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    Causes of fatigue failure of diaphragm coupling

    Release Date: 2021-06-24 Publisher: admin

    The specific conditions of the failure, damage and deformation of the diaphragm coupling of the front pump, through the analysis of the cold state alignment data and the vibration data of the pump operation during the capital construction period, the main reasons that may cause the fatigue failure of the diaphragm coupling are summarized.

    (1) The intermediate short section of the coupling is connected with an insulating section (anti-shaft current), which reduces the overall strength of the coupling short section.

    (2) There is a problem with the quality of the diaphragm of the diaphragm coupling.

    (3) Since the motor and the water pump are not in the same frame (the integral common base is not used), the foundation settlement on the motor side causes a large radial deviation of the coupling.

    Since the supplier has a lot of supply performance and other factories are basically operating in good condition, the second and third reasons can basically be ruled out. Therefore, the possibility of coupling failure due to misalignment due to foundation settlement is higher. .

    Diaphragm breakage under tension is a common failure. It was found that the dangerous section near the bolt hole of the coupling diaphragm was easy to break.The force analysis of the tensioned diaphragm found that: when the four sides are tensioned and the load is evenly distributed, the diaphragm will not break and fail; if the load distribution is uneven, it may be in the process of pulling the diaphragm. There was a phenomenon that several diaphragms were pulled off.Working under the condition of misalignment for a long time, if the deviation exceeds the compensation range of the coupling, the diaphragm coupling will be subjected to peak torque, of which 4 groups of compressed diaphragm groups are unstable, and the other 4 groups of tensioned diaphragms Will bear all the torque, and the tensile force will be doubled.If the diaphragm is in a state of non-uniform stress for a long time, the stress on the inner side of the bolt holes at both ends of the diaphragm will exceed the curved clothes of the material, causing it to be broken and damaged. As the number of load-bearing diaphragms gradually decreases and the stress is uneven, the original The diaphragm with lower stress will also be broken, and then the entire group of diaphragms will be broken.

    Misalignment of the diaphragm coupling is one of the main reasons for the failure of the diaphragm coupling, and it is also the main reason for the abnormal vibration of the rotating machinery.There are two main types of coupling misalignment: angular deflection and parallel misalignment. Parallel misalignment can be converted into angular deflection.Misalignment between shafts will inevitably occur during assembly. Even if the alignment is good at the beginning, after the equipment runs for a period of time, due to ground settlement and other reasons, the coupling will still appear to be misaligned.If the misalignment is serious, it will increase the vibration of the equipment. If the vibration is not large, it does not mean that there is no problem. It can only mean that the compensation function of the diaphragm coupling has worked, and the vibration of the equipment will be controlled within the correct range.If the deviation continues to expand, the damage of the diaphragm continues to increase, and the inspection is not found and handled in time, the diaphragm compensation function will be weakened, the vibration of the pump body will increase or even cause the pump to stop accidents, so the vibration of the pump body is to check whether the diaphragm is damaged. The important inspection items should be used as monitoring means during unit operation.

    What are the advantages of using a diaphragm coupling?

    (1) Transmission rate, especially suitable for medium and high power transmission scenarios.Simple, lightweight structure, small size, convenient for assembly and disassembly.For example, a diaphragm coupling with an intermediate shaft type structure can be assembled and disassembled without having to move the machine.

    (2) Large-scale damping effect, low noise and no wear.

    (3) It can adapt to high temperature and harsh working environment, and can resist shock and vibration during equipment operation.

    (4) It can accurately transmit the rotating speed, without slip, suitable for mechanical transmission.

    (5) Compared with gear couplings, diaphragm couplings have no relative sliding, which eliminates the trouble of lubrication and sealing. The low maintenance cost and convenient manufacturing process make it widely used in various industries.

    (6) For the compensation of the misalignment of the two axes of the motor and the equipment, the angular displacement of the gear coupling can be doubled; the large flexibility and small reaction force during radial displacement allow axial, radial and angular displacement. Displacement.

    The diaphragm coupling bolt connection does not need to be threaded on the connecting piece, the use is not restricted by the connecting piece, the structure is simple, and the disassembly and assembly are convenient.Stud bolts can be used in occasions where bolts cannot be used due to structural restrictions, but a compact connection structure is required.The bolt connection does not have a nut and has a smooth exposed surface, but it is not suitable for frequent disassembly and connection to avoid damage to the threaded hole.

    During the service life of the diaphragm coupling, it is necessary to maintain the wedge-shaped clearance surfaces that are inclined to each other, add lubricating oil, and exit from the large port into the small port.The two surfaces have sufficient relative movement speed, the fluid has sufficient viscosity, and sufficient oil is required.In the maintenance process, it is important to grasp the basic scope of hydrodynamic lubrication, which is also the theoretical basis of sliding bearing design.

    The diaphragm coupling can actively compensate the axial, radial and angular offset caused by the motor, as well as the influence caused by factors such as manufacturing error, installation error, bearing deformation and temperature rise.Diaphragm coupling is a metal elastic element in flexible coupling. The advantages of driven torque transmission, elastic vibration, no noise, and no lubrication are the ideal products to replace gear couplings and general couplings.