DO-160-Section-9-Explosion-Proofness

RTCA DO-160 Section 9.0 Explosive Atmosphere Testing

The RTCA DO-160 explosive atmosphere test standard outlines requirements for aircraft equipment that may come into contact with flammable substances. These substances could be fluids, vapors or both.  The DO-160G test standard also refers to normal and fault conditions that may occur could be subjected to flammable materials during flight operations.

The flammable test fluids, vapors and gasses simulate those used in conventional aircraft that require oxygen for combustion. It is important to note that equipment is considered explosion proof when it has been determined that there is little risk that it will cause an explosion of flammable vapor or gas within the declared environment. There are three types of test specified in the RTCA/DO-160. These tests are containment test, non-ignition test and components or surface temperature test.

RTCA DO-160 Explosive Atmosphere Test Equipment Categories:

The DO-160G test standard specifies three primary categories of equipment.

Category A Equipment:

  • In normal operation the temperature of any surface of this equipment will not rise to a level capable of causing ignition. Also, no other operating part will cause ignition so that it meets the non ignition test.
  • Ignition of an explosive mixture is contained within the equipment without igniting an explosive atmosphere surrounding it so that it meets the containment tests.
  • Hermetically sealed equipment shall be identified as Category A equipment.
  • Equipment meeting this description must go through RTCA-DO-160 explosive atmospheric testing.

Category E Equipment:

  • This equipment is not hermetically sealed.
  • This equipment is also not contained in cases designed to prevent flame and explosion propagation.
  • Such equipment is designed so that in operation the temperature of any internal or external surface will not rise to a level capable of causing ignition.
  • Also, no operating internal part will cause ignition so that it meets the non ignition test.
  • Equipment meeting this description must go through RTCA-DO-160 explosive atmosphere testing.

Category H Equipment:

  • This equipment contains hot spot surfaces and are non-spark producing under normal operating conditions.
  • Hot surfaces could be internal or external.
  • Such equipment is designed so that in normal operation the temperature of any internal or external surfaces will not rise to a level capable of causing ignition.
  • Hermitically sealed equipment meeting temperature requirement on external surface shall be identified as Category H equipment.
  • Equipment meeting this description must go through RTCA-DO-160 explosive atmosphere testing.

RTCA/DO-160 Explosion-Proof Testing Equipment Zones:

The RTCA DO-160G test standard states that equipment should be installed in aircraft zones. These zones depend on their ability to prevent vapor explosion during their normal functioning. Another consideration, depending on the probability that exists in the considered zone, is the ability to prevent vapor explosion during abnormal functioning in failure mode.

Aircraft Zone 1 is an aircraft area in which uncovered flammable fluids or vapors exist, or can exist, either continuously or intermittently. This includes within fuel tanks or within fuel or hydraulic systems. Equipment installed in such environment should not be able to ignite the surrounding atmosphere in their normal or double failure conditions of operation.

Aircraft Zone II is an aircraft area in which flammable mixtures can be expected to occur. This zone only applies as a result of a single fault-causing spillage or leakage. Equipment installed in such environments should not be able to ignite the surrounding atmosphere in their normal or faulty possible operation modes. Only equipment single failure should be considered.

Aircraft Zone III is an aircraft area in which flammable mixtures cannot be expected to occur. These could be as a result of a single fault-causing spillage or leakage. Equipment installed in such environment should not be able to ignite the surrounding atmosphere in their normal operation modes.

Aircraft Zone IV is a designated fire zone or an aircraft area in which flammable mixtures cannot be expected to occur as a result of a double fault-causing spillage or leakage. No requirement applies to equipment located in such zone.

As an RTCA DO-160G accredited test lab, we have the resources to meet nearly every explosive atmosphere test need. In addition to being accredited to complete RTCA-DO-160G testing, Keystone is also accredited to all previous versions of the standard as well. Please contact us to see firsthand why so many manufacturers rely on Keystone Compliance to be their RTCA DO-160 test lab.

Looking for other testing to other sections of RTCA DO-160 testing? Click on the links below:

Modifications from one Version of RTCA DO-160 to the Next:

Changes from DO-160C Explosive Atmosphere Testing to DO-160D Explosive Atmosphere Testing

Fuel mixture calculation was corrected for hexane explosive proofness test. Atmospheric test pressure requirements were clarified.

Changes from DO-160D Explosive Atmosphere Testing to DO-160E Explosive Atmosphere Testing

Minor changes were made in the procedure to improve repeatability.

Changes from DO-160E Explosive Atmosphere Testing to DO-160F Explosive Atmosphere Testing

Environment definition and category definitions were revised.  Reference to 100/130 octane fuel was deleted from figure 9-4.

Changes from DO-160F Explosive Atmosphere Testing to DO-160G Explosive Atmosphere Testing

The environment descriptions are improved and category description details are moved to the user’s guide. The sensor for determining the explosiveness of the environment is changed from a spark plug or glow plug to a pressure sensor or thermocouple.  Also, the containment test was changed such that if the test case volume is greater than 1/50 of chamber volume an alternative to purging entire chamber would be to prove explosive mixture is correct after each case explosion.