MIL-S-901

Chassis Plans Rugged 901D Computer
Close-up of Equipment Failure from MIL-S-901D Barge Test

Military Specification MIL-S-901D is a military specification for High Impact mechanical shock which applies to equipment mounted on ships. Two levels apply. Grade A items are items which are essential to the safety and continued combat capability of the ship. Grade B items are items whose operation is not essential to the safety and combat capability of the ship but which could become a hazard to personnel, to Grade A items, or to the ship as a whole as a result of exposure to shock. "Grade C", signifying that no shock qualification is required, is also sometimes referenced in acquisition documents even though the term has no official standing in the specification document.. Qualification testing is performed on a specified machine or on a barge floating in a pond where an explosive charge is detonated at various distances and depths in the pond to impart shock to the barges. See Barge Test.

Publication Date: Mar 17, 1989

The MIL-S-901D specification covers shock testing requirements for ship board machinery, equipment, systems, and structures, excluding submarine pressure hull penetrations. The purpose of these requirements is to verify the ability of shipboard installations to withstand shock loadings which may be incurred during wartime service due to the effects of nuclear or conventional weapons.

Shock testing machine for lightweight equipment
Shock testing machine (hi impact) for mediumweight equipment

Tests shall be classified in accordance with one of the following test categories, as specified.

Items to be tested shall be classified in accordance with one of the following grades, as specified:

Items to be tested shall be classified in accordance with one of the following classes, as specified:

Tests shall be classified in accordance with one of the following types, as specified:

Barge Test

MIL-S-901D Barge Test at moment of explosion, 60 lbs of HBX-1 explosive detonated 20 feet from test barge, for SPAWAR NAVSSI Navigation System
MIL-S-901D Barge Test Video at Moment of Explosion

The Barge Test or Heavyweight Test requires the item under test to be mounted on a floating barge. For the Standard Floating Platform, 60 pounds of HBX-1 explosive is placed 24 feet under water at various distances from the barge and detonated. There are four 'shots'. The first is placed on the Fore-and-Aft axis, 40 feet from the barge. Shots 2, 3, and 4 are placed athwart ship at distances of 30, 25 and 20 feet. The distance refers to the near side of the floating platform.

For the Large Floating Platform, 300 pounds of HBX-1 is placed 20 feet under water and the distances are 110, 80, 65, and 50 feet from the barge with the first shot Fore-and-aft and the other three shots athwart ship.

A hammer test can be used to pre-qualify an item and to identify deficiencies but, ultimately, the items to be certified compliant with MIL-S-901D will be tested on a barge.

Applicability to products

Suppliers can and some do take significant latitude with how they test their products, as well as how they report the test results. As a result, claims of "compliance with MIL-S-901" can be misleading. Users who require rugged products should verify the test methods (i) against which compliance is claimed; ii) to which parameter limits were actually tested; and (iii) whether the testing was done internally or externally by an independent testing facility.

References

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