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Electrical grounding on medical gas piping

  • Friday, May 29, 2020 10:18 AM
    Message # 9000917

    Has anyone seen this? According to the engineer, his source at NFPA says it's OK. 

    1 file
  • Friday, May 29, 2020 1:44 PM
    Reply # 9001357 on 9000917

    NFPA 99 2012 edition  5.1.14.1.2  Piping systems  shall not be used as a grounding electrode..  sorry he's wrong.  Same citation in 2015 & 2018 edition.

  • Saturday, May 30, 2020 8:50 AM
    Reply # 9002964 on 9000917
    Mathis Carlson (Administrator)

    Grounding vs Bonding.... While NFPA 99 specifically says that medical gas pipelines can't be used as a grounding electrode, that is different than bonding.
    There are numerous jurisdictions that require all metallic piping systems (including medical gas) to be bonded in the event they somehow become energized. (very possible with a fault in a vac or med air cabinet)
    So if the picture is actually using the medical gas lines as a ground, than no it is not OK. If the medical gas lines in the picture are simply being bonded as a protection it is likely OK and required at the install location. 

    So they first need to define what they are doing/trying to accomplish, then determine if it was done correctly. 

  • Saturday, May 30, 2020 2:34 PM
    Reply # 9003525 on 9000917
    Al Moon (Administrator)

    Right a nice statement within the NFPA 99 Code, that been their for many years.


    Its clear as mud.


    The difference between being a grounding electrode and being grounded.



  • Monday, June 01, 2020 11:44 AM
    Reply # 9007110 on 9000917

    Maybe its time to look at this code item. It seems that this code item has been in the NFPA 99 code since 1934 (Anesthetic Gases and Oxygen NFPA 565) and the wording has not changed since 1951 (NFPA 565 standard).

     

    I am not sure if a change or additional clarification is needed or not in the NFPA 99 code, but an educational discussion about the differences between grounding and bonding, current status of grounding and bonding potentially used in medical gas and vacuum distribution systems today, and NEC and NFPA electrical experts views on this subject would be a good start.  

     

    Today NFPA 99, 2018 definition for grounding:

    3.3.68 Grounding. See 3.3.69, Grounding System.

    3.3.69* Grounding System. A system of conductors that provides a low-impedance return path for leakage and faultcurrents. (ELS)

    No definition of BONDING found in the NFPA 99.

     

    NEC defines grounding as, "Establishing a connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth." Grounding provides a path for conducting electrical energy to earth to prevent arcing, heating, or explosion during a lightning strike.

     

    NEC defines bonding as, "The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed." The primary purpose of bonding is to equalize ground potential of, and eliminate static discharge between, equipment. If a potential difference exists between two objects connected by a conductor, electrons will flow along the conductor from the negatively charged object to the positively charged object, damaging electronics in its path. The flow of electrons happens until the two charged objects are equalized and the potential difference no longer exists.

     

     

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