts and nuts before demolition, the use of kerosene soaked, and find out the direction of the spiral, and then slowly loosen 1/4 or so, back to the original position; so repeatedly repeated several times, You can gradually screw out the bolt. You can also tap the bolt and nut around the hand hammer to loosen the thread, then loosen the bolt nut (but do not knock the thread down during the tap). With the percussion method is difficult to disassemble the nut, blowtorch or acetylene flame can be used to heat, so that the nut heat expansion, quickly screw out the nut. Difficult to disassemble the studs, saturated with kerosene, pipe clamps can be used in the middle of the polished rod out of position. (3) How to disassemble the end-cap bolt The bolt is broken in the screw hole and is troublesome to dismantle. Figure 4.4 shows how to remove several bolts. File tenon screwing out the law and the pipe clamp method, suitable for bolts in the screw hole 5mm above the height of the bolt; Spot welding out of the law applicable to the decapitation bolt in the screw hole or decadent bolt and screw hole phase Under the condition that it is made of flat steel drilled with holes smaller than the screw hole, which is filled out after the spot welding is screwed out; the square hole wedge screw-out method is suitable for the bolt broken in the screw hole by first Drill a small hole in the middle of the hole, tapping the hole with a square hole taper, and then screw out; drilling tapping recovery method can not be removed for the case of bolts, it is the first bolt section leveling, proofing Chong, Slightly smaller than the inner diameter of the drill bit drilling, tapping the last by the original thread. Bolt Before using the above screw-out method, take some conventional measures, such as kerosene soaked, remove the surface rust oil stains (this point is particularly important for the spot welding screw-out method, otherwise the welding is not strong). If necessary, the bolt can also be heated around and the bolt can be unscrewed under thermoplastic conditions. The decapitation bolts can also be screwed out by chemical etching method, proper cleaning rust and corrosion of the bolts, screw holes, will speed up the decapitation bolt out (screw out the screw holes after the application of water to prevent residual chemical corrosion Valve parts). (4) Tightening the bolt sequence When the valve is assembled, the tightening degree and sequence of the bolts have a direct influence on the quality of the assembly. Tighten the bolts for the general easier to handle, the connector is not loose on it. However, the gasket, packing structure of the bolt tightening, there should be prior, symmetrical, turns Tightening. When each bolt is tightened, check whether the flange is skewed and measure the gap between the flanges for correctness. Tighten the bolts symmetrically in turn, and tighten the screws a little until each 1/4 to 1/2 turn until the required preload is reached. Pay special attention not to over-tighten, so as not to crush the gasket, the general twist to leak does not prevail. Finally check the flange clearance, the gap should be consistent and maintained at 2mm above. The bolt tightening sequence is shown in Figure 4.5. Bonds are in the form of flat keys, sliding keys (guide keys), diagonal keys (key), semicircle keys (crescent keys), and splines. Figure 4.6 shows the assembly of key links. (1) flat key flat key in the valve on the more common application, it has a cross-sectional shape of two square and rectangular. Flat key assembly should be cleaned before the keyway, trim the edge of the key, repair key with the size, precision, filing keys at both ends of the round head. The assembly of the keys on both sides should be slightly over the key, the top of the key and the hub should ask clearance, the key bottom contact with the keyway bottom. Assembly can be tapped with a hand hammer or vise will be flat key slowly clamping, into the shaft keyway. Copper pads for the assembly of the pad, so as not to damage the shaft and keys. Flat key removal should be removed when the wheel can be used screwdriver and other tools dial in the flat key at both ends, you can also use a thin copper bag flat key on both sides, with a wire clamp or vise clamp pulled out. (2) The sliding key The sliding key is actually a special form of the flat key. It not only drives the hub to rotate but also makes the shaft and the hub move relative to each other. It is used in the clutch mechanism on the transmission and the grinder. The sliding key can be fitted on the shaft and can also be fitted on the hub. Slide key and its keyway should be fitted with tight, no loose, and with countersunk screws. There should be some clearance on both sides and the top of the sliding keyway relative to its sliding keyway. In addition to countersunk screws, slip key assembly and disassembly methods and flat key the same. Countersunk screws should be fastened, not loose, should be lower than the sliding surface. ⑶ oblique oblique keys and flat key similar, but the top bevel, slope 1: 100, and a key head for the demolition purposes. Oblique key assembly should be cleared edges, repair key and the groove with the precision; Then align the hub and sleeve keyway, oblique bevel painted color slot, check the contact surface, the contact surface should not be less than 70% If less than 70% should be scraping correction. Finally, white lead coated with a layer of oblique, the oblique keys into the slot. Diagonal key removal tool diagonal slide and diagonal keys. ⑷ semi-circular key Semicircular key with smaller diameter shaft and tapered shaft, can automatically adjust the pitch in the keyway. Half-round key assembly and disassembly methods and flat key similar. ⑸ spline spline like a pair of internal and external meshing gear, high precision machining, transmission torque, the valve used very little.