History and Applications Using MIL-STD-901

Military standard 901 is one of many ways the United States Department of Defense (DOD) ensures that the Navy has reliable equipment. Established in 1949, it helps confirm the safety and reliability of equipment in naval operations. Over the years, this testing has applied to a wide range of shipboard installation machinery, from electronic devices to large mechanical systems. Subjecting equipment to these tests ensures it can endure explosions and extreme shock impacts.

Government agencies and organizations sourcing or contracting naval equipment rely on this testing method to establish how this equipment will fare in maritime applications. 

Understanding MIL-STD-901

What is MIL-STD-901? We use this military specification for high-impact mechanical shock. It verifies Navy shipboard installations’ ability to withstand shock loadings common in combat. It outlines various shock testing procedures, including the use of mechanical shock test machines and actual explosive charges to simulate the effects of shock on equipment. It is widely used by naval equipment manufacturers to assess control panels, electronic systems and other components.

MIL-STD-901E is the current standard and supersedes the 1963 MIL-STD-901C and 1989 MIL-STD 901D.

The MIL-STD-901 standard uses three test categories, two degrees of shock, three equipment classes, three types of shock testing and several potential shipboard mounting locations. The test categories depend on equipment weight and each test uses different shock machines. Engineers subdivide the heavy-weight category depending on how equipment is mounted onto the vessel.

MIL-STD-901 Lightweight Test

The MIL-STD-901 lightweight test simulates real-world conditions using an anvil plate and lightweight shock machine. It subjects equipment to a high-level shock pulse. It ensures that lightweight components like small machinery and electronic devices can withstand the jolts and vibrations common in a naval environment. 

Test items with standard mounting fixtures are attached to the shock machine’s anvil plate. Three top, side and back hammer blows at the hammer heights of one, three and five are applied parallel to each 90-degree axis.

MIL-STD-901 Medium-Weight Test

The MIL-STD-901 medium-weight test checks if Navy ship equipment can handle moderate shock impacts and explosions. It may simulate the shock effects of a nuclear explosion.

Test items not exceeding 7,400 pounds are mounted and subject to six hammer blows, divided into two rounds. The first round simulates vertical shipboard shocks and items are in their regular altitudes. During round two, items are at an incline, simulating athwartship shocks.

MIL-STD-901 Heavyweight Test

The heavyweight or barge test checks how well military equipment handles extreme conditions like explosions. It ensures that equipment can remain intact during shockwaves and in working condition afterward. This well-known test sets off explosive charges near a floating shock platform (FSP) housing the testing equipment.

There are four shots. On a standard test, a 60-pound explosive charge detonates 24 feet below the water surface. The large FSP test sees a 300-pound charge detonate 20 feet below. These explosive charges can be located between 20 and 110 feet from the near side of the FSP, detonating both the athwartship and fore-and-aft directions.

Shock Grades

MIL-STD-901 splits equipment and test items into two categories. These determine the equipment’s importance in relation to the ship’s operation. These shock grades include:

• Grade A: Grade A items are essential to continued combat capabilities and safety. They are subject to the highest level of shock testing, as this equipment needs to work under all conditions.
• Grade B: Grade B items are non-essential and subject to a moderate level of shock testing. These items still need to work following extreme conditions.

Equipment Classes

MIL-STD-901E classifies equipment under three classes, each addressing different mounting applications. It helps engineers to tailor their assessments based on where and how it is installed on a ship. The equipment classes are:

• Class I: Hull-mounted equipment that needs no resilient mountings between the shipboard foundation or structure and equipment.
• Class II: Class II equipment is not mounted on the hull. It must meet shock requirements while using tough mountings installed between the equipment and the shipboard foundation or structure.
• Class III: Non-operational equipment or temporary installations are classified as Class III. They are a hybrid of the first two classes that meet both of these class requirements.

Shipboard Shock Test Types

The MIL-STD-901 shock test divides its tests into three categories to test the equipment’s ability to withstand shocks and vibrations. It measures the survivability of electronics and other equipment in naval situations. These shock test types include:

• Type A: Type A assesses principal units that are supported by the ship structure or attached directly to it. It includes items mounted in ducting and piping systems like switchboards, air conditioning plants, missile launchers, valves and radio transmitters.
• Type B: Type B tests focus on the subsidiary components, like an air conditioning unit’s electric motor or the radio transmitter’s power supply.
• Type C: The Type C tests are for subassemblies comprising a principal unit or the subsidiary component. These include sensitive electronics, gauges, meters, thermometers and resistors.

The Importance of Securing Equipment

MIL-STD-901 tests prove the importance of securing electronics and other equipment on naval ships. This helps to protect sensitive components susceptible to damage from shock and vibration, which in turn helps to avoid system malfunctions. Data loss and complete system failure can compromise a vessel’s mission readiness and the safety of the crew onboard.

It is crucial to partner with a manufacturer who can design hardware and brackets to secure equipment by withstanding MIL-STD-901 shock tests. By ensuring that electronics and other critical equipment are protected against shocks like explosions, naval and other defense vessels can maintain their operational effectiveness and readiness even in unpredictable environments.

Defend Critical Electronics With Jonathan Engineered Solutions

MIL-STD-901E plays a crucial role in the certification, design and testing of naval equipment. It helps to enhance the effectiveness and survivability of naval vessels in challenging operational environments. The MIL-STD-901 shock test certification confirms that the equipment is safe and ready to use when needed. It qualifies shipboard equipment as shock-hardened and ready for action. Over the years, its applications have benefited various industries that require robust equipment. 

For over 60 years, Jonathan Engineered Solutions has manufactured custom engineering solutions, including cable organizing systems, fasteners and brackets to secure equipment. We have quality management AS9100 and ISO 9001 certifications with ITAR compliance, offering reliable linear and rack-mounting applications. Our rack-mounting hardware specifically caters to sea, air, grand, space and cyber defense forces, being subject to the 901D barge testing. Contact us today for modified solutions that suit your applications.