In the assembly of the coupling, it is necessary to master the assembly of the coupling on the shaft, the alignment of the two shafts connected by the coupling, the inspection of the components and the assembly of the coupling according to the drawings.
1. Finding the aligned coupling
(1) When the coupling is aligned, the coaxiality (radial displacement or radial clearance) and parallelism (angular displacement or axial clearance) are mainly measured. There are four methods depending on the tools used in the measurement. The coaxiality (radial displacement) of the coupling is measured by a square ruler, and the parallelism (angular displacement) of the coupling is measured by a plane gauge and a wedge gap gauge. This method is simple and widely used, but the accuracy is not High, generally used on low-speed or medium-speed operating equipment that is not too demanding.
Measuring the warp displacement of the coupling with a ruler and a feeler gauge. Measuring the angular displacement of the coupling with the wedge gauges of the plane gauge.
(2) Measure the coaxiality and parallelism of the coupling directly with a dial gauge, feeler gauge, and center card. Adjustment method: usually by adding or subtracting the spacer under the foot of the active machine (motor) in the vertical direction or moving the position of the active machine in the horizontal direction.
2. Assembly method of coupling on the shaft
The assembly of the coupling on the shaft is one of the keys to coupling installation. The coupling between the coupling and the shaft is mostly an interference fit. The coupling is divided into a keyed connection and a keyless connection. The shaft hole of the coupling is divided into a cylindrical shaft hole and a tapered shaft hole. The assembly methods include static pressing method, dynamic pressing method, temperature difference assembly method and hydraulic assembly method.
(1) Static pressing method: This method is based on the different pressing force required for assembly, using clamps, jacks, manual or motorized presses, and static pressing method is generally used for tapered shaft holes. . Since the static press-in method is limited by the pressure machine, it is difficult to apply a large force when the interference is large. At the same time, during the pressing process, the uneven peaks on the mating surface between the coupling and the shaft are cut off, so that the mating surface is damaged. Therefore, this method is generally not widely used.
(2) Power indentation method: This method refers to the use of impact tools or machinery to complete the assembly process, generally used in the case where the coupling between the coupling and the shaft is a transition fit or a small interference. The assembly site usually hits with a hammer by placing a wooden block or other soft material on the end face of the hub as a cushioning member. The impact of the hammer is used to knock the coupling into it. This method poses a risk of local damage to couplings made of brittle materials such as cast iron, hardened steel, and cast alloys, and should not be used. This method also damages the mating surface and is often used in the assembly of low speed and small couplings.
(3) Temperature difference assembly method: The coupling is heated and expanded by heating or the shaft end is cooled and contracted by heating, so that the wheel coupling can be conveniently mounted on the shaft. This method has more advantages than the static press-in method and the dynamic press-in method. For the hub made of brittle material, the temperature difference assembly method is very suitable. Most of the temperature difference assembly methods use a heating method, and the cooling method is used less. There are various methods of heating. Some of them are placed in a high flash point oil for oil bath heating or torch baking, and some are heated by an oven. The assembly site is often heated by oil bath and torch. The maximum temperature that can be achieved by oil bath heating depends on the nature of the oil and is generally below 200 °C. When the hub is heated by other methods, the temperature of the coupling can be higher than 200 ° C. However, from the viewpoint of metallurgy and heat treatment, the heating temperature of the coupling cannot be arbitrarily increased, and the recrystallization temperature of the steel is 430 ° C. If the heating temperature exceeds 430 ° C, it will cause a change in the internal structure of the steel, so the upper limit of the heating temperature must be less than 430 ° C. For insurance purposes, the upper limit of the heating temperature should be below 400 °C. As for the actual heating temperature required for the coupling, it can be calculated according to the interference value of the coupling and the shaft and the requirements when the coupling is heated and assembled on the shaft.
(4) Inspection after assembly: After the coupling is assembled on the shaft, the perpendicularity and coaxiality of the coupling and the shaft should be carefully checked. Generally, two dial gauges are arranged on the end face and the outer circle of the coupling. When the cranking rotates the shaft, observe the values of the full runout of the coupling (including the end face runout and the radial runout), and determine the coupling and the shaft. The case of perpendicularity and concentricity. Couplings with different speeds and different types have different requirements for full runout. After the coupling is assembled on the shaft, the deviation of the full runout of the coupling must be within the tolerance range of the design. This is the coupling. One of the main quality requirements for assembly. There are many reasons why the full runout value of the coupling does not meet the requirements. First, it may be due to machining errors. For field assembly, the coupling is not the same as the shaft due to improper assembly of the keys. The correct installation of the key should make the two sides of the key closely fit the wall of the keyway. Generally, it is checked by coloring during assembly. If the fit is not good, it can be repaired with a file or a blade to meet the requirements. The top of the key generally has a gap of about 0.1-0.2 mm.
The high-speed rotating machine has high requirements on the coaxiality of the coupling and the shaft, and high coaxiality cannot be obtained by single-key connection, and the coaxiality of the two can be improved by the double-key connection or the spline connection.
3. Coupling assembly
Before installing the coupling, clean the parts. After cleaning, wipe off the oil on the parts. Couplings that are ready to run in a short period of time, after drying, apply some turbine oil or oil to the surface of the parts to prevent rust. For couplings that need to be used for a long time, they should be coated with anti-rust oil.
For the couplings used in high-speed rotating machinery, the dynamic balance test is generally carried out in the manufacturing factory. After the dynamic balance test is passed, the markings of the mutual matching directions between the components are drawn. It is important that the assembly must be assembled according to the markings given by the manufacturer. If it is not assembled arbitrarily according to the mark, it is likely that the unit will vibrate due to the poor dynamic balance of the coupling. In addition, the coupling bolts on the flanges of such couplings are subjected to load-bearing, so that the coupling bolts on each coupling can be substantially uniform in weight. For gear couplings used in large centrifugal compressors, the weight of the coupling bolts used is generally less than 0.05g. Therefore, the bolts between the couplings cannot be interchanged arbitrarily. If one of the coupling bolts is to be replaced, its weight must be the same as the weight of the original coupling bolts. In addition, when tightening the coupling bolts of the coupling, it should be symmetrical and stepwise tightened so that the locking force on each coupling bolt is basically the same, so that the coupling will not be skewed after assembly due to uneven force of the bolts. Phenomenon, conditional torque wrench can be used. For rigid movable couplings, after assembly, check whether the rigid movable parts of the coupling can be moved a little or not.
After the various couplings are assembled, they should be turned to see if the rotation is good. In short, the correct installation of the coupling can improve the operation of the equipment, reduce the vibration of the equipment, and extend the service life of the coupling.
