In the coupling assembly in the key to master the coupling on the shaft assembly, coupling coupled to the alignment of the two shafts, parts of the inspection and assembly of couplings in accordance with the requirements of the drawings and other links.
I. Methods of coupling alignment
When the coupling is being corrected, the main measurement of coaxiality (radial displacement or radial clearance) and parallelism (angular displacement or axial barrier), according to the measurement of different tools used in four ways.
(1) Measure the coaxiality (radial displacement) of the coupling using a right-angle ruler, and measure the parallelism (angular displacement) of the coupling using a plane gauge and a wedge-shaped clearance gauge, which is a simple and widely used method, but is not highly accurate, and is generally used for low or medium-speed operation, which is not very demanding.
This method is simple and widely used, but not very accurate, and is generally used for low or medium speeds and other less demanding equipment. Straightedge and plug gauge to measure the longitudinal displacement of the coupling with a plane gauge and wedge gauge to measure the angular displacement of the coupling.
(2) Measurement of the coaxiality and parallelism of the coupling by means of a dial gauge, a plug gauge and a centre card. Adjustment method: usually in the vertical direction to add or subtract the shims under the feet of the main engine (motor) or in the horizontal direction to move the position of the main engine to achieve the method.
二、the coupling on the shaft assembly method
The assembly of the coupling on the shaft is one of the keys to coupling installation. Most of the coupling and shaft fit for the interference fit, coupling is divided into keyed and keyless coupling, coupling shaft hole is divided into cylindrical shaft hole and tapered shaft hole two forms. Assembly methods include static press-in method, power press-in method, temperature difference assembly method and hydraulic assembly method.
(1) static pressure into the method: this method is based on the assembly of different sizes of the required pressure into the force, the use of clamps, jacks, manual or motorised press, static pressure into the method of a stream for tapered shaft holes. Due to the limitation of the static press-in method by the pressure machinery, in the case of large interference, it is more difficult to exert a large force. At the same time, in the process of indentation will cut off the coupling and the shaft between the mating surface of the uneven tiny peaks, so that the mating surface is damaged. Therefore, this method is generally not much used.
(2) Power press-in method: this method refers to the use of impact tools or machinery to complete the assembly process, generally used between the coupling and the shaft is a transitional fit or not much surplus occasions. The assembly site usually use a hand hammer micro-beating method, the method is in the hub
The method is in the hub of the end of the surface of the wooden block or other soft materials as a buffer, relying on the impact of the hammer, the coupling knocked into. This method should not be used for couplings made of brittle materials such as cast iron, hardened steel, casting alloys, etc., as there is a risk of localised damage. This method will also damage the mating surface, so it is often used for low-speed and small coupling assembly.
(3) Temperature difference assembly method: heating method to make the coupling thermal expansion or cooling method to make the end of the cold contraction, so that can be easily installed on the shaft wheel coupling, this method than static pressure into the method of power pressure into the method has more advantages for the use of brittle materials made of hubs, the use of temperature difference assembly method is very suitable. Temperature difference assembly method mostly adopts the heating method, the cooling method is used less. Heating method has a variety of methods, some will be put into the hub of the high flash point of oil for oil bath heating or welding torch baking, there are some with the oven to heat, assembly site more oil bath heating and welding torch baking. The maximum temperature that can be reached by oil bath heating depends on the nature of the oil, generally below 200℃. When using other methods to heat the hub, the temperature of the coupling can be higher than 200°C. However, from the metallographic and heat treatment point of view, the heating temperature of the coupling can not be arbitrarily increased, the recrystallisation temperature of steel is 430°C. If the heating temperature is higher than 430°C, it will cause the internal organisation of the steel to change, so the upper limit of the heating temperature must be less than 430°C. In order to insure that the set upper limit of heating temperature should be 400°C or less. To be on the safe side, the upper limit of the heating temperature should be below 400°C. The actual heating temperature of the coupling can be calculated on the basis of the coupling-axis mating surplus value and the requirements of the set when the coupling is heated up to 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 inspected. Generally, two pieces of percentage gauges are set up at the end face and outer circle of the coupling, and when the shaft is rotated by the pan-truck, the full runout of the coupling (including the end face runout and radial runout) should be observed to determine the perpendicularity and coaxiality of the coupling and the shaft. Different rotational speeds, different types of couplings on the full runout requirements of different values, couplings in the shaft after assembly, must make the coupling full runout deviation value in the design requirements of the tolerance range, which is one of the main quality requirements of the coupling assembly. There are many reasons why the full runout value of the coupling does not meet the requirements, first of all, it may be due to errors caused by machining. For on-site assembly, the coupling and shaft are not in axis due to improper assembly of the key. The correct installation of the key should make the key on both sides of the wall and the key groove closely fit, generally in the assembly with the colouring method to check, with the bad with a file or spatula can be used to repair the summer so that it meets the requirements. The top of the key generally have a barrier, about 0.1-0.2mm or so. High-speed rotating machinery for the coupling and shaft coaxiality requirements, with a single key coupling can not get a high degree of coaxiality, with a double-key coupling or spline coupling can make the two coaxiality to improve.
三. Coupling Installation
Before installing the coupling, clean the parts, after cleaning the parts, need to dry the oil stained on them. If the coupling is to be operated in a short period of time, after drying, the surface of the parts can be coated with turbine oil or machine oil to prevent rusting. For couplings that are to be used for a longer period of time, they should be coated with anti-rust oil. For the application of high-speed rotating machinery on the coupling, generally in the factory have done dynamic balance test, dynamic balance test after passing the drawing of the components to match each other the orientation of the mark, in the assembly must be assembled in accordance with the mark given by the manufacturer, which is very important. If not according to the mark arbitrary assembly, it is likely to occur due to the coupling dynamic balance is not good to cause unit vibration phenomenon. In addition, the coupling bolts on the flange of this type of coupling are load-bearing, so that the weight of the coupling bolts on each coupling is basically the same. Such as large centrifugal compressor with a tooth-type coupling, the coupling bolts used between each other's weight difference is generally less than 0.05 g. Therefore, the coupling bolts can not be arbitrarily interchanged, if you want to replace the coupling bolts of the coupling of a certain one, it must be made to make the weight of its weight and the original weight of the coupling bolts consistent. In addition, when tightening the coupling bolts of the coupling, should be symmetrical, step by step tightening, so that each coupling bolt on the locking force is basically the same, not because of the uneven force of the bolts and the coupling in the assembly of the phenomenon of skew, if possible, can be used torque spanners. For rigid removable couplings, the rigid removable parts of the coupling should be checked after assembly to see if they can move a small amount and whether there is any jamming phenomenon. All kinds of couplings in the assembly, should be disc car, to see whether 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, to extend the service life of the coupling.
