Dielectric Fittings

  • Sunday, August 13, 2017 5:41 AM
    Message # 5027286
    Deleted user

    Has anyone seen stainless used for Vacuum tubing?  What kind of fitting must be used to make the transitions to the smaller copper tubing?  The concerns are the fitting melting point, dissimilar metals, the dielectric fitting context is allowed to electrically isolate special equipment.

    The larger tubing will be stainless and the smaller tubing will be copper.  This is the only reference that I've found.  The code regarding dissimilar metals touching is in regards to piping supports.

    Reference:  NFPA 99, 2015      Dielectric Fittings. Dielectric fittings that comply with the following shall be permitted only where required by the manufacturer of special medical equipment to electrically isolate the equipment from the system distribution piping:

    (1) They shall be of brass or copper construction with an appropriate dielectric.

    (2) They shall be permitted to be a union.

    (3) They shall be clean for oxygen where used for medical gases and medical support gases.   Tubes for Vacuum. Piping for vacuum systems shall be constructed of any of the following:

    (2) Stainless steel tube in accordance with the following:

  • Monday, August 14, 2017 8:16 AM
    Reply # 5028546 on 5027286
    Mathis Carlson (Administrator)

    The one that I was on, they brazed the stainless to a brass coupling, then used a BAg rod to braze the brass to the copper. The brass served as a dialectic fitting. 

  • Tuesday, August 15, 2017 7:00 AM
    Reply # 5030498 on 5027286

    If the brazing was done in the field did they have their brazing certification for the dissimilar joints. Just asking.

  • Tuesday, August 15, 2017 10:43 AM
    Reply # 5030779 on 5027286
    Deleted user

    Nobody has done anything yet.  So it is possible to braze brass to stainless?

  • Tuesday, August 15, 2017 5:21 PM
    Reply # 5031403 on 5027286
    Mathis Carlson (Administrator)

    Bob, Yes, All of the installers had their qualifications for each type of joining method and size/wall thickness range. Be it stainless welded, dissimilar stainless to brass, or brass to copper. 

  • Tuesday, August 15, 2017 6:58 PM
    Reply # 5031498 on 5027286
    Deleted user

    Would a dielectric fitting be permitted for the purpose of transitioning from stainless to copper?  e.g. copper adapter with extension, electrolysis insulator, & stainless flange

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