This is part 6 of a series delving into the intricacies of Mil-Std-810G.

 

hazardous-chemical-sign810G covers contamination by fluids in 504.1.  Use the contamination by fluids tests to determine if equipment is affected by temporary exposure to contaminating fluids such as may be encountered during its life cycle.  In the case of rugged computers in the military environment, these fluids can include:

  • Water and salt water
  • Jet fuel (kerosene)
  • Gasoline
  • Diesel fuel
  • Hydraulic fluids
  • Lubricating oils
  • Solvents and cleaning fluids
  • Deicing and antifreeze fluids
  • Disinfectant
  • Fire extinguishants.

 

Fluids can be intentionally applied in the normal course of operation such as cleaning fluids or there may be inadvertent exposure such as splashing, spillage, or fluids on hands or gloves.

 

The effects of such fluids can include:

  • Dissolving or softening paint on the equipment
  • Damaging plastic parts
  • Conductive effects
  • Insulation effects such as leaking across switch contacts
  • Gumming up the works such as a full-travel keyboard
  • Binding or slackening of moving parts
  • Differential contraction or expansion rates or induced strain rates of dissimilar materials
  • Changes in electrical and electronic components
  • Electronic or mechanical failures due to rapid water or frost formation.
  • Excessive static electricity
  • Interruption of electrical continuity (such as “grounding” fingers on EMI strips)
  • Increase in electrical resistance due to thermo-mechanical “fretting corrosion”

 

In general, it is best to test material samples instead of the entire product.  Painted samples can be used to test impact on the paint or powder coating.  Individual components such as switches and drive carriers can be easily tested.

 

It should be noted that testing for contamination by fluids should be done after other tests for 810G as contamination by the fluids may potentially damage test equipment required for other tests.

 

The tests are not intended to demonstrate suitability of materials in continuous contact with a fluid such as a pump, nor should it be used to demonstrate resistance to electrolytic corrosion.

 

810G includes consideration of temperature effects of exposure to fluids and the operating environment should be evaluated in preparing for the tests.  Many chemicals are much more reactive at higher temperatures and may not have any impact at lower temperatures.

 

Sections of 504.1 include for testing:

  • Length of exposure
  • Test fluids
  • Combination of test fluids
  • Test Temperature
  • Test item temperature
  • Test fluid temperature
  • Soak temperature
  • Fluid exposure duration
  • Methods of application

 

The goal of the testing is to analyze any contamination effects for their immediate or potential (long-term) effects on the proper functioning of the test item or safety during its life cycle.