MIL-STD-167-2A is a United States military standard specifically covering mechanical vibration requirements for reciprocating machinery and propulsion system shafting on naval ships. While its counterpart, MIL-STD-167-1A, focuses on environmental and internally excited vibrations for general equipment, 167-2A addresses more specialized heavy machinery. Core Features of MIL-STD-167-2A
Target Equipment: Primarily covers reciprocating machinery (like diesel engines) and the propulsion system including shafting.
Vibration Types: Specifically addresses Type III (Reciprocating Machinery), Type IV (Propulsion System), and Type V (Shafting) vibrations.
Status: The original version was published on May 21, 1992, and it remains valid for use in naval acquisitions, as confirmed by its latest Notice of Validation on February 9, 2023.
Distribution: Unlike 167-1A, this document is typically marked for controlled distribution, meaning it is generally accessible only to authorized government agencies and contractors. Accessing the PDF
Because this is a Department of Defense (DoD) standard with controlled distribution, it is not always hosted on public-facing commercial sites. You can verify its status or request access via official military document repositories:
ASSIST QuickSearch: The primary official portal for searching and downloading DoD standards.
Intertek Inform: Provides metadata and purchasing options for the standard's documentation. mil-std-167-2a pdf
GlobalSpec: Offers information on the standard and related referencing documents. MIL-STD-167-2 Revision A:1992 - Intertek Inform
MIL-STD-167-2A is a Department of Defense standard specifically covering mechanical vibrations of shipboard equipment, focusing on reciprocating machinery and propulsion systems. It is the companion to the more common MIL-STD-167-1A, which focuses on environmental and internally excited vibrations for general equipment. 🛠️ Core Purpose
The standard provides the criteria for ensuring that critical naval propulsion systems and heavy machinery can survive the harsh, continuous vibration environment of a ship at sea. It helps prevent fatigue failure, performance degradation, and safety risks. 📋 Vibration Classifications (Types III, IV, and V)
While MIL-STD-167-1 covers Types I and II, 167-2A handles the following complex categories: Type III: Torsional Vibration
Targets reciprocating machinery (like diesel engines) and propulsion shafting.
Focuses on the twisting stress that can snap shafts or damage gears. Type IV: Longitudinal Vibration
Analyzes the "back-and-forth" motion along the axis of the propulsion system. Crucial for preventing thrust bearing failures. Type V: Lateral Vibration Type IV (Propulsion System)
Deals with the "side-to-side" or whirling motion of the propulsion shafting.
Ensures the shaft doesn't hit its own supports or "whip" at high speeds. 🔍 Key Technical Requirements
Balancing Standards: Establishes strict limits for the balance of rotating parts to minimize internal forces.
Testing Protocols: Equipment is often tested across three principal axes: vertical, athwartship (side-to-side), and fore-and-aft.
Acceptance Criteria: Defines exactly how much displacement or velocity is "safe" before equipment is rejected. For instance, some environmental tests require withstanding displacements of 0.030 inches at various frequencies. ⚠️ Critical Limitations
Narrow Scope: It does not address transient excitations like heavy seas or collision impacts.
Modern Systems: Experts note it may lack sufficient guidance for complex, non-linear phenomena found in modern advanced naval systems. 2023. Distribution : Unlike 167-1A
Distribution: Because it relates to sensitive propulsion technology, some versions of this document are marked for Controlled Distribution and are not available for public download on open repositories.
For a copy of the actual PDF, the DLA Quick Search is the official starting point, though access may require a Common Access Card (CAC) or specific authorization. If you're working on a specific project, let me know: Are you designing a new part or troubleshooting an old one?
Which machinery type are you most concerned about (diesel engine, shafting, etc.)?
MIL-STD-167-2A is a U.S. Department of Defense standard regulating mechanical vibrations specifically for shipboard propulsion systems and reciprocating machinery. The standard defines acceptance criteria, testing, and measurement methodologies to ensure equipment reliability under operational stress. For direct access to the document, search the ASSIST QuickSearch database. MIL-STD-167-2A CONT. DIST. - NAVY - Standards | GlobalSpec
The DLA’s Land and Maritime division provides access to unclassified standards. However, verification of the latest revision is essential, as some third-party sites host outdated versions.
The standard separates testing into specific types and severities. The most commonly referenced is Type I – Vibration (for shipboard equipment on surface ships and submarines).
The standard mandates a resonance search before, during, and after a durability run. If resonances exist within the equipment’s operating frequency range, the test must dwell at those resonant frequencies for a specified duration (typically 2 hours per resonance) to simulate fatigue life.