MIL-STD-810G – Part 30 – (Mechanical Vibration of Shipboard Equipment) is discussed in Method 528. Method 528 is applicable to shipboard equipment subjected to mechanical vibrations on Navy ships with conventional shafted propeller propulsion. Method 527 is 14 pages long with 4 annexes.
Method 528 provides for analysis for Environmental Vibration (Procedure I) and Internally Excited Vibration (Procedure II).
This test method should be used to establish a degree of confidence that the materiel can structurally and functionally withstand a specified dynamic environment that is defined in more than a single-degree-of-freedom (SDOF) motion; i.e., in multiple-degree-of-freedom (MDOF) motion.
Environmental Vibration subjects test items to a simulated environment as may be encountered aboard navy ships. This is low frequency continuous vibration through the hull or attached equipment as generated by rotating propulsion shafts. The method can also be tailored for non-conventional Navy shafted propeller systems such as waterjet, podded, or other propulsor types, including those that have been designed to minimize blade-rate forces. Frequencies in the range of 4 to 33Hz are of interest in Method 528, Procedure I.
Internally Excited Vibration is covered in Procedure II. This procedure examines vibration produced by the equipment being tested but does not apply to reciprocating machinery and does not include analysis from a noise standpoint. All rotating machinery should be balanced to minimize vibration, bearing wear and noise. However, there will always be some residual vibration. In addition, the pitch of each propeller blade should be the same, otherwise the mass on the propeller bladed will be different and the propeller will be unbalanced. The method discusses, at length, proper methods and tolerances for balancing rotating equipment.