Common problems with coupling

Equilibrium level

(1) The balance level of any coupling assembly is determined by the square and root values of possible values of eccentricity in the barycenter position between the inertia spindle line of the coupling and the axis of rotation. Its unevenness is expressed in microns. (2) The potential unbalance factors of coupling components have been introduced, and the steps to determine the balance levels of various types of coupling components and calculate the balance are shown in the calculation examples. (3) The standard classification table of the coupling balance grade is shown in the following table. The deviation caused by the principal axis of inertia to the axis of rotation at the position of the balance plane is expressed in RMS. The value is the displacement (root mean square) of the coupling's principal axis of inertia on the equilibrium plane calculated according to AGMA method

Balance problems

Coupling make its center of mass for a variety of reasons or the inertial principal axis and axis misalignment, the operation will generate unbalanced centrifugal inertia force, the centrifugal inertia coupling force and dynamic deflection (modal) phenomenon, known as the imbalance of the rotor, this imbalance is bound to cause the vibration of shaft system, which affects the normal work and service life of the machine, therefore attaches great importance to them. The degree of unbalance (unbalance U) is usually expressed as the product Mr Of the mass of the rotor, m, and the distance r from the center of mass to the rotor axis of rotation, known as the mass radial product. It is also expressed by the mass diameter product per unit mass, called eccentricity E (not eccentricity in the geometric sense). The mass diameter product Mr Is a relative quantity related to rotor mass, while the eccentricity E is a quantity independent of rotor mass. The former is more intuitive and is often used for the balancing operation of a given rotor, while the latter is used to measure the balance of the rotor or detect the balance accuracy. The balance grade standard of the coupling is evaluated according to E. For flexible rotors, vibration mode eccentricity (NTH vibration mode) en=Un/ Mn, Un and Mn are the NTH vibration mode and mode mass respectively.

In order to correct or minimize the unbalance of the coupling, the appropriate balance grade shall be selected as required, and after the product is manufactured and installed on the machine, the balance grade shall be achieved by adding or reducing the appropriate mass on the specified balance (correction) plane of the coupling. This process is called balance correction, or balancing for short.

Relative displacement

The coupling of the two shafts due to manufacturing errors, installation errors, deformation caused by shaft load, base deformation, bearing wear, temperature change (thermal expansion, cold contraction), the relative movement between components and other factors resulting in relative displacement. In general, the relative displacement of two axes is unavoidable, but the displacement direction, namely axial (x), radial (y), angular (A) and displacement amount are different under different working conditions. Only flexible couplings can compensate the relative displacement of two axes, so flexible couplings are widely used in practical applications. Rigid couplings do not have compensation properties and are limited in application, so they are rarely used.