What Is MIL-STD-167-1?

MIL-STD-167-1 sets vibration test requirements for equipment fitted to US Navy ships. Its full title covers mechanical vibrations of shipboard equipment, and the current revision is MIL-STD-167-1A. A ship vibrates constantly: propellers, shafts, engines and waves all shake the hull, and equipment bolted to it has to survive years of that without loosening, cracking or failing.

The standard has two parts. Type I covers environmental vibration, the vibration equipment receives from the ship. Type II covers internally excited vibration, the balancing of rotating machinery so equipment does not generate its own damaging vibration in service.

Most electronics, including computers and displays, only need Type I. Type II applies to equipment with rotating parts of its own, such as pumps, motors and fans large enough to shake the structure.

Vibration is only half of the naval environment. MIL-S-901D, replaced in 2017 by MIL-DTL-901E, covers high-impact mechanical shock: the sudden loads from underwater explosions near the hull. Equipment is classed as Grade A, which must keep working through the shock, or Grade B, which must stay in place without becoming a hazard. Tests use lightweight and medium-weight shock machines for smaller items and a floating shock platform for heavy equipment.

MIL-STD-167-1 and MIL-S-901D are typically specified together, so shipboard equipment is qualified for both sustained vibration and shock events.

Shipboard vibration is low in frequency and high in displacement compared with vehicles or aircraft, which is why naval programs use their own standard. The table compares it with the standards it is most often confused with.

MIL-STD-810H added Method 528 so programs using 810 can call up shipboard vibration without citing 167-1 separately. Our guide to MIL-STD-810G vs 810H covers that update, and our guide to maritime computing requirements covers IEC 60945 for commercial vessels.

A computer destined for a naval deployment is specified against these standards so it keeps running through the ship’s vibration and shock over a long service life. The design measures are mechanical: solid-state storage with no moving parts, soldered or locked memory and connectors, boards stiffened and fixed at more points to push resonances above the test range, and anti-vibration or shock mounts sized for the equipment’s weight.

Testing is done with the equipment on a fixture that represents its shipboard mounting, often including the shock and vibration isolators it will use in service. Isolators help with shock but can amplify vibration near their own resonance, so they are chosen to keep that resonance below the test range or well damped. Cable runs, connector strain relief and the mass of anything fitted to the chassis all change the result. Results come from a test report on a specific configuration, so a change of mounting or a heavier fit-out can need new evidence. Our overview of US military standards shows how this fits alongside the others.

Few commercial computers are tested to MIL-STD-167-1, because it is a naval requirement. Commercial vessels more often use IEC 60945 and classification society rules such as DNV. Our marine computers are built for shipboard use under those commercial standards, and our military computers cover defense programs where MIL-STD-810 and the military EMC and power standards apply. Where a naval program calls up 167-1 or 901E, the system and mounting are qualified together, usually at a specialist test house, and the report is supplied with the equipment for the ship’s records.

We supply marine and military computers with the mounting and test evidence matched to the vessel and program, and integrate and test each system before it ships. Tell us the platform and the standards your contract calls up, and we will shortlist systems to suit.