Thus analysis of vibration will be best determined by progressive approximation, i.e. Machine classes are defined as follows: Class I Small machines to 20 hp Class II Medium-size machines 20-100 hpĬlass III Large machines 600-1200 r/min, 294 kW and larger, mounted on rigid supports Class IV Large machines 600-1200 r/min, 294 kW and larger, mounted on flexible supports Acceptance classes:Ī=Good B = Satisfactory C = Unsatisfactory D = Unacceptable. RPM velocity in the range 10-1000 Hz at the limiting mm/s Ranges of radial vibration Quality judgement for separate classes of machines severity Table 14.8 The vibration standard ISO 2372 and ISO 3945 of the International Standard Organization Taking the intermediate shafts of the propeller shaft system as an example, they are only a section of the propeller shaft system, which are supported on the bearing mountings, then to the panel of superstructure, to the main structure of hull and finally supported by the buoyancy tank. It is difficult to calculate the natural frequency of bearing mountings, because the boundary conditions of supports are complex. Thus it can be called the general design for vibration absorption. Owing to the importance and complicated nature of hovercraft vibration, the considerations for vibration absorption should take in the whole course of craft developments from preliminary design, construction to sea trials.

Iso 2372 vibration standard