Mechanical Vibrations of Shipboard Equipment

MIL STD 810 G – Test Method 528 – Mechanical Vibrations of Shipboard Equipment

 

SCOPE

 

Purpose
This method specifies procedures and establishes requirements for environmental and internally excited vibration testing of Naval shipboard equipment installed on ships (see Annex B, paragraphs 1e and f).
Applicability
The test procedures specified herein are applicable to shipboard equipment subjected to mechanical vibrations on Navy ships with conventional shafted propeller propulsion and can be tailored according to Paragraph 5.1 for non-conventional propulsor types such as waterjet or podded propulsors. For internal excitation caused by unbalanced rotating components of Naval shipboard equipment use the balance procedure according to paragraph 5.2.2. For those mechanical vibrations associated with reciprocating machinery and lateral and longitudinal vibrations of propulsion systems and shafting, see MIL-STD-167-2A.
Classification
The following types of vibration are covered in this method:
  • Type I – Environmental vibration
  • Type II – Internally excited vibration

 

TEST PROCESS

 

Procedure I (Type I) – Environmental Vibration
When Type I vibration requirements are specified (see Annex B, paragraph 2e), the test item shall be subjected to a simulated environmental vibration as may be encountered aboard naval ships. This method provides an amplitude sufficiently large within the selected frequency range to obtain a reasonably high degree of confidence that equipment will not malfunction during service operation.
  1. For Type I vibration testing, this method shall be used for equipment subjected to the vibration environment found on Navy ships with conventionally shafted propeller propulsion.
  2. For Type I vibration testing this method can 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. The revised test method shall be recommended by the purchaser and approved by the Government.
  3. For equipment installed on ships with propulsion systems with frequency ranges not covered by Table 528-I, this method shall not apply.
 
Basis of acceptability
For equipment that can be vibration tested, acceptability shall be contingent on the ability of the equipment to withstand tests specified, and the ability to perform its principal functions during and after vibration tests. Minor damage or distortion will be permitted during the test, providing such damage or distortion does not in any way impair the ability of the equipment to perform its principal functions (see Annex B, paragraphs 2f(1) and 2f(6)). Because of the numerous types of equipment covered by this method, a definite demarcation between major and minor failures cannot be specified. Therefore, during testing acceptability a determination shall be made as to whether or not a failure is minor or major to determine whether testing should continue (see Annex B, paragraph 2f(2)). In general, a major failure is one that would cause mal-operation or malfunction of the item of equipment for a long period. Non-repetitive failures of such parts as connectors, knobs/buttons, certain fasteners, and wiring, that can be easily replaced or repaired, are generally considered minor failures. As such, the repair could be made and the test continued with no penalty to the remainder of the test item. The critical use of the equipment shall be considered when determining the category of failure; e.g., a failure of a part in a lighting circuit may be considered minor. The same failure in a control circuit may be major.
Test procedures
The tests specified herein are intended to expose equipment to:
  1. Vibration magnitudes in prescribed frequency and amplitude ranges to reveal any critical response prominences (see paragraph 2.2v) or potential deficiencies.
  2. A 2-hour minimum endurance test at the response prominence frequency or frequencies most seriously affecting its functional or structural integrity.
Many are the vibration procedures provided, please, ask to your confidence laboratory for further details.
Procedure II (Type II) – Internally Excited Vibration
Unless otherwise specified (see Annex B, paragraph 2e), Type II balance and vibration requirements shall apply to the procurement of rotating machinery. This does not apply to suitability from a noise standpoint, nor does it apply to reciprocating machinery. Special vibration and balance requirements may be specified (see Annex B, paragraph 2g(1)). The limitations set forth herein may also be used as criteria on overhaul tolerances, but should not constitute a criterion for the need for overhaul.
Basis of acceptability
All rotating machinery shall be balanced to minimize vibration, bearing wear, and noise. Types of balancing shall be as specified in Table 528-IV. Machinery with rigid rotors shall meet the limits of allowable residual unbalance given in paragraph 5.2.2.2. For machinery with rotors that are unable to meet the balance requirements of rigid rotors, shall be balanced in accordance with the requirements of paragraph 5.2.3.1.
Balance procedure
  • for rigid rotors
  • for flexible rotors
See details in the text of the methods.

 

NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.

 

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