Medical Gas Professional Healthcare Organization

Leading through education, we save lives


Vacuum Filtration and Handbook Commentary (2018 & 2021 edition)

  • Friday, October 22, 2021 9:34 AM
    Message # 11764857

    I discovered today that the handbook commentary has some language that seems to be out of step with the requirements within 5.1.3.7.4 vacuum filtration (same commendation and reference for 2018 and 2021 editions).  The commentary states that there are two layouts to meet the intent of the requirements:


    Option 1: place a filter with each pump

    Option 2: place filters into valved pairs in a duplex arrangement


    I do not understand how option 1 can meet the requirements of subparagraph (1) and (10) under 5.1.3.7.4.  I get that the handbook commentary isn't enforceable, but it also shouldn't directly contradict the code.


    (1) Filtration shall be at least duplex to allow one filter to be

    exchanged without impairing vacuum system


    (10) In normal operation, one filter or filter bundle shall be

    isolated from the system to be available for service

    should a blockage in the operating filter occur or rotation

    of the filters be desired after filter element

    exchange.


    If you have to turn a pump off to exchange a filter, wouldn't that "impair" the vacuum system?  Further, subparagraph (10) seems pretty straight forward that you need to have one filter isolation from the system and one available.  If you have a filter inline ahead of each pump how can you meet that requirement?  You would have to leave one pump valved off all the time.


  • Saturday, October 23, 2021 3:48 PM
    Reply # 11827340 on 11764857

    The system isn't impaired if two or more pumps/ filters / regulators / etc are sufficient to serve the peak calculated demand with the largest single vacuum pump out of service (2021 edition 5.1.3.7.1.1 (1)). The piping options you mentioned are the alternate ways of piping an equipment package. Both options meet 5.1.3.7.4 (1) and (10) as long as you meet the peak calculated demand.

  • Sunday, October 24, 2021 3:57 PM
    Reply # 11876739 on 11764857
    Al Moon (Administrator)

    wow, so many things can go wrong / without a duplex system as the code clearly spells out and list in the CODE / Not the handbook.



  • Monday, October 25, 2021 11:32 AM
    Reply # 11916955 on 11827340
    Dane Robertson wrote:

    The system isn't impaired if two or more pumps/ filters / regulators / etc are sufficient to serve the peak calculated demand with the largest single vacuum pump out of service (2021 edition 5.1.3.7.1.1 (1)). The piping options you mentioned are the alternate ways of piping an equipment package. Both options meet 5.1.3.7.4 (1) and (10) as long as you meet the peak calculated demand.

    Dane,


    So how do you choose which of the "options" or requirements that you are going to comply with under 5.1.3.7.4 (1) - (10)?  


    Within the actual text of NFPA 99, I do not see any of the (10) characteristics under 5.1.3.7.4 as optional.  The text states: "Shall be provided...with the following characteristics" and then it lists 10 items / subparagraphs.  


    "In normal operation one filter or filter bundle shall be isolated from the system"


    If you have inlet filtration piped inline with each pump like the drawing from annex A, would be to have a filter, along with the associated pump, isolated from the system under normal operation.

    1 file
  • Monday, October 25, 2021 12:54 PM
    Reply # 11919603 on 11764857

    This is interesting, because two different people read and see this differently.


    A system with filters on each pump is duplexed (redundant). The reason for duplexing, is so the the system can be maintained without disrupting the systems ability to flow. If the filter is changed (all of 60 seconds to change) on a single pump, and the other pumps are not affected, the code requirements are met.


    (1) Filtration shall be at least duplex to allow one filter to be

    exchanged without impairing vacuum system


    (10) In normal operation, one filter or filter bundle shall be

    isolated from the system to be available for service

    should a blockage in the operating filter occur or rotation

    of the filters be desired after filter element

    exchange.

    In a system with individual filters for each pump, the off line pumps and filters are available to supply the system if needed.



  • Monday, October 25, 2021 3:05 PM
    Reply # 11924276 on 11919603
    Robert Kroening wrote:

    This is interesting, because two different people read and see this differently.


    A system with filters on each pump is duplexed (redundant). The reason for duplexing, is so the the system can be maintained without disrupting the systems ability to flow. If the filter is changed (all of 60 seconds to change) on a single pump, and the other pumps are not affected, the code requirements are met.


    (1) Filtration shall be at least duplex to allow one filter to be

    exchanged without impairing vacuum system


    (10) In normal operation, one filter or filter bundle shall be

    isolated from the system to be available for service

    should a blockage in the operating filter occur or rotation

    of the filters be desired after filter element

    exchange.

    In a system with individual filters for each pump, the off line pumps and filters are available to supply the system if needed.



    I guess it really boils down to your meaning of impaired??  "lacking full functional or structural integrity"  since the system is still fully functional (per NFPA Design) during the swap either way should be good to go.  
  • Tuesday, October 26, 2021 6:51 AM
    Reply # 11956573 on 11764857

    If you have "isolation valves" on a filter bundle (see subparagraph 6) what does it mean when a filter bundle is "isolated"?  The requirement from subparagraph 10 is that "In normal operation, one filter or filter bundle shall be isolated from the system..."


    The same wording "isolated from the system" is used 5.1.3.6.3.9 (J) when discussing medical air dryers.  Maybe this is the exception, but it still seems to me like the drawing from the annex is quite incompatible with the wording from 5.1.3.7.4.

    Last modified: Tuesday, October 26, 2021 6:53 AM | Cary Darden
  • Tuesday, October 26, 2021 8:34 AM
    Reply # 11960002 on 11764857

    Good one Cary - quite an interesting question.


    The original submission was based on the idea that the filters would be "standalone", eg. placed patient side of all the equipment in the Central Supply System.  Thus they would "protect" the receiver, pumps, piping, etc. and of course the main goal - the community.


    However, even at the meeting where this was discussed the question came up about the idea of one filter, one pump.  My recollection is that there was general agreement that this would meet the requirement as well, albeit it would only "protect" the pump and community, so it was understood to be an inferior implementation.


    You have correctly noted that there is no explicit wording to allow this (because there was none in the original submission) but equally nothing that prohibits it. The wording is adaptable and all the requirements in 5.1.3.7.4 can be met by the "filter per pump" variant (albeit (6) is probably fudged most of the time).


    This underlying philosophy runs through the whole code.  It is inherent in "two-source" (N+1) construction.  If one pump is down for maintenance, we assume you will manage on one until it's finished. Downtime is always a planned event.  As in this case, when you take down a pump/filter combination for filter service.


    The annex and commentary in the Handbook of course follow the text.  I agree it seems an oversight that at least the Handbook commentary makes no mention of the one filter per pump alternative implementation.  I've not seen the 2021 Handbook yet, but sounds like it did not get any attention in the 2021 rewrite.


    A good subject for the MGPHO Standards submissions forum. 

16339 Kranker Drive, Stilwell, KS 66085

mgpho@me.com