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MIL-STD 810 Low Pressure Testing

What is the Purpose of MIL-STD 810 Altitude Compliance Testing?

MIL-STD-810 low pressure altitude testing helps determine the ability of material to withstand low pressure environments and rapid pressure changes. Use this method for material likely to be at high ground elevation sites, or exposed to rapid/explosive decompression. This may include material that is transported or operated in aircrafts or carried externally on aircraft. Determine if its failure will damage the aircraft or present a hazard to personnel.

This method should not be used for material in space vehicles, aircrafts, or missiles flying at above 21,300 m. Use the maximum altitude (minimum pressure) normally reached by an appropriate mode of transportation. Procedure IV should not be used to test material transported in a cargo bay.

Keystone Compliance is a fully equipped altitude testing lab with significant experience in Method 500.7 of MIL-810 altitude.  Even though the language is from MIL-STD 810H altitude, it applies the previous version, MIL-STD 810G altitude. The following information is extremely technical in nature. It is a summary of  MIL-810H altitude testing and MIL-810G altitude testing.

What Should Be Considered When Selecting the MIL-810H Low Pressure Testing Method?

Review required documents, to determine if the material will be exposed to a low pressure environment during its life cycle. For these materials the LCEP may require this Method in combination with other Methods within MIL-STD-810. Therefore this test may need to be performed in conjunction with other tests like high temperature, low temperature, or vibration. All testing should be performed in a low pressure testing lab.

Below is a list of some of the typical problems that arise when materials are exposed to low pressure environments. In addition to thermal effects, consider the following to determine if this test method is appropriate. This list is not all-inclusive and there may be overlap, but some problems arising from low pressure environment are:

  • leakage of gases or fluids from gasket-sealed enclosures
  • deformation, rupture or explosion of sealed containers
  • change in physical and chemical properties of low-density materials
  • overheating of material due to reduced heat transfer
  • evaporation of lubricants
  • erratic starting and operation of the engine
  • failure of hermetic seals.
  • erratic operation or malfunction of material resulting from arcing or corona

When Should MIL-810 Low Pressure Testing Occur in Relation to Other Tests?

Use the anticipated life cycle sequence of events as a general sequence guide. This method generally occurs early in the life cycle, because it has limited damage potential. However, other testing may significantly contribute to the effects of low pressure on the test item. Therefore, other tests may have to be conducted before this Method.

For example, low temperature and high temperature testing may affect seals. Dynamic tests may affect the structural integrity of the test item. And testing that causes aging of non-metallic components may reduce their strength.

How Should the Correct Procedure For This Method Be Selected?

This Method includes four low pressure tests. The tests are, Procedure I (Storage), Procedure II (Operation), Procedure III (Rapid Decompression), and Procedure IV (Explosive Decompression). Based on the test data requirements, determine which of the test procedures or combination of procedures is applicable.

Select the procedure that represents the most severe exposure anticipated. When selecting a procedure consider the material configuration, and the operational requirements of the material. Also consider the shaker test data required to determine if the operational purpose of the material has been met. Understand the procedure sequence, and whether the cargo compartment is pressurized.

What Are the Differences Amongst the Four Procedures?

Procedure I is used for material transported or stored at high ground elevations. And for material transported by air in its shipping/storage configuration. Evaluate the material with respect to known effects of low pressure and the LCEP to determine if this procedure is appropriate.

Procedure II determines the performance of the material under low pressure conditions. It may be preceded by Procedure I. If there are no low pressure storage, rapid, or explosive decompression requirements, this procedure can stand alone.

Procedure III determines if a rapid decrease in pressure will cause a material reaction endangering nearby personnel or the transportation vehicle. This procedure may be preceded by Procedure I and/or Procedure II.

Procedure IV is similar to Procedure III except that it involves an “instantaneous” decrease in the pressure of the surrounding environment. This procedure is more appropriate for items such as sealed cockpit equipment whose failure could endanger cockpit personnel. Carefully consider the appropriateness of the application of this procedure for large cargo items. This procedure may be preceded by Procedure I and/or Procedure II.

Below is some guidance for instances where the altitude change (climb/descent rate) is unspecified or unknown. Except for decompression tests, or when justified by deployment platforms, don’t use an altitude change exceeding 10 m/s. Military transport aircrafts typically have an average altitude change rate of 7.6 m/s in a full military power takeoff. Use the value of 10 m/s for ground tests unless otherwise specified.

What Low Pressure Lab Offers the Best Altitude Testing Services?

Keystone Compliance has been recognized as one of the best altitude labs in the country. We employ expert test engineers and properly equip our altitude laboratory in order to provide low pressure certifications. Are you looking to get an altitude certification for your product? Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their compliance testing needs.

There have been several versions of low pressure testing procedures in MIL-STD-810 altitude testing. Below is a list of each version and the appropriate method number: