MIL-STD-167-1A
3.2 Amplitude, single. See amplitude, vibratory displacement.
3.3 Amplitude, vibratory displacement. Vibratory displacement amplitude is the maximum displacement of simple linear harmonic motion from the position of rest. This is also referred to as single amplitude. It is expressed in inches, mils (0.001 inch), or mm (0.001 meter).
3.4 Balancing. Balancing is a procedure by which the radial mass distribution of a rotor is adjusted so that the mass centerline approaches the geometric centerline of the rotor, and, if necessary, adjusted in order to ensure that the vibration of the journals and/or forces on the bearings, at a frequency corresponding to operational speed, are within specified limits.
3.4.1 Balancing, multi-plane. Multi-plane balancing refers to any balancing procedure that requires unbalance correction in more than two axially separated correction planes.
3.4.2 Balancing, single-plane (static). Single-plane (static) balancing is a procedure by which the mass distribution of a rigid rotor is adjusted in order to ensure that the residual static unbalance is within specified limits and which requires correction in only one plane. (Note: Single-plane balancing can be done on a pair of knife edges without rotation of the rotor but is now more usually done on centrifugal balancing machines.)
3.4.3 Balancing, two-plane (dynamic). Two-plane (dynamic) balancing is a procedure by which the mass distribution of a rigid rotor is adjusted in order to ensure that the residual unbalance in two specified planes is within specified limits.
3.5 Critical speed. Critical speed is the speed of a rotating system that corresponds to a natural frequency of the system.
3.6 Environmental vibration. Environmental vibration is vibratory force, which is imposed on equipment installed aboard ships, caused by the hydrodynamic forces on the propeller blades interacting with the hull and by other sources.
3.7 Equipment. Equipment is any machine, subsystem, or part thereof, which is intended to be installed aboard ship.
3.8 Grade, balance quality. Balance quality grade, G, refers to the amount of permissible unbalance of a rotor. The balance quality grade is the product of the maximum permissible eccentricity (distance between the shaft axis and the rotor center of gravity (in mm)) and the rotational velocity (radians/sec). The units for balance quality
grade, G, are mm/sec. By this definition, a particular grade rotor will be allowed a mass eccentricity (e=G/ω), which is inversely proportional to the operating speed.
3.9 Internally excited vibration. Internally excited vibration is vibration of machinery generated by mass unbalance of a rotor.
3.10 Isolation mount. An isolation mount is a device used to attenuate the force transmitted from the equipment to its foundation.
3.11 Mass unbalance. Mass unbalance occurs when the mass centerline does not coincide with the geometric centerline of a rotor.
3.12 Maximum design rpm. Maximum design rpm is the highest shaft rpm for which the ship is designed.
3.13 Method of correction. A method of correction is a procedure whereby the mass distribution of a rotor is adjusted to reduce unbalance, or vibration due to unbalance, to an acceptable value. Corrections are usually made by adding material to, or removing it from, the rotor.
3.14 Mode. Mode is the manner or pattern of vibration at a natural frequency and is described by its natural frequency and relative amplitude curve.
3.15 Plane, correction. A correction plane is a plane transverse to the shaft axis of a rotor in which correction for unbalance is made.
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